Ram Frame Steel Post Processor 654q6a

RAM Structural System V8i (SELECTseries 6)

RAM Frame Steel Post-Processors Last Updated: October 15, 2013

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RAM Structural System

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RAM Frame Steel Post-Processors

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Disclaimer The software and related documentation, including this documentation, are protected by both United States copyright law and international treaty provisions. Any unauthorized copying or reproduction is strictly prohibited and subject to civil and criminal penalties. Please refer to the License Agreement (EULA) for authorization to make a backup copy of the software. You may not sell this software or documentation or give copies of them to anyone else. Except as expressly warranted in the License Agreement (EULA), Bentley Systems, Incorporated disclaims all warranties, expressed or implied, including but not limited to implied warranties or merchantability and fitness for a particular purpose, with respect to the software, the accompanying written materials, and any accompanying hardware. All results should be verified to the 's satisfaction. The contents of these written materials may include technical inaccuracies or typographical errors and may be revised without prior notice.


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Disclaimer

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Table of Contents Chapter 1: Introduction .....................................................................................................11 Chapter 2: Steel Standard Provisions Post-Processors ....................................................... 13 2.1 2.2 2.3 2.4 2.5

2.6

Model Status ............................................................................................................................................................................... 13 Saving the Model .......................................................................................................................................................................13 Modes ............................................................................................................................................................................................ 13 Load Combinations .................................................................................................................................................................. 14 Generated Load Combinations ........................................................................................................................14 2.4.1 Custom Load Combinations ...............................................................................................................................14 2.4.2 Design Criteria ........................................................................................................................................................................... 15 Codes .......................................................................................................................................................................... 15 2.5.1 AISC ASD / LRFD Criteria .................................................................................................................................. 15 2.5.2 Eurocode Criteria ..................................................................................................................................................20 2.5.3 CAN/CSA S16-01, S16-09 ................................................................................................................................... 21 2.5.4 BS5950 ........................................................................................................................................................................22 2.5.5 Australia AS4100 Criteria ................................................................................................................................. 24 2.5.6 Assign Menu ................................................................................................................................................................................26 Columns ......................................................................................................................................................................26 2.6.1 Beams ..........................................................................................................................................................................27 2.6.2 Horizontal Braces ...................................................................................................................................................29 2.6.3 Braces ..........................................................................................................................................................................30 2.6.4 Sidesway .................................................................................................................................................................... 31 2.6.5 Sway-Sensitive Design Method (BS5950:2000 Only) ............................................................................ 31 2.6.6 Frame Numbers ...................................................................................................................................................... 32 2.6.7 Process Menu ...........................................................................................................................................................32 2.6.8 The Design Process ............................................................................................................................................... 34 2.6.9 Exiting and Changing Modes .............................................................................................................................35 2.6.10

Chapter 3: Steel Standard Provisions Technical Notes ......................................................... 37 3.1

General 3.1.1 3.1.2 3.1.3 3.1.4 3.1.5 3.1.6 3.1.7 3.1.8 3.1.9 3.1.10 3.1.11 3.1.12 3.1.13 3.1.14 3.1.15


........................................................................................................................................................................................... 37 Steel Design Codes .................................................................................................................................................37 Steel Shapes ..............................................................................................................................................................38 Load Combinations ................................................................................................................................................39 Sloping Beams ......................................................................................................................................................... 39 Cross Section Classification ............................................................................................................................... 40 Torsion ........................................................................................................................................................................41 Tension Capacity .................................................................................................................................................... 41 Compression Flange Bracing ............................................................................................................................ 41 Major Axis Bracing .................................................................................................................................................41 Minor Axis Bracing ................................................................................................................................................ 42 Assigned Unbraced Length ..................................................................................................................... 43 Flexural-Torsional Buckling of Tees ..............................................................................................................44 Horizontal Braces ...................................................................................................................................................44 Column Moments ................................................................................................................................................... 44 Kinked Column Equivalent Uniform Moment ........................................................................................... 45

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3.2

3.3

Member Code Check .................................................................................................................................................................45 AISC 360 (ASD and LRFD) ..................................................................................................................................45 3.2.1 ASD 9th / LRFD 3rd .............................................................................................................................................. 53 3.2.2 BS5950:1990 / 2000 ............................................................................................................................................ 56 3.2.3 CAN/CSAS16-01 ..................................................................................................................................................... 67 3.2.4 CAN/CSA S16-09 .................................................................................................................................................... 70 3.2.5 EUROCODE ................................................................................................................................................................72 3.2.6 AS 4100-98 ............................................................................................................................................................... 75 3.2.7 t Code Check ........................................................................................................................................................................ 82 Assumptions and Limitations ...........................................................................................................................82 3.3.1 t Forces ............................................................................................................................................................... 84 3.3.2 t Design ...............................................................................................................................................................86 3.3.3

Chapter 4: Steel Standard Provisions Reports ..................................................................... 95 4.1 4.2 4.3

4.4

4.5

4.6

4.7 4.8 4.9

Code Check Criteria .................................................................................................................................................................. 97 Load Combinations ................................................................................................................................................................... 97 AISC 360 Direct Analysis Validation ................................................................................................................................. 98 Design Code .............................................................................................................................................................. 98 4.3.1 Second-Order Analysis ........................................................................................................................................ 98 4.3.2 Notional Loads ........................................................................................................................................................ 99 4.3.3 Reduced Stiffness ................................................................................................................................................... 99 4.3.4 Member Code Check .............................................................................................................................................................. 100 AISC ........................................................................................................................................................................... 100 4.4.1 Eurocode ................................................................................................................................................................. 100 4.4.2 CAN/CSA S16-01 / S16-09 Member Code Check .................................................................................. 100 4.4.3 BS 5950 Member Code Check ........................................................................................................................ 101 4.4.4 AS 4100-98 Member Code Check ................................................................................................................. 101 4.4.5 Member Check Summary .................................................................................................................................................... 102 Criteria ..................................................................................................................................................................... 102 4.5.1 Code Check Criteria ............................................................................................................................................ 102 4.5.2 Load Combinations .............................................................................................................................................102 4.5.3 Summary Results .................................................................................................................................................102 4.5.4 t Code Check ......................................................................................................................................................................102 Story Number ........................................................................................................................................................102 4.6.1 t Number ......................................................................................................................................................... 103 4.6.2 Final Design ........................................................................................................................................................... 103 4.6.3 t Data and Material Properties .............................................................................................................. 103 4.6.4 Criteria ..................................................................................................................................................................... 103 4.6.5 Results ......................................................................................................................................................................103 4.6.6 Stiffener Design [AISC 9th Only] ...................................................................................................................105 4.6.7 Web Plate Details [AISC 9th Only] ............................................................................................................... 105 4.6.8 BS5950 – Draft Amend, April 1998 / BS5950-1:2000 ........................................................................ 105 4.6.9 Eurocode 3: BS EN 1993-1-8:2005 ..............................................................................................................106 4.6.10 Member Forces ........................................................................................................................................................................ 106 Member Force Summary ..................................................................................................................................................... 107 Member Force Envelope ......................................................................................................................................................107

Chapter 5: Steel Seismic Provisions Post-Processors ..........................................................109 5.1 5.2

Modes ...........................................................................................................................................................................................109 Load Combinations ................................................................................................................................................................ 109 Generated Load Combinations ...................................................................................................................... 110 5.2.1


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5.3 5.4 5.5

5.6 5.7

Custom Load Combinations ............................................................................................................................111 5.2.2 Criteria .........................................................................................................................................................................................111 Codes .........................................................................................................................................................................111 5.3.1 ASD/LRFD Criteria ..............................................................................................................................................112 5.3.2 Assign Menu .............................................................................................................................................................................. 113 Frame Types .......................................................................................................................................................... 113 5.4.1 Frame Numbers ................................................................................................................................................... 113 5.4.2 Process Menu ............................................................................................................................................................................114 Member View/Update .......................................................................................................................................114 5.5.1 Member Code Check ...........................................................................................................................................115 5.5.2 t View/Update .............................................................................................................................................. 115 5.5.3 t Code Check .................................................................................................................................................. 116 5.5.4 View/Update Result Icons ...............................................................................................................................116 5.5.5 The Design Process ................................................................................................................................................................ 117 Exiting and Changing Modes ..............................................................................................................................................119 To switch to Steel-Standard Provision Mode ..........................................................................................119 5.7.1 To exit RAM Frame ............................................................................................................................................. 119 5.7.2

Chapter 6: Steel Seismic Provisions Technical Notes ..........................................................121 6.1 6.2

Load Combinations ................................................................................................................................................................ 122 Code Check .................................................................................................................................................................................123 Assumptions and Limitations ........................................................................................................................ 123 6.2.1 Reduced Beam Section Check ........................................................................................................................ 123 6.2.2 AISC 2005/2010 (ANSI 341-05/10) – ASD and LRFD ........................................................................ 124 6.2.3 AISC 2002 (ANSI 341-02) – LRFD ................................................................................................................ 137 6.2.4 AISC 1997 – LRFD ............................................................................................................................................... 146 6.2.5 UBC97 – ASD ..........................................................................................................................................................155 6.2.6 UBC 1997 – LRFD ................................................................................................................................................ 158 6.2.7

Chapter 7: Steel Seismic Provision Reports ........................................................................163 7.1 7.2 7.3 7.4 7.5

Load Combinations ................................................................................................................................................................ 164 Member Code Check .............................................................................................................................................................. 164 Member Check Summary .................................................................................................................................................... 164 t Code Check ......................................................................................................................................................................164 t Check Summary ............................................................................................................................................................ 165


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Introduction

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The RAM Frame Steel Post-Processors are used to check steel beams, columns, braces and ts against the specification requirements of several steel design codes. The steel post-processors consist of the Standard Provisions Steel Post-Processor and the Seismic Provisions Steel Post-Processor. The Standard Provisions Steel Post-Processor is utilized to check all frame steel , and moment frame ts, according to the requirements of the selected steel design code. Specifically, the ability of the steel to resist the applied gravity and lateral (including seismic) loads is checked. The Seismic Provisions Steel Post-Processor is utilized to check all frame steel according to the requirements of the selected seismic design code. These requirements ensure that the structure is well proportioned and detailed to resist seismic loads in a ductile and life-safe manner. Chapter 2, Steel Standard Provisions Post-Processors on page 13, describes the powerful Standard Provisions Post-Processor used to check steel and moment frame ts for a selected steel design code. Chapter 3, Steel Standard Provisions Technical Notes on page 37, provides an explanation of the technical issues, assumptions, and code interpretations implemented in the Steel Standard Provisions Mode. It is critical that the engineer read and understands this chapter so as to be aware of how these assumptions affect the design. Chapter 4, Steel Standard Provisions Reports on page 95, provides a detailed description of the information contained within the Standard Provisions report output. Chapter 5, Steel Seismic Provisions Post-Processors on page 109, describes the powerful Seismic Provisions Post-Processor used to check steel and moment frame ts for a selected seismic design code. Chapter 6, Steel Seismic Provisions Technical Notes on page 121, provides an explanation of the technical issues, assumptions, and code interpretations implemented in the Steel Seismic Provisions Mode. It is critical that the engineer read and understands this chapter so as to be aware of how these assumptions affect the design. Chapter 7, Steel Seismic Provision Reports on page 163, provides a detailed description of the information contained within the Seismic Provisions report output.


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Introduction



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Steel Standard Provisions Post-Processors

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The purpose of the Standard Provision Post-processors is to investigate each steel frame member and restrained (fixed) beam-column t for the stress and capacity requirements of the selected steel design specification. The specifications currently implemented are the AISC, Eurocode, CAN/CSAS16-01, CAN/CSA S16-09, and BS 5950:1990 and 2000. Using Code-generated and/or -defined load combinations the controlling interaction equation value is calculated for each member and the results displayed graphically. The stiffeners and web plate (doubler) required to resist moment-frame t forces are also calculated and displayed graphically. In addition to the screen display, several output reports are also available.

2.1 Model Status To access the Model Status dialog box, go to the File menu and select the Model Status command. The dialog that appears for each module is similar and provides a list of what critical model data is available to this module. If it is indicated that the model cannot be run in the selected module, the dialog box will also list what information is still needed. Refer to the RAM Manager Manual for more information on the Model Status.

2.2 Saving the Model Any operations performed in RAM Frame are only saved to the permanent Database when the File – Save command is invoked in any module. This includes changes to Criteria, Combinations and even Update Database in View/Update. If the RAM Structural System is closed without performing a save in at least one of the modules then all changes made in RAM Frame will be discarded. Refer to the Saving the Model Section of the RAM Manager manual for more information.

2.3 Modes The RAM Frame Program contains three modes of operation, namely: Analysis mode (as described previously), Steel Mode (the Standard Provision sub-mode which is described here) and the Drift Control mode. To access the Steel Standard Provision mode select the Mode-Steel-Standard Provision command. This mode can also be entered by selecting the Steel mode and Standard Provision submode from the dropdown controls located on the dialog bar below the toolbars. Upon initially entering this mode, the Standard Provision Steel Code dialog will automatically appear. The engineer selects the desired steel design code in this dialog. This dialog can be subsequently displayed at any time when in this mode by selecting the Criteria-Codes command.


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Steel Standard Provisions Post-Processors Load Combinations

2.4 Load Combinations Load combinations can be generated by the program and/or defined by the engineer. Load combinations must be defined before any post-processing can be done. After the Steel Design Code dialog is closed the Load Combination Generation dialog box appears. This dialog is used to select a desired building code and automatically generate load combinations based on those load cases previously analyzed. The engineer can select to include any or none of the load cases in the generated list of combinations. Click the Apply button after selecting the appropriate load cases to automatically generate and view load combinations in this dialog. After load combinations are generated the engineer can decide which combinations to consider in the design. All rows of load combinations with the Use check box selected will be considered during post-processing. When this dialog is closed the can return to view or change their combinations by selecting the Combinations-Generate command. Custom load combinations (where the can select their own load factors) can be generated in the dialog displayed by selecting Combinations-Custom. Once load combinations have been defined and selected, the Process commands become available. The Code Check, View/Update and Reports commands can then be used as described in the next several sections. Refer to the Load Combination Generator Manual for more information about this component.

2.4.1 Generated Load Combinations All generated combinations are normalized so that they can be compared against an interaction equation value of 1.0. For some implementations of ASD the allowable stresses can be increased by 1/3 for wind and seismic loads. This is handled in the program by asg factors of 0.75 in the load combinations (i.e., the loads are factored down rather than the allowable stresses being factored up). Note that Dynamic and Other type load cases are not included in the automatically generated load combinations; if desired, custom combinations which include these must be created by the . Refer to the Load Combination Generator Manual for more information about the generated load combination templates installed with the program.

2.4.2 Custom Load Combinations The custom load combination dialog is displayed by selecting the Combinations-Custom command. The load factors should be normalized such that for all load combinations the allowable interaction equation value is 1.0. For example, as explained for Generated Load Combinations, the allowable stresses for ASD can be increased by 1/3 for wind and seismic loads. This should be handled in the custom load combinations by asg factors of 0.75 rather than 1.0 (i.e., the loads are factored down rather than the allowable stresses being factored up).


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Steel Standard Provisions Post-Processors Design Criteria Separate combinations of plus and minus factors should be created where appropriate; the program does not automatically reverse the signs of the factors on lateral load cases for -specified custom load combinations. Refer to the Load Combination Generator Manual for more information about custom load combinations.

2.5 Design Criteria Below is a brief description of the global criteria that pertain to the Member and t Code Checks performed by all the steel design specifications. Technical descriptions of how each criterion is used in the Code Check are provided later in the manual. The system sets default criteria at the time of installation. They can be modified on a model-by-model basis by issuing the commands described in this section. Changes can be made on a permanent basis by selecting the Tools-Defaults Utility in the RAM Manager. Note that these criteria are “global” in that they apply to all the appropriate in the model. However, the also has the ability to override these global criteria on a member-by-member basis. Refer to the description of the Assign commands for additional information. The Criteria menu items are divided into three sections based on functionality. Namely there is a codes command, followed by the group of member criteria items, followed by the t criteria items.

2.5.1 Codes The dialog displayed by selecting the Criteria-Codes command displays all the available steel design codes. Select the code by which to perform design checks. Select the option “Show this dialog when entering Standard Provision Mode” to automatically have this dialog displayed each time the engineer switches to the Steel-Standard Provisions mode. The commands available under the Criteria menu (as described next) will change depending on the steel code selected. The Load Combinations Generation will automatically be displayed directly after this dialog is closed. Modifying the Steel Code will remove all previously generated load combinations and will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run.

2.5.2 AISC ASD / LRFD Criteria This section applies to AISC 360-10 (ASD and LRFD), AISC 360-05 (ASD and LRFD) as well as ASD 9th Edition and LRFD 3rd Edition. Some differences are noted.

B1 and B2 Factors This only applies to AISC 360, the command is only available when that code is selected. With the Criteria – B1 and B2 Factors command, the can specify whether or not to apply the B1 and B2


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Steel Standard Provisions Post-Processors Design Criteria factors. Generally the option to apply B1 factors should be selected. Generally, if the model was analyzed without using the P-Delta option, the option to apply B2 factors should be selected. For braced frames, RM should be set to 1.0, for moment-frame and combined systems it should be set to 0.85.

Sidesway This does not apply to AISC 360, the command is not available when that code is selected. With the Criteria - Sidesway command, the can indicate whether a frame is Braced , Unbraced or Partially Braced against sidesway. This affects the calculation of K, Cb and Cm. Partially Braced refers to structures that are braced in one direction but not in the other. When Partially Braced is selected the must specify the range of member orientation, with respect to the global coordinate axes, for which the member is to be considered braced. Modifying the Sidesway criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

K-Factor This does not apply to AISC 360, the command is not available when that code is selected. With the Criteria - K-Factor command, Kx and Ky values are set for the beams, columns and braces in the structure . For columns, the K-Factor can be calculated by the program using Nomograph values or can be specified by the engineer. Modifying the K-Factor criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Flange Bracing With the Criteria - Flange Bracing command, the bracing condition of beams and columns is defined. Beam flanges can be braced continuously along the top flange, continuously along the bottom flange or not braced. Column flanges can be defined to be braced by the deck or by knee braces and beams that frame in within a given angle of a column face, or not braced. Modifying the Flange Bracing criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Column Moments With the Criteria – Column Moments command the can specify the portion of the calculated Gravity load moments to be included in the design of the columns. Percentages for Dead Load, Live Load and Roof Load may be specified individually. For the Live and Roof Loads, this reduction is in addition to any Live Load Reduction calculated for the column. This feature should be used cautiously, as it causes


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Steel Standard Provisions Post-Processors Design Criteria the program to ignore portions of the calculated moments. See the Technical Notes for more information. Normally the percentages should be specified as 100% to include the full-calculated moments. This feature is available for each of the steel design codes. Modifying the Column Moments criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run.

Axial Slenderness Limit Within the RAM Frame Standard Provisions Steel Post-Processor the can use the Criteria - Axial Slenderness Limits to specify a slenderness limit KL/r < 200 to apply to all in compression within the model and a limit L/r < 300 for all (except round bars) in tension as detailed in and ASD 9th and LRFD 3rd Specification Section B7. This is not a code requirement but is common practice.

ts The criteria by which the t web plate and stiffeners will be designed for moment (rigid) frame connections can be viewed and modified through the dialog displayed by invoking the Criteria-ts command. The four tab sheets, as described in detail below, allow the engineer to provide the appropriate information regarding the material of the web plates and stiffeners, the geometric restrictions of the t, the design forces and the optimization criteria of the web plate and stiffeners. Modifying the t criteria after a t Code Check has been performed will invalidate the results of that t Code Check. The model will be redrawn on the screen without any t colors indicating that the t Code Check must be re-run. t Code Checks are not performed on hanging columns. Where offset beams framing into the column flanges are offset from the plane of the web of the column, the t Code Check assumes no offset between the beam and the plane of the web of the column.

Material The engineer should provide the strength of the material to be used for stiffeners and web plates. The capacity of each of the column, web plate and stiffener is calculated independently of each other and is a function of each of their material strengths.

Geometry For the RAM Structural System to determine if a particular t is valid (refer to limitations section for definition of valid) the engineer must provide the maximum angle that a beam can frame into the column and still be considered attached to the flange of the column. This angle refers to the angle between the major axis of the column and the longitudinal axis of the beam. Beams framing into a column beyond this angle are assumed to frame into the web of the column. Several codes require the engineer to do specific checks only where two compressive forces are applied to opposite sides of a column at the same elevation (concurrent-compression check). For a valid t with a single lateral beam framing into each flange of an I-Section column, the top flanges of the beams are assumed to be at the same elevation. In the event that the top flanges of both beams apply a compressive force on the column, these concurrent-compression checks will be performed. However, depending on the depth of each beam, the bottom flanges may not be at the same elevation. The engineer is responsible for determining the maximum difference in elevation that can exist between the


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Steel Standard Provisions Post-Processors Design Criteria bottom flanges of the two beams for which they still want the concurrent-compression checks performed. The distance provided by the engineer for the concurrent-compression check is also used to determine the maximum difference in elevation for a single diagonal stiffener to be used. When necessary, beams whose difference in bottom flange elevation exceeds the value provided by the engineer will be provided with two horizontal stiffeners (one for each beam’s bottom flange). For beams whose difference in bottom flange elevation is less than the value provided by the engineer, one diagonal stiffener will be provided between the beam flange elevations.

Forces The forces applied at the beam-column connection can be determined from either the design load forces or from the bending capacities of the at the ts. When design load forces are selected, the program will determine the largest -zone shear, as well as the largest concentrated force at each beam flange, from all load combinations. The forces are calculated as described in the technical section. The engineer also has the option of indicating which method the program uses to apply beam axial load to the t. The ramifications of each of the three available options on the t design forces are indicated in the following figure. Case A illustrates the flange forces when the has indicated to use the design moment ignoring the axial load. Case B is where the engineer is using the design moment considering the axial load and Case C is where the engineer only considers axial load if it increases the force on the column. M

M P

d

M/d

M/d + P/2

M/d + P/2

M/d

M/d - P/2

M/d

A

B

C

If the plastic capacity of the section is selected, then the engineer must specify an appropriate overstrength factor. The plastic capacity of the member is calculated as the product of the member’s plastic modulus, yield strength and the over-strength factor. The force applied to the column flange is thus the member plastic capacity divided by the distance between the centers of the beam flanges. In the event that the member has a reduced beam section specified (refer to Criteria-Reduced Beam Section) the moment at the face of the column used to calculate the t forces is taken as: Mpr + Vp*Xf where, as illustrated in the following figure: Mpr is the member plastic capacity at the reduced beam section, L is the distance between reduced beam sections, Xf is distance from the center of the reduced beam section to the face of the column, and


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Steel Standard Provisions Post-Processors Design Criteria Vp is taken as 2 Mpr / L. Xf

L

Optimization The engineer has many options for controlling how RAM Frame designs stiffeners and web plates (doublers). The engineer can specify minimum values for stiffener dimensions, and web plate thickness. If stiffeners or a web plate are required they will be sized no smaller than the minimum dimensions specified. The increment to which the stiffener dimensions and web plate thickness should be rounded should also be provided. If the stiffener dimension required to resist the forces is larger than the minimum specified stiffener thickness, it will be rounded up to the closest increment. The same applies to the web plate thickness. The maximum permissible stiffener thickness is taken as three times the thickness of the thinnest beam flange framing into the t. This limit is an arbitrary limit not mandated by any code. The engineer can specify a maximum permissible web plate thickness. If the engineer wants all the stiffeners at a t to have the same width and thickness, then the top check box should be selected. The maximum thickness and width will be applied to all the stiffeners at a t, but the lengths may differ. As shown in the following figure the cope dimension refers to the “dog-ear” cut that must be made in the stiffener so that the plate will avoid conflict with the web toe of the column flange-to-web fillet. While this is typically a detailing decision the engineer should (and RAM Frame does) consider this dimension in their calculations, and a conservative value should be specified. The engineer has a couple of options to specify to the program how the web plates are to be detailed for attachment to the columns. The engineer can choose to weld the plate to the flanges of the column using a CJP weld or a fillet weld. They can also decide to plug weld the web plate to the column web. These selections are currently only relevant to the AISC code checks. Where the check box for the fillet weld is not selected, the program assumes that the web plate is attached to the column flange with a CJP weld. The assumption made is that the web plate is cut short of the web toe of the column flange-to-web fillet radius, and the weld is made onto this toe. Alternatively, if the fillet weld check box is selected the engineer is indicating that the web plate is to be welded directly to the column flange. In this case the edge of the web plate will need to be beveled so as to avoid the root of the columns web-flange weld (see the following figure).

Cope Dimension


Stiffener

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Web Plate


Steel Standard Provisions Post-Processors Design Criteria To accommodate the detailing requirement of the fillet weld attachment the thickness of the web plate may need to be increased beyond the thickness required just to resist the applied loads (refer to AISC Design Guide 13 for more information). Note that in the output the thickness required to meet the fillet weld-detailing requirement is specified separately from the design thickness required to resist the loads. Refer to the report descriptions for more details on the output. The engineer can also choose to plug-weld the web plate to the column web (as is recommended in high seismic zones). If this is done then there are no checks required for web plate buckling. If the engineer indicates that no plug welds are to be used RAM Frame will determine the thickness of the web plate to prevent buckling. This is an AISC code requirement that may control the required thickness of the plate as needed to resist the applied loads. In general the web plate is designed to resist the applied forces, and the thickness used is controlled by the constraints the engineer provided, the code-specified limits and the detailing requirements. However, some codes have specific limitations on web plate design. Where these specifications have been implemented they are described in the technical section. Important: Where a web plate is specified by RAM Frame it is assumed the plate extends above and below the top and bottom elevation of the beam flanges respectively. That is, the web plate does not stop at the same elevation as the bottom flange of the deepest beam at the t, but rather extends some distance below this point. This is important as all checks that considered the contribution of the web plate assume that the plate is effective both above and below the point at which the beam flange applies the concentrated load to the column flange.

Beam with End Connections RAM Frame performs a check of all beams with the following end connections: Standard, Spring, Custom, Reduced Beam Section (RBS) and SidePlate. Refer to Section 6.19 in the RAM Frame Analysis manual for details on Beams with End Connections.

2.5.3 Eurocode Criteria Sidesway With the Criteria - Sidesway command, the can indicate whether a frame is Braced, Unbraced or Partially Braced against sidesway. This affects the method by which the l/L is calculated for the lateral . Partially Braced refers to structures that are braced in one direction but not in the other. When Partially Braced is selected the must specify the range of member orientation, with respect to the global coordinate axes, for which the member is to be considered braced. Modifying the Sidesway criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.


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Steel Standard Provisions Post-Processors Design Criteria

Effective Length (ℓ/L)Factor With the Criteria - Effective Length command, ℓ/L major and minor values are set for the beams, columns and braces in the structure. Modifying the ℓ/L criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Flange Bracing With the Criteria - Flange Bracing command, the bracing condition of beams and columns is defined. Beam flanges can be defined to be braced continuously along the top flange, continuously along the bottom flange or not braced. Column flanges can be defined to be braced by the deck, by the beams that frame in within a given angle of a given column face, or not braced. Modifying the Flange Bracing criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Column Moments Refer back to the AISC Criteria (Section 2.5.2) for a description of the Criteria-Column Moments command.

ts Refer back to the AISC Criteria (Section 2.5.2) for a description of the Criteria-ts command.

Reduced Beam Section Refer back to the AISC Criteria (Section 2.5.2) for a description of the Criteria-Reduced Beam Section command.

2.5.4 CAN/CSA S16-01, S16-09 No sidesway criteria are required for the Canadian Design Code, however, performing a p-delta analysis captures secondary forces that result from sway in the structure. A P-Delta analysis must be performed prior to selecting the CAN/CSA S16-01 post-processor.


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K Factor With the Criteria - K-Factor command, major and minor effective length factors are set for the beams, columns and braces in the structure. The K factor only applies to the calculation of axial capacity for loaded with axial load. Modifying the K-Factor criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Flange Bracing With the Criteria - Flange Bracing command, the bracing condition of beams and columns is defined. Beam flanges can be braced continuously along the top flange, continuously along the bottom flange or not braced. Column flanges can be defined to be braced by the deck, by the beams that frame in within a given angle of a given column face, or not braced. Modifying the Flange Bracing criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.


Axial Slenderness limits With the Criteria-Axial Slenderness command the can designate whether the program will fail a member if its L/r exceeds 300 (excludes rods which are allowed to exceed this limit).


Beam with End Connections RAM Frame performs a check of all beams with the following end connections: Standard, Spring, Custom, Reduced Beam Section (RBS) and SidePlate. Refer to Section 6.19 in the RAM Frame Analysis manual for details on Beams with End Connections.


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2.5.5 BS5950 BS 5950-1:1990 and BS 5950-1:2000 are implemented. This section describes criteria required by both code versions. For BS5950-2000 there are additional criteria related to hollow structural sections and distance to axis of restraint of a beam that are specified in the RAM Manager. Refer to the British Criteria in the RAM Manager for more information. There are also new tables provided for cold-formed steel sections as specified in BS5950-2000 and described in the Tables section of the RAM Manager manual.

Sidesway With the Criteria - Sidesway command, the can indicate whether a frame is Non-sway, Sway Sensitive or Non-Sway on Axis. Non-Sway on Axis refers to structures that are Non-Sway in one direction but Sway-sensitive in the other. When Non-Sway on Axis is selected the must specify the range of member orientation, with respect to the global coordinate axes, for which the member is to be considered non-sway. For BS5950:2000 the program can determine the sway state of a particular member axis if the Calculate (Per Load Combination) option is selected. When this option is applied the program will calculate the lateral story drifts at the position of each member being designed, for each floor. Drifts are calculated using only the factored notional load cases in each load combination. These drifts are then used to calculate λcr per 2.4.2.6, which if between 4.0 and 10.0 will then result in the member being designated as a sway-sensitive member in that axis. NOTE that the will need to have created and analyzed notional load cases to make use of this option. Refer to the technical section for more information on calculating λcr for load combinations. These settings affect the method by which the effective length Le is calculated for the lateral Modifying the Sidesway criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Effective Length With the Criteria - Effective Length command, Le/L major and minor values are set for the beams, columns and brace struts in the structure. For columns, the Le/L values can be calculated by the program using Appendix E provisions or can be specified by the engineer. The Engineer provides the effective length factor for RHS and I-section beams. If Use LTB (Lateral Torsional Buckling) Factor is selected then the Le/L factor for the beam will be based on the Le/L calculated according to the data provided in the LTB section of the dialog. Connection information is required to determine the effective length of channels subject to axial load. The LTB section of the dialog is used to calculate the effective length of the unbraced beam for Lateral Torsional Buckling consideration. This information is required whenever a beam that is subject to bending has an unbraced flange. For I, RHS and CHS sections the Le/L factor must be entered directly, for double angle connection details are required to be input from which the effective length factor will be determined.


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Steel Standard Provisions Post-Processors Design Criteria Refer to the online help for additional information on this dialog. Capacity of Tee and Channel sections is computed based on the connection type per the code. To specify the appropriate connection type for the T-Section and Channel braces, select the Criteria-Effective Length Command and choose the appropriate option in the dialog: Two or more Rows of Fasteners or Two or More Fasteners in One Row. Modifying the Effective Length criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Flange Bracing With the Criteria - Flange Bracing command, the bracing condition of beams and columns is defined. Beam flanges can be considered braced continuously along the top flange, continuously along the bottom flange or not braced. Column flanges can be defined to be braced by the deck, by the beams that frame in within a given angle of a given column face, or not braced. Modifying the Flange Bracing criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Design The Criteria - Design dialog is used to provide information on the maximum allowable slenderness for a brace member. This applies to all brace sections subject to an axial compression load. This criteria is based on the BS5950:Part1:1990 requirement in Section 4.7.3.2 (b) and (c).



Reduced Beam Section Refer back to the AISC Criteria for a description of the Criteria-Reduced Beam Section command.

2.5.6 Australia AS4100 Criteria


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Sidesway With the Criteria - Sidesway command, the can indicate whether a frame is Braced, Unbraced or Partially Braced against sidesway. This affects the method by which the effective length (ke) is calculated for the lateral . Partially Braced refers to structures that are braced in one direction but not in the other. When Partially Braced is selected the must specify the range of member orientation, with respect to the global coordinate axes, for which the member is to be considered braced. Modifying the Sidesway criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Effective Length (ke) Factor With the Criteria - Effective Length command, ke major and minor values are set for the beams, columns and braces in the structure. For columns, the effective length values can be calculated by the program using the AS4100-98 figure 4.6.3.3 chart or can be specified by the engineer. Modifying the effective length criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.

Flange Bracing With the Criteria - Flange Bracing command, the bracing condition of beams and columns is defined. Beam flanges can be defined to be braced continuously along the top flange, continuously along the bottom flange or not braced. Column flanges can be defined to be braced by the deck, by the beams that frame in within a given angle of a given column face, or not braced. Modifying the Flange Bracing criteria after a Code Check has been performed will invalidate the results of that Code Check. The model will be redrawn on the screen in its original colors (rather than the Code Check colors) indicating that the Code Check must be re-run. Refer to the Assign chapter for information on how this criterion can be overridden on a member-bymember basis.




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Steel Standard Provisions Post-Processors Assign Menu

Reduced Beam Section Refer back to the AISC Criteria (Section 2.5.2) for a description of the Criteria-Reduced Beam Section command.

2.6 Assign Menu The engineer has the ability to assign several design criteria and properties to each individual member. By selecting one of the Assign commands the appropriate criteria or property can be assigned to one or more in the model. The assign options available to the engineer in this mode are typically organized based on member type (beam, column or brace). All the assign options are described below.

2.6.1 Columns Size Selecting the Assign-Columns-Size command causes the Assign Size dialog box to be displayed. From this dialog the engineer can assign new sizes to any lateral columns. Select the appropriate material from the material box at the top of the dialog. Select the appropriate size from the size box. For concrete and other materials the sizes displayed are those sizes created by the in the RAM Modeler. For steel sections the sizes shown are based on the member type (column) and the currently selected master steel table (refer to the RAM Manager). Note that only columns of the material selected in the dialog can be assigned the size selected. After a size is selected the engineer can assign the size to a single member (click on Single), to multiple (click on Fence) or to all (click on All). If Single is clicked the dialog will close and a target cursor will be made available. Click on each member to assign the size to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all of the to assign the size to. Note that sizes are only assigned to columns comprised of the same material selected in the assign dialog. To return to the dialog to select a different size to assign click on the right mouse button.

Effective Length Factor Selecting the Assign-Column-K Factor/Effective Length command causes the Assign K Factor (ASD 9th, LRFD 3rd and Canada) or Effective Length Factor (Eurocode, AS4100 and BS5950) dialog box to be displayed. From this dialog the engineer can override, on a member-by-member basis, the global effective length factors specified in the Criteria-K Factor/Effective Length Factors dialog. Select the appropriate values from the dialog. Refer to Criteria-K Factor/Effective Length Factor section for more information on the various options. The engineer can choose to override the global criteria in one or both axes of the member. The criteria are applied to the column’s local axes. After the appropriate values are specified the engineer can assign the criteria to a single member (click on Single), to multiple (click on Fence) or to all (click on All). If Single is clicked the


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Steel Standard Provisions Post-Processors Assign Menu dialog will close and a target cursor will be made available. Click on each section to apply the criteria to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the sections to apply the criteria to. Note that the criteria are only assigned to steel columns. To return to the dialog to select a different effective length criteria click on the right mouse button. To view which member axes are using the global criteria and which have been overridden select the appropriate option from the View- Dialog.

Flange Bracing Selecting the Assign-Column-Flange Bracing command causes the Assign Column Bracing dialog box to be displayed. From this dialog the engineer can override, on a member by member basis, the global column bracing criteria specified in the Criteria-Flange Bracing dialog. The engineer should specify whether the TOP of the column is braced or unbraced (or should consider the global criteria) in each axis. This command acts with respect to the top of the column element. Note that if a column is broken up by an intermediate story such that separate column finite elements comprise the physical column, then the top of the selected column element will be assigned the specified criteria. When asg these criteria the must be careful to select the correct column. After the appropriate values are specified the engineer can assign the criteria to a single member (click on Single), to multiple (click on Fence) or to all (click on All). Be careful of using the ALL and FENCE options for the reason described above. If Single is clicked the dialog will close and a target cursor will be made available. Click on each column to apply the criteria to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the sections to apply the criteria to. Note that the criteria are only assigned to steel columns. To return to the dialog to select a different effective length criteria click on the right mouse button. To view which member axes are using the global criteria and which have been overridden select the appropriate option from the View- Dialog.

Unbraced Length Selecting the Assign- Column-Unbraced Length command causes the Assign Unbraced Length dialog box to be displayed. From this dialog the engineer can specify on a column-by-column basis whether to override the automatically calculated unbraced lengths. These can be assigned for each of the two axial buckling axes (Major and Minor) and the bending compression flange (out-of-plane from bending axis) for lateral torsional buckling consideration. By asg Global to any of the column axes for consideration of unbraced length the program will automatically calculated the values as described in section 3.1.8. Asg a specific value to an axis the program will use that value for the appropriate strength calculation. Asg a specific value to an axis the program will use that value for the appropriate strength calculation for every segment of the column that is checked. To view which columns have an assigned unbraced length, select unbraced length from the frame column tab in the View- Dialog.


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2.6.2 Beams Selecting the Assign-Beam-Size command causes the Assign Size dialog box to be displayed. Refer to the Assign Column Size section for a detailed description of this command.

Effective Length Selecting the Assign-Beam-K Factor/Effective Length command causes the Assign K Factor (ASD 9th, LRFD 3rd and Canada) or Effective Length Factor (Eurocode, AS4100 and BS5950) dialog box to be displayed. From this dialog the engineer can override, on a member-by-member basis, the global effective length factors specified in the Criteria-K Factor/Effective Length dialog. Select either the global criteria or otherwise specify an appropriate effective length factor. (Refer to Criteria-K Factor/ Effective Length for more information on the available options). The engineer can choose to override the global criteria on one or both axes of the beam. The criteria are applied to the beam’s local axes. After the appropriate values are specified the engineer can assign the criteria to a single member (click on Single), to multiple (click on Fence) or to all (click on All). If Single is clicked the dialog will close and a target cursor will be made available. Click on each section to apply the criteria to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the sections to apply the criteria to. Note that the criteria are only assigned to steel beams. To return to the dialog to select a different effective length criteria click on the right mouse button. To view which member axes are using the global criteria and which have been overridden select the appropriate option from the View- Dialog.

Flange Bracing Selecting the Assign-Beam-Flange Bracing command causes the Assign Beam Flange Bracing dialog box to be displayed. From this dialog the engineer can override, on a member by member basis, the global beam flange bracing criteria specified in the Criteria-Flange Bracing dialog. The engineer should specify whether the top and or the bottom flange of the beam is braced or unbraced, or whether the global beam flange bracing should be applied to the beam. The bracing of the compression flange influences the calculated axial and bending capacity of the beam. After the appropriate values are specified the engineer can assign the criteria to a single member (click on Single), to multiple (click on Fence) or to all (click on All). If Single is clicked the dialog will close and a target cursor will be made available. Click on each beam to apply the criteria to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the sections to apply the criteria to. Note that the criteria are only assigned to steel beams. To return to the dialog to select a different beam flange bracing click on the right mouse button. To view which are using the global criteria and which have been overridden select the appropriate option from the View- Dialog.

Unbraced Length Selecting the Assign-Beam-Unbraced Length command causes the Assign Unbraced Length dialog box to be displayed. From this dialog the engineer can specify on a beam-by-beam basis whether to override the automatically calculated unbraced lengths. These can be assigned for each of the two axial buckling


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Steel Standard Provisions Post-Processors Assign Menu axes (Major and Minor) and the bending compression flange (out-of-plane from bending axis) for lateral torsional buckling consideration. By asg Global to any of the beam axes for consideration of unbraced length the program will automatically calculated the values as described in section 3.1.8. Asg a specific value to an axis the program will use that value for the appropriate strength calculation for every segment of the beam that is checked. To view which beams have an assigned unbraced length, select unbraced length from the frame beam tab in the View- Dialog.

Reduced Beam Section (RBS) Selecting the Assign-Beam-Reduced Beam Section command causes the Assign Reduced Beam Section dialog box to be displayed. From this dialog the engineer can specify on a beam-by-beam basis whether to apply the reduced beam section (RBS) properties to the section. The reduced beam properties assigned to the section are those specified in the Criteria-Reduced Beam Section dialog. By selecting “clear reduced beam section” the engineer can remove the application of the RBS from any beam. This command is only applicable to steel, I-section beams. After the appropriate values are specified the engineer can assign the criteria to a single member (click on Single) or to multiple (click on Fence). If Single is clicked the dialog will close and a target cursor will be made available. Click on each steel I-section to apply the criteria to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the sections to apply the criteria to. Note that the criteria are only assigned to the steel I-beams. To return to the dialog to select a different effective length criteria click on the right mouse button. To view which beams have a reduced beam section applied, select RBS from the beam tab in the View Dialog.

2.6.3 Horizontal Braces A distinction is made between horizontal braces and beam . Horizontal braces are used to carry lateral forces between the vertical lateral resisting systems; they carry no gravity loads, cannot be assigned as reduced beam sections and are not braced by any of the gravity beams that they intersect. Other than these distinctions the horizontal braces are analyzed and designed in the same way lateral beams are.

Size Selecting the Assign-Horizontal Brace-Size command causes the Assign Size dialog box to be displayed. All sections that are appropriate to be used for horizontal braces can be assigned. Refer to the Assign Column Size section for a detailed description of this command.

Effective Length Factor Selecting the Assign-Horizontal Brace-K Factor/Effective Length command causes the Assign K Factor (ASD 9th, LRFD 3rd and Canada) or Effective Length Factor (Eurocode and BS5950) dialog box to be displayed. Refer to the Assign Beam K-Factor / Effective Length Factor for a detailed description of this command.


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Flange Bracing Selecting the Assign- Horizontal Brace -Flange Bracing command causes the Assign Horizontal Brace dialog box to be displayed. From this dialog the engineer can override, on a member by member basis, the global horizontal brace flange bracing criteria specified in the Criteria-Flange Bracing dialog. Refer to the Assign Beam Flange Bracing section for a detailed description of this command.

Unbraced Length Selecting the Assign-Horizontal Brace-Unbraced Length command causes the Assign Unbraced Length dialog box to be displayed. From this dialog the engineer can specify on a brace-by-brace basis whether to override the automatically calculated unbraced lengths. These can be assigned for each of the two axial buckling axes (Major and Minor) and the bending compression flange (out-of-plane from bending axis) for lateral torsional buckling consideration. By asg Global to any of the brace axes for consideration of unbraced length the program will automatically calculated the values as described in section 3.1.8. Asg a specific value to an axis the program will use that value for the appropriate strength calculation. To view which horizontal braces have an assigned unbraced length, select unbraced length from the brace tab in the View- Dialog.

2.6.4 Braces Size Selecting the Assign-Brace-Size command causes the Assign Size dialog box to be displayed. Refer to the Assign Column Size section for a detailed description of this command.

Effective Length Selecting the Assign-Brace-K Factor/Effective Length command causes the Assign K Factor (ASD 9th, LRFD 3rd and Canada) or Effective Length Factor (Eurocode, AS4100 and BS5950) dialog box to be displayed. From this dialog the engineer can override, on a member by member basis, the global effective length factors specified in the Criteria-K Factor/Effective Length dialog. Select either the global criteria or otherwise specify an appropriate effective length factor. (Refer to Criteria-K Factor/ Effective Length for more information on the available options). The engineer can choose to override the global criteria in one or both axes of the member. The criteria are applied to the brace local axes. After the appropriate values are specified the engineer can assign the criteria to a single member (click on Single), to multiple (click on Fence) or to all (click on All). If Single is clicked the dialog will close and a target cursor will be made available. Click on each section to apply the criteria to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the sections to apply the criteria to. Note that the criteria are only assigned to steel braces. To return to the dialog to select a different effective length criteria click on the right mouse button.


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Steel Standard Provisions Post-Processors Assign Menu To view which member axes are using the global criteria and which have been overridden select the appropriate option from the View- Dialog.

Unbraced Length Selecting the Assign- Brace-Unbraced Length command causes the Assign Unbraced Length dialog box to be displayed. From this dialog the engineer can specify on a brace-by-brace basis whether to override the automatically calculated unbraced lengths. These can be assigned for each of the two axial buckling axes (Major and Minor) and the bending compression flange (out-of-plane from bending axis) for lateral torsional buckling consideration. By asg Global to any of the brace axes for consideration of unbraced length the program will automatically calculated the values as described in section 3.1.8. Asg a specific value to an axis the program will use that value for the appropriate strength calculation. Asg a specific value to an axis the program will use that value for the appropriate strength calculation for every segment of the beam that is checked. To view which horizontal braces have an assigned unbraced length, select unbraced length from the brace tab in the View- Dialog.

2.6.5 Sidesway Selecting the Assign-Sidesway command causes the Sidesway dialog box to be displayed. From this dialog the engineer can override on a member-by-member basis the global sidesway criteria specified under Criteria-Sidesway. The sidesway criteria is currently used by the steel design codes and is therefore only applicable to the steel . Select the appropriate sidesway criteria for each local axis of the member (or specify that the global criteria are to be used for that axis). After the appropriate values are specified the engineer can assign the criteria to a single member (click on Single), to multiple (click on Fence) or to all (click on All). If Single is clicked the dialog will close and a target cursor will be made available. Click on each section to apply the criteria to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the sections to apply the criteria to. Note that the criteria are only assigned to steel . To return to the dialog to select a different effective length criteria click on the right mouse button. To view which member axes are using the global criteria and which have been overridden select the appropriate option from the View- Dialog. This command is neither applicable to, nor available for, AISC 360.

2.6.6 Sway-Sensitive Design Method (BS5950:2000 Only) For BS5950:2000, selecting the Assign-Sway-Sensitive Method… command causes the Sway-Sensitive Design Method dialog box to be displayed. From this dialog the engineer can specify the design approach to be applied to the member for a specific axis. That is, per BS5950-2.4.2.7 the can designate to use the Effective Length approach per 2.4.2.7a. or the Amplified Sway Approach per 2.4.2.7b. For the amplified sway approaches the can designate to have the program calculate kAmp for each load combination or to use a specified value.


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Steel Standard Provisions Post-Processors Assign Menu For the Amplified Sway Approach if the Calculate (Per Load Combination) option is selected then the program will calculate the lateral story drift at the position of each member being designed (for all floors), for only the factored notional loads in the load combination. For that specific combination the drifts are then used to calculate λcr per 2.4.2.6 and in turn are used to calculate kAmp per 2.4.2.7b.1. Note that the will need to create and analyze notional load cases to make use of this option. Refer to the technical section for more information on calculating λcr for load combinations. The sway-sensitive design method criteria are only used by the BS5950:2000 steel design codes and ONLY if p-delta analysis was not performed. Select the axis checkbox to make an assignment to a specific member axis. After the appropriate values are specified the engineer can assign the criteria to a single member (click on Single), to multiple (click on Fence) or to all (click on All). If Single is clicked the dialog will close and a target cursor will be made available. Click on each section to apply the criteria to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the sections to apply the criteria to. Note that the criteria are only assigned to steel . To view what sway sensitive design method is assigned to each member select the appropriate option from the View- Dialog.

2.6.7 Frame Numbers Selecting the Assign-Frame Numbers command causes the Assign Lateral Frame Numbers dialog box to be displayed. From this dialog the engineer can assign frame numbers to Lateral Frame . The primary purpose of the frame numbers is to group frame for output purposes, but they may have design implications as in the case of seismic special provisions (refer to Seismic Provisions Chapter). Enter a number in the Frame Number edit box to assign to . Select the member types to assign this frame number to by clicking the appropriate option box under the Assign To area. Note that different member types, within the same frame, can be assigned different numbers. After the appropriate frame numbers and member types values are specified, the engineer can assign the criteria to a single member (click on Single), to multiple (click on Fence) or to all (click on All). If Single is clicked the dialog will close and a target cursor will be made available. Click on each section to assign the Frame Number to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the to assign the Frame Number to. To view member frame numbers select the appropriate option from the View- Dialog.

2.6.8 Process Menu The Standard Steel Post Processor has four actions that can be selected from the Process menu. These include Member View/Update, t View/Update, Member Code Check and t Code Check. In addition there is a link between the RAM Baseplate program and RAM Frame that is exposed in this menu if v1.5 or later of RAM Baseplate is installed.


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Member View/Update The Process-Member View/Update command is a powerful feature that allows the to view detailed results of the stress and capacity checks based on the currently selected steel design code (in the Criteria-Code command). If desired the member size and yield strength can be modified and the Code Check repeated. The modified data can then be saved to the database without requiring returning to the RAM Modeler. When the View/Update command is issued, the target cursor appears with which the selects the frame member on which the Code Check is to be performed. The steel standard provision member Code Check is then performed on the member selected. The check is performed for all generated and defined load combinations that are selected, and the results, along with other member data, are displayed in a dialog box. The header of this dialog box provides information about the frame member selected: floor type, member number, story level, and span coordinates. The currently assigned member size appears in the top box of the Member Sizes box with other available sizes listed below it. The yield strength (Fy, fy, or py) is also displayed. The results of the Code Check, in of an interaction equation value, appear at the bottom of the dialog box. If the interaction equation value is less than 1.0 the value appears in black and the stop light is green; if the interaction equation value is greater than 1.0 the value appears in red and the stop light is red, indicating that the member fails. Changes can be made to the member size by selecting any size in the list or to the yield strength by editing the value, and the member Code Check re-run by clicking the Analyze button. The interaction equation value and the stoplight will be updated based on the results of the new Code Check. The modified member size and yield strength can be saved to the database using the Update Data Base button. When the database is changed in this way, the status indicator light at the right end of the status bar turns yellow. The model should be reanalyzed to calculate an accurate distribution of forces. The View Results button causes the Member Code Check output to appear on the screen. It is a detailed report of the Code Check results. The report includes design parameters and criteria, the controlling load combinations, calculated stresses and capacities, and the interaction equation results.

Member Code Check The Process - Member Code Check command causes the stress and capacity checks based on the currently selected steel code, to be run on all steel frame . The Code Check is performed for all generated and -defined load combinations that are selected. Once the Code Check is complete, the model is drawn on the screen with color-coded to indicate the degree of stress experienced by each member as determined by the Interaction Equations. A color chart correlates member color with Interaction Equation values. This display reflects the controlling condition for each member based on the load combination specified for the load cases analyzed. Click the “Show Values” button in the legend to display the interaction values directly on the .

t View/Update The Process-t View/Update command is a powerful feature that allows the to check the capacity of an I-Section steel column at a moment (rigid) frame t to resist the applied loads without requiring stiffeners or web plates. Design checks are based on the currently selected steel design code (in the Criteria-Code command). If desired, the columns size and yield strength can be modified and the


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Steel Standard Provisions Post-Processors Assign Menu Code Check repeated. The modified data can then be saved to the database without requiring returning to the RAM Modeler. Selecting t View/Update causes the target cursor to appear. Click the cursor near a steel t. This will cause the t View/Update dialog box to appear. The t will be rendered in the dialog and the code check results displayed both in text and on the graphic. The header of this dialog box provides information about the t selected: its floor type, number, story level, and plan coordinates. The assigned column size is displayed in the Column Size dropdown. A new member size or new yield strength value can be analyzed by selecting the new size from the dropdown control or by entering a new yield strength value in the edit box and then issuing the Analyze command. Immediately after a new size has been selected or yield strength modified, but before Analyze is invoked, the stoplight will light up yellow and the t results will be cleared. Once an analysis has been performed, if the t can be adequately designed, the stoplight will light up green and new results will appear in black. If it does not the code check, the stoplight will light up red and the appropriate error message will be displayed. To view a detailed report of the t code check, click the View Results button. This includes Input Design Parameters, Controlling Load Combinations, and calculated values. A print out of this report is available when the report is displayed or by using the Reports - Member Code Check command. Once a satisfactory t column member has been found, click the Update Database button to save it. Notice that when a new size is saved to the database the status indicator light turns yellow and a reanalysis is suggested to obtain accurate member forces.

t Code Check The Process-t Code Check command causes all lateral I-Section moment (rigid) connection ts to be evaluated based on the selected steel design specification. The Code Check is performed for all generated and -defined load combinations that are selected. Refer to the technical section for the criteria by which the ts are validated and checked. No t code check is performed for hanging columns. Once the Code Check is complete, the model is drawn on the screen with the ts color-coded indicating if the t requires reinforcing and if a web plate and stiffener could be adequately designed. A color legend correlates t color with the code check status values.

2.6.9 The Design Process In RAM Frame an iterative process is used to quickly hone in on an optimal steel frame design. Initial member sizes are assigned to frame in the RAM Modeler, or for steel beams and columns, by performing a Design All in the RAM Steel Beam and Column Design module. Load cases are defined and an initial analysis is run in Analysis mode. The engineer switches to SteelStandard Provision mode, selects a steel design code and performs a member and/or t code check. For the member code check the color-coding identifies over- and under-stressed . The can then be investigated on an individual basis, and resized using the View/Update command until a suitable design is found. The new size is then saved to the database using the Update Database command in View/Update. Sizes can also be assigned to using the assign size commands (from the Assign-Beam/Column/Brace-Size command) in this mode.


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Steel Standard Provisions Post-Processors Assign Menu For the t code check the color-coding of the ts identifies which ts could be checked, and if checked which required reinforcing. The ts can then be investigated on an individual basis, and the column at the t resized using the View/Update command, until no t reinforcing is required. The new size is then saved to the database using the Update Database command in View/Update. Sizes can also be assigned to columns using the assign size commands in this mode (from the Assign-ColumnSize command). Once the interaction equation values for all are within acceptable limits, and all ts are suitably reinforced, the structure should be reanalyzed in Analysis Mode. This is to obtain a valid analysis (member forces) based on the new sizes. Once reanalyzed member and t code check should once again be invoked. It is possible that some will again be overstressed or under-stressed, or some ts requiring to be reinforced when they were adequate before. This is because of the redistribution of forces caused by the new sizes. If so, they can be modified once again with the View/ Update command, and the process repeated. This process of analyzing, Code Checking and modifying is repeated until all are within the limits acceptable to the engineer.

2.6.10 Exiting and Changing Modes To switch to Analysis Mode: • Select the Mode-Analysis-Load Cases command. Alternatively select Analysis from the Mode dropdown control available on the dialog bar below the toolbar. To switch to Steel-Seismic Provision Mode: • Select the Mode-Steel-Seismic Provisions command. Alternatively, select the Seismic Provision item from the dropdown control on the dialog bar below the toolbar. To exit RAM Frame: • Double clicking the Control Bar in the upper left corner of the RAM Frame Window or alternatively click the Control Bar and selecting the Close command from the drop down menu. • Select the File - Exit command.


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36


Steel Standard Provisions Technical Notes

3

Code-check capabilities are available for steel and moment frame ts. The standard provision checks include checking the member allowable stresses and capacities for all applied loads, including seismic. These checks do not include the additional seismic detailing and strength checks required by several building codes. These additional checks are performed in the steel seismic provision mode.

3.1 General The following provisions apply to all steel design codes unless explicitly noted otherwise. Refer to the technical notes for each steel design code for requirements specific to those codes.

3.1.1 Steel Design Codes RAM Frame Steel Design is based on the requirements of several U.S. and international steel design specifications. These specifications include: • ANSI/AISC 360-10, Specification for Structural Steel Buildings (June 22, 2010) , published by the American Institute of Steel Construction in Steel Construction Manual (14th Edition). • ANSI/AISC 360-05, Specification for Structural Steel Buildings (March 9, 2005) , published by the American Institute of Steel Construction in Steel Construction Manual (13th Edition). • Specification for Structural Steel Buildings - Allowable Stress Design and Plastic Design (June 1, 1989) , published by the American Institute of Steel Construction in Manual of Steel Construction - Allowable Stress Design (9th Edition). The requirements of Supplement No. 1 (December 17, 2001) are also included as an option in t design. • Load and Resistance Factor Design Specification for Structural Steel Buildings (December 27, 1999) , published by the American Institute of Steel Construction in Manual of Steel Construction - Load and Resistance Factor Design (3rd Edition). • Design of Steel Structures, CAN/CSA S16-09, publish by the Canadian Standards Association, September 2009 • Limit States Design of Steel Structures , CAN/CSA S16-01, published by the Canadian Institute of Steel Construction, June 2004 • Structural use of steelwork in building , BS 5950 : Part 1, “Code of practice for design in simple and continuous construction: hot rolled sections” (1990). Some portions of the 20th April 1998, Draft Amendments to BS 5950 are incorporated as described below. • Structural use of steelwork in building , BS 5950 : Part 1, “Code of practice for design: rolled and welded sections” (2000), published by the British Standards Institute. • Structural use of steelwork in building , BS 5950 : Part 3, Section 3.1, “Code of practice for design of simple and continuous composite beams” (1990), published by the British Standards Institute.


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Steel Standard Provisions Technical Notes General • Steel Structures , Australia Standard, Building Code of Australia, AS 4100-98, published June 5, 1998. Includes Amendments No 1-1992, No. 2 – 1993, No.3 – 1995 and Draft No.4 • Eurocode 3 - Design of Steel Structures, BS EN 1993-1-1:2005, published by the European Committee for Standardization in Design of Steel Structures (Eurocode 3). In the RAM Frame program, its outputs and throughout the remainder of this manual, these are referred to as AISC 360 ASD and LRFD, ASD, LRFD, CAN/CSA S16-01 and S16-09, BS 5950 and Eurocode respectively. Since the requirements of AISC 360-05 and AISC 360-10 are nearly identically they will often be referred to collectively as AISC 360.

3.1.2 Steel Shapes Standard Columns: I-shape (e.g., Wide Flange) Square and Rectangular Hollow Sections Round Hollow Sections Hanging Columns: I-shape (e.g., Wide Flange) Square and Rectangular Hollow Sections Round Hollow Sections Channels Single Angles Double Angles Tees Round Bars (Rods) Flat Bar Sections (Plates) Beams: I-shape Channel Square and Rectangular Hollow Sections Horizontal and Vertical Braces: I-shape C-Shape (Channels) Square and Rectangular Hollow Sections Round Hollow Sections Single Angles Double Angles Tees Round Bars (Rods) Flat Bars (Plates)


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Steel Standard Provisions Technical Notes General Note: For Double Angles, Single Angles, Tees, Round Bars and Flat Bars the bending capacities are not calculated (effectively 0.0). For Single Angles, Round and Flat Bars the axial compression capacity is not calculated (effectively 0.0). If a section that has an axial compressive capacity of 0.0 has been assigned to a member that takes a compressive force in RAM Frame Analysis, an error message will be given to the in both the View/ Update dialogue and the Member Code Check report. Likewise, an error will be generated if a section that has a bending capacity of 0.0 is assigned to a member that takes a moment in the RAM Frame analysis. It should be noted that these error messages are based on the forces in the respective member, not on whether an actual Tension-Only assignment has been made to the member.

3.1.3 Load Combinations The load combinations required by the specified Building Code or Standard are generated automatically by the program. The can have the program generate the combinations specified by the AISC Specifications, or the more detailed combinations specified by ASCE 7, IBC, BOCA, SBC, UBC, Eurocode, CAN/CSA S16-01, S16-09, AS/NZS 1170 and BS 5950. See the Load Combination Generator manual for more information. In generated combinations, the load factors are “normalized” so that all combinations are compared against an allowable interaction equation value of 1.00 (this only affects some earlier implementations of ASD where a one-third stress increase was allowed – rather than using an allowable interaction equation value of 1.33, the relevant combinations are multiplied by 0.75). Dynamic and “Other” load cases are not included in the generated combinations but can by used in combinations created by the . The can create any number of additional load combinations. When creating -specified load combinations, the plus and minus combinations should both be explicitly created. The load factors should be “normalized” as explained above. Refer to the appropriate design code in “Member Code Check” for more information on each code’s specific load combination requirements.

3.1.4 Sloping Beams Sloping beams in the model will directly affect the member code check when a member is subject to gravity loads. In the Steel Standard Provisions the design of sloping beams will consider the varying axial load that exists along the length of the member when carrying vertical gravity loads. the following figure illustrates the axial force in the beams local longitudinal axis for both a sloped and a horizontal beam when carrying a gravity load.


39


Steel Standard Provisions Technical Notes General

Uniform Gravity Loads

T Axial Force Diagrams No Axial Force C

As illustrated, only the sloped member will experience the axial force due to a vertical load. When performing a design of a sloped beam in RAM Frame each unbraced segment of the beam is checked for a minimum of two sets of forces. One set consists of the maximum bending moments in the segment along with the maximum axial load in the segment, and the other set consists of the maximum bending moments in the segment along with the minimum axial load in the segment. Although the maximum and minimum axial load may not occur as the same location as the maximum moment, it is conservative to consider them as such for design purposes. Note that the unbraced segment refers to the length of beam in which the compression flange is unbraced for lateral torsional buckling (bending) consideration.

3.1.5 Cross Section Classification For CAN/CSA S16-01, S16-09, BS 5950, and Eurocode, sections are classified as Class 1 (Plastic), Class 2 (Compact), Class 3 (Semi-compact), or Class 4 (Slender) based on member dimensions and applied loads. For US and Australia design codes, sections are classified as compact, non-compact or slender. The following rules apply to the classification of all (except for AS4100, where the effective section modulus is calculated for bending according to AS4100-98 Section 5.2): • Cross sections are classified as plastic, compact or semi-compact. No consideration is given to slender (Class 4) sections. Sections of class 4 (slender) will be flagged and reported as an error. • Sections subject to axial tension load only are classified as Class 1. • Each element (flange, web) of a section is evaluated independently. The highest element class value will be assigned to the member as a whole. • Any element (flange or web) required to resist axial compression load will be evaluated to determine into which class the element falls. • Any element (flange or web) required to resist axial tension load only will be assumed to be class 1. • Any element fully ed (e.g. a fully braced flange) will not be considered in determining the section class value. • A flange element that carries tension due to bending moment will be Class 1 unless the section is under sufficient axial compression force to locate the plastic neutral axis within the tension flange. In this case the flange will be evaluated as if it were in complete axial compression. • The flanges of a flange section subject to minor axis bending will be evaluated assuming full compression on each flange.


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Steel Standard Provisions Technical Notes General • Webs are considered as Class 1 if the section is only subject to axial tension or only minor axis moment (or a combination of these), otherwise the code evaluation rules are followed. • Hollow rectangular sections subject to only minor axis bending (with or without axial load) will cause the ‘web’ of the hollow section to be considered as the flange, and the flanges to be considered as webs for class determination purposes. • Double angles are always evaluated using the criteria for “Legs of single angle and double angle with components separated” in table 7.

3.1.6 Torsion No check is made for torsion, nor are its effects included in the interaction equation results.

3.1.7 Tension Capacity The tension allowable stresses and tension capacities are based on the gross section properties of the cross section. No consideration is given to the connector configuration and hence the net section of the shape.

3.1.8 Compression Flange Bracing The may specify a number of parameters related to unbraced length considerations. These criteria are found in the Criteria - Flange Bracing command. Based on these criteria RAM Frame automatically determines the braced condition for each member. Unbraced lengths can also be directly specified by the engineer from the Assign menu as described in section 2.6. If overridden, the assigned values will be used for all checks on the assigned member. The program checks each unbraced segment to determine the controlling condition of moment and unbraced length. In RAM Frame, in the calculation of axial and bending capacity of a member it is necessary to determine the unbraced segment lengths. There are four pertinent values: Lu in the major axis for axial, Lu in the minor axis for axial, Lu in the major axis for bending, and Lu in the minor axis for bending. All four values are listed in the Member Code Check report for beams.

3.1.9 Major Axis Bracing For the calculation of the axial capacity and the bending capacity, the unbraced length of the compression flange in the plane of the major-axis of a beam is determined as follows:

A major axis brace point list is created.


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Steel Standard Provisions Technical Notes General Important: The following are assumed to brace both the top and the bottom flange in the plane of the major axis: • Beam ends are assumed to be braced at a and at a cantilever end. • Beams are assumed to be braced at both s. • Beams are assumed to be braced wherever another lateral frame beam frames in (even though the beam frames into the weak axis). They are not assumed to be braced wherever gravity beams frame in. • Beams are assumed to be braced wherever a brace frames in (such as for a chevron brace system) and wherever a frame column (but not a gravity column) from above sits on the beam (as for a transfer girder situation). The unbraced length of the segment in the strong axis is then taken as the distance between brace points. This value is used in the calculation of both the axial capacity and the minor moment capacity.

3.1.10 Minor Axis Bracing Two Minor axis flange brace point lists are created, one for the top flange and another for the bottom flange. Important: These brace points are determined in the following way: • Beams are assumed to be braced at s on both the top and the bottom flange. • Cantilever ends are assumed to be braced on both the top and the bottom flange. • Beams framing into the member brace both the top and the bottom flange, regardless of the relative depth. • Steel joists framing into the member brace the top flange only. Those points are added to the top flange brace point list only. • Beams are assumed to be braced on both the top and the bottom flange wherever a brace frames in (such as for a chevron brace system) or a column from above sits on the beam (as for a transfer girder situation). This assumes that the Engineer is going to specify some kind of bracing at these locations, as is commonly done, as such columns do not intrinsically provide weak axis bracing by themselves. • -assigned brace points, specified in the RAM Modeler by the with the Layout - Beams Brace Points command, brace the specified flange. In addition to these brace points the may specify that the top and / or bottom flanges are continuously braced using the Criteria - Flange Bracing command (or using the Assign command on an individual member).

Beams - Lu for Axial For the calculation of the axial capacity, the unbraced length of the compression flange in the plane of the minor-axis of a beam is determined as follows: The unbraced length is set to 0.0 if the specifies in the Criteria / Flange Bracing command that both the top flange and the bottom flange are continuously braced.


42


Steel Standard Provisions Technical Notes General If the specifies either that the top flange or that the bottom flange (but not both) is continuously braced, the member is not assumed to be fully braced under axial load; RAM Frame does not consider continuous bracing of a single flange by itself sufficient to brace the member under axial loads. Otherwise, the unbraced length is the distance between points where there is both a top flange physical brace point and a bottom flange physical brace point at the same location. If there are both top and bottom flange brace points but they do not coincide, the program uses the greater of the distance between top flange brace points and bottom flange brace points.

Beams - Lu for Bending For the calculation of the moment capacity, the unbraced length of the compression flange in the plane of the minor-axis of a beam is determined as follows: Except as explained below, the unbraced length is determined the same as is described in Section Compression Flange Bracing in RAM Steel Beam Design, including the effect that the Consider Point of Inflection option has. When determining the moment capacity associated with a moment at a given point, if the flange that is in compression at that point is braced based on the Top Flange Continuously Braced or Bottom Flange Continuously Braced criteria or assignment, the unbraced length is set to 0.0.

Columns - Unbraced Length For columns the may indicate whether or not the Deck braces the column. This option is only applicable for Integrated models. If a particular column is outside the deck perimeter it is not considered to be braced by the deck regardless of the selection for this option. Bracing is also provided by beams that frame into the column. The may indicate the maximum angle from a given column axis that a beam is considered to be providing bracing to the column. If the angle between the beam and the column axis exceeds the value selected, the beam is not considered to provide bracing to the column in that axis. In the case of a column that slopes between two levels at which the column is braced, the un-braced length will be considered the (sum of) actual length of the column(s), NOT just their vertical height between end point elevations. Also, where more than one column slopes to the same point at a story all the columns that intersect (above and below the intersecting story) will be considered braced at this intersection in BOTH axis. The engineer can override these calculated unbraced lengths if they are not what are desired Note that these criteria can be overridden on a member-by-member basis using the Assign menu. Also, the member unbraced length can also be directly specified by the engineer through the AssignColumns-Unbraced Length command. If not directly assigned the column unbraced length is the distance between braced levels for a given axis. If a particular level is unbraced, the program will sum the story heights as necessary to determine the unbraced length.

3.1.11 Assigned Unbraced Length As described in the specific member type sections of section 2.6 the engineer can assign an unbraced length for axial and bending design consideration. This length will override the default calculated value


43


Steel Standard Provisions Technical Notes General and be used for ALL unbraced segments considered in the design of beams, columns and braces. The should be careful to assign an appropriate controlling unbraced length to be considered for the entire section. Lateral torsional buckling is typically only an issue for bending in the major axis plane and buckling perpendicular to that axis. However, for some codes and section shapes, such as a square hollow section, this limit state also applies to bending in the minor axis buckling in the plane of the major axis of the section. There is no explicit override of the bending (LTB) unbraced length for this minor axis bending case, but the assigned major axis axial unbraced length is used to determine this length. If the major axis axial unbraced length is overridden this value will also be assigned to the lateral torsional buckling limit.

3.1.12 Flexural-Torsional Buckling of Tees In the calculation of the allowable compression capacity of Tee sections, the limit state of flexuraltorsional buckling is checked per the AISC 360 ASD and LRFD requirements but is not considered for ASD 9th or LRFD 3rd. In those Specifications the E3 Commentary says that this check is typically not required for most common Tee shapes.

3.1.13 Horizontal Braces Horizontal braces are designed the same way as beams are in the RAM Structural System, with one major exception. Unlike beams the horizontal braces are not considered braced by gravity beams that cross the horizontal brace. Any defined brace points will be considered in the design.

3.1.14 Column Moments With the Criteria – Column Moments command the can specify the portion of the calculated Gravity load moments to be included in the design of the columns. The purpose of this command is to reduce or eliminate the Gravity load moments on the columns. For the Live and Roof Loads, this reduction is in addition to any Live Load Reduction calculated for the column. This does not have any impact on the axial load in the column, and it does not have any impact on the beam design forces. One application of this command is when the so-called “Type 2 connection” or “Wind connection” design methodology is being employed, wherein it is assumed that the beam-to-column connection acts as a moment connection under wind loads, but acts as a pinned connection under gravity loads. It allows the to specify that the Gravity load moments on the column be ignored, while considering the full design axial forces. This command has no impact on Wind or Seismic moments and axial forces. The beam design moments are not affected by this command; beams must be investigated as necessary. Note that this is not a true “Partially Restrained” analysis; the values specified by the do not represent some type of t softening or t capacity; there is no redistribution of the column moments into the beam. This command merely causes the program to ignore a portion of the column gravity moments, and therefore, must be used cautiously.


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Steel Standard Provisions Technical Notes Member Code Check This command only impacts the calculation of the design moments when performing a Code Check on the column. It does not impact the values shown for the Member Forces listed in any reports elsewhere in the program.

3.1.15 Kinked Column Equivalent Uniform Moment A kinked column is defined as a column that extends unbraced through more than one story and is not braced by the slab or another member at the level that the column bends (is kinked). For these columns the unbraced length is taken as the entire length of the column (sum of individual column lengths) and an equivalent Uniform Moment factor (AISC-Cb, BS5950 – mLTB, CAN – W2, Euro - βLTB, AS - αm) is considered to equal 1.0.

3.2 Member Code Check This section describes the code specific design criteria and design checks.

3.2.1 AISC 360 (ASD and LRFD) Direct Analysis Method AISC 360-10 and AISC 360-05 contain specific requirements regarding the analysis of the lateral frames. Three methods are listed: The Effective Length Method, the First-Order Analysis Method, and the Direct Analysis Method. Generally any of the three approaches is acceptable, but if the ratio of the 2nd -order drift to 1st -order drift is greater than 1.5 (based on a model with nominal member properties), the Direct Analysis Method is required. The Direct Analysis Method, found in Appendix 7 of the Specification of the AISC 360-05 specification, is implemented in the program. See Section C2-1b in Chapter 2 and Appendix 7 in AISC 360-05 for further information. In the AISC 360-10 specification, the method can be found in Chapter C. The Direct Analysis Method requires: • 2nd order analysis (such as an iterative 2nd order analysis or amplified 1st order analysis), including both P-Δ and P-δ • Notional loads • Reduced flexural and axial stiffness

2nd Order Analysis To for the P-Δ effects, the has the option of either performing a p-delta analysis based on the geometric stiffness method (see the section titled “P-Delta Effects” in the Technical Notes chapter in the RAM Frame Analysis manual) or by specifying that the B2 factor be calculated and applied (amplified 1st order analysis).


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Steel Standard Provisions Technical Notes Member Code Check To for the P-δ effects, the should specify that the B1 factor be calculated and applied (amplified 1st order analysis). The advantage to these methods (geometric stiffness and amplified 1st order analysis) is that they do not require an iterative analysis and allow the analysis of individual load cases, with the results combined in the load combinations (the principle of superposition can be used).

2nd Order Analysis by Geometric Stiffness Method In Criteria – General in RAM Frame Analysis mode there is an option to perform a P-delta analysis. This analysis employs the geometric stiffness method. The masses used in this analysis are those assigned as part of the floor and roof loads, and self-weight if that option was selected. The mass values are listed in the Loads – Masses command in RAM Frame Analysis mode. Those masses are also used in the calculation of building periods and modes and for the generation of seismic story forces. Therefore, those values generally only include the masses associated with Dead Loads. In order to perform an appropriate P-delta analysis the effects of Live Load should be included, therefore a P-delta Factor should be specified such that the factored Mass values are approximately equivalent to the combined Dead and Live Loads. Furthermore, in order for the principle of superposition to be valid, the P-delta effects should be determined at an ultimate value of loads. Thus the P-delta Factor should be additionally increased to for the load factors. For example, assume that the Dead Load and Live Load are approximately equal; this means that the Mass value should be factored by 2 for the P-delta analysis in order to for the effects of both the Dead and Live Load. For LRFD the mass should be further factored by the load combination factors, which for the most conservative combination is 1.2 on both the Dead Load and 1.6 on the Live Load, for an average in this example of 1.4 (note that if the Live Load is greater than the Dead Load, this value should be greater than 1.4, if the Live Load is less than the Dead Load, this value could be less than 1.4). Thus the P-delta factor that should be specified is (1.4)(2.0) = 2.8 For ASD the mass should be similarly factored (1.0 would not be appropriate, 1.6 has been conservatively recommended, hence the P-delta Factor would be (1.6)(2.0) = 3.2). These factors can be refined as appropriate. An additional benefit of utilizing the P-delta analysis as described is that the effects of “leaning” columns (e.g., the gravity columns that are leaning on the frames for lateral stability) are automatically ed for.

2nd Order Analysis by Amplified 1st Order Analysis The requirement to perform a second-order analysis is satisfied by performing a first-order analysis and calculating and applying B1 and B2 factors to the design forces as outlined in Section C2.1b of the Specification. Those factors need to be calculated for each load combination. They are applied to the member forces as indicated in the following equations: Mr = B1Mnt + B2Mlt

Eq. (C2-1a)

Pr = Pnt + B2Plt

Eq. (C2-1b)

where Mnt Mlt Pnt Plt

= = = =

the non-translational Moments the lateral translational Moments the non-translational axial forces the lateral translational axial forces

B1 and B2 are defined below


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Steel Standard Provisions Technical Notes Member Code Check The program assumes that Mnt and Pnt are the moments and axial loads due to the vertical gravity load cases and that Mlt and Plt are the moments and axial loads due to the lateral load cases.

B1 Factor The B1 factor is a moment amplifier to for the P-δ effects (small P-delta, second order effects caused by displacement of the member between brace points). The B1 factor is to be calculated for each member individually, and differs for each combination. B1 is calculated for each axis of the member: B1 =

Cm 1−α

Pr Pe1

Eq. (C2-2)

≥1

where Cm

=

α

=

Pr

=

Pe1

=

Pe1 =

form with no transverse loading between s in the plane of bending: 0.6 - 0.4(M1/M2) for with transverse loading between s in the plane of bending: Cm = 1.0 1.0 for LRFD 1.6 for ASD total axial load in the member (combined using the appropriate LRFD or ASD Load Combinations) is the “elastic critical buckling resistance for the member in the plane of bending”: Eq.(C2-5)

π 2 EI

( K 1 L )2

where I K1 L

= = =

Ix or Iy, of the axis for which B1 is being calculated 1.0 the unbraced length, in the axis for which B1 is being calculated

The B1 factor is applied to moments from the gravity load cases (this is based on the assumption that all of the non-translational moments are due to gravity loads). The B1 factor is calculated for both the local X- and Y-axes. Note that it is not required to apply the B1 factors for a given load combination if the following limit is met for all whose flexural stiffness is considered to contribute to the stability of the structure: αPr < 0.15 PeL

Eq. (A-7-1)

where Pr

=

PeL α

= =

the required axial compressive strength under LRFD or ASD load combinations π2EI/L2, evaluated in the plane of bending 1.0 for LRFD 1.6 for ASD


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Steel Standard Provisions Technical Notes Member Code Check The program applies B1 based on the criteria that the engineer has specified, not based on this exception, although this exception is checked and reported as part of the “AISC 360 Direct Analysis Validation” report.

B2 Factor The B2 factor is an amplifier to for the P-Δ effects (large P-delta, second order effects caused by relative displacement of the member ends). The B2 factor is calculated for each rigid diaphragm, and differs for each combination. B2 is given as: B2 = 1−

1 αΣPnt

Eq. (C2-3)

≥1

ΣPe2

where α

=

ΣPnt

=

ΣPe2

=

1.0 for LRFD 1.6 for ASD total vertical load ed by story using LRFD or ASD load combinations, including gravity column loads the “elastic critical buckling resistance for the story”; it is permitted to use:

ΣPe2 = RM

ΣHL ΔH

RM

=

1.0 for braced-frame systems

ΣH L ΔH

= = =

0.85 for moment-frame and combined systems the story/diaphragm shear (calculated per load combination) he story height the interstory drift (calculated per load combination) and it is based on the drift at the center of diaphragm masses

where

The B2 factors are found in such a way that diaphragm shear forces and story drift values are first resolved along member local system and then the B2 factors are calculated according to Eq. (C2-3). Note that these factors are applied to the axial loads and moments from the lateral load cases.

Notional Loads Notional loads are required to be applied. They are generated using the Loads – Load Cases command in RAM Frame Analysis mode. If the ratio of 2nd order drift to 1st order drift (i.e., B2) is greater than 1.5, the notional loads must be applied in addition to the other lateral loads (wind and seismic); if the ratio is less than 1.5, it is permissible to apply the notional loads to the gravity-only combinations (note that the value 1.5 is based on a model with nominal member properties. otherwise, it is 1.7 for models with reduced member stiffness properties). This is specified when the load combinations are generated using the Combinations – Generate command in RAM Frame Steel Standard Provisions mode. The notional loads are defined as: Ni = 0.002Yi where Yi is the gravity load. The values used for the gravity loads at each diaphragm are automatically calculated, but can be modified using the Loads – Gravity for Notional command in the RAM Frame Analysis mode.


48


Steel Standard Provisions Technical Notes Member Code Check If τb used in the reduced stiffness is set to 1.0, it may be necessary to increase the notional load by an additional 0.001Yi. Note that for LRFD the notional loads are unfactored for analysis; they are factored in the Load Combinations. For ASD the notional loads are factored by 1.6 for analysis as required by the Specification. Options for these various requirements are available at the time the notional loads are generated.

Reduced Stiffness A reduced flexural stiffness is to be used for columns and beams: EI* = 0.8τbEI

Eq. (A-7-2)

where τb

=

Pr

1.0 if α P ≤ 0.5 y

4 α

=

Pr

=

Py

=

α Pr Py

(

1−

α Pr Py

)

Pr

if α P > 0.5 y

1.0 for LRFD 1.6 for ASD total axial load in the member (combined using the appropriate LRFD or ASD Load Combinations) AsFy

Note that in the second equation given for τb the analysis must be iterative since Pr is a function of τb, and vice versa. In lieu of that, the Specification permits the application of an additional notional load equal to 0.001Yi. The program does not perform any iterations on τb, the has the option of conservatively specifying a value of τb to use in all cases (using the Criteria – General command in the RAM Frame Analysis mode) or to use τb = 1.0 and specify the larger notional load. Note that if a value of τb is specified it is used for all for all combinations, even though in many cases a smaller value may be permissible for some for some combinations; this feature is just offered as a simplification, as an alternative to applying the larger notional load. Although technically τb is distinct for each load combination for each member, the program uses the specified value for all . The program does not provide an Assign command to assign different τb values to different , nor will it use a different stiffness for each different load combination. A reduced axial stiffness is also to be used: EA* = 0.8EA

Eq. (A-7-3)

The option to Use Reduced Stiffness should be selected prior to analysis using the Criteria – General command in the RAM Frame Analysis mode. Note that the program uses the reduced stiffness for all load cases. It is not clear from the Specification whether the reduced stiffness is required to be used for the drift analysis. Thus, it is up to the engineer to decide whether or not to run the analysis twice: once for drift with the full stiffness and once for member design with the reduced stiffness, or once for both drift and member design with the reduced stiffness. The reduced flexural stiffness is applied to “whose flexural stiffness is considered to contribute to the lateral stability of the structure”. Thus, it is not applied to that are pinned at both ends.


49


Steel Standard Provisions Technical Notes Member Code Check The reduced axial stiffness is applied to “whose axial stiffness is considered to contribute to the lateral stability of the structure”. All lateral beams, columns and braces are reduced for their axial stiffness.

Load Combinations Load Combinations for AISC 360 are defined in ASCE 7-05 for both ASD and LRFD. In some cases the notional loads must be included in all combinations, in other cases they need only be combined with the gravity load combinations as explained above in the Notional Loads section. In the load combination generator four options are given for Notional Loads: • • • •

Consider with Combinations containing only gravity loads Consider with all Combinations in direction of lateral load Consider with all Combinations in all directions Do Not Include in any Combinations

It is generally agreed that the Specification does not require that the notional loads need to be considered in all directions (i.e, perpendicular or opposite of the direction of the lateral load case), but only in the same direction as the lateral load case; however it is provided as an option. In the majority of cases the Notional Loads need only be considered with the gravity load cases.

IBC 2009 / IBC 2006 / ASCE 7-05 When Roof Snow Loads are used (see the Criteria – Member Loads command in RAM Manager) instead of roof live loads, the can specify how the snow loads are treated when in combination with seismic loads. If the “Do Not Include Snow” option is selected, the snow load case(s) will not be combined with seismic load cases. If the “Use Full Factor on Snow” option is selected the normal load factors on the snow load case(s) will be used when in combination with seismic load cases. In some cases it is permissible to use a reduced snow load when in combination with seismic loads. If the “Use Reduced Factor on Snow” option is selected, the following factors on the snow load case(s) will be used: For ASD, the normal factor is 0.75, the reduced factor is 0.2. For LRFD, the normal factor is 0.7, the reduced factor is 0.2. When the IBC 2006 / ASCE 7-05 load combinations are selected it is assumed that the Wind and Seismic forces used in those combinations are also based on the ASCE 7-05 requirements, or are compatible with them.

Allowable Strength Design Combinations (ASD) The ASD combinations in IBC 2009 and IBC 2006 are based on ASCE 7-05, and are given in Section 1605.3, Load combinations using allowable stress design. Basic and Alternate sets of equations are given. The template file is RamSteelIBC2006_ASD.cmb. The Alternate combinations of 1605.3.2 are not implemented. The Basic load combinations used are those given in Section 1605.3.1: D

(Formula 16-8)

D+L

(Formula 16-9)

D + Lr

(Formula 16-10)

D + 0.75L + 0.75Lr

(Formula 16-11)

D+W

(Formula 16-12)


50


Steel Standard Provisions Technical Notes Member Code Check D + 0.7E

(Formula 16-12)

D + 0.75L + 0.75Lr + 0.75W

(Formula 16-13)

D + 0.75L + 0.75Lr + 0.75(0.7E)

(Formula 16-13)

0.6D + W

(Formula 16-14)

0.6D + 0.7E

(Formula 16-15)

where E is defined as: E = ρ QE ± 0.2 SDS D

(see ASCE 7-05 Sec. 12.4)

QE is the Seismic force from the analysis. ρ is the Reliability/Redundancy Coefficient as explained in the previously. This definition of E results in the seismic combinations given in ASCE 7-05 Sec. 12.4.

Load and Resistance Factor Design Combinations (LRFD) The LRFD combinations in IBC 2006 are based on ASCE 7-05, and are given in Section 1605.2, Load combinations using strength design or load and resistance factor design. The template file is RamSteelIBC2006_LRFD.cmb. The basic load combinations are given in Section 1605.2.1: 1.4D

(Formula 16-1)

1.2D + 1.6L + 0.5Lr

(Formula 16-2)

1.2D + f1L + 1.6Lr

(Formula 16-3)

1.2D + 1.6Lr + 0.8W

(Formula 16-3)

1.2D + f1L + 0.5Lr + 1.6W

(Formula 16-4)

1.2D + f1L + f2Snow + E

(Formula 16-5)

0.9D + 1.6W

(Formula 16-6)

0.9D + E

(Formula 16-7)

where E

=

defined as (see Sec. 1617.1.1)

QE ρ

= =

E = ρ QE +/- 0.2 SDS D the Seismic force from the analysis the Reliability/Redundancy Coefficient as explained previously

The f1 factor may be specified as either 0.5 or 1.0 when the load combinations are generated. The f2 factor applied to Snow loads when in combination with Seismic loads may be specified as described previously. The generated load combinations can be viewed using the Reports – Load Combinations command.

Direct Analysis Validation Report It is the engineer’s responsibility to ensure that the selection of P-delta, B1, B2, fraction of gravity loads for Notional Loads and τb used in the stiffness reduction are all consistent and correct. To aid the engineer, a report (see AISC 360 Direct Analysis Validation) is implemented in the Steel Standard Provisions module of RAM Frame that is available when AISC 360-10 or AISC 360-05 has been selected as the design code. The report examines the selection of options for P-delta, B1, B2, Notional Loads,


51


Steel Standard Provisions Technical Notes Member Code Check Reduced Stiffness and τb, along with analysis results, and reports on the validity of each criteria selection. If the analysis is deemed invalid, it is the responsibility of the engineer to make the necessary corrections to those criteria selections, or in some cases to modify the structure so that limitations are satisfied.

K-Factor When the analysis is performed conforming to the Direct Analysis Method, the K-factor is allowed to be equal to 1.0 for all .

Connector Spacing for Double Angles For Double Angles in compression, the spacing of intermediate connectors used in the calculation double angle compression capacity is based on the requirements of E6.2 Dimensional Requirements which indicates “…connected to one another at intervals, a, such that the effective slenderness ratio Ka/ri of each of the single angles, between fasteners, does not exceed three-fourths times the governing (largest) slenderness ratio of the built-up member.” The spacing calculated by this method is adjusted to ensure equal spacing along the member length. For example, for a member of length 15 feet, if the minimum connector spacing is calculated to be 6 feet to meet E6.2, the program will identify that to meet this requirement two connectors are needed, and spacing them evenly along the member results in a 5ft distance between connectors. This modified spacing is reported in the Member Code Check report and used for the member design.

Buckling Restrained Braces (BRB) Braces can be assigned as Buckling Restrained in RAM Frame Analysis mode (refer to Analysis manual for details). If a brace is assigned as a BRB then the axial capacity of the brace member assigned is always considered as the plastic capacity of the section adjusted by appropriate strength modifiers (φ or Ω ); the compressive strength is considered equal to the tensile strength for the design of the brace. The output will indicate that the brace is designated as a Buckling Restrained brace. Braces not originally designated as BRBs are automatically handled as BRBs when a Star Seismic BRB size is assigned. When the size is cleared through a re-assignment of a size that is not Star Seismic, the BRB designation is lost. Braces originally designated as BRBs do not lose the BRB designation even when an assigned Star Seismic size is cleared.

Error Messages The following error messages may appear during the design process. KLR > 200 or LR > 300

Displayed when the slenderness of a section in compression exceeds the specified limit of 200, or when the slenderness of a section in tension exceeds the -specified limit of 300 (when the has selected to consider this check in Criteria-Axial Slenderness Limits).

Pr > Pe1x or Pr > Pe1y

Displayed when B1 is considered in the design and the axial force on the section exceeds the elastic buckling capacity of the section. This has implications in the calculation of interaction values.

Pnt > Pe2x or Pnt > Pe2y

Displayed when B2 is considered in the design and the sum of axial forces on the sections in a diaphragm exceeds the elastic buckling capacity of all the sections in that diaphragm. This has implications in the calculation of interaction values.


52


Steel Standard Provisions Technical Notes Member Code Check T-O in Bend

Some tension-only (flat bars, rods etc) do not have bending capacities calculated. This error is issued if one of these member types is subject to a bending force following an analysis.

T-O in Comp

Some tension-only (flat bars, rods etc) do not have compression capacities calculated. This error is issued if one of these member types is subject to a compression force following an analysis. This should only occur if the assigns a tension-only shape to a member that is then not designated to be tension-only.

A-O in Bend

Some capable of withstanding both tension and compression forces only do not have bending capacities calculated. This error is issued if one of these member types is subject to a bending force following an analysis.

3.2.2 ASD 9th / LRFD 3rd Load Combinations When Roof Snow Loads are used (see the Criteria – Member Loads command in RAM Manager) instead of roof live loads, the can specify how the snow loads are treated when in combination with seismic loads. If the “Do Not Include Snow” option is selected, the snow load case(s) will not be combined with seismic load cases. If the “Use Full Factor on Snow” option is selected the normal load factors on the snow load case(s) will be used when in combination with seismic load cases. In some cases it is permissible to use a reduced snow load when in combination with seismic loads. If the “Use Reduced Factor on Snow” option is selected, the following factors on the snow load case(s) will be used: For ASD (the normal factor is 1.0): BOCA: 0.20 SBC: 0.20 UBC: 0.25 For LRFD (the normal factor is 0.7): BOCA: 0.2 SBC: 0.2 For all other Code options the “Use Reduced Factor on Snow” option does not apply. When SBC or BOCA 93 is selected in the AISC ASD Postprocessor, the combinations generated do not include those with the Av term. When UBC is selected, the combinations generated do not include those with the 3R/8 term.

IBC 2000 / 2003 When the IBC load combinations are selected it is assumed that the Wind and Seismic forces used in those combinations are also based on the IBC 2003, or are compatible with them.


53


Steel Standard Provisions Technical Notes Member Code Check

Allowable Stress Design Combinations (ASD) The ASD combinations are based on ASCE 7-98, and are given in Section 1605.3, Load combinations using allowable stress design. Basic and Alternate sets of equations are given. The template files are RamSteelIBC2000_ASD.cmb and RamSteelIBC2003_ASD.cmb. The Alternate combinations of 1605.3.2 are not implemented. The Basic load combinations used are those given in Section 1605.3.1: D

(Formula 16-7)

D+L

(Formula 16-8)

D + L + Lr

(Formula 16-9)

D + L + Lr + W

(Formula 16-10)

D + L + Lr + 0.7E

(Formula 16-10)

0.6D + W

(Formula 16-11)

0.6D + 0.7E

(Formula 16-12)

where E QE

= =

ρQE ± 0.2 SDS D (see Sec. 1617.1.1) the Seismic force from the analysis. ρ is the Reliability/Redundancy Coefficient as explained in the previous section

In combinations with two or more cases in addition to Dead Load, those cases may be multiplied by 0.75 (Sec. 1605.3.1.1). When this factor is applied, the 0.7 factor is not applied to E. Note that when the 0.75 factor is applied to load cases with E, it is also applied to the 0.2SDS term (which becomes 0.15SDS) and that when the 0.7 factor is applied to load cases with E, it is also applied to the 0.2SDS term (which becomes 0.14SDS). If the Roof Load has been specified as Snow in the Criteria – Live Load Reduction command in the RAM Manager, the may specify whether to use the full factor (1.0) or the partial factor (0.2) on the Snow load, or disregard the Snow entirely when in combination with seismic forces, as specified in Exception 2 of Section 1605.3.1.

Load and Resistance Factor Design Combinations (LRFD) The LRFD combinations are given in Section 1605.2, “Load combinations using strength design or load and resistance factor design”. The template files are RamSteelIBC2000_LRFD.cmb and RamSteelIBC2003_LRFD.cmb The IBC lists the following combinations: 1.4D

(Formula 16-1)

1.2D + 1.6L + 0.5Lr

(Formula 16-2)

1.2D + 0.5L + 1.6Lr

(Formula 16-3)

1.2D + 1.6Lr + 0.8W

(Formula 16-3)

1.2D + 0.5L + 0.5Lr + 1.6W

(Formula 16-4)

1.2D + 0.5L + Snow + E

(Formula 16-5)

0.9D + 1.6W

(Formula 16-6)

0.9D + E

(Formula 16-6)


54


Steel Standard Provisions Technical Notes Member Code Check where E QE

= =

ρ QE ± 0.2 SDS D (see Sec. 1617.1.1) the Seismic force from the analysis. ρ is the Reliability/Redundancy Coefficient as explained previously

If the Roof Load has been specified as Snow in the Criteria – Live Load Reduction command in the RAM Manager, the may specify whether to use the full factor (0.7) or the partial factor (0.2) on the Snow load, or disregard the Snow entirely when in combination with seismic forces, as specified for f2 in Section 1605.2.1. Note: The 0.5 factor on Live Load should be 1.0 in cases of public assembly loads, live loads greater than 100 psf, and parking garage loads, but that is not implemented. Custom combinations can be created if necessary. The generated load combinations can be viewed using the Reports – Load Combinations command.

K-Factor The K-factors for beams and braces are specified by the using the Criteria - K-Factor command, or on a member-by-member basis using the Assign menu. The K-factors for columns can be either specified by the or calculated by the program. For braced frames the calculated value is always 1.0. For unbraced frames the calculated value is based on the Nomograph found in the AISC Steel Specifications. The recommendations contained therein for determining G at column bases is followed. G is limited to 10.0 for columns when there are no beams framing in, or when only pinned end beams are framing in; this limits K to a value of 3.0, rather than the theoretical value of infinity. G is limited to 1.0 at the bottom of the column if it is fixed to the footing. Columns that are pinned top and bottom are given K-factors of 1.0. Knee brace columns are assigned a K factor of 1.0 in the direction of the knee brace.

Round Bar Slenderness Limits Per ASD and LRFD Specification B7 the slenderness limit of l/r<300 does not apply to Round Bars in tension and hence is not considered in the design for this shape even if the global criteria is set for this check to be considered (See Criteria – Axial Slenderness Limits)

Design Yield Strength The design yield strength, Fy, is the value specified by the . No reduction is made for thick sections.

Unbraced Bending Length By default the unbraced length is taken as the distance between brace points. At ing columns, it is taken to column centerline. Beams are designed for the forces at two locations within each unbraced segment: the location of maximum moment and that of maximum shear.

Connector Spacing for Double Angles For Double Angles in compression, the maximum spacing of intermediate connectors such that the requirements of ASD and LRFD Specification E4.2 are met is reported in the View/Update dialogue and the Member Code Check report. The calculation of axial compressive capacity for Double Angles for U.S. codes considers the limit state of flexural-torsional buckling as detailed in ASD and LRFD Specification


55


Steel Standard Provisions Technical Notes Member Code Check E3. The calculation of the maximum intermediate connector spacing per ASD and LRFD Specification E4.1 likewise considers flexural-torsional buckling.

Buckling Restrained Braces (BRB) Braces can be assigned as Buckling Restrained in RAM Frame Analysis mode (refer to Analysis manual for details). If a brace is assigned as a BRB then the axial capacity of the brace member assigned is always considered as the plastic capacity of the section adjusted by appropriate strength modifiers (ϕ or Ω ); the compressive strength is considered equal to the tensile strength for the design of the brace. The output will indicate that the brace is designated as a Buckling Restrained brace. Braces not originally designated as BRBs are automatically handled as BRBs when a Star Seismic BRB size is assigned. When the size is cleared through a re-assignment of a size that is not Star Seismic, the BRB designation is lost. Braces originally designated as BRBs do not lose the BRB designation even when an assigned Star Seismic size is cleared.

Error Messages The following error messages may appear during the design process. KLR > 200 or LR > 300

Displayed when the slenderness of a section in compression exceeds the code specified limit of 200, or when the slenderness of a section in tension exceeds the code specified limit of 300 (and the has selected to consider this check in the Criteria-Axial Slenderness Limits).

fa > Fex or fa > Fey

Displayed when the axial force on the section exceeds the elastic buckling capacity of the section. This has implications in the calculation of interaction values.

T-O in Bend


T-O in Comp


A-O in Bend


3.2.3 BS5950:1990 / 2000 Cross Section Classification For RHS subject to biaxial bending the class is taken as the worst class that results from independent bending about each axis. For biaxial loading all sides will be considered as both web and flange to determine worst class. Limits will be from Table 12. Built-up RHS are assumed to be symmetric when calculating the section classification per Table 12. Unsymmetrical RHS will result in incorrect section classification.


56


Steel Standard Provisions Technical Notes Member Code Check According to 4.8.1 Circular Hollow Sections (CHS) should be classified separately for bending and axial load. RAM Frame and RAM Steel Column only calculate one classification for the section that is the most conservative of the classifications for bending (when it exists) and that for axial load (when it exists) calculated independently.

Load Combinations The load combinations are based on Table 2 of Clause 2.4 of BS 5950:Part1:1990. The following combinations are created: 1.4 DL ± 1.4 Notional DL 1.4 DL ± 1.4 Notional DL + 1.6 LL ± 1.6 Notional LL 1.0 DL ± 1.0 Notional DL + 1.6 LL ± 1.6 Notional LL 1.0 DL ± 1.4 W 1.4 DL ± 1.4 W 1.2 DL + 1.2 LL ± 1.2 W 1.0 DL ± SF1 E 1.4 DL ± SF1 E 1.2 DL + 1.2 LL ± SF2 E where SF1 and SF2 are specified factors for seismic loads. The default values for SF1 and SF2 are 1.4 and 1.2 respectively. Note that there is no explicit seismic load requirement in the British Code. However, it is anticipated that s in countries that have adopted the British Code may run seismic load cases based on some other codes if necessary.

Non-Sway and Sway Sensitive (BS5950-1:2000) BS 5950-1:2000 Section 2.4.2.5 requires that all structures “have sufficient sway stiffness, so that the vertical loads acting with the lateral displacements of the structure do not induce excessive secondary forces or moments in the or connections. Where such “second order” (“P-Δ”) effects are significant, they should be allowed for in the design…”. BS 5950 defines two drift limits by which the engineer can determine whether they are required to consider second order effects on the design of their structure. Section 2.4.2.6 defines a parameter λcr that is used to define whether a structure is “non-sway” or “sway-sensitive” for drift in a particular direction. Note that in the RAM Structural System “non-sway” is sometimes referred to as “braced against sidesway”, whereas “sway-sensitive” is sometimes referred to as being “unbraced (against sidesway)”. When λcr is larger than 10.0 the code classifies the structure as a non-sway frame and the second order effects are deemed to be insignificant and do not need to be considered. When λcr is less than 10.0 the structure is classified as sway-sensitive in that direction and secondary effects should be considered. The engineer can determine whether the building, its frames, and within those frames are to be considered “sway-sensitive” or “non-sway”, or it can have the program make that determination. The engineer can create a global criteria for the sway state (“Non-sway”, “Sway Sensitive”, or “Calculate Per Combo”) and override that global setting on a member by member basis (See BS5950 on page 22 and Sidesway on page 31).


57



Calculating Sway State per Load Combination The can designate to have the program calculate the sway state for each load combination (refer to Sections 2.5.5.1 and 2.6.5). With this designation the program will calculate λcr based on the current combination for the axis of the member (refer to 3.2.3.4). If λcr is determined to be less than 10.0 the member will be considered sway-sensitive in that axis for THAT one combination. For each load combination the sway state will be determined and may differ from other load combination sway-states. If the selects to have the program calculate the sway state per load combination, and if P-Delta is not run but a λcr < 4.0 is calculated, the program will issue a warning following a design-all suggesting that P-Delta be performed.

Calculating λcr per Load Combination (BS5950-1:2000) If the has designated to have a member’s sway state (see 2.5.5.1) or amplified sway factor - kamp (see 2.6.6 ) calculated per load combination, then λcr needs to be calculated for that specific member axis for each combination. That is, the program needs to determine the building drift (and hence λcr) in the specific direction of the axis of the member we are considering for the current load combination. Per the code λcr is required to be calculated using ONLY the factored notional load cases in the combination being considered. The notional loads are required to be applied in the direction of the axis being considered but the program only generates notional loads in the global orthogonal axes. Also, for some load combinations (those with lateral load cases) there are no notional load cases. As such the program needs to determine appropriate notional load cases and factors for combinations that do not contain them, and the program needs to adjust the notional load factors to achieve a notional load force that is oriented with the desired direction (member axis).The program addresses these issues as follows.

Notional Loads in Load Combinations For combinations that do not contain notional loads the program will determine what gravity load cases and factors are contained and insert appropriate notional load cases. So for example given the following load combination: 1.2DL + 1.2LP + 1.3W1 The program will create the following load combination for the calculation of λcr: 1.2ND + 1.2NL, where ND = Notional Dead Load and NL = Notional Live Load. Note that the original (gravity and lateral) load cases are not considered in the combination used to determine λcr but the appropriate load case factors are. For a gravity only load combinations, notional loads are typically included automatically. For a combination such as: 1.2DL + 1.2ND + 1.6Lp + 1.6NL, The program will remove the gravity load cases to only consider the notional as follows for calculating λcr: 1.2ND + 1.6NL Note that these notional are then further expanded as described in the next section to for the direction that notional loads are required to be acting in.


58



Aligning Notional Load Cases with a Specific Direction To determine λcr for a particular member axis, the drift due to notional loads applied in the direction of the axis is required to be calculated. However, the notional loads are currently only generated along the models global axis, as illustrated below for gravity dead and live notional loads:

NDy, NLy

Y

NDx, NLx

X Figure 1: Generated Notional Load Cases Given a specific member axis orientation the program will calculate the correct components of the orthogonal notional loads to obtain the required force in the direction of the axis of the member (frame). So for a column major axis oriented as illustrated below (where α = 30 degrees), the components of the orthogonal notional loads required to be applied simultaneously to achieve a 30 degree applied force are as follows: For Notional Dead: NDx Cos (30) + NDy Sin (30) = 0.866NDx + 0.5NDy For Notional Live: NLx Cos (30) + NLy Sin (30) = 0.866NLx + 0.5NLy

NDy, NLy

Required Force Direction α NDx, NLx

Figure 2: Notional Load in Member Axis Direction Note that when these expanded are applied to a load combination such as 1.2ND + 1.2NL the load combination will expand to the following: 1.2 (0.866NDx + 0.5NDy) + 1.2 (0.866NLx + 0.5NLy) This will be applied and appear as follows in the generated report: 1.04NDx + 0.6NDy + 1.04NLx + 0.6NLy.


59



Effective Length (BS 5950-1:1990) There are numerous parameters that can affect the effective length of a member subject to axial load. The criteria are set in the dialog shown by selecting Criteria-Effective Length, or on a member-bymember basis using the Assign menu. For columns, the engineer can specify an appropriate effective length factor per Table 24 in BS 5950. Otherwise, the engineer can specify that the effective length be calculated according to the requirements of Appendix E. This appendix considers the framing into the column, and whether a section is sway-sensitive or non-sway (See Post-Processing Criteria above for making this designation) to calculate the effective length of the column. The equations used to calculate the Le/L factor are taken from Annex E in the Draft Amendments for BS 5950, dated April 1998. The structure is assumed to be comprised of rigid ts where moment connected, and is either fully braced against sidesway (k3=infinity) or has unrestricted sidesway (k3=0), no partial lateral is considered. The effective length factor used to calculate the axial capacity of the column is also used to calculate the lateral torsional buckling capacity for the beam when subject to bending. The following assumptions are made in implementing Appendix E: A column pinned top and bottom (or where all beams and columns framing into the column in question are pinned) will be assigned an effective length factor of 1.0. This is true even when the column is indicated as being subject to sidesway. • A column fixed at the foundation will be assigned a k2 value of 0.5 per BS 5950, Clause 5.1.2.4. (a). • A column pinned at the foundation will be assigned a k2 based on a base stiffness equal to 10% of the column itself. This is according to BS 5950, Clause 5.1.2.4. (b) and results in a k factor of 0.909. • Any other columns, which are continuous but have no rigid connected beams framing into the t will be assigned a k value of 0.909, similar to the factor at a pin per BS 5950 Clause 5.1.2.4. • A beam designated as composite is assumed to carry a concrete slab and the relevant beam stiffness kb is taken equal to I/L. Per Appendix E.4.1, the beam stiffness for non-composite beams is taken as 0.5I/L if braced against sidesway and as 1.5I/L if not braced against sidesway. Knee brace columns are assigned a Le/L value of 1.0 in the direction of the knee brace. The effective length factor for brace subject to axial load is provided by the engineer for all shapes except double angles. For double angles, the connection detail must be provided and the effective length factor is then determined according to Clause 4.7.10.3 of BS 5950. Single angles are not currently accommodated in the structural system. Capacity of T-Section struts is computed per section 4.7.10. As described in table 4.15 the capacity of the T-Section is affected by the connection configuration. To specify the appropriate connection type for the T-Section select the Criteria-Effective Length Command and choose the appropriate option in the dialog that appears as shown below The Le/L factor used to calculate the axial capacity is also used in the calculation of bending capacity lateral torsional buckling where a brace is subject to end moments. The compression capacity of I-section and RHS beams subject to axial load is calculated using the effective length factors provided by the engineer. For channels, the end connection details are used to determine the effective length factor according to Section 4.7.10.4 of BS 5950. Double channels are not currently accommodated in the structural system. In calculating the bending capacity of an unbraced beam the effect of end fixity on the lateral torsional buckling (LTB) capacity of the section is considered. Loads are assumed to be normal loads (applied at the shear center). For a segment continuous through brace points, the Le is equal to the unbraced length. Where a beam is continuous through a column or ing girder an effective length factor of 0.7 is assigned to that end of the segment. This is indicative of the column providing the beam a measure of restraint for bending about the minor axis. Where a beam is pinned at a , or where a cantilever tip occurs, the effective length factor is taken


60


Steel Standard Provisions Technical Notes Member Code Check as the value provided by the engineer in the Criteria-Effective Length dialog. The effective length factor for an unbraced segment is taken as the average of the factors at the segment ends (Refer to Table 10). For I and RHS struts the minor axis effective length factor can be the same as the effective length calculated for the segment for lateral torsional buckling if the engineer indicates as such in the Effective Length dialog described previously.

Effective Length (BS 5950-1:2000) For design purposes the engineer can select to apply the column effective length factors in the CriteriaEffective Length dialog (See BS5950-1:1990 discussion above), or specify a specific value to be used. The engineer may specify that the effective length ratio LE/L either be calculated per Annex E or that it be set to a specific value. Per Annex E the LE/L ratio will be calculated based on whether the column is non-sway or sway-sensitive. This is true in all cases except as described in the section on moment amplification below. Refer to the BS5950-1:1990 discussion of Effective length for more detailed description of the calculation of the effective length factor. The method used by the program to calculate the columns effective length factor is as depicted in the following figure. The following discussion regarding effective length for columns assumes that the columns axis sway state is known. That is, the program knows if a column is sway-sensitive or non-sway in a particular axis. For a non-sway axis the program will consider if the has designated a specific effective length value or indicated to use Annex E to calculate the effective length. In the case of using Annex E the program will use the No-Sway Annex E formulations. For a Sway-Sensitive column axis the program first determines if P-Delta has been performed. • If P-Delta is performed the program will either use the specified effective length factor (if assigned) or will use the No-Sway Annex E effective length factors per 5.6.4(b). The No-Sway effective length factors are used as in this case it is assumed that the amplified sway approach (2.4.2.7b) is being applied and the “ kAMP x Ms ” values will be replaced by the sway moments from the P-Delta Analysis (refer to Moment Amplification (BS5950-1:2000) ). • If P-Delta is not performed the program will respond based on one additional criteria the can assign. The can designate to either use the effective length factor per 2.4.2.7a or the amplified sway method per 2.4.2.7b (refer to 2.6.6 Sway-Sensitive Design Method (BS5950:2000 Only) ). If the effective length approach is selected the program will use the specified effective length factor or the Sway-Sensitive Annex E Formulations per 5.6.4(a)/2.4.2.7(a). If the amplified sway approach is selected the program will use the specified effective length factor or the Non-Sway Annex E Formulations per 5.6.4(b)/2.4.2.7(b). The logic used to calculate the effective length factor for columns is illustrated below.


61



Is the column sway in axis ?

No

Yes

No Sway Sensitive

NO: Kamp M = kampMs + mMns

Column Effective Length Choice

Use Annex E

Column Effective Length Choice

Specified

Provided Value

Use No-Sway Annex E

Use 2.4.2.7a

Specified

Is P-delta Performed

YES: Effective Len m>0.85 M = m(Mns + Ms)

Column Effective Length Choice Use Annex E

Provided Value

Use Annex E

Use No-Sway Annex E

Yes Sway M=Ms + mMns

Use Sway Annex E

Column Effective Length Choice Specified

Provided Value

Moment Amplification (BS5950-1:2000) This section addresses the requirements of BS5950:2000 5.6.3 (and 2.4.2.7) that indicates when a member is determined to be “sway-sensitive” in an axis, one of two methods can be used to for the secondary effects. The first method is to use effective lengths for the columns, and the second method is to amplify the sway moments in design. In both these cases only a first-order elastic analysis is required. The engineer can assign which method is to be used for each axis of a member through assignment (refer to Sway-Sensitive Design Method (BS5950:2000 Only) on page 31). For frames more susceptible to second order forces (λcr less than 4.0) a second order (P-Delta) analysis is mandated. This analysis should accurately determine the secondary forces that will result from the deformation of the structure, and will result in member forces following the analysis that incorporate these secondary effects. Where a second-order analysis is performed the are designed according to the amplified sway method as described below. The engineer can indicate that RAM Frame should perform a first or second order analysis by selecting “Ignore P-delta” or “Consider P-Delta” respectively, in the Criteria-General dialog box in Analysis mode, as described on the Criteria section of this manual. The BS5950:2000 5.6.3 indicates that for sway-sensitive frames one of two approaches should be taken to perform the code check, these are described below.


62



Effective Length Method (2.4.2.7a) Using this method design forces are not directly amplified. Rather the code stipulates that beams need to remain elastic and the columns sway-sensitive effective length factors need to be applied. The is responsible for ensuring beams remain elastic if this option is used. The can assign an explicit effective length factor to the column axis or have the program calculate the appropriate value (refer to 3.2.3.6). • Per 4.8.3.3.4 a lower limit of 0.85 will be placed on the magnitude of mx, my and myx.

Amplified Sway Method (2.4.2.7b) Using this approach the can designate one of three methods to determine the amplified sway moments. By performing a second order analysis, by asg a specific kamp factor or by requesting the program calculate kamp per load combination.

P-Delta The second order analysis method (P-Delta) is available to directly calculate the second order moments (assumed to be equivalent to kAMP x Sway Moment). By indicating that a P-delta analysis be performed (see RAM Frame Analysis Criteria) for a sway member, the is effectively implementing the moment amplification method. The design assumptions are as follows. For each load combination, design moments will be calculated for the gravity (non-sway), and lateral (sway) load cases independently. That is, the sum of all gravity load case moments is stored separately from those of the lateral load cases in the combination. • Per 4.8.3.3.4 the factors mx, my and myx, are only applied to the non-sway (gravity) moments. That is of the form mM are replaced by Msway + mMnonsway. Note that Msway will already be amplified as it is calculated from a second order analysis, and no kamp term is applied. • If the effective lengths are calculated per Annex E then RAM Frame will use the non-sway mode inplane effective length factors. • No lower limit of 0.85 will be placed on the magnitude of mx, my and myx . Using this approach any kamp assignments made to the member are ignored.

Amplified Sway Factor Kamp If a first order analysis is performed, the can designate either the effective length method or the amplified sway method be performed. For the amplified sway method either a specific kamp value is assigned or the program can calculate kamp per load combination. Similar to the case of second order design is performed as follows. For each load combination, design moments will be calculated for the gravity (non-sway), and lateral (sway) load cases independently. That is, the sum of all gravity load case moments is stored separately from those of the lateral load cases in the combination. • Per 4.8.3.3.4 the factors mx, my and myx, are only applied to the non-sway (gravity) moments. That is of the form mM are replaced by kampMsway + mMnonsway. • If the effective lengths are calculated per Annex E then RAM Frame will use the non-sway mode inplane effective length factors. • No lower limit of 0.85 will be placed on the magnitude of mx, my and myx.


63


Steel Standard Provisions Technical Notes Member Code Check Where designated to be calculated per load combination the amplified sway factor kamp is calculated assuming cladding, architectural walls etc are not considered in the lateral stiffness and thus: Kamp = λcr / (1.15 λcr – 1.5) Refer to the section Calculating λcr per Load Combination (BS5950-1:2000) for an explanation of how the program calculates λcr for each load combination.

Design Yield Strength The design yield strength is the yield strength according to the material grade as defined in Table 6 of BS5950:Part1:1990 and Table 9 of BS5950:Part1:2000. To assign a grade to a section the engineer assigns a nominal yield strength (py) to the column section. Based on the magnitude of the nominal yield strength the section is assigned a grade from the table 6 (1990) or 9(2000). If the nominal yield strength is within a range of yield strengths indicated in the table then the associated grade is assigned to the section and the rules relating material thickness to design yield strength are followed. If the nominal yield strength is not within a range of yield strengths indicated in the table then the design yield strength is assigned the nominal yield strength value, and no reduction is made for material thickness. The design yield strength will never be larger than the engineer provided nominal yield strength.

Unbraced Bending Length Unbraced length is taken as the distance between brace points. At ing columns, it is taken to column centerline. Beams are designed for the forces at two locations within each unbraced segment: the location of maximum moment and that of maximum shear.

BS 5950-1:1990 RAM Frame calculates the lateral torsional buckling capacity based on the Draft Amendments to BS5950 Structural Use of Steelwork in Building. Part 1:1990, Dated April 20th 1998. In these proposed amendments the calculation of an equivalent uniform moment factor (mLT) has superceded the calculation of the slenderness factor n and the old equivalent uniform moment factor (m). The calculated value of mLT is provided on all detail output. Any section in which the lateral torsional buckling capacity is larger than the section bending capacity (without LTB) is designed without considering lateral torsional buckling. For all sections of class 3 the capacity of the section is considered to be the compression flange section modulus multiplied by the design yield strength. CHS and double angles subject to high shear (Fv > 0.6Pv) will be assigned a small nominal capacity. The shear area required to determine the plastic modulus of the web of an unsymmetrical I-section, when subject to high shear, does not include the thickness of the flanges.

Bending Capacity (BS5950-1:2000) In addition or in lieu of some of the 1990 code provisions the following apply to the BS5950-1:2000 implementation. • Loads are not considered “destabilizing” per 4.3.4. However, in RAM Frame and RAM Steel Beam the engineer has the option of supplying the appropriate Le factor per table 13 or 14 in the CriteriaEffective Length dialog box. • For lateral torsional buckling per 4.3.6.7 the u and x term are calculated per B2.3, not 4.3.6.8.


64


Steel Standard Provisions Technical Notes Member Code Check • The monosymmetry index Ψ is calculated per 4.3.6.7. In the case of highly unsymmetric sections, with values of n outside the range of 0.1 to 0.9, the engineer is responsible for calculating the appropriate buckling capacity. • For channels, loads are assumed to be through the shear center per 4.3.6.7b. • G.2. is implemented for I-sections where the tension flange is fully braced and the program is calculating the lateral torsional buckling capacity of the unbraced compression flange. When G.2. is implemented for a beam, the program sets mLT = 1.0 and calculates nt based on the shape of the moment diagram. In the calculation of Mb in section G.2. there is a reference to the distance between the axis of restraint and the axis of the beam. In RAM this distance is determined from the distance between top-of-steel and axis-of-restraint, as provided by the engineer in the RAM Manager (see RAM Manager Manual). This calculation will only apply where the engineer indicates that the topflange is fully braced. Where the bottom flange is fully braced the dimension is assumed to be half the depth of the beam. • No option is provided to select that double angles are connected to both sides of a gusset plate by two bolts in each line per 4.7.10.3 (d), however, the engineer can select (b) to get the same results. • For tension , no reduction is made for connection detailing per 4.6.3.

Section Capacity (BS5950-1:1990) For class 1 and 2 subject to axial tension load, only the alternative equation in Clause 4.8.2 is implemented. For class 1 and 2 subject to axial compression load, only the alternative crosssection capacity equation of 4.8.3.2 is performed. The interaction requirements (Clause 4.8) of the Draft Amendments to BS5950 Structural Steelwork in Buildings. Part1:1990 has been adopted in RAM Frame. However, all member capacities and the specifications to calculate these capacities are taken from BS5950:Part1:1990, without modification. This includes the requirement that Mcy need not be restricted to 1.2Zy for the equations in Clause 4.8.3.3.2. A flange section is considered an I-Section as opposed to an H-Section when the depth is larger than 1.2 times the Flange Width. This determines which buckling curve is selected from Table 25 for a flange section. Built up channels subject to compression are assumed to belong to strut table 27(c) per Table 25. The spacing between connectors of a double angle is calculated to provide a minimum of three bays per Clause 4.7.13.1. The distance may also be controlled by Clause 4.7.9 (c), which requires the maximum slenderness of a main component to be less than 50. This requirement is referenced from Clause 4.7.13.1(d). No other provisions of Clause 4.7.9 (c) are implemented, as the double angle is not considered a battened section. Lamda is calculated based on this maximum allowable connector spacing and the end connection of the double angle as specified by the engineer (see previous discussion on the Criteria command) per Clause 4.7.10.3. As described in the RAM Manager documentation the engineer can specify whether built-up flange sections are comprised of milled plate or flame cut plate. This designation affects the axial capacity of the flange sections as specified in footnote 2 of Table 25 in the BS 5950 specification.

Section Capacity (BS5950-1:2000) In addition or in lieu of the requirements of BS5950-1:1990 these provisions apply. • For class 3 sections the program uses the elastic section modulus in all cases, it does not calculate an effective plastic modulus as allowed by 4.2.5.1. • Per 4.2.5 Mc is limited to 1.2pyZ for simply ed beams and 1.5pyZ for other continuous beams. In RAM Frame the 1.5pyZ limit is applied if any one of the ends of the beam are fixed in the


65


Steel Standard Provisions Technical Notes Member Code Check major axis to a column. For the cantilever portion the 1.2pyZ limit applies at all times. NOTE: If the beam is fixed major axis, but the columns are pinned, the beam will still be considered fixed for the purposes of limiting Mc. To avoid this situation, always model the fixity conditions of the beams to represent the true fixity condition of the beam. In RAM Steel Beam the 1.2pyZ limit applies at all times.

Web Shear Interaction (BS5950-1:2000) In accordance with section 4.8.1 of the code, if the shear force demand (Fv) exceeds 60% of the Pv or Vw capacity, then the web shear, bending axial interaction is checked per H.3. There remains some uncertainty whether the code intended for this provision to apply to rolled sections. However, pending further clarification, the letter of the code as currently written has been implemented. A reduction factor (ρ) is applied to the interaction equations only where Vw exceeds Pv. To perform this check, Vw is calculated for the section even in the case where it is not necessary for shear capacity calculations in 4.2.5.3 (d/tw < 70ε). In order to compare the section 4.8 checks (with an upper interaction limit of 1.0) to the H.3 checks (with an upper limit of 1-ρ)2, RAM Frame divides the left-hand of the equations in H.3 by (1-ρ)2. Thus all interaction values have an upper limit of 1.0 for comparison purposes. • For RHS sections an additional internal moments are applied according to C-3 for “strut-action” and J.5.1 for moment amplification. In both these sections the engineer is allowed to reduce the additional moment depending on the location along the length of the member, relative to the buckling shape of the member. In RAM Frame the program conservatively uses the full amplification irrespective of where along the member the design moments are taken from. These moment amplifications are only performed in the case of uniaxial bending, or where minor axis moment is less than 2% of Mcy, in the RHS. In all other cases the error message “H3. Not Impl” is issued.

Error Messages Class 4

If a section contains a slender element it will be indicated as a class 4 section and no additional design checks will be performed.

Lamda > ##

Displayed when the slenderness of a section exceeds the code or specified limit ##.

F > Pcx or F > Pcy

Displayed when the axial force on the section exceeds the capacity of the section about the axis indicated by the subscript. This could have some unexpected consequences in the calculation of interaction values.

T-O in Bend


T-O in Comp


A-O in Bend



66



BS5950-1:2000 Specific “H3. Not implemented” will be issued in the case of a RHS with bi-axial load when minor axis moment exceeds 2% of Mcy, and subject to high shear such that section H.3 checks are required (see Web Shear Interaction above). These H.3 checks are only performed in the case of uni-axial loaded RHS. “Lambda Critical Error”: Displayed if there is an error evaluating a specific load combination to determine λcr. This is a result of the load combination being evaluating not containing any notional load cases (only notional load cases are used to determine λcr). Confirm that notional load cases have been created in the analysis mode and have been analyzed. “Per 2.4.2.7 P-Delta Analysis is recommended”: This indicates that due to a large sway the BS5950:2000 2.4.2.7 mandates that a second order analysis be performed, which is not currently the case. This will only show as a warning following a Design-All if all the following are true: • For at least one member axis the sway state is designated to be calculated per load combination. • For such a member the λcr calculated is less than 4.0. • P-Delta was not selected for the analysis.

3.2.4 CAN/CSAS16-01 Load Combinations The load combinations are based on Table 2 of Clause 2.4 of BS 5950:Part1:1990. The following combinations are created: 1.4 DL ± 1.4 Notional DL 1.4 DL ± 1.4 Notional DL + 1.6 LL ± 1.6 Notional LL 1.0 DL ± 1.0 Notional DL + 1.6 LL ± 1.6 Notional LL 1.0 DL ± 1.4 W 1.4 DL ± 1.4 W 1.2 DL + 1.2 LL ± 1.2 W 1.0 DL ± SF1 E 1.4 DL ± SF1 E 1.2 DL + 1.2 LL ± SF2 E where SF1 and SF2 are specified factors for seismic loads. The default values for SF1 and SF2 are 1.4 and 1.2 respectively. Note that there is no explicit seismic load requirement in the British Code. However, it is anticipated that s in countries that have adopted the British Code may run seismic load cases based on some other codes if necessary.

Effective Length All models to be designed with the Canadian design standard must be analyzed using the P-Delta factor. No sidesway criteria is required for the Canadian Design Code, all structures must consider secondary moments as determined using the p-delta analysis. As such the K value is typically set to 1.0, however


67


Steel Standard Provisions Technical Notes Member Code Check where the engineer specifies a different effective length the member capacity will be calculated considering this designated effective length factor.

Design Yield Strength The design yield strength is associated with the member’s material grade as defined in Table 6-3 of the CISC handbook of Steel Construction, Seventh Edition. To assign the grade for a member the engineer selects the appropriate material type using the Criteria – Canada Parameters command in the RAM Manager. In the RAM Modeler the engineer assigns a nominal yield strength (Fy) to the column section. Based on the combination of the nominal yield strength and the material type a grade are selected. For example, a nominal Fy of 350N/mm2 and a material type W results in a section of grade 350W. Note that a nominal yield strength slightly less than 350N/mm2 will result in a section of grade 300W. If no appropriate grade is available (based on the -entered values) then the design yield strength will effectively be set to 0.0 and NoGrade will be assigned as the grade for the section.


Bending Capacity The effective length of a beam can be controlled by setting the criteria with the Criteria-Design Defaults command. The specifications of CAN/CSA S16-01 have been implemented with the following modifications according to the Structural Stability Research Council (SSRC), “Guide to stability Design Criteria for Metal Structures”, Galambos, 1998. For cantilever beams, the effective length is taken as 1.5 times the unbraced length. This assumes the cantilever tip is restrained against torsion. Omega 2 (ω2) is taken as 1.0 for cantilevers. For unsymmetrical flange sections the following equation per SSRC has been implemented to calculate the lateral torsional buckling capacity: M cr =

ω2E KyL

(

)

E I y GJ B1 + 1 + B2 + B12

where B1 B2

= =

πβx 2K y L

EIy GJ

π 2 E Cw

( K y L )2GJ βx d' Iyc

= = =

(

0.9d ′ 2

I yc Iy

) ( )

−1 1−

Iy 2 Ix

distance between center of the top and bottom flange The moment of inertia of the compression axis about the section minor axis.

For all sections of class 3 the capacity of the section is considered to be the compression flange section modulus multiplied by the design yield strength.


68


Steel Standard Provisions Technical Notes Member Code Check Channels are designed using the symmetrical provisions of the design specification with the assumption that loading is through the shear center. The loads applied along the length of a section considered as being applied at the shear center.

Section Capacity As described in the RAM Manager documentation the engineer can specify whether hollow structural sections are of class C (cold-formed non-stress-relieved) or Class H (hot or cold-formed stress-relieved). The engineer can also indicate whether built-up flange sections are comprised of milled plate or flame cut plate. These designations affect the axial capacity of the HSS and flange sections as specified in Clause 13.3.1 of the design specification. The calculation of shear area of a circular hollow section is according to Gere and Timoshenko, Mechanics of Materials, 3rd edition, Section 5.5 as follows: Av =

3 4

(

A

r22 + r12 r22 + r2r1 + r12

)

where r1 and r2

=

the inner and outer radius of the CHS respectively

Connector Spacing for Double Angles For Double Angles in compression, the maximum spacing of intermediate connectors such that the requirements of CAN/CSA S16-01 Section 19.1.4 are met is now reported in the View/Update dialogue and the Member Code Check report. The calculation of axial compressive capacity for Double Angles for Canadian codes considers the limit state of flexural-torsional buckling as detailed in CAN/CSA S16-01 Appendix D. The calculation of the maximum intermediate connector spacing per CAN/CSA S16-01 Section 19.1.4 likewise considers flexural-torsional buckling.


If a section contains a slender element it will be indicated as a class 4 section and no additional design checks will be performed.

SlenderWeb

If a section subject to shear has a web whose depth to thickness ratio exceeds the limit of 502 kv / F y then no further design checks will be performed.

KLR > 200 or KLR > Displayed when the slenderness of a section in compression exceeds the code 300 specified limit of 200, or 300 when the section is subject to tension (and the has selected to consider this check in the Criteria-Axial Slenderness Limits). Cf > Cex or Cf > Cey

Displayed when the axial force on the section exceeds the elastic buckling capacity of the section. This could have some unexpected consequences in the calculation of interaction values.

T-O in Bend


T-O in Comp

Some tension-only (flat bars, rods etc) do not have compression capacities calculated. This error is issued if one of these member types is


69


Steel Standard Provisions Technical Notes Member Code Check subject to a compression force following an analysis. This should only occur if the assigns a tension-only shape to a member that is then not designated to be tension-only. A-O in Bend


3.2.5 CAN/CSA S16-09 Load Combinations The load combinations are based on Clause 7, “Factored Loads and Safety Criterion” and Table 13 of Supplement No. 1. If notional load cases have been analyzed, they will be included in the load combinations. When the load combinations are generated, an option is given to generate the combinations such that when the load combination contains a lateral load case (wind or seismic), only the notional load that is concurrent with the lateral load case (i.e., in the same direction) is included in that combination. If that option is not selected, additional sets of combinations will be generated containing notional loads acting in each of the four global axis directions for each lateral load case. It does not appear that the code requires these additional load combinations, so generally the option to combine only in the direction of the lateral load case should be selected.

Effective Length All models to be designed with the Canadian design standard must be analyzed using the P-Delta factor. No sidesway criteria is required for the Canadian Design Code, all structures must consider secondary moments as determined using the p-delta analysis. As such the K value is typically set to 1.0, however where the engineer specifies a different effective length the member capacity will be calculated considering this designated effective length factor.

Design Yield Strength The design yield strength is associated with the member’s material grade as defined in Table 6-3 of the CISC handbook of Steel Construction, Tenth Edition. To assign the grade for a member the engineer selects the appropriate material type using the Criteria > Canada Parameters command in the RAM Manager. In the RAM Modeler the engineer assigns a nominal yield strength (Fy) to the member section. Based on the combination of the nominal yield strength and the material type a grade is selected. For example, a nominal Fy of 350 N/mm2 and a material type W results in a section of grade 350W. Note that a nominal yield strength slightly less than 350 N/mm2 will result in a section of grade 300W. If no appropriate grade is available (based on the -entered values) then the design yield strength will effectively be set to 0.0 and NoGrade will be assigned as the grade for the section.



70



Bending Capacity The effective length of a beam can be controlled by setting the criteria with the Criteria > Design Defaults command. The specifications of CAN/CSA S16-09 have been implemented.

Section Capacity As described in the RAM Manager documentation the engineer can specify whether hollow structural sections are of class C (cold-formed non-stress-relieved) or Class H (hot or cold-formed stress-relieved). The engineer can also indicate whether built-up flange sections are comprised of milled plate or flame cut plate. These designations affect the axial capacity of the HSS and flange sections as specified in Clause 13.3.1 of the design specification.

Connector Spacing for Double Angles For Double Angles in compression, the maximum spacing of intermediate connectors such that the requirements of CAN/CSA S16-09 Section 19.1.4 are met is now reported in the View/Update dialogue and the Member Code Check report. The calculation of axial compressive capacity for Double Angles for Canadian codes considers the limit state of flexural-torsional buckling as detailed in CAN/CSA S16-09 Annex D. The calculation of the maximum intermediate connector spacing per CAN/CSA S16-09 Section 19.1.4 likewise considers flexural-torsional buckling.

Single Angles Single angles in compression typically have an eccentric connection that induces a moment. The eccentricity currently cannot be modeled in RAM Frame. However, CAN S16-09 clause 13.3.3 provides a methodology for ignoring the eccentricity for some configurations. The program assumes that the general requirements in clause 13.3.3.1 are met. Effective length factors and/or unbraced lengths must be assigned to produce the modified kL/r ratios per clause 13.3.3.2 or 13.3.3.4.

Error Messages SlenderWeb

If a section subject to shear has a web whose depth to thickness ratio exceeds the limit of 502 kv / F y then no further design checks will be performed.

KLR > 200 or KLR >300

Displayed when the slenderness of a section in compression exceeds the code specified limit of 200, or 300 when the section is subject to tension (and the has selected to consider this check in the Criteria > Axial Slenderness Limits).

Cf>Cex or Cf>Cey

Displayed when the axial force on the section exceeds the elastic buckling capacity of the section. This could have some unexpected consequences in the calculation of interaction values.

T-O in Bend


T-O in Comp

Some tension-only (flat bars, rods etc) do not have compression capacities calculated. This error is issued if one of these member types is subject to a compression force following an analysis. This should only occur if the


71


Steel Standard Provisions Technical Notes Member Code Check assigns a tension-only shape to a member that is then not designated to be tension-only.

3.2.6 EUROCODE Load Combinations ENV 1991-1 Clause 9.4.5 allows the use of simplified combinations for building structures (Eq 9.13 and Eq 9.14). These combinations are implemented in RAM Frame. Combinations that include seismic forces are given by Eq 9.12. The Partial Safety Factors (γ Gsup , γ Ginf , γ I , and γ Q ) and Psi Factors (Ψ2) for those equations are specified in the RAM Manager Criteria - Eurocode Factors command. The special requirement that orthogonal seismic load cases be combined using 100% of one and 30% of the other is not implemented.

Effective Length (ℓ/L) The Eurocode values for ℓ/L is specified by selecting the Criteria-Effective Length menu command, or on a member-by-member basis using the Assign menu. The effective beam stiffness does consider the fixity conditions and is reduced by 25% if the beam is pinned at the end (closest node) away from the t. The beam length is considered to be the distance from the t to the closest node away from the t. This length is not necessarily the full length of the member but could be the distance from the t to the location where a brace or column-from-above intersects the beam. Columns pinned top and bottom are given ℓ/L values of 1.0 in both non-sway mode and sway mode. If a column is continuous but all beams coming into a t are pinned, then η for that end of the column is assigned a value of 0.95. This results in a ℓ/L of 4.88 for a sway column and 0.96 for a non-sway column. Knee brace columns are assigned a ℓ/L value of 1.0 in the direction of the knee brace.

Design Yield Strength For steel with a nominal fy less than or equal to 460 N/mm2 and greater than or equal to 275 N/mm2 the design yield strength is adjusted to for material thickness according to Table 3.1, BS EN 1993-1-1:2005, EN10025-3 rules. Both nominal and design Fy appear on all design output. Steel with a nominal fy larger than 460N/mm2 or less than 275 N/mm2 is assigned no design yield. For steel with a nominal Fy outside of the ranges specified no steel material will be found and the section will be assigned a small yield strength and fail in design. A large interaction value on a design is indicative of assigned yield strength outside the ranges indicated above. Yield strength depends on the thickness of the elements (flange, web etc) of the cross section being designed. Refer to table 3.1 of BS EN 1993-1-1:2005 for details on the material and yield strengths for different thickness elements.



72



Bending Capacity In the calculation of the lateral torsional buckling capacity for a section of beam with an unbraced compression flange the location of load application on the beam can have an impact on the beam’s capacity. For the Eurocode the engineer can specify whether the load is applied at the top flange or at the shear center by choosing the appropriate option in the Criteria-Eurocode Factors command in the RAM Manager. The elastic critical moment is as calculated in Elastic Critical Moment.

Elastic Critical Moment Within each unbraced segment the points of maximum moment and shear and the segment end points are all checked against the segment capacity. When calculating the member capacity for an unbraced segment the lateral torsional buckling must be considered. In these cases it is necessary to calculate the elastic critical moment (Mcr). While BS EN1993-1-1:2005 does not provide exact information on how to compute Mcr, RAM Frame calculates the elastic critical moment using procedures, described in these articles: 1. SN003a-EN-EU NCI: Elastic critical moment for lateral torsional buckling 2. M.A Serna, A.Lopez, I. Puente, D.J. Yong “Equivalent uniform moment factors for lateral-torsional buckling of steel ” (2006) Journal of Constructional Steel Research, 62. 3. Rubrique du Praticien, “Abaques De Deversement Pour Profiles Lamines”, Construction Metallique no 1 - Mars 1981. RAM Frame assumes that the factors k and kw are equal to 1.0. The following procedures are implemented to calculate the C factors, depending on the beam major axis loading: with end moments only—according to the French Annex: C1 = 1/(√0.325 + 0.432·ψ + 0.252·ψ2) C2 = 0.0 C3 = 0.5(1.0 + ψ)·C1 If end moments negative, middle positive, shape of moment is symmetric and there is a straight line between center and ends of segment use case 4 from SN030a-EN-EU, table 4.2: C1 = 1.68 C2 = 1.64 C3 = 2.64 If end moments negative, middle positive, shape of moment is symmetric and there is no straight line between center and ends of segment use case 2 from SN030a-EN-EU, table 4.2: C1 = 2.57 C2 = 1.55 C3 = 0.75 If end moments are zero and shape of moment is symmetric and there is straight line between center and ends of segment use values from case 3 SN030a-EN-EU, table 4.2: C1 = 1.35


73


Steel Standard Provisions Technical Notes Member Code Check C2 = 0.63 C3 = 1.73 If end moments are zero and shape of moment is symmetric and there is no straight line between center and ends of segment use French Annex formulas based on the procedure detailed in the French Journal, Rubrique du Praticien, “Abaques De Deversement Pour Profiles Lamines”, Construction Metallique no 1 Mars 1981: C1 = C10|Mmax/M| C2 = 4/π2·|μ|·C10 C3 = 0.525 if ends pinned, 0.753 if ends fixed, 0.64 for one end pinned, other fixed. where 1 1 3 2 2 = C10 1 + γ + 3 + 2 γ 2 − 8μ − 2γμ 1 − 2 + 8μ 2 5 − 2 +

(

= = = = =

γ μ f M L

2π

)(

)

(

π

)

(

π

3 π4

)

4μ + β - 1 fL2/(8M) Uniform load Maximum end moment Member Length

For all other cases use formula (13) from M.A. Serna article “Equivalent uniform moment factors for lateral - torsional buckling of steel ”: k A1 +

2 1− k 1− k A2 + A2 2 2 A1

C2 = 0.0 C3 = 0.0 where A1 A2

= =

2 M max + 9k M 22 + 16M 32 + 9k M 42

|

2 (1 + 9k + 16 + 9k )M max

M max + 4M 1 + 8M 2 + 12M 3 + 8M 4 + 4M 5 37M max

|

Coefficient k is related to the lateral bending and warping prevention at end s. It is equal to 1 if lateral bending and warping are free and equal to 0.5 if lateral bending and warping are prevented. Moments M1 and M5 are begin and end moments respectively, moment M3 is the moment at the middle of the span, moment M2 is moment on L/4 position and moment M4 is the moment on 3L/4 position. Moments M1 through M5 must have its corresponding signs. Note: Values of C for cantilevers are calculated as for all other as RAM Frame assumes the ends of a cantilever to be laterally braced. The output shows the values of: class, the design shear and moments at the indicated beam location, the segment unbraced length (Lb), the type of moment that controls the member capacity (Mb = buckling, Mc = plastic capacity, Mv = is shear reduced capacity) and the member capacity. Note that the controlling condition may not correspond to any of the maximum or minimum moment conditions. This indicates that the controlling condition occurs in a segment with a lesser moment but greater unbraced length.


74




Displayed when the section is slender and no design will be performed.

T>100mm

The thickness from a segment (flange, web etc) of a member is exceeds the codes upper limit of 100mm. No design is performed.

NEd>NplRd

The applied axial capacity exceeds the buckling capacity of the section. The interaction equations are undefined in this case.

T-O in Bend Some tension-only (flat bars, rods etc) do not have bending capacities calculated. This error is issued if one of these member types is subject to a bending force following an analysis. T-O in Comp Some tension-only (flat bars, rods etc) do not have compression capacities calculated. This error is issued if one of these member types is subject to a compression force following an analysis. This should only occur if the assigns a tension-only shape to a member that is then not designated to be tension-only. A-O in Bend Some capable of withstanding both tension and compression forces only do not have bending capacities calculated. This error is issued if one of these member types is subject to a bending force following an analysis.

3.2.7 AS 4100-98 Analysis Method AS 4100 contains specific requirements regarding the analysis of the lateral frames. RAM Frame currently implements the First-Order Elastic Analysis method considering rigid and simple according to Section 4 of the specification. All lateral (frame) of the structure are considered in a full building analysis (no sub structuring) with spans taken as centre-to-centre of s. Pattern loading is considered in the design of all “gravity steel” beam and columns in their design in RAM Steel, and for all concrete in RAM Concrete, but is not currently considered for steel frame in RAM Frame. Note that per AS 4100 Section 4.4.2.1changes in geometry and effective stiffness due to axial load on is not considered in the analysis.

Second Order Effects Per 4.4.1.2 of the AS 4100 “Second-order effects The analysis shall allow for the effects of the design loads acting on the structure and its in their displaced and deformed configuration. These second-order effects shall be taken into by using either—(a) a first-order elastic analysis with moment amplification in accordance with Clause 4.4.2, provided the moment amplification factors (δb ) or (δs ) are not greater than 1.4; or (b) a second-order elastic analysis in accordance with Appendix E” In RAM Frame the can choose to consider either of these methods. If P-Delta is selected to be considered in the analysis (see RAM Frame Analysis Manual - Analysis Criteria and P-Delta Sections) then this is equivalent to 4.4.1.2(b) being considered. Without P-Delta the requirements of 4.4.1.2(a) are effectively considered. See the next section for a discussion on differences and advantages of the P-Delta and the Amplified First Order approach.


75


Steel Standard Provisions Technical Notes Member Code Check The following rules are applied to the determination of design moments considering the sway status (braced or unbraced) and whether P-Delta was considered in the analysis. Braced 4.4.2.2: M* = δb M*m Unbraced 4.4.2.2: M* = max( δb, δs)M*m PDelta Considered Appendix E: M* = δbM*e Where: Calculate db

Y

Braced in Axis ?

M*axis = db * M*m

N

Calculate ds

P-Delta Considered ?

Y

M*axis = db * M*e

N

M*axis = max(db,ds) * M*m

• Only design moments are amplified for the secondary affects. Axial and shear forces remain unadjusted. • P-Delta when selected will be considered for all both braced and unbraced (cannot have PDelta only apply to unbraced in a structure). These secondary forces will be relatively small assuming the member is truly braced against sidesway by other frame in the model. That is so that there is little lateral displacement of the braced . • When P-Delta is considered the secondary multiplier (δb) is applied directly to the moment calculated from the analysis. That is the gravity transverse loads are not considered as a simple load that is superimposed with the lateral load case forces, rather all forces are applied to the structure in separate load cases and superimposed in a load combination to produce final design forces. • When calculating Nomb for consideration in the calculation of for δb the effective length (ke) is set to 1.0, that is the member is assumed braced.


76



2nd Order Analysis by Geometric Stiffness Method (P-Delta) In Criteria – General in RAM Frame Analysis mode there is an option to perform a P-delta analysis. This analysis employs the geometric stiffness method. The masses used in this analysis are those assigned as part of the floor and roof loads, and self-weight if that option was selected. The mass values are listed in the Loads – Masses command in RAM Frame Analysis mode. Those masses are also used in the calculation of building periods and modes and for the generation of seismic story forces. Therefore, those values generally only include the masses associated with Dead Loads. In order to perform an appropriate P-delta analysis the effects of Live Load should be included, therefore a P-delta Factor should be specified such that the factored Mass values are approximately equivalent to the combined Dead and Live Loads. Furthermore, in order for the principle of superposition to be valid, the P-delta effects should be determined at an ultimate value of loads. Thus the P-delta Factor should be additionally increased to for the load factors. For example, assume that the Dead Load and Live Load are approximately equal; this means that the Mass value should be factored by 2 for the P-delta analysis in order to for the effects of both the Dead and Live Load. For AS the mass should be further factored by the load combination factors, which for the most conservative combination is 1.2 on both the Dead Load and 1.5 on the Live Load, for an average in this example of 1.35 (note that if the Live Load is greater than the Dead Load, this value should be greater than 1.35, if the Live Load is less than the Dead Load, this value could be less than 1.35). Thus the P-delta factor that should be specified is (1.35)(2.0) = 2.7. An additional benefit of utilizing the P-delta analysis as described is that the effects of “leaning” columns (e.g., the gravity columns that are leaning on the frames for lateral stability) are automatically ed for.

2nd Order Analysis by Amplified 1st Order Analysis The requirement to perform a second-order analysis is satisfied by performing a first-order analysis and calculating and applying δb and δs factors to the design forces as outlined in Section 4.4.2 of the Specification. Those factors need to be calculated for each load combination. They are applied to the member forces as indicated in the following equations: M* = max(δb, δs)M*m

Eq. (C2-1a)

where δb and δs M*m

= =

as defined in the following the forces produced from the analysis (considers gravity and lateral forces applied simultaneously)

δb Factor The δb factor is a moment amplifier to for the P-δ effects (small P-delta, second order effects caused by displacement of the member between brace points). The δb factor is to be calculated for each member individually, and differs for each combination. δb is calculated for each axis of the member: Cm

δb = 1−

N* N omb

Eq. (4.4.2.2)

≥1

where


77


Steel Standard Provisions Technical Notes Member Code Check =

Cm

N*

=

Nomb

=

0.6 – 0.4(M1/M2) for with no transverse loading between s in the plane of bending 1.0 for with transverse loading between s in the plane of bending total axial load in the member (combined using the appropriate AS/NZS Load Combinations) is the “elastic critical buckling resistance for the member in the plane of bending” 2 π EI ( KeL )2

= = =

I Ke L

Ix or Iy, of the axis for which δb is being calculated 1.0 the unbraced length, in the axis for which δb is being calculated

δs Factor The δs factor is an amplifier to for the P-Δ effects (large P-delta, second order effects caused by relative displacement of the member ends). The δs factor is calculated for each rigid diaphragm, and differs for each combination. δs is given as: δs =

1 Δs Σ N * 1− h s ΣV *

Eq. C4.4.2.3(i)

≥1

where ΣN*

=

ΔS

=

ΣV* hs

= =

total vertical load ed by story using AS/NZS load combinations, including gravity column loads the interstory drift (calculated per load combination) and it is based on the drift at the center of diaphragm masses the story/diaphragm shear (calculated per load combination) the story height

The δs factors are found in such a way that diaphragm shear forces and story drift values are first resolved along member local system and then the δs factors are calculated according to Eq. (C4.4.2.3(i)). Note: AS 4100 mandates that if δs exceeds 1.4 the should consider applying a second order analysis according to the provisions of Appendix E. It is the engineers responsibility to select P-Delta for the analysis in the event that situation occurs.

Notional Loads Notional loads are required to be applied. They are generated using the Loads – Load Cases command in RAM Frame Analysis mode. This is specified when the load combinations are generated using the Combinations – Generate command in RAM Frame Steel Standard Provisions mode. The notional loads are defined as: Ni = 0.002Yi where Yi is the gravity load. The values used for the gravity loads at each diaphragm are automatically calculated, but can be modified using the Loads – Gravity for Notional command in the RAM Frame Analysis mode.


78


Steel Standard Provisions Technical Notes Member Code Check Note: The notional loads are unfactored for analysis; they are factored in the Load Combinations. Options for these various requirements are available at the time the notional loads are generated.

Design Yield Strength The design yield strength is a function of both the material and the element thickness properties of the section. The provided Nominal Yield Strength (Fy) is first mapped to an appropriate material according to Table 2.1 of the AS 4100-98 code. The material that is used is based on the material that most closely matches the yield strength specified and the section shape. The following materials are used based on the yield strength assigned to the member. Specified Fy (MPa)

Shape

Material Used

250-280

Non-Hollow Sections

AS/NZS 3679.1 250

280-330

Non-Hollow Sections

AS/NZS 3679.1 300

330-380

Non-Hollow Sections

AS/NZS 3679.1 350

380-400

Non-Hollow Sections

AS/NZS 3679.1 400

200-350

Pipe, Tube

AS/NZS 1163 450

350-450

Pipe, Tube

AS/NZS 1163 350

450-500

Pipe, Tube

AS/NZS 1163 250

For steel with a nominal Fy outside of the ranges specified no steel material will be found and the section will be assigned a small yield strength and fail in design. A large interaction value on a design is indicative of assigned yield strength outside the ranges indicated above. Each of these materials provides a different yield strength depending on the thickness of the elements (flange, web etc). of a cross section being designed. The yield strength used in the final design is printed in the detailed report output.

Load Combinations Load Combinations for AS 4100 are defined in AS/NZS 1170. When Notional loads are created they will be included in all combinations that contain only gravity load cases when selecting the AS/NZS 1170 load combination code to generate the load combinations.

AS/NZS 1170 Load combination template files were generated based on AS/NZS 1170.0:2002, Section 4.2 “Combinations of Actions for Ultimate Limit States”. Section 4.2.2 Strength The combinations included in the load combination template are: a. [1.35G] b. [1.2G, 1.5Q] c. [1.2G, 1.5ψ1Q]


79


Steel Standard Provisions Technical Notes Member Code Check d. e. f. g.

[1.2G, Wu, ψcQ] [0.9G, Wu] [G, Eu, ψcQ] [1.2G, Su, ψcQ]

where G Q Wu Eu Su ψc

= = = = = =

ψ1

=

the Dead Load (“permanent action”) the Live Load (“imposed action”) the Wind Load the Earthquake Load the Snow Load (per Section 4.2.3(a)) the “combination factor for imposed action” and can provide in the generator dialog box the “factor for determining quasi-permanent values (long term) of actions”

ψc and ψl are given in Table 4.1. The program does not explicitly distinguish long-term imposed loads from other imposed loads, so the combinations of Combination (c) will not be generated, as they would always result in combinations with smaller factors than the corresponding combinations of Combination (b). Notably, the values listed in Table 4.1 for Storage loads are different from those listed for, say, Office and Residential loads. However, since all of the different types of Live Loads are analyzed and combined prior to the application of load combinations, the program will not be able to apply a different ψc value to different Live Loads; the will specify the value of ψc and the program will apply that to all of the Live Load in the appropriate combinations. The combinations are expanded as follows: (a) 1.35DL + 1.35ND (b) 1.2DL + 1.2 ND + 1.5LL + 1.5NL (b) 1.2DL + 1.2 ND + 1.5LLRoof + 1.5NR (b)1.2DL + 1.2 ND + 1.5sLL + 1.5NL + 1.5LLRoof+ 1.5NR (d) 1.2DL + Psic * LL ± W (d) 1.2DL ± W (e) 0.9DL ± W (f) DL + Psic * LL ± E (f) DL ± E (g) DL ± E Psic is ψc specified by the . The program pattern loads (“skip loads”) the Live Load; PosLL is the member forces resulting from the loading patterns that create the normal downward acting load conditions, while NegLL is the member forces resulting from the loading patterns that create uplift. Likewise for PosSnow and NegSnow. The generated load combinations can be viewed using the Reports – Load Combinations command.

Effective Length Ke-Factor The K-factors for beams and braces can be specified by the using the Criteria – Effective Length command, or on a member-by-member basis using the Assign menu. The Ke-factors for columns can be either specified by the or calculated by the program. For braced frames the calculated value is always 1.0. For unbraced frames the calculated value is based on an approximation to the graphs


80


Steel Standard Provisions Technical Notes Member Code Check provided in AS 4100 -98 section 4.6.3.3. The approximation is currently based on the AISC nomograph equations. If the is not satisfied with the values calculated by these equations they should assign the effective length value directly to the . For determining γ at column bases the following rules are followed. γ is limited to 10.0 for columns when there are no beams framing in, or when only pinned end beams are framing in; this limits ke to a value of 3.0, rather than the theoretical value of infinity. γ is limited to 0.6 at the bottom of the column if it is fixed to the footing. Columns that are pinned top and bottom are given ke-factors of 1.0. Knee brace columns are assigned a ke factor of 1.0 in the direction of the knee brace. If a spring exists at the base of a column the spring rotational stiffness is considered as the γ that end of the column.

Design Assumptions The following assumptions and criteria have been made in the implementation of the AS 4100 design code in RAM Frame (all references are to Sections in AS 4100-98): • The analysis is Elastic per 4.4 with second order affects based on both amplified moments per 4.4.2/3 and directly per Appendix E. • No net area checks are performed (i.e. no consideration is given for bolt holes due to connection details). • The program conservatively assumes the unbraced segments are not rotationally restrained at the ends of the segment as discussed in 5.4.3.4 and 5.6.3(3). • The structure is assumed to be a rectangular for the purposes of calculating secondary moment of sway frames per clause 4.4.2.3. • The corrective factor for distribution of forces according to 7.3 is assumed as follows. Note however as bolt areas are not provided these should not impact the design currently.

• •

•

•

• 0.75 for braces • 0.90 for Tee and Channels • 1.00 for other No torsion is considered in the design In the RAM Manager the engineer can designate if loads applied transverse to a member are applied at the shear centre or top of section. This setting is considered only for beam design in RAM Frame. For columns and braces where forces are only applied at the ends of a member they are assumed to be through the shear center. Similarly for beams the longitudinal position of the load with respect to Table 5.6.3(2) is considered to be within the segment, for braces and columns it is considered to be at the segment ends. Rolled sections other than tubes and pipes are assumed to be Hot Rolled (HR) per table 5.2. Rolled tubes and pipes are assumed cold formed (CF) per Steel Designer Handbook. All welded sections must be designated as either Heavy Welded (HW) or Light Welded (LW) as selected by the in the RAM Manager. For beam design the twist restraint factor (Kt) is conservatively set to 1.1 per 5.6.3.

Connector Spacing for Double Angles Maximum connector spacing for double angles is assumed to be limited to no more than 75% of the largest effective length divided by radius of gyration of the single angles that comprise the double angle. Based on this maximum spacing the Max Connector Spacing = 0.75 x max ( L major/r maj, L minor/r minor ) * rz


81


Steel Standard Provisions Technical Notes t Code Check RAM Frame then calculates the minimum number of equal length segments that don’t exceed this maximum spacing length.

Error Messages The following error messages may appear during the design process. N* > Nomx or N* > Nomy

Displayed when total axial load in the member exceeds the elastic critical buckling resistance for the member in the plane of bending. This has implications in the calculation of interaction values.

DelatSx Undef.., DelatSy Undef., DeltaSAxial Undef.

Displayed when P-Delta is selected to be considered in the analysis and total vertical load ed by story exceeds the story/diaphragm shear. This has implications in the calculation of interaction values.

DeltaBx DeltaBy DeltaSx DeltaSy

Displayed when the moment amplification factor exceeds the code specified limit 1.4. The engineer can choose to consider P-Delta in Analysis if δs exceeds the code limits.

> > > >

1.4, 1.4, 1.4, 1.4

T-O in Bend


T-O in Comp


A-O in Bend


3.3 t Code Check RAM Structural System has implemented a design check of the restrained (fixed or rigid) frame ts. This check involves evaluating the ability of a column’s flanges and web to resist the shears and concentrated forces imposed on the t from the framing beams. Where the column is found inadequate to resist the imposed loads, a web plate (doubler) and/or stiffeners will be designed. Prior to performing a t check the engineer should confirm the criteria by which the design is to be performed. These criteria can be viewed and modified through the dialog displayed by invoking the Criteria-ts command. No t code check is performed for hanging columns.


82


Steel Standard Provisions Technical Notes t Code Check

3.3.1 Assumptions and Limitations RAM Structural System assumes that all beams framing into a t have the same top of steel elevation. For the case of beams with different depths (and sloped beams) this assumption differs from the geometric assumption made in RAM Frame for analysis. As illustrated in below, in RAM Frame all (beams and columns) at a t are assumed to have coincident longitudinal axes. It is the engineers’ responsibility to determine the effect and validity of these assumptions with respect to their particular application. Design Assumptions

Analysis Assumptions

t checks can be performed on all valid steel beam-column ts. A valid t is defined as one in which the column is an I-section (Wide Flange) and where at least one steel member (designated as a frame member) is rigidly connected to the flange of the column. If more than two rigidly connected steel sections frame into one flange of a steel I-Section column, or if there are no rigidly connected steel attached to the flanges of the section, then no checks are performed. RAM Frame considers two sides of the column and refers to them as Side A and Side B. Side A refers to the flange of the column orientated along the local axis of the member as shown in the following figure. Side B is the column flange located opposite Side A. A

B

A Rotated 0° A

B Rotated 45° A

B B Rotated 90°

Rotated 135°

Figure 3: Line parallel to column web indicates local axis direction.


83



3.3.2 t Forces For all valid ts (refer to the above section on limitations for the definition of a valid t) the program will calculate the capacity of the column web and flanges to resist the applied forces. For all codes the zone shear checks are performed before any of the other required t checks. RAM Frame calculates the shear in the zone as the net sum of the shear from the column above, the shear applied to the t from the story (through the diaphragm), the axial load in the beams (divided between the beam flanges) and the shear due to beam moments. As illustrated in the following figure, the story shear applied to the t is assumed to be the net difference of the shear in the column above the t, the axial load in the beams framing into the t, and the column shear directly below the t. Note that the angle of the column above the t, and the beams framing into the t, is considered when calculating Vcol above, PA and PB. With the Criteria – Column Moments command in Steel – Standard Provisions mode in RAM Frame, the can specify the portion of the calculated Gravity moments to be included in the design of the columns. This feature is described in the Column Moments Section of this manual. The t Checks also for these specified reductions; the Gravity beam moments at the t are reduced as specified.

VCol above + Vstory PB

PA Vbelow

Vstory =Vbelow -VCol above +PA +PB Figure 4: When calculating the design zone shear the program assumes that this story shear is applied above the t. In the case where a valid t is not connected to the diaphragm there should be no story shear applied to the t. An exception to this is the case where a brace frames into the t from above. The engineer should use the t checks with caution whenever a brace member frames into the t. The zone forces are calculated as shown in the following figure.


84



VCol above + Vstory VPTB VMTB PB

VMTA VPTA

P MB Zone MA A

VPBB VMBB

VMBA VPBA

Vcol below

Figure 5: Dashed arrows represent the moments and axial loads applied to the t by the beams. To determine the zone shear these moments and axial loads are resolved into concentrated flange forces as shown by the solid arrows. In this figure, the applied beam moments (MA and MB) are resolved into a couple by dividing by the beam depth (VMTA = VMBA = MA/Beam depth [between mid heights of flanges]). The story shear is assumed applied above the zone. The axial load in the beams is applied to the t through the beam flanges based on their areas. VPTA is therefore calculated as PA x Area of Top flange of Beam A / Total flange area for beam on side A. The zone shear for the forces shown in the previous figure (all forces shown are positive in magnitude) is calculated as: zone shear = Vcol above + Vstory – VPTB – VPTA – VMTB – VMTA The beam flange-to-column-flange force used for the other t checks is taken as: Concentrated top flange force side B of t = VPTB + VMTB The other beam flange-to-column-flange forces are calculated in the same manner. With a sloped beam the calculation of design forces for consideration in the t design (design of stiffeners and web plates) are modified as illustrated in the following figure. The figure illustrates the forces a beam exerts on a column at the t. In this example the beam is considered to be in compression.


85


Steel Standard Provisions Technical Notes t Code Check M

V

M P

φ

V

d

M.cos(φ)/d

M.cos(φ)/d + P.cos(φ)/2 V.sin(φ)/2

M.cos(φ)/d

M.cos(φ)/d + P.cos(φ)/2 V.sin(φ)/2

M.cos(φ)/d + P.cos(φ)/2

A

B

C

M.cos(φ)/d + P.cos(φ)/2

Figure 6: A) Ignore axial and shear, B) Include Axial and Shear, C) Include axial and shear if inc. force When the beam frames into a sloping column which makes an angle λ with the vertical, φ is substituted with (φ + λ) in the equations above. The beam flange forces on the column are resolved horizontally for the design of the column stiffeners and web plates. However, local flange column flange checks are performed using beam flange forces acting orthogonally to the column flange. M

V

M P

λ

V

φ

d

M.cos(φ+λ)/d

M.cos(φ+λ)/d + P.cos(φ+λ)/2 V.sin(φ+λ)/2

M.cos(φ+λ)/d

M.cos(φ+λ)/d + P.cos(φ+λ)/2 V.sin(φ+λ)/2

A

B

M.cos(φ+λ)/d + P.cos(φ+λ)/2 M.cos(φ+λ)/d + P.cos(φ+λ)/2

C

Figure 7: A) Ignore axial and shear, B) Include Axial and Shear, C) Include axial and shear if inc. force

3.3.3 t Design In the event that the ability of the column web to resist the applied shear is exceeded, then an appropriate web plate (doubler) will be designed. RAM Frame will only provide a web plate where the zone shear capacity of the column is exceeded by more than 1%. If a web plate is required, then where the capacity of a column’s flanges and web (including the contribution of the web plate) is exceeded for any of the concentrated force checks, RAM will attempt to increase the thickness of the web plate to increase the columns capacity. If an adequate web plate cannot be designed, then a stiffener will be used and the web plate will once again only be sized for the zone shear. Where no web plate is required for zone shear check, but the capacity of the column flanges and web is


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Steel Standard Provisions Technical Notes t Code Check exceeded for any of the concentrated force checks, RAM will provide a stiffener to meet the code requirements. The design of the web plate and stiffeners at a t is based on the criteria provided by the engineer through the dialog displayed by invoking the Criteria-ts command.

AISC –ASD 9th The requirements of Supplement No. 1 (December 17, 2001) are included as an option in the ASD t design. Select ASD Supplement No.1 to implement the following revision: “Pbf = the computed force delivered to the flange or moment connection plate multiplied by 5/3” This removes the distinction between lateral load cases and gravity load cases on the value of Pbf.

Zone Check For calculation of strength purposes the depth of the web plate (when one is required) is assumed to be the clear distance between column flanges. This is true for both rolled and built-up sections. For a rolled section the full depth of the section is considered when calculating the web zone capacity, for built up sections only the clear distance between the column flanges is used to calculate the web capacity. When zone check is performed for sloping columns, the depth of the web plate (when one is required) is assumed to be the horizontal clear distance between column flanges.

Local Web Yielding According to AISC the column capacity to prevent local web yielding is diminished at the ends of a member. In RAM Frame this provision applies to the top of the column, when no column exists above. To calculate the column capacity at these locations RAM Frame uses the maximum of the framing beams flange thickness or the columns k dimension (distance from outside face of column flange to the web toe of the web-to-flange fillet) in equations K1-2, K1-3. If a web plate is present then the plate thickness and yield strength are used in these equations, along with the column properties (flange thickness etc).

Web Crippling The same restrictions are applied in calculating the Web Crippling Capacity according to chapter K1.4 as are taken when calculating the Local Web Yielding capacity. That is, when calculating the column capacity at these locations RAM Frame uses the maximum of the framing beams flange thickness or the column’s k dimension (distance from outside face of column flange to the web toe of the web-to-flange fillet) in equations K1-4, K1-5. If a web plate is present then the plate’s thickness and yield strength are used in these equations along with the column properties (flange thickness etc).

Stiffener Design Stiffeners are designed in accordance with Specification K1.8. The force used to design stiffeners is considered to be the difference between the applied load and the capacity of the column to resist this load. For some of the above t checks the forces are converted from working stress to capacity values. Where these forces resulted in the use of stiffeners they are converted back to working stress forces for stiffener design. Refer to AISC K1.2 for conversion from working stress to capacity values.

AISC 360, LRFD 3rd


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Zone Check For calculation of strength purposes the depth of the web plate (when one is required) is assumed to be the clear distance between column flanges. This is true for both rolled and built-up sections. For a rolled section the full depth of the section is considered when calculating the web zone capacity, for built up sections only the clear distance between the column flanges is used to calculate the web capacity. Two different equation sets are presented in AISC when performing zone checks. The first set (equations LRFD 3rd: K1-9, K1-10 / AISC 360: J10-9, J10-10) is applicable when -zone deformation is not considered in the analysis. The second set (LRFD 3rd: K1-11, K1-12 / AISC 360: J10-11, J10-12) is applicable where -zone deformation is considered in the analysis. RAM Frame looks at the rigid end factor to determine into which group the structure falls. If full rigid ends are used then RAM Frame assumes that the Zone is not considered in the analysis. If any value less than the full rigid end zone is used, then the program assumes that the zone is considered in the analysis and equations LRFD 3rd: K1-11, K1-12 or AISC 360: J10-11, J10-12 are used. When zone check is performed for sloping columns, the depth of the web plate (when one is required) is assumed to be the horizontal clear distance between column flanges.

Local Web Yielding According to AISC the column capacity to prevent local web yielding is diminished at the ends of a member. In RAM Frame this provision applies to the top of the column, when no column exists above. To calculate the column capacity at these locations RAM Frame uses the maximum of the framing beams flange thickness or the columns k dimension (distance from outside face of column flange to the web toe of the web-to-flange fillet) in equations LRFD 3rd: K1-2, K1-3 and AISC 360: J10-2, J10-3. If a web plate is present then the plates thickness and yield strength are used in the equations along with the column properties (flange thickness etc).

Web Crippling The same restrictions are applied in calculating the Web Crippling Capacity according to section LRFD 3rd: K1.4 and AISC 360: J10.4 as are taken when calculating the Local Web Yielding capacity. That is, when calculating the column capacity at these locations RAM Frame uses the maximum of the framing beams flange thickness or the column k dimension (distance from outside face of column flange to the web toe of the web-to-flange fillet) in equations LRFD 3rd: K1-4, K1-5a and K1-5b, AISC 360: J10-4, J10-5a, J10-5b. If a web plate is present then the plate thickness and yield strength are used in these equations, using the column properties when necessary (flange thickness etc).

Stiffener Design Stiffeners are designed in accordance with Specification LRFD 3rd: K1.9, AISC 360: J10.8. The forces used to design stiffeners are calculated to be the difference between the applied load and the capacity of the column to resist this load. The minimum required area of the stiffeners is calculated per the AISC design guide 13, equation 4.3-1.

BS5950 Part 1 : 1990


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Web Buckling (4.5.2.1) RAM Structural System assumes that when calculating the slenderness of an unstiffened web of depth d, lambda is taken as 2.5d/t. This assumption implies that the column flange on which the load is applied is effectively restrained against rotation relative to the web, and lateral movement relative to the other flange. Where stiffeners are used to resist this load they will be designed according to 4.5.2.3. The stiffeners are also checked as bearing stiffeners per 4.5.3.2.

Web Bearing – Tension and Compression (4.5.3.1) If stiffeners are required they are designed in accordance with 4.5.3.2. If the column does not have the capacity to carry the applied load, then the web bearing capacity is recalculated using the lower of the nominal yield strength of the column web and the stiffener.

Web Tensile Force (4.5.4, 6.7.6) Where required, stiffeners are designed in accordance with 4.5.4. Per 6.7.6, the dimension rc (and zc) is assumed to equal the column k (dimension from outer column flange face to the root of the web-toflange weld) less the thickness of the column flange (k-tf). For built up sections the engineer should provide the appropriate k value in the master steel table to obtain the correct zc value.

Web Shear (4.5.6) RAM Structural System will not design diagonal web stiffeners. However, the required force for diagonal stiffener design is provided in the output. The capacity of the column web is calculated using the design yield strength of the column. If this capacity is not sufficient, then the column web capacity is recalculated using the lower of the column web and stiffener plate yield strengths. The reported stiffener design force is the horizontal shear calculated as the difference between the applied force and the capacity of the web (calculated using the lower of the web and stiffener nominal yield strength’s).

Stiffener Design Where stiffeners are required for web buckling (4.5.2.1) then they are designed in accordance with 4.5.2.3. Note that a 20 N/mm2 reduction is not taken on the design yield strength of the stiffeners. The stiffeners are designed using the lower of the web and stiffener yield strengths. Where stiffeners are checked for bearing per 4.5.3.2 the cope dimension is considered. The stiffeners are always designed in accordance with 4.5.2.3, 4.5.3.2 and 4.5.4 when applicable. Note that the stiffeners are not considered to be intermediate stiffeners per 4.5.5., i.e. they are not considered necessary to resist shear buckling. The engineer has significant control over the stiffener design dimensions. The criteria by which the stiffener dimensions are calculated can be modified in the dialog displayed by invoking the criteria-ts command. The width of the stiffener is calculated first. If the thickness is calculated per code then per specification 4.5.1.2 the outstand of the stiffener from the face of the column web will not exceed 13 ts Epsilon. The length of the stiffener (when not required to be full length) is calculated according to 4.5.10. The minimum length of stiffener that will be provided by RAM Frame is one-third of the depth of the column.

BS5950 Part 1 : 2000 The provisions of BS 5950-1:2000 for web bearing (4.5.2.1), web buckling (4.5.3.1) and local flange bending (6.7.5) have been implemented in RAM Frame. Note that for the beam flange that frames into


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Steel Standard Provisions Technical Notes t Code Check the absolute top of a column, the ae and be values in 4.5.2.1 and 4.5.3.1 are conservatively taken as 0.0. Refer to the previous section on BS5950 Part 1:1990 for more information.

CAN/CSA S16-01, S16-09 Compression 21.3 (a) The capacity of the column flange to resist an applied compression force is calculated per specification 21.3a. When calculating the class of the web per Table 1, the axial load (Cf) is calculated for the load combination that resulted in the maximum compression force on flange, as shown in the output. The capacity of a web plate (doubler), when provided is added to that of the column. Where the column (and web plate) capacity is exceeded, a stiffener is provided. Note that for the top flange of a beam at the top of a column, the coefficient of k, in section 21.3a is reduced from 5.0 to 2.5.

Tension 21.3 (b) The capacity of the column flange to resist an applied tension force is calculated per specification 21.3b. This capacity is based only on the column flange, and the addition of a web plate is ignored.

Zone – Web Shear The capacity of the column to resist zone shear is calculated in accordance with 13.4.1.2. For a rolled section the full depth of the section is considered when calculating the web zone capacity, for built up sections only the clear distance between the column flanges is used to calculate the web capacity. Where a web plate is required its capacity is also calculated based on 13.4.1.2 with d taken as the clear depth between flanges.

Eurocode 3: BS EN 1993-1-8:2005 Zone – Web Shear The capacity of the column to resist the applied zone shear is calculated according to 6.2.6.1 RAM Frame assumes that bs is the distance between flanges of welded I-Sections, and the distance between the toe of the flange-to-web welds in rolled I-Sections. Where a supplementary web plate is required the program will automatically use a web plate equal in thickness to that of the column web (per 6.2.6.1 (6) – (12)), but rounded up to the closest web plate increment (see Criteria section). When the capacity is calculated only the thickness of the plate equal to that of the web is considered (per 6.2.6.1). This implementation may result in a confusing output in the following situation. If a column has an 11 mm thick web, and based on forces a 12.5 mm thick plate is required, then obviously a suitable web plate cannot be designed and the program will indicate that no web plate can be designed. However, when looking at the output the provided web plate may be 15 mm thick. This occurs as the maximum thickness of the provided web plate is 11 mm (same as column web), but this is rounded up to the next increment which if the set to 5mm, results in a plate 15mm thick. While a 15mm thick web plate is provided, when we calculate the strength of the web plate the program only considers 11 mm of the plate effective and states that it fails. This situation will only occur when the required thickness of the plate is between the column web thickness, and the web thickness rounded up to the next thickness increment. No web buckling requirements are checked. The engineer is also responsible for specifying a web plate yield strength that is similar to that of the column (as required by specification 6.2.6.1 (8)).


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Resistance of Tension Zone (Flange Bending) 6.2.6.4.3 The ability of the column flange to resist a concentrated tension force applied to its flange is calculated according to 6.2.6.4.3. For both welded and built up sections the rc value is calculated as the difference between the columns k dimension and the thickness of the column flange. For built-up sections the engineer should therefore specify the appropriate k factor in the master table to for the web-toflange fillet weld dimension. Where the specifies that the member capacity is to be used to calculate forces (see Criteria-ts), the program will instead calculate the force as: Beff,b,fc Tfb Fyb / Gamma Mo (Eqn 6.20). Beff,b,fc is calculated according 4.10. The should specify an over-strength factor (see Criteria-ts) of 1.0 if no strain hardening is to be considered.

Resistance of Tension Zone (Web Bearing) 6.2.6.3 The ability of the column web to resist a concentrated tension force applied to its flange is calculated according to 6.2.6.3. For both welded and built up sections the ab value is ignored as a complete t penetration weld is assumed. If a web plate is used then the web plates capacity is calculated independently of the column web. If the thickness of web plate required exceeds 0.5 times the column web thickness (6.17) then no thickness of web plate is adequate, and the required thickness is reported as -25.4mm (-1.0in). Refer to flange bending section above for information on the web-to-flange weld dimension (ac) in a built up section. Note that at the top of a column (where no column exists above, the coefficient for (tfc + rc) is assumed to be 2.5 instead of 5.0.

Resistance of Compression Zone (Web Bearing) 6.2.6.2 (1) The ability of the column web to resist a concentrated compression force applied to its flange is calculated according to 6.2.6.2. For both welded and built up sections the ab value is ignored as a complete t penetration weld is assumed. If a web plate is used then the web plate’s capacity is calculated independently of the column web. If the thickness of web plate required exceeds 0.5 times the column web thickness (6.17) then no thickness of web plate is adequate, and the required thickness is reported as negative 25.4mm (-1.0in). Refer to flange bending section above for information on the web-to-flange weld dimension (ac) in a built up section. Note that at the top of a column (where no column exists above, the coefficient for (tfc + rc) is assumed to be 2.5 instead of 5.0. The program assumes that transverse movement of the column flanges (see Eurocode figure 6.7) is prevented. Where the capacity of the framing beams is used to perform the design, no axial load is assumed on the t column.

Stiffener Design Where stiffeners are required only for web bearing or flange bending checks, half column depth stiffeners will be designed. The engineer should confirm that half the column depth is adequate. The stiffener dimensions are based on the criteria settings (see Criteria-ts), the area required to resist the applied flange force (less the capacity of the column), and the code requirements (thickness at least equal to the ading beam flange thickness). The program also dimensions the stiffener thickness to ensure a fully effective section i.e. class 1 or 2, but the stiffener thickness is arbitrarily limited to three times the framing beam flange thickness. The lower of the stiffener and column web yield strengths is used for the “column” strength when performing this check. The program assumes one stiffener is provided each side of the column web.


91



AS 4100-98 Web Buckling – Compression (5.13.4) RAM Frame checks each column flange when subject to compression force according to the requirements of 5.13.4. In this section bb (total bearing width) is based on a 45 degree dispersion from the applied load point. Where a flange is deemed to be near the top of a column this dispersion is assumed to be in one direction only and bb = bs + 2.5x tf + bbw, where bbw = d2/2. The capacity of the web acting as a column is calculated according to Section 6.3.3 using a column width of bb and thickness equal to that of the column web and following per 5.13.4: le/r = 2.5 x clear depth of column / thickness web column, αb = 0.5, and kf = 1.0. A web plate if it exists will be ignored when performing this check. Where required stiffeners will be used to resist this load, they will be designed according to discussion on stiffener design below.

Web Bearing Yielding – Tension and Compression (5.13.3) A web plate, if provided, is not considered when performing this check. The dimension bbf will only use 2.5tf if the beam flange being considered is at the top of the column. The web plate if it exists is not considered in the calculation of the bearing capacity. If stiffeners are required they are designed in accordance with the discussion on stiffener design below.

Local Flange Bending - Tension A local flange bending check has been performed according to the design provisions as documented in the Steel Designers Handbook. The flange capacity at the column is calculated as follows: Rt = fyc(tfbbrc + 7tfc2) where fyc tfb brc tfc

= = = =

Yield strength of the column thickness flange of beam column web thickness plus two column fillet radius thickness of the flange of the column

Where required, stiffeners are designed in accordance with the discussion below.

Web Shear (5.11.2/4/5) RAM Frame will perform a check on the zone strength of a column at a beam column t. The column web capacity will be based on the provisions of 5.11.2, 5.11.4 and 5.11.5. The capacity of the column web is calculated using the design yield strength of the column. If this capacity is not sufficient then a web plate that will be added according to the engineer specified criteria, and the zone capacity including the web plate will be calculated. The capacity of the web plate will only include the plate thickness over the clear depth of the column.


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Stiffener Design Where stiffeners are required for web buckling, bearing or flange bending they will be designed as full length stiffeners (complete depth of column web). The engineer has significant control over the stiffener design dimensions. The criteria by which the stiffener dimensions are calculated can be modified in the dialog displayed by invoking the Criteria - ts command. The minimum thickness of the stiffener will be the same as the beam flange thickness. Where a stiffener is designed it will be considered as a simple column comprised of the two stiffeners and a width of column web to create a cross (+) shaped column section. The effective length of the stiffener will be considered as 0.75 x length of the stiffener, kf = 1, αb = 0.5. If stiffeners are not able to be designed the stiffener optimization criteria may need to be adjusted or a larger column size used.


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94


Steel Standard Provisions Reports

4

A number of reports are available in Steel-Standard Provision Mode. Many of these have already been described in the RAM Frame Analysis Chapter. The reports presented below are those that are not described in the Analysis chapter and are specific to the Steel Standard Provision Mode. Many of the reports are based on load combinations (member forces, reactions etc). In Steel – Standard Provision Mode these reports are all based on the standard provision load combinations (generated and custom) from this mode only. Below is a summary of the reports available in the Steel-Standard Provision Mode. The on-line help also provides information on each of the reports. Printer/Screen/ The first four items in the Reports menu allow the engineer to specify where the Text File/Viewer output is to be sent. The engineer can choose to send output directly to the printer, File to the screen, to a comma separated text file or to a viewer file format. This last option allows the engineer to later view the file, with all its formatting, using the file viewer application provided with the program. This file can also be delivered, along with the viewer, to anyone wishing to view the report. Model Data

The Model Data report is a listing all lateral , their fixity, boundary conditions and section properties. This is data that can be modified using the Assign menu items.

Code Check Criteria

The Code Check Criteria is a listing of all criteria specified in the Criteria command in the Post-Processor Mode in addition to the criteria used for Roof Live Loads.

Load Combinations

The Load Combinations report is a listing of the analyzed load cases of which the combinations are comprised, the program-generated load combinations, and the -defined load combinations from this mode only.

AISC 360 Direct Analysis Validation

The AISC 360 Direct Analysis Validation report checks the validity of the analysis based on the requirements of the Direct Analysis Method outlined in AISC 360. Warnings are given if the proper analysis and design criteria options have not been selected or if they are inconsistent with the notional loads or combinations used. This report is only available when the selected Code is AISC 360. The Process – Member Code Check command must be performed before the report is available.

Member Code Check

The Member Code Check report lists detailed results of the currently selected Steel Design Code Specifications check for individual . The report includes member information, design parameters, the calculated member forces for the controlling load cases, and the interaction equation results. Member Code Check reports can be printed for a single frame member, all frame included in a fenced area, all of a selected frame, all frame shown in the current view or for every frame member in the model.


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Steel Standard Provisions Reports t Code Check The t Code Check report lists detailed results of the currently selected Steel Design Code Specifications check for individual moment-frame (rigid) steel ts. The report includes t information, design parameters, t forces and the required stiffeners and/or web plates. t Code Check reports can be printed for a single frame member, all t included in a fenced area, all ts of a selected frame, all frame ts shown in the current view or for every frame t in the model. Member Check Summary

The Member Code Check Summary report lists abbreviated results of the selected Steel Design Code Specification checks for every steel frame member. It includes a listing of all criteria set in Analysis Mode and Steel-Standard Provision Mode, all analyzed load cases and all load combinations. For each member the calculated member forces for the controlling load combination and the interaction equation results are shown.

t Check Summary

The t Code Check Summary report lists abbreviated results of the selected Steel Design Code Specification checks for every moment frame (fixed beamcolumn flange) t. It includes a listing of some of the criteria set in the Criteriats dialog. For each t the calculated member forces for the controlling load combination and the required web plate and stiffeners are shown.

Member Forces

The Member Forces report lists the member forces for an individual frame member for the generated and -specified load combinations. This includes axial load, major and minor moment, major and minor shear, and torsion. It includes member information and criteria settings. The member forces are those that occur at the member or segment ends. Member Force reports can be printed for a single frame member, all frame included in a fenced area, all of a selected frame, all frame shown in the current view or for every frame member in the model. This output does not include any Code Check results, but has been included in the Post-Processor Mode as a convenient tool for listing member forces for the generated combinations.

Member Force Summary

The Frame Member Force Summary report lists the member forces for every frame member for the generated and -specified load combinations. This includes axial load, major and minor moment, major and minor shear, and torsion. The analysis criteria are also included in the report. The member forces are those that occur at the member or segment ends. This output does not include any Code Check results, but has been included in the Post-Processor Mode as a convenient tool for listing member forces for the generated combinations.

Member Force Envelope


The Member Force Envelope report lists the maximum and minimum member forces for an individual member for the generated and -specified load combinations. The member forces are those that occur at the member ends as well as at any point along the member. The controlling load combination and location are indicated. The load cases are listed but the combinations are not; rather, the number of generated and -defined combinations that were investigated is shown.

96


Steel Standard Provisions Reports Code Check Criteria

This output does not include any Code Check results, but has been included in the Post-Processor Mode as a convenient tool for listing member forces envelope for the generated combinations. Reactions

The Reactions report lists the reactions for each foundation node for each of the generated and -specified combinations. This output does not include any Code Check results, but has been included in the Post-Processor Mode as a convenient tool for listing reactions for the generated combinations.

Reactions Envelope

The Reactions Envelope report lists the maximum and minimum reactions at each foundation node for the generated and -specified combinations. The analysis criteria are also listed. Reactions Envelope reports are printed frame by frame.

Screen Print

A printout of the screen using the Reports - Print Screen command or the Print button after Code Check has been invoked will show the color coded and will include a color key. If the printer is capable of printing in color, this output will be in color.

Print Preview

Use the Reports - Print Preview command to preview the printout for the current view.

Print Setup

Use the Reports - Print Setup command to configure the selected printer.

4.1 Code Check Criteria The Frame Code Check Criteria report lists the criteria used in the Steel Standard Post-Processors. The sidesway condition, braced or unbraced, is indicated. The Effective Length (K-Factor) values for columns, beams and braces are listed. For columns, “Nomograph” (ASD/LRFD), “Appendix E” (BS5950) may be printed. This indicates that the effective length factor for ASD and LRFD will be calculated based on the nomograph published in the AISC Manual of Steel Construction, Appendix E in the BS5950. The criteria used to determine the compression flange bracing conditions for columns and beams is listed The Roof Live Load is indicated as being either Reducible or Snow. If Snow, the criteria and/or the load factor for including Snow loads in combinations with Seismic loads is indicated. The criteria for Sidesway, Effective length and Compression flange bracing are specified from the Criteria menu command, or are assigned to individual from the Assign menu command. The designation of Roof Live Load type is specified in Criteria - Live Load Reduction in RAM Manager. The criterion for Snow Factor is set in the Combinations-Generate menu command.

4.2 Load Combinations The Load Combinations report lists the combinations used in the standard provision steel code checks. The report includes the Roof Live Load criteria, which affects the generated load combinations.


97


Steel Standard Provisions Reports AISC 360 Direct Analysis Validation The load cases included in the load combinations are listed along with the generated and -specified load combinations, as well as which of the combinations are selected to be used in the code check. For generated combinations the Code specified as the basis of the generation is indicated. For example, “AISC ASD + UBC” indicates that the generated combinations are for ASD design, based on the combinations specified by the Uniform Building Code.

4.3 AISC 360 Direct Analysis Validation For AISC 360 LRFD or ASD design specifications, it is the engineer’s responsibility to ensure that the selection of options for P-delta, B1, B2, fraction of gravity loads for Notional Loads, Stiffness Reduction and τb used in the stiffness reduction are all consistent and correct as required by the Direct Analysis Method. To aid the engineer, this report is provided when AISC 360-10 or AISC 360-05 has been selected as the design code. The report examines the selection of options for P-delta, B1, B2, Notional Loads, Stiffness Reduction and τ b , along with analysis results, and reports on the validity of each criteria selection. If the analysis is deemed invalid, it is reported. It is then the responsibility of the engineer to make the necessary corrections to those criteria selections, or in some cases to modify the structure so that limitations are satisfied. If criteria options are not selected that are required, a warning is printed in red (which must be rectified in order for the analysis to be valid); if criteria options are selected that are not required, a warning is printed in blue (which need not be rectified as they are conservative). The Process – Member Code Check command must be performed before the report is available. The report is composed of four sections. In the following paragraphs, these sections are explained.

4.3.1 Design Code The chosen design code is printed in this section. It is either AISC 360-10 (ASD or LRFD) or AISC 360-05 (ASD or LRFD).

4.3.2 Second-Order Analysis The criteria selections by the engineer regarding 2nd order analysis are reported in this section. This includes the options to perform a P-Delta analysis based on the Geometric Stiffness method and to apply the B1 and B2 factors. B1 Factors


The worst B1 ratio for any member for any combination is calculated and reported, and the necessity of including P-d in the analysis or not is indicated according to C2.1(2)(b) of AISC 360-10 or Eq. (A-7-1) of AISC 360-05 (i.e., αPr < 0.15PeL). The member number and load combination corresponding to the worst ratio is printed. Note that the program searches all load combinations for member’s major and minor axis (except with pinned ends), and then it reports the worst ratio among all . The report also shows the number of elements where αPr exceeds 0.15PeL.

98


Steel Standard Provisions Reports AISC 360 Direct Analysis Validation B2 Factors

In this section, information regarding B2 and its parameters (i.e., RMx and RMy) is printed. If B2 factors are applied, the maximum values of B2x and B2y on any diaphragm on any level for any combination is determined and reported. This can be used to determine if the notional loads need be applied to all combinations or to only the gravity combinations. If both B2 and the current P-delta option are chosen, the engineer is notified that both options are not needed in order to include 2nd order effects.

4.3.3 Notional Loads If no notional load cases are included in any load combination, an error message is printed. The fractions of Gravity loads used in the generation of notional loads are printed for both X and Ydirections. If more than one set of notional load cases are found, the report only includes the set with smallest fraction of gravity loads. The report also indicates whether the notional loads are included only in gravity combinations or in all combinations. Under certain conditions, notional loads may not be needed in all load combinations according to the Specification (notional loads should be included in all combinations if B2>1.5 for models with nominal member properties, or B2>1.7 for models with reduced member properties). The program checks this and reports whether notional loads should be included for all load combinations or for only the gravity load combination.

4.3.4 Reduced Stiffness The Specification mandates reduction of both flexural and axial stiffness of steel . This should be carried out for all lateral that provide lateral stiffness to structure. The report first checks if all are pinned or not. If this is the case, it is not necessary to reduce the flexural stiffnesses and this is indicated in the report. If the option to reduce the stiffnesses was not selected in RAM Frame Analysis mode, an error message is given. Flexural Stiffness

The program calculates τb based on αPr / Py for all load combinations for all contributing lateral stiffness ( with pinned ends or with no moments at their ends are skipped). The smallest value of τb is determined and reported, as well as the number of with τb less than 1.0. The member with the smallest τ b is indicated in the report. Note that τb value used in analysis is defined by the engineer in Criteria – General in RAM Frame Analysis mode. The value used in analysis is compared to smallest calculated value of τb , and validity of the value used is reported.

Axial Stiffness


If the option to include the reduction to the axial stiffness is not selected, an error message is given.

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Steel Standard Provisions Reports Member Code Check

4.4 Member Code Check 4.4.1 AISC The AISC Member Code Check report lists the results of the ASD and LRFD Code Check for an individual member.. In the output, standard nomenclature is used. The x- and y subscripts indicate the strong and weak axis, respectively. In many cases the term Minor and Major axis are used. Major axis refers to the strong axis of the member, and minor to the weak axis. For columns and braces the member forces at both the top and bottom are shown. For beams, only the controlling member forces are shown, with the associated segment indicated. The controlling load combination and the corresponding member forces and stresses (ASD) or capacities (LRFD) are shown for both shear and flexure/axial force conditions. The member is controlled by the greater of the Shear Check results and the Interaction Equation results. The curvature of the member, either single or double, is listed for the Cm calculation when applicable. In lieu of interaction equation results, slender are indicated as such.

4.4.2 Eurocode The Eurocode Member Code Check report lists the results of the Eurocode Code Check for an individual member. In the output, standard nomenclature is used. Major refers to the strong axis of the member and minor to the weak axis. For columns and braces the member forces at both the top and bottom are shown. For beams the controlling segment and the associated end member forces are shown. The controlling load combination and the corresponding member forces and capacities are shown. The member is controlled by the greater of the interaction values from the Cross Section resistance, Buckling resistance or Web Shear Buckling resistance. Pertinent intermediate values used to calculate cross section and buckling capacities are printed. In lieu of interaction equation results, that are determined to be class 4 (slender) are indicated as such.


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Steel Standard Provisions Reports Member Code Check

4.4.3 CAN/CSA S16-01 / S16-09 Member Code Check The CAN/CSA S16-01 or S16-09 Member Code Check report lists the results of the Code Check for an individual member. In the output, standard nomenclature is used. For columns and braces the member forces at both the top and bottom are shown. For beams, only the controlling member forces are shown, with the associated segment indicated. The controlling load combination and the corresponding member forces and capacities are shown for both shear and flexure/axial force conditions. The member is controlled by the greater of the Shear Check results and the Interaction Equation results. In the event that a capacity could not be calculated (See Error Messages on page 69) then the appropriate reason will be printed on the output.

4.4.4 BS 5950 Member Code Check The BS 5950 Member Code Check report lists the results of the Code Check for an individual member. In the output, standard nomenclature is used. For columns and braces the member forces at both the top and bottom are shown. For beams, only the controlling member forces are shown, with the associated segment indicated. The controlling load combination and the corresponding member forces and capacities are shown for both shear and flexure/axial force conditions. The member is controlled by the greater of the Shear Check results and the Interaction Equation results. In the event that a capacity could not be calculated (See Error Messages) then the appropriate reason will be printed on the output.

4.4.5 AS 4100-98 Member Code Check The AS 4100-98 Member Code Check report lists the results of the Code Check for an individual member. In the output, standard nomenclature is used. For columns and braces the member forces at both the top and bottom are shown. For beams, only the controlling member forces are shown, with the associated segment indicated. The controlling load combination and the corresponding member forces and capacities are shown for both shear and flexure/axial force conditions. The member is controlled by the greater of the Shear Check results and the Interaction Equation results. In the event that a capacity could not be calculated (See Error Messages) then the appropriate reason will be printed on the output.


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Steel Standard Provisions Reports Member Check Summary

4.5 Member Check Summary The Code Check Summary report lists the abbreviated results of the Steel Standard Provision Code Checks for every steel member.

4.5.1 Criteria The Analysis Criteria are listed as described in the Analysis chapter.

4.5.2 Code Check Criteria The Code Check Criteria are listed as described in the Design Criteria section. The Load Cases used in the Load Combinations are listed.

4.5.3 Load Combinations A list of the Generated and Selected -specified load combinations is listed.

4.5.4 Summary Results The design forces of the controlling load combination are listed, with the controlling load combination and Interaction Equation results. LC

This is the controlling load combination number.

Interact The controlling Interaction Equation value is listed, with a reference to the Code equation that produced the controlling value. In lieu of interaction equation results, slender (Class 4 in Eurocode) are indicated as such.

4.6 t Code Check


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Steel Standard Provisions Reports t Code Check

4.6.1 Story Number The number of the story on which the t is located.

4.6.2 t Number The node number of the t.

4.6.3 Final Design Web Plate Design Thickness

The thickness of the web plate required to resist all the applied loads.

Web PL Thk Req’d The required thickness of the web plate to allow the web plate to be fillet welded w/Fillet Weld to the column flanges. This is a detailing requirement and is specified separately from the thickness required to resist the applied loads. Stiffener Dimension

The Length (L), width (W) and thickness (T) of the stiffeners. Refer to the assumptions and limitations section for the meaning of Side A and Side B. Top refers to the stiffeners required at the elevation of the upper flange of the framing beam/s. Bot refers to the stiffeners required at the elevation of the bottom flange of the framing beam/s.

4.6.4 t Data and Material Properties Yield Strengths The material strength of the stiffeners and web plate. t Data

The size, angles and yield strengths of the column and framing beams at the t. Note that if the beams are not at the same angle (or exactly 180 degrees greater) of the column, then they do not frame perpendicularly into the column flange.

4.6.5 Criteria Some of the relevant data considered in the design of the t. Refer to the code check criteria report for all the t check criteria. These criteria are changed in the diavoked through the criteria-ts command.


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Steel Standard Provisions Reports t Code Check

4.6.6 Results Zone

Refer to the design approach for information regarding the calculation of the design zone shear. The moments and shears that controlled the zone design are shown. Where a column exists above the t, the shear in that column for the controlling load combination is reported. Where a web plate is required the thickness of web plate required to resist the applied load is provided. The capacity of the column web with the actual thickness of the web plate as reported in the final design section is reported. If the plastic capacities of the beams at a t are used to determine zone forces, then no load combinations are reported.

Equation K1-9 [AISC ASD 9th Only], Required Stiffener Area [LRFD, CAN, AS4100]

For ASD 9th, the force, associated load combination and the required area of stiffeners is reported per AISC specification K1.9. For AISC 360 and LRFD 3rd the required area is calculated per equation 4.3-1 of the AISC Design Guide 13. For AS4100/CAN/CSA it represents the tension or compression force on a column flange, less the column capacity at that point. The Ast shown in the report represents the total area required at that location, i.e. it represents the sum of the areas of two individual stiffeners.

Compression (Tension similar)

The flanges of a framing beam apply a compression force on the flange of the column, depending on the loads applied on the member, and the load combination under consideration. The type of t check performed is listed in the left most column. Note that some checks such as Web Buckling, are only reported where concurrent-compression forces are calculated (refer to t-criteria, geometry section).

Flange

The beam flange under consideration. Top refers to the top flange of the beam framing into the column flange.

Force

The maximum compressive force, from all the load combinations, for each flange.

LCo

The load combination number that resulted in the maximum compressive force reported in the previous column. Where the beam capacities are used for forces (refer to t-criteria, design-forces section), then no load combination is reported and the maximum flange force is assumed to apply for all checks.

Allow, Cap, Cap w/t

The allowable (or capacity) of the column for the check currently being performed. This may vary for each side of a column depending on the column and beam flange dimensions. If a web plate is provided then the allowable load (or capacity) includes the contribution of the web plate (hence the w/t designation). Note that for ASD if both a web plate and stiffeners are provided, then the Allow always includes the web plate contribution even though the column header only shows “Allow” and not “Allow w/t”.

Stiffen

If stiffeners are provided and the column capacity is exceeded on either side of the column then the need to provide a stiffener is indicated. Note that in some circumstances there is a need to only stiffen on one flange of the column, but if either side requires stiffening, then a Yes is displayed in this column.

tReqd

If a web plate (doubler) is provided without any stiffeners then this column is displayed. This column represents the thickness of the web plate required for the column to obtain adequate capacity to resist the applied load for this check. It


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Steel Standard Provisions Reports t Code Check represents the largest required thickness from side A and Side B (which may differ). All. W/t, Cap w/t If a web plate (doubler) is provided without any stiffeners then this column is displayed. This column represents the t capacity considering both the column and web plate. It should exceed the applied force for both side A and B for this check. It represents the smallest capacity calculated from side A and side B (which may differ).

4.6.7 Stiffener Design [AISC 9th Only] Where a stiffener is required to be designed as a column per ASD K1.8, or LRFD K1.9 then the results of this design are reported. The “stiffener column” dimensions are calculated as prescribed in these sections. Refer to the technical notes and the t criteria section for more information on the stiffener design.

4.6.8 Web Plate Details [AISC 9th Only] This section displays several items that may be of use to the engineer, as well as may have controlled the design of the web plate. The results displayed in this section are dependent on the criteria selected in the criteria-ts dialog. The maximum stiffener force through the web plate refers to the maximum load that must be transferred from a stiffener, through the web plate, into the column. This load can be used to size the welds of the stiffener to the web plate (or column web). The required web plate thickness for stiffener force is the thickness required of the web plate to resist the shear in the plate due to the maximum stiffener force reported above. The required web plate thickness to prevent plate buckling is the thickness required to avoid having to provide plug welds in the web plate. Refer to the AISC Design Guide 13 for more information on all of these checks.

4.6.9 BS5950 – Draft Amend, April 1998 / BS5950-1:2000 All output is the same as AISC ASD/LRFD unless noted otherwise.

Final Design Diagonal Stiffeners

RAM Structural System does not design the diagonal web stiffeners. However, the program does indicate where these are required and also reports the magnitude of the horizontal shear in the -zone section.

Results Zone


Diagonal Stiffener Req’d to Resist = The horizontal shear force that the diagonal stiffeners are required to resist.

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Steel Standard Provisions Reports Member Forces Required Stiffener Area

This is the total area of the two stiffeners required at a location to meet the bearing and tension requirements per 4.5.3.2 and 4.5.3.3. The reported area s for the cope dimension, which reduces the area of the stiffener at the column flange. The smaller of the column and the stiffener yield strength is used to calculate the required area. Note the stiffener yield strength specified by the engineer is not modified according to the final thickness the stiffener.

Stiffener Design Where a full-length stiffener is required to resist web buckling, then the design is performed according to specification 4.5.2.3. The “stiffener column” dimensions are calculated as prescribed in these sections. The smaller of the column design yield strength and the stiffener nominal yield strength is used to perform the check according to 4.5.2.3. Refer to the technical notes and the t criteria section for more information on the stiffener design.

4.6.10 Eurocode 3: BS EN 1993-1-8:2005 All output is the same as AISC ASD/LRFD unless noted otherwise in this section.

Zone Where required the web plate is sized to be equal to the column web thickness, but is rounded up to the closest web plate increment (as entered by the in the criteria-ts dialog). For design purposes only the thickness of the plate equal to the thickness of the web of the column is considered. In some rare circumstances the program may indicate that an adequate web plate cannot be designed, but the report will show that the provided web thickness exceeds that required. Refer to the technical section for a detailed explanation of why this might occur.

Stiffener Design The design parameters used to design the stiffeners as columns are reported. Note that while Lamda major is reported, the capacity of the stiffener Nb.Rd is calculated only based on the out-of-plane (Lamda minor) bending.

4.7 Member Forces The Member Forces report in Steel-Standard Provision Mode lists the member force results for a single member for all the selected load combinations (-defined and generated) in this mode. It also includes member information and the analysis criteria. This report can be printed for one member at a time (Single), for all in a fenced area (Fence), all of a specified frame number (Frame), all currently visible on the screen (Current View) or for all in the model (All). A separate output for each member is created. A report for all in a model can be quite lengthy. See the RAM Frame manual Reports chapter for a description of the various elements of this report.


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Steel Standard Provisions Reports Member Force Summary

4.8 Member Force Summary The Member Force summary report in Steel-Standard Provision Mode lists the member force results for all selected for all the selected load combinations (-defined and generated) in this mode. It also includes member information, the analysis criteria, and a list of load cases analyzed. This report can be printed for all of a specified frame number (Frame). A report for all in a model can be quite lengthy depending on the number of load combinations. See the RAM Frame manual Reports chapter for a description of the various elements of this report.

4.9 Member Force Envelope The Member Forces Envelope report in Steel-Standard Provision Mode lists the maximum and minimum member force results for all the selected load combinations (-defined and generated) in this mode. It includes member information, the analysis criteria and a list of load cases analyzed. This report can be printed for one member at a time (Single), for all in a fenced area (Fence), all of a specified frame number (Frame), all currently visible on the screen (Current View) or for all in the model (All). A separate output for each member is created. A report for all in a model can be quite lengthy. See the RAM Frame manual Reports chapter for a description of the various elements of this report.


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Steel Standard Provisions Reports Member Force Envelope



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Steel Seismic Provisions Post-Processors

5

While the standard provision specifications address the ability of the steel to adequately resist all the forces applied to the structure, the special seismic provisions ensure that the building is appropriately designed, proportioned and detailed to resist seismic loading in a ductile and life-safe manner. Therefore, the purpose of the Special Seismic Provision Post-Processors is to investigate each steel frame member and restrained (fixed) beam-column t for the design and detailing requirements of the selected steel design specification. The special seismic provisions are not meant to supplant the standard provision checks, in fact, the special seismic provisions depend on forces and combinations generated to perform standard provision checks. To this end the special seismic and the standard provision checks are tightly linked. Changes in forces, combinations, member sizes, criteria when in standard provision mode will change the available options and the results when in seismic provision mode. The seismic specifications currently implemented are the American Institute of Steel Construction Inc, (ANSI341-05) 2005 – Seismic Provisions for Structural Steel Buildings ASD and LRFD (Including Supplement No 1, November 2005), Steel Construction Inc, (ANSI341-02) 2002 – Seismic Provisions for Structural Steel Buildings LRFD, (AISC) 1997 – Seismic Provisions for Structural Steel Buildings LRFD (Supplement No.2), the Uniform Building Code (UBC) 1997 – Section 2210, Seismic Provisions for Structural Steel Buildings LRFD, and UBC 1997 – Section 2212, Seismic Provisions for Structural Steel Buildings ASD. Using Code-generated and/or -defined load combinations the detailing and strength requirements are checked for each member and valid ts, and the results displayed graphically. In addition to the screen display, several output reports are also available.

5.1 Modes RAM Frame is divided into three modes; Analysis mode (as described previously), Steel Mode (the Seismic Provision sub-mode which is described here) and the Drift Control mode. To access the Steel Seismic Provision Mode select the Mode-Steel-Seismic Provision command. This mode can also be entered by selecting the Steel mode and Seismic Provision sub-mode from the dropdown controls located on the dialog bar below the toolbars. Note that to access the Seismic Provision mode the engineer must first select the AISC ASD or LRFD steel design code in the Standard Provision Mode. Also, at least one selected load combination in the standard provision mode must contain a seismic load case. On initially entering Seismic Provision mode the Design Code dialog will automatically appear. The engineer selects their desired design code and associated design options in this dialog. This dialog can be displayed at any time when in this mode by selecting the Criteria-Codes command.


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Steel Seismic Provisions Post-Processors Load Combinations

5.2 Load Combinations Load combinations can be generated by the program and/or defined by the engineer. Load combinations must be defined before any post-processing can be done. The load combinations generated and created in this mode are only used where the selected code requires that the “Special (Amplified) Seismic Load Combinations” be applied. For AISC341-05 these Amplified Load Combinations refers to the combinations referenced in Section 4.1. The ASCE 7-05 amplified seismic combinations have been provided. In AISC 2002 (ANSI341-02) the term “Special Seismic Load Combinations” refers to the combinations referenced in section 4.1, for AISC 1997 they refer to load combinations 4-1 and 4-2, for UBC 1997 LRFD this refers to load combinations 3-7 and 3-8, while for UBC 1997 ASD this refers to load combinations described in section 2213.5.1. It is important to note that a large portion of the checks performed in the Seismic Provision mode use the load combinations defined in the Steel-Standard Provision Mode. The engineer should ensure that the currently selected standard provision load combinations (generated and custom) are appropriate for the checks to be performed in the Seismic Provision mode. The provisions of AISC341-05 are written for consistency with load combinations given in ASCE 7 (ASCE 2005) and IBC (ICC 2006). The provisions of AISC 2002 and 1997 are written for consistency with load combinations given in ASCE 7 (ASCE 2002) and IBC (ICC 2000). While AISC 2002 refers to the applicable building code as the source of the load combinations they should be consistent with the codes above to be applicable to the design provisions. Refer to the Section C4 in the commentary of the AISC 2002 specification for more information. After the Seismic Design Code dialog is closed the Load Combination Generation dialog box appears. This dialog is used to show the “Special Seismic Load Combinations” automatically generated by the program. The combinations generated are based on those load cases previously analyzed and selected in this dialog. The engineer can select to include any or none of the load cases in the generated list of combinations. Click the Apply button after selecting the appropriate load cases to automatically generate and view load combinations in this dialog. After load combinations are generated the engineer can decide which combinations to consider in the design. All rows of load combinations with the “Use” check box selected will be considered during post-processing. When this dialog is closed the can return to view or change their combinations by selecting the Combinations-Generate command. Custom load combinations (where the can select their own load factors) can be generated in the dialog displayed by selecting Combinations-Custom. Note that combinations created in any other mode are not automatically available in this mode, but must be copied and pasted into the appropriate mode if required. Once load combinations have been defined and selected, the Process menu commands become available. The Code Check, View/Update and Report commands can then be used as described in the next several sections.

5.2.1 Generated Load Combinations Refer to 2.4.1 Generated Load Combinations for additional information on generated load combinations. Note that the load combinations generated in this mode are only applied where the special amplified seismic load combinations are referenced in the selected design code. The system over-strength factor


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Steel Seismic Provisions Post-Processors Criteria (Omega) is required to automatically generate the seismic design load combinations. Omega is based on the building frame type and should be taken from the appropriate building code. For a structure that contains frames of more than one type (with different omega factors) the engineer will have to repeat the post-processing checks. The omega factor for a single frame type should be used to generate load combinations and the associated frames should be checked. This process should be repeated for each frame type.

5.2.2 Custom Load Combinations Refer to Section Custom Load Combinations for additional information on custom load combinations.

5.3 Criteria Below is a brief description of the global criteria that pertain to the Member and t Code Checks performed by all the design specifications. Technical descriptions of how each criterion is used in the Code Check are provided later in the manual. Most of these criteria are the same as that specified in the Standard Provision Mode (Refer to 2.5 Design Criteria). Only the code criteria dialog offers additional options, which are described below. Note that any changes to the criteria will invalidate not only the code checks already performed in this mode, but in the Standard Provision mode also. The Criteria menu commands are divided into three sections based on functionality. Namely there is a code command, followed by the group of member criteria items, followed by the t criteria items. Only the code command is discussed below as the other commands remain mostly unchanged from the Standard Provision Mode.

5.3.1 Codes On initially entering Steel-Seismic Provision Mode, the engineer is presented a Seismic Design Code. This dialog can subsequently be displayed by selecting the Criteria-Codes command. The choice of codes available to the engineer in this dialog is based on the steel design code specified in the standard provision mode. Strength seismic provision codes (AISC341-05 LRFD, UBC 1997 – LRFD, AISC-1997, AISC-2002) will be available if LRFD is the steel design code selected in standard provision mode. Similarly AISC341-05 ASD, UBC 1997 – ASD will be available if ASD is the steel design code selected in standard provision mode. This is because many of the checks performed in the seismic mode are dependent on the load combinations created in the standard provision mode. Depending on the seismic code selected different options will be made available to the engineer. A description of all the options follows. Apply One-andTwo Story Exceptions


This option typically applies to braced frame structures. Several of the design provisions provide exceptions if the structure is a low building (one-or two stories in height). Checking this option will indicate to the program that these exceptions are appropriate for this structure. If this option is selected then where applicable

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Steel Seismic Provisions Post-Processors Criteria and necessary the exception will be attempted. For AISC341-05 this criteria is only applicable to the exception for the column-beam moment ratio. Use Frame Nos. to Designate a Frame Line

This option applies to several of the braced frame types. While most of the seismic checks are performed on individual structural , some are performed on complete frames. By applying unique frame numbers to of individual braced frames, and checking this option, RAM Frame will perform these complete frame checks.

Perform FEMA 350

This option applies only to special moment resisting frames. When checked, the AISC 1997 and UBC1997 -zone and strong-column-weak-beam checks will be superseded by the equivalent checks in the Federal Emergency Management publication 350. If reduced beam sections are applied to beams they will be considered.

Use AISC358-05 Applicable only when AISC 341-05 is selected. This option indicates the provisions RBS Moment of AISC358-05 with respect to Beam Limitations, Column Limitations and t Connection (Beam-Column Limitations) will be verified for SMF and where applicable IMF frame and ts. Selection of this option provides the the ability to designate. Zone

The seismic zone of the structure. Affects which checks are performed for each frame type, as described in the associated building code.

Importance Factor

The importance factor assigned to the structure. Affects which checks are performed for each frame type, as described in the associated building code.

Over-Strength Factor / r Factor

This factor is used where required by the code to increase the yield strength of beams to ultimate levels. Only where specifically required by the code will the over-strength factor be applied. For example UBC 1997 refers to the over-strength factor in section 2213.7.5. For the AISC 1997/2002/2005 provisions this value is calculated by the program (Ry) and is based on the yield strength of the base material (according to the specification). For AISC341-05 if Use AISC358-05 RBS Moment Connection is selected this option is required to designate the factor to for peak connection strength per 2.4.3 of AISC 358-05.

EBF-Cd Factor

(AISC 1997/2002/2005 Only) This factor is used in accordance with AISC97/02 section 15.2g, AISC 341-05 15.2c, where the design story drift is required. RAM Frame considers the design story drift as Cd times the elastic story drift. Refer to the technical section and the AISC commentary for additional information. Selecting the option “Show this dialog when entering Seismic Provision Mode” will automatically display the code dialog each time the seismic provision mode is entered.

5.3.2 ASD/LRFD Criteria Refer to AISC ASD / LRFD Criteria for additional information on the steel design criteria associated with calculating the allowable stress or capacity of a member. Only the column moments and t forces criteria in the standard provision mode are not applicable to the seismic provision mode.


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Steel Seismic Provisions Post-Processors Assign Menu

5.4 Assign Menu The engineer has the ability to assign several design criteria and properties to each individual member. By selecting one of the Assign commands the appropriate criteria or property can be assigned to one or in the model. The assign options available to the engineer in this mode are typically organized based on member type (beam, column or brace). Most of the assign options were described in Section 2.6 Assign in the Standard Provision chapter. Only the Assign Frame Type and Assign Frame Number options are described below.

5.4.1 Frame Types Selecting the Assign-Frame Types command causes the Assign Frame Types dialog box to be displayed. From this dialog the engineer can assign frame types to all the Lateral Steel . The engineer must assign a Frame Type before a Code Check can be performed. The engineer should assign a frame type to all the of the frame. For example, the concentric frame designation should be assigned to the beams, columns and the braces of a concentric braced frame. If the engineer does not want the program to check an individual member then the member should have no type assigned to it. Note that the available frame types are dependent on the selected seismic provisions code. Note that the EBF frame type is only available if AISC 1997, AISC 2002 or AISC341-05 is the selected seismic code. A member code check can be performed for frame type BRB and BRB-V when a Star Seismic BRB size is assigned. After the appropriate frame type is selected from the dialog the engineer can assign the criteria to a single member (click on Single) or to multiple (click on Fence). If Single is clicked the dialog will close and a target cursor will be made available. Click on each section to assign the frame type to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the to assign the frame type to. To view member frame types select the appropriate option from the View- Dialog. If a frame type is assigned and then the seismic code is changed, all frame types not valid in the new seismic code will appear with a line drawn through the name.

5.4.2 Frame Numbers Selecting the Assign-Frame Numbers command causes the Assign Lateral Frame Numbers dialog box to be displayed. From this dialog the engineer can assign frame numbers to Lateral Frame . The primary purpose of the frame numbers is to group frame for output purposes. In Seismic Provision mode the frame numbers have design implications as described in the option Use Frame Nos. to Designate a Frame Line described in Codes. Enter a number in the Frame Number edit box to assign to . Select the member types to assign this frame number to by clicking the appropriate option box under the Assign To area. Note that different member types, within the same frame, can be assigned different numbers.


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Steel Seismic Provisions Post-Processors Process Menu After the appropriate frame numbers and member types values are specified, the engineer can assign the criteria to a single member (click on Single), to multiple (click on Fence) or to all (click on All). If Single is clicked the dialog will close and a target cursor will be made available. Click on each section to assign the Frame Number to. If Fence is clicked the dialog will close and a fence cursor will be made available. Click and drag a rectangle around all the to assign the Frame Number to. To view member frame numbers select the appropriate option from the View- Dialog.

5.5 Process Menu The Seismic Steel Post Processor has four actions that can be selected from the Process menu, these include Member View/Update, t View/Update, Member Code Check and t Code Check.

5.5.1 Member View/Update The Process-Member View/Update command is a powerful feature that allows the to view detailed results of the design and detailing checks performed on the member for the currently selected seismic code (in Criteria-Code command). If desired the member size and yield strength can be modified and the Code Check repeated. The modified data can then be saved to the database without requiring returning to the RAM Modeler. When the View/Update command is issued, the target cursor appears with which the selects the frame member on which the Seismic Code Check is to be performed. The steel seismic provision member Code Check is then performed on the selected member. The check is performed for all the selected standard provision mode load combinations, as well as all the selected seismic mode load combinations where specified in the seismic code. The result of each check performed (including the code section), are displayed in the results list. The result of each check is indicated in the form of an icon in row of the performed check, in the dialog results list. Double-click on a particular check to get a brief description of the icon displayed for that check. The icons are discussed briefly at the end of this section (refer to 5.5.5 View/Update Result Icons). The header of this dialog box provides information about the frame member selected: floor type, member number, story level, and span coordinates. The currently assigned member size appears in the drop down Member Size control, along with the yield strength. The results of all the Seismic Code Checks for that member are represented by the stoplight color. If green the member successfully met all the requirements of the seismic code. If yellow then there are one or more seismic code checks that could not be performed and the engineer is responsible for completing. The results will clearly state which checks were not performed. If the stoplight is red then one or more of the seismic checks failed on that member. Changes can be made to the member size by selecting any size in the dropdown list, or to the yield strength by editing the value, and the member Code Check re-run by clicking the Analyze button. The results in the result list and the stoplight will be updated based on the results of the new Code Check. The modified member size and yield strength can be saved to the database using the Update Data Base button. When the database is changed in this way, the status indicator light at the right end of the status bar turns yellow. The model should be reanalyzed to calculate an accurate distribution of forces.


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Steel Seismic Provisions Post-Processors Process Menu The View Results button causes the Seismic Provision Member Code Check output to appear on the screen. It is a detailed report of the Seismic Code Check results. The report includes design parameters and criteria, the controlling load combinations, calculated stresses and capacities, and the result of all checks performed.

5.5.2 Member Code Check The Process - Member Code Check command causes the design and detailing checks to be performed on all steel frame of the structure. The check is performed for all the selected standard provision mode load combinations, as well as all the selected seismic mode load combinations where specified in the seismic code. Once the Code Check is complete, the model is drawn on the screen with color-coded to indicate the status of each member. A color chart correlates member color with the status. This display reflects the controlling condition for each member based on all the checks performed on each member.

5.5.3 t View/Update The Process-t View/Update command is a powerful feature that allows the to view detailed results of the design and detailing checks performed on a restrained (moment, rigid) t, for the currently selected seismic code. If desired the column size and yield strength can be modified and the Code Check repeated. The modified data can then be saved to the database without requiring returning to the RAM Modeler. Selecting t View/Update causes the target cursor to appear. Click the target cursor on a steel t. This will cause the t View/Update dialog box to appear. The steel seismic provision t Code Check is then performed based on the frame type of the column at the t. For example, if the column is assigned a Special Moment Frame Type, and the beams Ordinary Moment Frame Type, then the t is checked as a Special Moment Frame t (Same as column). The check is performed for all the selected standard provision mode load combinations, as well as all the selected seismic mode load combinations where specified in the seismic code. The result of each check performed (including the code section), are displayed in the result list. The result of each check is indicated in the results list in the form of an icon in the row of the performed check. Double-click on a particular check to get a brief description of the icon displayed for that check. The icons are discussed briefly at the end of this section (refer to View/Update Result Icons). The header of this dialog box provides information about the frame member selected: floor type, member number, story level, and span coordinates. The currently assigned column size appears in the drop down Column Size control, along with the column yield strength. The results of all the Seismic Code Checks for that t are represented by the stoplight color. If green the t successfully met all the requirements of the seismic code. If yellow then there are one or more seismic code checks that could not be performed and the engineer is responsible for completing. The results will clearly state which checks were not performed. If the stoplight is red then one or more of the seismic checks failed on that t. Changes can be made to the member size by selecting any size in the dropdown list, or to the yield strength by editing the value, and the member Code Check re-run by clicking the Analyze button. The results in the results list and the stoplight will be updated based on the results of the new Code Check.


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Steel Seismic Provisions Post-Processors Process Menu Once a satisfactory t column member has been found, click the Update Database button to save it. Notice that when a new size is saved to the database the status indicator light turns yellow and a reanalysis is suggested to obtain accurate member forces. The View Results button causes the Seismic Provision t Code Check output to appear on the screen. It is a detailed report of the Seismic Code Check results. The report includes design parameters and criteria, the controlling load combinations, calculated stresses and capacities, and the result of all checks performed.

5.5.4 t Code Check The Process-t Code Check command causes all lateral I-Section moment (rigid) connection ts to be evaluated based on the selected seismic design specification and frame type. The check is performed for all the selected standard provision mode load combinations, as well as all the selected seismic mode load combinations where specified in the seismic code. Refer to Assumptions and Limitations, for the criteria by which the ts are validated and checked. Once the Code Check is complete, the model is drawn on the screen with ts color-coded to indicate the status of each member. A color chart correlates member color with the status. This display reflects the controlling condition for each t based on all the checks performed on each t. No t Code Checks are performed for hanging.

5.5.5 View/Update Result Icons An icon that represents the result of each seismic check appears in each row in the results list of the View/Update dialog. Double-click on a particular row to get a brief description of the icon displayed for that check. Icon

Description This icon represents that information is going to be provided to the . For example, this result will appear if the engineer performs a view update on a member to which no frame type has been assigned. Refer to Frame Types for how to assign frame types to prior to performing a view update.

Information Only

Detailing Requirements Only


This icon represents the fact that this check is a detailing requirement. For these checks RAM Frame will provide the engineer with any required values to assist them in completing the detailing requirement. The member cannot fail because of these type checks.

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Steel Seismic Provisions Post-Processors The Design Process Icon

Caution

Additional Check Required

No Good, Exception Not Attempted (Yellow)

Description This icon represents a check that could not be performed by RAM Frame because some unusual situation was encountered. It is the engineer’s responsibility to perform these additional checks. For example, a t check where the t is invalid (Refer to Assumptions and Limitations) will cause this result. This icon represents a check that could not be completed. It is the engineer’s responsibility to perform these additional checks. For these checks RAM Frame will provide the engineer with most of the information required to complete this check.

This icon represents a check that was unsuccessful, but one or more exception could not be performed. RAM Frame will try and exhaust all possibilities (attempt all exceptions) before failing a member or t. If the member fails all the checks RAM Frame performs, but one or more exceptions could not be performed then Caution Failure is reported. If the engineer can successfully perform the exception then this member may be acceptable. This icon represents a check that was unsuccessful. All exceptions for that check were also performed and failed. RAM Frame will try and exhaust all possibilities (attempt all exceptions) before failing a member or t.

No Good (Red) Successful

This icon represents a check that was successful.

Note: Some checks may contain a “-” to the left of the icon. The symbol represents the fact that this check has another check as an exception. The first subsequent result listed in the results lists without the “-” is that exception check. Therefore, if a check fails but has a “-” symbol, and the exception check is OK, then that member will be acceptable and the stoplight will be green.

5.6 The Design Process The design of a structural steel building is iterative in nature. The engineer is responsible for meeting the requirements of several specifications. It is customary for the engineer to initially proportion and design to adequately resist the applied gravity and lateral loads. Within the context of the RAM Structural System this is performed in the standard provision mode. The engineer can then check the structure in the seismic provision mode for compliance with the requirements of the appropriate special seismic provision code.


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Steel Seismic Provisions Post-Processors The Design Process Initially member sizes are assigned to frame in the RAM Modeler, or for steel beams and columns, by performing a Design All in the RAM Steel Beam and Column Design module. Load cases are defined and an initial analysis is run in Analysis mode. The engineer switches to SteelStandard Provision mode, selects a steel design code and performs a member and/or t code check. The engineer can then use the tools available in the Steel - Standard Provision mode to adequately size the steel beams, columns and braces of the structure, to resist the applied gravity and lateral loads. Once adequate member sizes are assigned the engineer can switch to the Steel - Seismic Provision mode to check the selected against the requirements of the selected Seismic specification. On initially entering Steel – Seismic Provision Mode the engineer is required to select a special seismic provision code. The choice of codes available to the engineer is based on the steel design code specified in the standard provision mode. Strength seismic provision codes (UBC 1997 – LRFD, AISC 1997, AISC 341-02 and AISC341-05 LRFD) will be available if LRFD is the steel design code selected in standard provision mode. Similarly AISC341-05 ASD or UBC 1997 – ASD will be available if ASD is the steel design code selected in standard provision mode. Depending on the seismic code selected different options will be made available to the engineer on this dialog. Refer to Codes for a description of all the options available. When the code dialog is closed the load combination dialog will automatically appear. This dialog is used to generate the special seismic provision load combinations. These combinations only apply to those checks that explicitly specify their use (refer to Load Combinations). Note that for many of the seismic checks the standard provision load combinations are used. For those checks RAM Frame uses the valid (selected and available) generated and custom combinations from the Standard Provision Mode. Before performing a code check on the structure the engineer is responsible for specifying the frame type of each structural steel member. Each frame member is assigned a frame type by selecting the command Assign-Frame Type, choosing the appropriate frame type from the available types, and asg the type to the appropriate . The engineer should refer to the appropriate building code for details on classification of frames. All the that comprise a single frame should be assigned the same frame type. That is, the columns, beams and braces of a braced frame should all be assigned the same frame type. The same is true for a moment frame structure. The model will now be available to perform special seismic provision checks. For the member and t code check the color-coding identifies the status of the member or t for all the seismic checks performed. The and ts can then be investigated on an individual basis, and resized using the View/Update command until a suitable design is found. The new size is then saved to the database using the Update Database command in View/Update. Sizes can also be assigned to using the assign size commands (from the Assign-Beam/Column/Brace-Size command) in this mode. Once the status of all the are acceptable to the engineer the structure should be reanalyzed in Analysis Mode. This is to obtain a valid analysis (member forces) based on any new sizes. Once reanalyzed the Standard Provision member and t code check should be performed again before returning to the Special Provision Mode. In Seismic Provision mode the and ts should be rechecked (Process-Member Code Check, Process-t Code Check). It is possible that the status of some or ts will now be unacceptable. This is because of the redistribution of forces caused by the new sizes. If so, they can be modified once again with the View/Update command, and the process repeated. This process of analyzing, standard and seismic code checking and modifying is repeated until all are within the limits acceptable to the engineer.


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Steel Seismic Provisions Post-Processors Exiting and Changing Modes

5.7 Exiting and Changing Modes To switch to Analysis Mode 1. Select the Mode-Analysis-Load Cases command. Alternatively select Analysis from the Mode dropdown control available on the dialog bar below the toolbar.

5.7.1 To switch to Steel-Standard Provision Mode 1. Select the Mode-Steel-Standard Provision command. Alternatively, select the Standard Provision item from the dropdown control on the dialog bar below the toolbar.

5.7.2 To exit RAM Frame 1. Do either of the following: Double clicking the Control Bar in the upper left corner of the RAM Frame Window or alternatively click the Control Bar and selecting the Close command from the drop down menu. or Select the File - Exit command.


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Steel Seismic Provisions Post-Processors Exiting and Changing Modes



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Steel Seismic Provisions Technical Notes

6

Seismic code-check capabilities are available for steel and moment frame ts. The seismic provision checks include checking the member design and detailing requirements against the requirements of the selected seismic code. Note that for CAN/CSA S16-01, the Seismic Design Requirements of Chapter 27 have not been implemented. Steel Design Codes The seismic steel post-processors are based on the requirements of the code specifications published by: The International Conference of Building Officials (ICBO) as found in the 1997 Uniform Building Code, Volume 2, American Institute of Steel Construction as found in Seismic Provisions for Structural Steel Buildings. These specifications include: • American Institute of Steel Construction, Inc. – Seismic Provisions for Structural Steel Buildings (2005, ANSI/AISC 341-05, March 9, 2005, including supplement No.1 Dated November 16, 2005) • American Institute of Steel Construction, Inc. – Seismic Provisions for Structural Steel Buildings (2002, ANSI 341-02, May 21, 2002) • American Institute of Steel Construction, Inc. – Seismic Provisions for Structural Steel Buildings (April 15, 1997) • Uniform Building Code 1997 – Section 2212, Seismic Provisions for Structural Steel Buildings – Allowable Stress Design and Plastic Design. • Uniform Building Code 1997 – Section 2210, Seismic Provisions for Structural Steel Buildings – Load and Resistance Factor Design Specifications for Structural Steel Buildings. The requirements of the latest Supplement to the AISC 341-05 requirements have been implemented: • AISC Seismic Provisions for Structural Steel Buildings. Supplement No.1. (November 16, 2005). The requirements of the latest Supplement to the AISC 1997 requirements have been implemented: • AISC Seismic Provisions for Structural Steel Buildings (1997) Supplement No.2. (February 1999). The requirements of the latest Federal Emergency Management Agency Guidelines have been implemented for UBC 1997 LRFD and AISC 1997: • FEMA 350, Recommended Seismic Criteria for New Steel Moment-Frame Buildings, (July 2000), including June 18, 2001 errata. When selected by the the provisions from this code can be checked in lieu of the equivalent UBC 97 or AISC 1997 provisions.


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Steel Seismic Provisions Technical Notes Load Combinations

6.1 Load Combinations The special seismic load combinations required by the specified Building Code or Standard are generated automatically by the program. The seismic load combinations are generated automatically based on the selected seismic code. The generated load combinations are those required by the seismic code when the ultimate seismic force is being calculated. For AISC 341-05 ASD the load combinations referred to in section 4.1 are taken from ASCE 7-05/IBC 2006 (12.4.3.2) and represent: ( 1.0 + 0.14 * Sds )D ± 0.7Ω o QE ( 1.0 + 0.105 * Sds )D ± 0.525Ω o QE + 0.75 L + 0.75(Lr or S) ( 0.6 – 0.14 * Sds )D ± 0.7Ω o QE For AISC 341-05 LRFD the load combinations referred to in section 4.1 are taken from ASCE 7-05/IBC 2006 (12.4.3.2) and represent: ( 1.2 + 0.2 * Sds )D + (1.0 or 0.5)L + 0.2 S ± Ω o QE ( 0.9 – 0.2 * Sds )D ± Ω o QE For AISC 2002 the load combinations referred to in section 4.1 are taken from IBC 2000/2003 and represent: ( 1.2 + 0.2 * Sds )D + 0.5L + ( 0.2 or 0.7 ) S ± Ω o QE ( 0.9 – 0.2 * Sds )D ± Ω o QE For AISC 1997 the load combinations refer to the load combinations 4-1 and 4-2 as follows: 1.2D + 0.5L + 0.2S ± Ω o QE

(4-1)

0.9D ± Ω o QE

(4-2)

For UBC 1997 LRFD the load combinations refer to the load combinations 3-7 and 3-8 as follows: 1.2D + 0.5L ± Ω o QE

(3-7)

0.9D ± Ω o QE

(3-8)

For UBC 1997 ASD the load combinations refer to the load combinations defined in section 2213.5.1 as follows: 1.0D + 0.7L ± Ω o QE

(5-1)

0.85D ± Ω o QE

(5-2)

It is important to note that a large portion of the checks performed in the Seismic Provision mode use the load combinations defined in the Steel-Standard Provision Mode. The engineer should ensure that the currently selected standard provision load combinations (generated and custom) are appropriate for the checks to be performed in the Seismic Provision mode. Dynamic and “Other” load cases are not included in the generated combinations but can by used in combinations created by the . The can create any number of additional load combinations.


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Steel Seismic Provisions Technical Notes Code Check When creating -specified load combinations, the plus and minus combinations should both be explicitly created. The load factors should be “normalized” as explained above.

6.2 Code Check The seismic provisions can typically be broken into those checks that apply to individual (columns, beams, and braces), a group of (columns and beams at a t) or to whole structural systems (individual frames or the entire building). RAM Frame has broken the provisions into those that apply to and those that apply to ts. Checks on entire frames or the structure as a whole are grouped into the individual member or t checks where required. Note that many of the seismic requirements are related to seismic detailing. RAM Frame provides information where possible to enable the engineer to complete the detailing requirements. For example, while RAM Frame does not currently design connections, the required connection forces will be reported to the engineer in the output. The engineer should refer to the applicable seismic code for those detailing and design requirements not currently addressed by RAM Frame. Note that no standard provision checks are performed in seismic provision mode. The engineer is responsible for confirming that all the are capable of resisting the standard provision load combinations. Only the “added provisions” are performed in the special seismic mode. The engineer should refer to Member Code Check, for a description of how member allowable stress and capacity values are calculated for the individual . Note that changes made to criteria in seismic mode will invalidate the results of the standard provision mode and require the engineer to redo the code check in the standard provision mode. Note: The “§” symbol is used in this chapter to indicate references to the specifications.

6.2.1 Assumptions and Limitations The special seismic provisions are typically prescriptive in nature and are sometimes open to interpretation by the engineer. This section provides the engineer with information on how RAM Frame has implemented many of the specification requirements. Specifically it attempts to identify all the assumptions that are made by the program, and list some of the limitations. The engineer is encouraged to refer to the actual code requirements in the applicable code as most of the nomenclature used below is taken directly out of the applicable code. The engineer is responsible for performing all code requirements that are not performed by RAM Frame. In this section the assumptions and limitations are organized according to the actual code section referenced. That is, each section is numbered according to the section in the code that is being discussed.


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Steel Seismic Provisions Technical Notes Code Check

6.2.2 Reduced Beam Section Check RAM Frame now performs a check of all beams that have reduced beam sections to that the beam has the capacity to carry the bending moment that occurs at the center of the reduced beam section, due to all standard provision load combinations. Refer to beam output to see the results of this design check.

6.2.3 AISC 2005/2010 (ANSI 341-05/10) – ASD and LRFD Note: AISC 2010 (ANSI 341-10) references placed in [ ] immediately follow the AISC 2005 (ANSI 341-05) references.

Limitations With the exception of the AISC 360-10 steel design code, the AISC 341-05 code check will always use the AISC 360-05 steel design code to perform any member design capacity calculations, irrespective of the selected code in the Steel Standard Provision mode. That is, if AISC LRFD 3rd is selected in Standard mode but AISC 341-05 LRFD is the selected code in Seismic Mode code, then all member capacities will be calculated using AISC 360-05 LRFD, not AISC LRFD 3rd. Conversely, when AISC 360-10 LRFD is selected in the Standard mode but AISC 341-05 LRFD is selected in Seismic Mode code, then all member capacities will be calculated using AISC 360-10 LRFD. A few individual checks are not performed. When a check is necessary and is not performed by the program it will be indicated in the output. It is recommended that P-Delta be performed in lieu of using B2 when performing an AISC 341-05 design check.

§3.[B1] General Seismic Design Requirements The is not required to assign a seismic category. If the engineer selects to use this code then all the provisions are assumed to be applicable.

§4.[B2] Loads, Load Combinations, and Nominal Strengths Where standard provision load combinations are referred to (such as in Section 4.1 in regard to the applicable building code), RAM Frame will use the current load combinations from the standard provision mode. The engineer is responsible for ensuring that an appropriate set of loads and combinations are defined in the standard provision mode prior to switching to special seismic mode and performing a code check. Amplified Seismic load combinations as referenced in section 4.1 are generated within this mode. For member code checks of SCBF and BRBF column frame types using the AISC 341-10 code, a set of generated load combinations independent of the generated combinations are evaluated. The set of combinations use (+ 1.0 Emh) for LRFD and (+ 0.7 Emh) for the ASD code as the seismic term in combinations with the analyzed gravity load cases. Emh is determined using the analysis conditions specified in Section F2.3 and F4.3 of AISC 341-10 for SCBF and BRBF columns respectively.


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Steel Seismic Provisions Technical Notes Code Check Note: It is recommended that generated seismic combinations are created to ensure that correct parameters (Sds etc.) are used. For models without generated seismic load combinations (where only custom seismic load combinations are defined), combinations are internally generated assuming the default template values. The provisions of AISC 2005 and AISC 2010 are written for consistency with load combinations given in ASCE 7 and IBC (ICC 2006 and ICC 2009). While AISC 341-05 refers to the applicable building code as the source of the load combinations they should be consistent with the codes above to be applicable to the design provisions. Refer to Sections C4 and B2, respectively, in the commentaries of the AISC 2005 and AISC 2010 specifications for more information. Nominal strengths are based on the following specifications: ANSI/AISC 360-10, Specification for Structural Steel Buildings (June 22, 2010), published by the American Institute of Steel Construction in Steel Construction Manual (14th Edition). ANSI/AISC 360-05, Specification for Structural Steel Buildings (March 9, 2005), published by the American Institute of Steel Construction in Steel Construction Manual (13th Edition).

§6.[A3] Materials §6.1 Material Specification No steel grade is specified in RAM Frame and as such the engineer is responsible for ensuring compliance with this provision.

§6.2 Material Properties for Determination of Required Strength of Connections or Related The Ry values are calculated according to Table I-6-1. Note that all Hollow Structural Sections (HSS and TS) are assigned a Ry of 1.4, Pipe (CHS) sections an Ry of 1.6 and for other rolled sections Ry is based on the engineer specified yield strength as follows: 36ksi – Ry = 1.5 42ksi – Ry = 1.3 All others Ry = 1.1 Ry = 1.0 for SidePlate Connections

§8.[D] §8.2 Local Buckling Only where specifically required by the specification and footnotes to Table I-8-1 are the checked against the limiting width to thickness rations of Table I-8-1 and AISC 360 Table B4.1. Where applicable, Pu (LRFD) and Pa (ASD) are taken as the maximum axial tension and compression force on the member from all the selected standard provision load combinations. The calculation of the b/t, d/t, and h/t ratios are based on the AISC 360 specification. Note that for webs of beams in Special Moment Frames (SMF) there are some conflicting limits. The program will limit the section web to the smaller of :


125


Steel Seismic Provisions Technical Notes Code Check 2.45 Es / F y and 1.12

Es Fy

(

2.33 − Ca

)

§[D1.1b] Width-to-Thickness Limitations of Steel and Composite Sections AISC 341-10, are checked against the limiting width to thickness ratios of Highly Ductile or Moderately Ductile of Table D1.1.

§8.3 [D1.4a] Column Strength AISC 341-10 The amplified load combinations are utilized to calculate Pu (LRFD) and Pa (ASD). AISC 341-05 This provision is applied to all columns, irrespective of frame type. The standard provision load combinations are utilized to calculate Pu (LRFD) and Pa (ASD). When Pu/ϕPn > 0.4 (LRFD) or Ωa/Pn (ASD) the amplified seismic load combinations generated in the seismic provision mode (see 4. above) are used to determine the required compressive and tensile strength. The limiting provisions of 8.3(2) are not applied which could result in conservative axial forces being considered in 8.3(1).

§8.4 [E2.6g] Column Splices Detailing information regarding the magnitude of the required splice force to be designed and detailed are calculated and presented. The engineer is responsible for the design of the splice connection components.

§8.5 Column Bases No calculations or information is provided with respect to column base design. Refer to the specification for additional information or requirements.

§9.[E3] Special Moment Frames (SMF) §9.2 Beam-to-Column ts and Connections Connections in Special moment frames require pre-qualification according to Section 9.2b achieving the performance requirements of §9.2a. The engineer is referred to §9.2b which references AISC 358-05 as a source for several connections that are considered pre-qualified. When calculating the required shear strength per §9.2a (9-1) all standard provision load combinations with seismic load cases are considered, replacing the seismic load case and factor with the force produced from a term 1.0E where E = 2.0 [1.1 Ry Mpr] / L. The 1.0 load factor will replace the load factor associated with the seismic load case in the underlying load combination. L is taken as the distance between reduced beam sections, if they exist, otherwise L is the distance between the face of


126


Steel Seismic Provisions Technical Notes Code Check the columns ing the beams. Mpr is the ultimate strength of the beam in bending at the reduced beam section, if it exists, otherwise it is from the full beam section. Note: For ASD the Mpr term is not divided by Ω (1.5) as is typically performed in other similar calculations such as §9.3a. This may produce conservative shear forces for ASD design if the Ω factor is then assigned to the capacity calculations. All SidePlate beam-to-column ts demonstrate conformance with 9.2a as indicated in 9.2b per ICC-ES ESR-1275 All SidePlate beam-to-column ts demonstrate conformance with §9.2a as indicated in §9.2b per ICCES ESR-1275

§358-05 5.8-6 [358-10 5.8-6] Moment force at Column Face Where AISC358-05 Section 5.8-6 RBS Connection is designated in the Codes dialog box the maximum force at the column face is calculated and checked relative to equation 5.8-6. If this check fails the RBS dimensions can be adjusted or section size changed to meet this requirement. The load applied between the face of the column and the RBS is not considered in the calculation of the maximum moment on the face of the column.

§9.3 [E3.6e] -Zone of Beam-to-Column Connections Only connections parallel to the column web are considered and checked by the program. The required shear strength of the -zone is determined from the summation of moments at the column faces as determined by projecting the expected moments at the plastic hinge locations (RBS if they exist) to the column faces. The material factor ϕv = 1.0 (LRFD) and Ωv = 1.50 (ASD) in all cases. Note, for the determination of the zone forces the moment at the face of the column is calculated as described above BUT for ASD the Mpr term is calculated as ( 1.1 / 1.5 ) Ry Fy (note the 1.5). This produces equivalent level of design for ASD and LRFD zones. If AISC 358-05 RBS Moment Frame Connections are designated in the Code Dialog then the 1.1 factor on the Mpr calculation is replaced with the r value provided by the for Special Moment Frame ts. Pu and Pa (for zone capacity calculation) is taken as the maximum axial load on the column at the t from all standard provision load combinations. If the beams frame into the flange of the column at some angle other than parallel to the column web, then the component of the beam force parallel to the column web is used. No torsion force in the beam, should it exist, is resolved into a force on the face of the column if the beam is not parallel to the column web. Zone shear is calculated as the moment divided by the distance between the center of the beam flanges. Note that the requirements of 9.3b are irrespective of the magnitude of the shear force. The program can consider the use of plug-welds to reduce the required web plate thickness, refer to the Criteria - ts menu command to select this plug weld option.

§9.4 Beam and Column Limitations Refer to the requirements of 8.2b [D1.1b]. Per Table I-8-1 footnote 3, SMF columns will be checked to comply with λps in Table I-8-1 when Equation 9-3 is less than 2.0, else they will be checked against AISC 360 Table B4.1.


127


Steel Seismic Provisions Technical Notes Code Check If AISC 358-05 RBS Connections are designated by the engineer in the Codes dialog then the beam bf / 2 x tf value is performed based on the dimensions of the RBS per AISC 358-05 (6). The value bf shall not be taken as less than the flange width at the ends of the center two-thirds of the reduced section.

§358-05 5.3.1 [358-10 5.3.1] Beam Limitations If AISC 358-05 Section 5.3.1 RBS Moment Connections are designated in the Codes dialog box then all the additional Beam Limitation requirements of this section, beyond those of AISC 341-05, will be performed. For 5.3.1(2) the beam depth will be used to assess if the section size exceeds the largest W36 section depth. It may be possible however that a beam with greater depth is appropriate (or shallower depth inappropriate) if they are not pre-qualified.

§358-05 5.3.2 [358-10 5.3.2] Column Limitations If AISC358-05 Section 5.3.2 RBS Moment Connections are designated in the Codes dialog box then all the additional Column Limitation requirements of this section, beyond those of AISC 341-05, will be performed.

§9.5 [E3.6f] Continuity Plates If AISC358-05 RBS Connections are designated by the engineer in the Codes dialog then the AISC 358-05 2.4.4 requirements will be performed. In this check the program will assess the column dimensions and indicate when stiffeners are required to be provided.

§9.6 [E3.4a] Column-Beam Moment Ratio The calculation of ΣM×pb is determined by summing the projections of the expected beam flexural strength(s). The applied loads between the RBS (if it exists) and the column face is not considered. If the beams frame into the flange of the column at some angle other than parallel to the column web, then the component of the beam force parallel to the column web is used to calculate M×pb If no reduced beam section is specified on a member than the capacity of the full member is utilized. If AISC 358-05 RBS Moment Frame Connections are designated in the Code Dialog then the 1.1 factor on the Mpr calculation is replaced with the r value provided by the for Special Moment Frame ts. If SidePlate Connections are designated in the Code Dialog then the 1.1 factor on the Mpr calculation is replaced with 1.2 and the Strong Column – Weak Beam check is performed as follows: ΣZ

(

)(

)

)(

)

Pu h f − c y Ag h − d pl − dc / 2 Σ1.21 f y Z b

ΣZ c

(

fy Pa h − 1.5 Ag h − d pl − dc 2 1.21 Σ f Z 1.5 y b

> 1.0 for LRFD, and

> 1.0 for ASD

where dpl dc h

= = =

depth of SidePlate depth of column average story height

For the Exception (if necessary) the design shear strength of a story is calculated as the component of the major axis shear strength, of all the columns in the direction of the column under consideration,


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Steel Seismic Provisions Technical Notes Code Check added together. All columns, not only those columns of the special moment frame type, are considered. The exception requiring consideration of only exempt columns is not considered.

§9.7 [E3.4c(2)] Beam-To-Column Connection Restraint A column will be assumed to remain elastic only if the ratio from Equation 9-3 is greater than 2.0. A t is considered restrained if contained within a deck, is a beam frames into the weak axis of the column, or by the specifying that the column is braced. If the indicates that the minor axis of the t column is unbraced then the physical bracing (deck or beams) is ignored and the t is considered unrestrained. The deck is only considered to brace the t at the elevation of the top flange of the beams framing into the flanges of the column. If a beam (not a joist) is determined to frame into the minor axis of the column at the t, then RAM Frame assumes that the t is restrained at the elevation of both the top and bottom flanges of the framing beams.

§9.8 [E3.4b] Lateral of Beams Pertinent detailing information regarding stiffness and spacing of lateral bracing required of beams is provided. Beams framing into the side of a lateral girder are assumed to brace both the top and bottom flange of the girder. Joists framing into the side of a lateral girder are assumed to brace only the top flange of the girder. If required the engineer can assign brace points to all lateral beams to meet this provision. The brace points should represent actual physical bracing to be provided on the constructed beam.

§10. [E2] Intermediate Moment Frames (IMF) §10.2 Beam-to-Column ts and Connections When calculating the required shear strength per 9.2a (by reference from 10.2) all standard provision load combinations with seismic load cases are considered, replacing the seismic load case and factor with the force produced from a term 1.0E where E = 2.0 [1.1 Ry Mpr] / L. The 1.0 load factor will replace the load factor associated with the seismic load case in the underlying load combination. L is taken as the distance between reduced beam sections, if they exist, otherwise L is the distance between the face of the columns ing the beams. Mpr is the ultimate strength of the beam in bending at the reduced beam section, if it exists, otherwise it is from the full beam section. Note: For ASD the Mpr term is not divided by Ω (1.5) as is typically performed in other similar calculations such as 9.3a. This may produce conservative shear forces for ASD design if the Ω factor is then assigned to the capacity calculations. IMF connections are required to be prequalified, refer to the AISC 358-05 for more information. All SidePlate beam-to-column ts demonstrate conformance with 10.2a as indicated in 10.2b per ICCES ESR-1275


129



§10.4a [E2.5a] Beam and Column Limitations Refer to the requirements of 8.2a – Only AISC 360 B4.1 limits are required to be met.

§358-05 5.3.1 [358-10 5.3.1] Beam Limitations If AISC358-05 Section 5.3.1 RBS Moment Connections are designated in the Codes dialog box then all the additional Beam Limitation requirements of this section, beyond those of 341-05, will be performed. For 5.3.1(2) the beam depth will be used to assess if the section size exceeds the largest W36 section depth. It may be possible however that a beam with greater depth is appropriate (or shallower depth inappropriate) if they are not pre-qualified.

§358-05 5.3.2 [358-10 5.3.2] Column Limitations If AISC358-05 Section 5.3.2 RBS Moment Connections are designated in the Codes dialog box then all the additional Column Limitation requirements of this section, beyond those of 341-05, will be performed.

§10.5 [E2.6f] Continuity Plates If AISC358-05 RBS Connections are designated by the engineer in the Codes dialog then the 358-05 2.4.4 requirements will be performed. In this check the program will assess the column dimensions and indicate when stiffeners are required to be provided.

§10.8 [E2.4a] Lateral Bracing of Beams Pertinent detailing information regarding stiffness and spacing of lateral bracing required of beams is provided. Beams framing into the side of a lateral girder are assumed to brace both the top and bottom flange of the girder. Joists framing into the side of a lateral girder are assumed to brace only the top flange of the girder. If required the engineer can assign brace points to all lateral beams to meet this provision. The brace points should represent actual physical bracing to be provided on the constructed beam.

§11.[E1] Ordinary Moment Frames (OMF) §11.2 [E1.6b] Beam-to-Column ts and Connections When calculating the required shear strength per Section 9.2a (by reference from Section 10.2) all standard provision load combinations with seismic load cases are considered, replacing the seismic load case and factor with the force produced from a term 1.0E where E = 2.0 [1.1 Ry Mpr] / L. The 1.0 load factor will replace the load factor associated with the seismic load case in the underlying load combination. Lis taken as the distance between reduced beam sections, if they exist, otherwise L is the distance between the face of the columns ing the beams. Mpr is the ultimate strength of the beam in bending at the reduced beam section, if it exists, otherwise it is from the full beam section. All SidePlate beam-to-column ts demonstrate conformance with 11.2

§11.5 [E1.6b] Continuity Plates The engineer should provide continuity plates in accordance with Section 11.5 of equal or greater dimension than the ed beam flanges. Refer to the code for detailing information regarding the strength of the welded ts.


130



§12.[E4] Special Truss Moment Frames (STMF) STMF’s are not designed or checked within the program.

§ [E5]. Ordinary Cantilever Column Systems (OCCS) - ANSI 341-10 ASD and LRFD OCCS's are designed and checked within the program.

§ [E6]. Special Cantilever Column Systems (SCCS) - ANSI 341-10 ASD and LRFD SCCS's are designed and checked within the program.

§13.[F2] Special Concentric Braced Frames (SCBF) §13.2 [F2.5] Bracing – Lateral Force Distribution The unbraced length of a brace is considered to be the length between the nodes at the brace ends. To perform the lateral force distribution checks on SCBFs, the engineer is required to assign the same frame number to all the braces in the same line of bracing. Also, the Use Frame Nos. to Designate a Frame Line option must be selected in the Seismic Code Dialog obtained by selecting the CriteriaCodes command. The b/t ratios of stiffened and un-stiffened elements are checked per §8.2b against the compactness requirements in AISC 360 specification Table B4.1 and the requirements of 8.2 (Table I-8-1). Angles are only checked for the requirements of Table I-8-1.

AISC 341-10 Analysis of SCBF Columns Member code check of SCBF columns follow the requirements of Section F2.3(i) where braces are assumed to resist forces corresponding to their expected strength in compression and tension and the requirements of Section F2.3(ii), in which braces in tension resist forces corresponding to their expected strength and braces in compression are assumed to resist their expected post-buckling strength.

Figure 8: To determine Emh for SCBF Column O, the effect of braces in frame lines A-O-B and X-O-Y are independently determined according to Section F2.3(i) and F2.3(ii). Frame lines A-O-B and X-O-Y are assumed to frame into the major and minor axes respectively of Column O. The tensile and compressive


131


Steel Seismic Provisions Technical Notes Code Check Emh values determined from the analyses are used in the load combinations for the applicable building code. Limitation: The analysis performed according to Section F2.3(i) and F2.3(ii) does not consider the interactive effect of axial loads on the column from braces in the two framing lines. The results from corner columns or columns with framing lines into the major and minor axes should be verified by the engineer.

§14.[F1] Ordinary Concentrically Braced Frames (OCBF) §14.2 Bracing To facilitate connection design the brace strength values are reported. All brace frames are not allowed to have braces with Kl/r larger than 4.0 Es / F y

§15.[F3] Eccentrically Braced Frames (EBF) The following frame configurations are considered valid EBF frames by the RAM Structural System.

Note: If any other lateral member (beam or column or brace) is ed by a link in any of the above configurations, the frame will not be considered a valid EBF frame.

§15.2 [F3.5b] Links §15.2a – The maximum axial force in the link is taken as the maximum axial load from all the standard provision load combinations. §15.2fb – The axial force (Pu (LRFD), Pa (ASD)) in the link is the same as that calculated for §15.2e. §15.2c – The link rotation angle is taken as the largest calculated link rotation from all seismic load cases. The program uses the approximate link rotation angle calculation described in the commentary. The formulae provided in the commentary are modified as follows to for unsymmetrical geometry. Note that the frame displacement (Delta) is calculated as the net difference in horizontal displacement of the column top node relative to the column bottom node, projected into the plane of the original frame. The story ht (h) is calculated as the node to node distance from the beam-column t


132


Steel Seismic Provisions Technical Notes Code Check down the column to the next braced level. The link length (e) is the clear length (from face of column if at a ). EBF beams are required to span between two steel, lateral columns.

Δ1

e γ

h θp L

Δ is calculated from the end furthest away from the link. Δ

θp = h γ=

θ p(L − e) e

Figure 9: Configuration 1

Δ1

a

e

γ2

b

γ1

h θp1

θp2 L


133



γ1 = θ p1 +

θ p2b + θ p1a e

γ2 = θ p2 +

θ p2b + θ p1a e


Δ1

γ1 e1

a

b

e2

Δ2 γ2

h θp1

θp2 L

γ1 = γ2 =

(θ p1 + θ p2) (e1 + a) 2

e1

(θ p1 + θ p2) (e2 + b) 2

e2

Figure 11: Configuration 3 The calculated angle is then multiplied by the Cd value provided by the engineer in the Codes dialog box, to produce the plastic link rotation angle. This magnified rotation angle is then compared to the code prescribed limits. The calculated plastic link rotation angle in conservatively not reduced by the elastic link rotation angle. For the central EBF configuration, where two different rotation angles are calculated, the larger angle is reported. Note: No additional consideration is given to the calculations for sloped beams, that is, the link displacement is assumed to be perpendicular to the link. Also, no consideration is given for rigid body translation and rotation that may exist in an EBF frame in the upper stories of a tall structure.

§15.3 [F3.5b(4)] Link Stiffeners Link Stiffeners are detailed in the output with a schematic diagram (not-to-scale) similar to that shown inf the following figure. In the output the table below the schematic provides details on the stiffener numbers and dimensions. The table contains the following columns.


134


Steel Seismic Provisions Technical Notes Code Check Link

link number on the beam (1 or 2)

e

the length of the link

#

number of equal spaces for the intermediate stiffeners

X

spacing of the first stiffener

WxT End

width and thickness of the end stiffeners

WxT Int

width and thickness of the intermediate stiffeners

Int. Stiff Sides the number of sides of the beam web that the intermediate stiffeners are required on

e # Equal Spc

LxWxT Int. (see table) LxWxT End (both sides)

§15.4 [F3.6c] Link-To-Column Connections §15.4a – Link-to-column connection design should be based on test results and are not designed in RAM Frame. §15.4b – If the beam-to-column connection is reinforced so as to preclude yielding over a length of the link the engineer is responsible for determining the applicability of the RAM Frame results. This situation is not currently considered in the EBF design performed by RAM Frame.

§15.6 [F3.6e] Diagonal Brace and Beam Outside of Link The design of Eccentric Braced Frames are sensitive to the geometric configuration of the braces (and link length). In particular the ability to get the beam outside the link to meet code specification may require a change in the geometry of the brace rather than an increase or decrease in beam size. The engineer is referred to the AISC website for references (Steel Tips) regarding efficient EBF brace configurations. §15.6a – To perform the diagonal brace capacity provision the link beam at the top of the brace is located and the link capacity (1.25 Ry Vn) is calculated. The analyzed load case that produces the largest shear in the identified link is also determined. The brace is then designed for a load combination that consists of a single term (load factor x load case). The combination factor is taken as the ratio of the link capacity to the maximum link shear force. The load case in the combination is that which produced the


135


Steel Seismic Provisions Technical Notes Code Check maximum link shear force. This load combination should thus produce the desired shear force (equal in magnitude to the link capacity) in the link. For example, if a link capacity is 100 kip, and the maximum shear in the link is 40 kip from load case E1, then the generated load combination is 100/40 E1 = 2.5 E1 (both positive and negative combinations are considered). All the above-mentioned parameters are shown on the report. Note: These calculated load factors could be fairly large in magnitude if the beam used for the link is overly conservatively sized or if the geometry of the braces is such that the link experiences more of a bending rather than a shear failure. §15.6b – The design of the beam outside the link is performed in a similar fashion to §15.6a. That is, the link(s) on a beam are identified and load combinations are generated based on the ratio of the link shear to link capacities. For each link on a beam there are two load combinations created (as described in §15.6a). These combinations are then used to determine if the beam (outside of the link) is adequate to resist the forces that would ensure link yielding before beam failure. Note: The code stipulates that the beam capacity (outside of the link) can be increased by Ry. In RAM Frame the program implements this provision by reducing the demand (load factor in the combination) by Ry. All the above mentioned parameters are shown on the report. §15.6d – The brace connection forces are taken as the maximum forces at the top of the brace, generated by the load combination(s) created according to §15.6a. The design of a column according to load combinations A4 and A5 is not performed as part of the seismic provisions, but rather as a part of the code check performed in standard provision mode. In seismic mode RAM Frame identifies all beams that frame into an EBF column and determines if they are EBF beams. If so, the links are identified and, similar to §15.6a, load combinations are generated that would result in the appropriate force being generated in the links and the column in consideration. In the event that there are non-EBF beams ed on the column the will be given a warning. The warning is to let the consider the fact that there may be a loading condition that would result in the non-EBF frame beam causing controlling loads on the column, prior to the EBF link beams yielding. This is most likely to be a consideration when the non-EBF beam frames into the column perpendicular to the EBF beams.

§16.[F4] Buckling Restrained Braced Frame (BRBF) §16.2 [F4.5] Bracing §16.2a. Steel Core – The brace design axial strength, ϕPysc (LRFD), and the brace allowable axial strength, Pysc /Ω (ASD), in tension and compression, according to the limit state of yielding, are determined as follows: Pysc = Fysc Asc ϕ = 0.90 (LRFD) Ω = 1.67 (ASD) Fysc is the Fymin value specified by the when asg the brace. Asc is the area of steel core of the size assigned by the . §16.2d. Adjusted Brace Strength – The adjusted brace strength in compression and tension are calculated as βωRyPysc and ωRyPysc respectively; where Ry is taken as 1.0.


136



AISC 341-10 Analysis of BRBF Columns Member code check of BRBF columns follow the requirements of Section F4.3 where braces are assumed to resist forces corresponding to their expected strength in compression or tension.

Figure 12: To determine Emh for BRBF Column O, the effect of braces in frame lines A-O-B and X-O-Y are independently determined according to Section F4.3. Frame lines A-O-B and X-O-Y are assumed to frame into the major and minor axes respectively of Column O. The tensile and compressive Emh values determined from the analysis are used in the load combinations for the applicable building code. Limitation: The analysis performed does not consider the interactive effect of axial loads on the column from braces in the two framing lines. The results from corner columns or columns with framing lines into the major and minor axes should be verified by the engineer.

§16.3 [F4.6] Bracing Connections §16.3a. Required Strength – The required strength of bracing connections in tension and compression (including beam-to-column connections if part of the bracing system) is taken as 1.1 times the adjusted brace strength in compression (LRFD) or 1.1/1.5 times the adjusted brace strength in compression (ASD).

§16.5 [F4.5a] Beams and Columns §16.5a The b/t ratios of stiffened and un-stiffened elements are checked per 8.2b against the compactness requirements in AISC360-05 specification Table B4.1 and the requirements of 8.2 (Table I-8-1). Angles are only checked for the requirements of Table I-8-1.

6.2.4 AISC 2002 (ANSI 341-02) – LRFD Limitations A few individual checks are not performed. When a check is necessary and is not performed by the program it will be indicated in the output.


137



§3. Seismic Design Categories The is not required to assign a seismic category. If the engineer selects to use this code then all the provisions are assumed to be applicable.

§4. Loads, Load Combinations, and Nominal Strengths Where standard provision load combinations are referred to (such as in Section 4.1 in regard to the applicable building code), RAM Frame will use the current load combinations from the standard provision mode. The engineer is responsible for ensuring that an appropriate set of loads and combinations are defined in the standard provision mode prior to switching to special seismic mode and performing a code check. Amplified Seismic load combinations as referenced in Section 4.1 are generated within this mode. The provisions of AISC 2002 are written for consistency with load combinations given in ASCE 7 (ASCE 2002) and IBC (ICC 2000). While AISC 2002 refers to the applicable building code as the source of the load combinations they should be consistent with the codes above to be applicable to the design provisions. Refer to the Section C4 in the commentary of the AISC 2002 specification for more information. Nominal strengths are based on Load and Resistance Factor Design Specification for Structural Steel Buildings (December 27, 1999), published by the American Institute of Steel Construction in Manual of Steel Construction - Load and Resistance Factor Design (3rd Edition).

§6. Materials §6.1 Material Specification No steel grade is specified in RAM Frame and as such the engineer is responsible for ensuring compliance with this provision.

§6.2 Material Properties for Determination of Required Strength of Connections or Related The Ry values according to Table I-6-1 have been implemented. Note that all Hollow Structural Sections (HSS and TS) are assigned a Ry of 1.3. For other rolled sections Ry is based on the engineer specified yield strength.

§8. §8.2 Local Buckling Only where specifically required by the specification and footnotes to table I-8-1 are the checked against the limiting width to thickness rations of Table I-8-1 and LRFD Table B5.1. Where applicable, Pu is taken as the maximum axial tension and compression force on the member from all the selected standard provision load combinations. The calculation of the b/t, d/t, and h/t ratios are based on the AISC LRFD 3rd specification. Note that for webs of beams in Special Moment Frames (SMF) there are some conflicting limits. The program will limit the section web to the smaller of:


138


Steel Seismic Provisions Technical Notes Code Check 2.45 Es / F y and 1.12

Es Fy

(

2.33 −

Pu ϕbP y

)

§8.3 Column Strength This provision is applied to all columns, irrespective of frame type. The standard provision load combinations are utilized to calculate Pu. When Pu/ϕPn > 0.4 the amplified seismic load combinations generated in the seismic provision mode (see 4. above) are used to determine the required compressive and tensile strength. The limiting provisions of 8.3(2) are not applied which could result in conservative axial forces being considered in 8.3(1).

§8.4 Column Splices Detailing information regarding the magnitude of the required splice force to be designed and detailed are calculated and presented. The engineer is responsible for the design of the splice connection components.

§8.4 Column Bases No calculations or information is provided with respect to column base design. Refer to the specification for additional information or requirements.

§9. Special Moment Frames (SMF) §9.2 Beam-to-Column ts and Connections Connections in Special moment frames require pre-qualification according to Section 9.2b to achieve the performance requirements of 9.2a. The engineer is referred to commentary on 9.2b which references FEMA350 as a source for several connections that are considered prequalified. When calculating the shear (Vu) based on 1.2D + 0.5L + 0.2S + 2Mpe/L, all combinations of 1.2D, 0.5L and 0.2S are calculated so as to determine the maximum shear load on the beam from the gravity loads. This is added to the contribution of 2Mpr/L. L is taken as the distance between reduced beam sections, if they exist, otherwise L is the distance between the face of the columns ing the beams. Mpr is the ultimate strength of the beam in bending at the reduced beam section, if it exists, otherwise it is from the full beam section.

§9.3 -Zone of Beam-to-Column Connections Only connections parallel to the column web are considered and checked by the program. The required shear strength of the -zone is determined from the summation of moments at the column faces as determined by projecting the expected moments at the plastic hinge locations (RBS if they exist) to the column faces. The material factor φv is taken as 1.0 in all cases. Pu is taken as the maximum axial load on the column at the t from all standard provision load combinations.


139


Steel Seismic Provisions Technical Notes Code Check If the beams frame into the flange of the column at some angle other than parallel to the column web, then the component of the beam force parallel to the column web is used. Zone shear is calculated as the moment divided by the distance between the center of the beam flanges. Not that the requirements of §9.3b are irrespective of the magnitude of the shear force. The program can consider the use of plug-welds to reduce the required web plate thickness, refer to the Criteria - ts menu command to select this plug weld option.

§9.4 Beam and Column Limitations Refer to the requirements of 8.2. Per table I-8-1 footnote 3, SMF columns will be checked to comply with λps in Table I-8-1 when Equation 9-3 is less than 2.0, else they will be checked against LRFD Table B5.1.

§9.6 Column-Beam Moment Ratio The calculation of ΣM×pb is determined by summing the projections of the expected beam flexural strength(s). If the beams frame into the flange of the column at some angle other than parallel to the column web, then the component of the beam force parallel to the column web is used to calculate M×pb If no reduced beam section is specified on a member than the capacity of the full member is utilized. For the Exception (if necessary) the design shear strength of a story is calculated as the component of the major axis shear strength, of all the columns in the direction of the column under consideration, added together. All columns, not only those columns of the special moment frame type, are considered.

§9.7 Beam-To-Column Connection Restraint A column will be assumed to remain elastic only if the ratio from Equation 9-3 is greater than 2.0. A t is considered restrained if contained within a deck, is a beam frames into the weak axis of the column, or by the specifying that the column is braced. If the indicates that the minor axis of the t column is unbraced then the physical bracing (deck or beams) is ignored and the t is considered unrestrained. The deck is only considered to brace the t at the elevation of the top flange of the beams framing into the flanges of the column. If a beam (not a joist) is determined to frame into the minor axis of the column at the t, then RAM Frame assumes that the t is restrained at the elevation of both the top and bottom flanges of the framing beams.

§9.8 Lateral of Beams Beams framing into the side of a lateral girder are assumed to brace both the top and bottom flange of the girder. Joists framing into the side of a lateral girder are assumed to brace only the top flange of the girder. If required the engineer can assign brace points to all lateral beams to meet this provision. The brace points should represent actual physical bracing to be provided on the constructed beam.


140



§10. Intermediate Moment Frames (IMF) §10.2 Beam-to-Column ts and Connections The required shear strength of the connection (Vu) is provided for the load combination 1.2D + 0.5L + 0.2S + 2.0 x (1.1 Ry Fy Z) / L. The maximum shear from the amplified seismic load combinations is also provided. IMF connections are required to be prequalified, refer to the commentary in AISC 2002 for more information.

§11. Ordinary Moment Frames (OMF) §11.2 Beam-to-Column ts and Connections The required shear strength of the connection (Vu) is provided for the load combination 1.2D + 0.5L + 0.2S + 2.0 x (1.1 Ry Fy Z) / L.

§11.5 Continuity Plates The engineer should provide continuity plates in accordance with Section 11.5 of equal or greater dimension than the ed beam flanges. Refer to the code for detailing information regarding the strength of the welded ts.

§12. Special Truss Moment Frames (STMF) STMF’s are not designed or checked within the program.

§13. Special Concentric Braced Frames (SCBF) §13.2 Bracing The unbraced length of a brace is considered to be the length between the nodes at the brace ends. To perform the lateral force distribution checks on SCBFs, the engineer is required to assign the same frame number to all the braces in the same line of bracing. Also, the Use Frame Nos. to Designate a Frame Line option must be selected in the Seismic Code dialog, which is opened by selecting the Criteria > Codes command. The b/t ratios of stiffened and unstiffened elements are checked against the compactness requirements in LRFD specification Table B5.1 and the requirements of 8.2 (Table I-8-1). Angles are only checked for the requirements of Table I-8-1.

§14. Ordinary Concentrically Braced Frames (OCBF) §14.2 Strength The required strength of is based on load combinations generated in the seismic provision mode (including the amplified seismic loads).


141


Steel Seismic Provisions Technical Notes Code Check To facilitate connection design the brace strength (Ry Fy Ag) is reported. Chevron (V or inverted V) brace frames are not allowed to have braces with Kl/r larger than 4.23 Es / F y .

§15. Eccentrically Braced Frames (EBF) The following frame configurations are considered valid EBF frames by the RAM Structural System.


§15.2 Links The maximum axial force in the link is taken as the maximum axial load from all the standard provision load combinations. The link rotation angle is taken as the largest calculated link rotation from all seismic load cases. The program uses the approximate link rotation angle calculation described in the commentary. The formulae provided in the commentary are modified as follows to for unsymmetrical geometry. Note that the frame displacement (Delta) is calculated as the net difference in horizontal displacement of the column top node relative to the column bottom node, projected into the plane of the original frame. The story ht (h) is calculated as the node to node distance from the beam-column t down the column to the next braced level. The link length (e) is the clear length (from face of column if at a ). EBF beams are required to span between two steel, lateral columns.


142



Δ1

e γ

h θp L


θp = h γ=

θ p(L − e) e


Δ1

a

e

b

γ2 γ1

h θp1

θp2 L

γ1 = θ p1 +


143

θ p2b + θ p1a e



γ2 = θ p2 +

θ p2b + θ p1a e


Δ1

γ1 e1

a

b

e2

Δ2 γ2

h θp1

θp2 L

γ1 = γ2 =

(θ p1 + θ p2) (e1 + a) 2

e1

(θ p1 + θ p2) (e2 + b) 2

e2

Figure 15: Configuration 3 The calculated angle is then multiplied by the Cd value provided by the engineer in the Codes dialog box, to produce the plastic link rotation angle. This magnified rotation angle is then compared to the code prescribed limits. The calculated plastic link rotation angle in conservatively not reduced by the elastic link rotation angle. For the central EBF configuration, where two different rotation angles are calculated, the larger angle is reported. Note that no additional consideration is given to the calculations for sloped beams, that is, the link displacement is assumed to be perpendicular to the link. Also, no consideration is given for rigid body translation and rotation that may exist in an EBF frame in the upper stories of a tall structure.

§15.3 Link Stiffeners Link Stiffeners are detailed in the output with a schematic diagram (not-to-scale) similar to that shown inf the following figure. In the output the table below the schematic provides details on the stiffener numbers and dimensions. The table contains the following columns. Link


e



144


Steel Seismic Provisions Technical Notes Code Check #


X


WxT End


WxT Int



e # Equal Spc


§15.4 Link-To-Column Connections §15.4a – Link-to-column connection design should be based on test results and are not designed in RAM Frame. §15.4b – If the beam-to-column connection is reinforced so as to preclude yielding over a length of the link the engineer is responsible for determining the applicability of the RAM Frame results. This situation is not currently considered in the EBF design performed by RAM Frame.

§15.6 Diagonal Brace and Beam Outside of Link The design of Eccentric Braced Frames are sensitive to the geometric configuration of the braces (and link length). In particular the ability to get the beam outside the link to meet code specification may require a change in the geometry of the brace rather than an increase or decrease in beam size. The engineer is referred to the AISC website for references (Steel Tips) regarding efficient EBF brace configurations. §15.6a – To perform the diagonal brace capacity provision the link beam at the top of the brace is located and the link capacity (1.25Ry Vn) is calculated. The analyzed load case that produces the largest shear in the identified link is also determined. The brace is then designed for a load combination that consists of a single term (load factor x load case). The combination factor is taken as the ratio of the link capacity to the maximum link shear force. The load case in the combination is that which produced the maximum link shear force. This load combination should thus produce the desired shear force (equal in magnitude to the link capacity) in the link. For example, if a link capacity is 100 kip, and the maximum shear in the link is 40 kip from load case S1, then the generated load combination is 100/40 S1 = 2.5 S1


145


Steel Seismic Provisions Technical Notes Code Check (both positive and negative combinations are considered). All the above-mentioned parameters are shown on the report. §15.6b – The design of the beam outside the link is performed in a similar fashion to §15.6a. That is, the link(s) on a beam are identified and load combinations are generated based on the ratio of the link shear to link capacities. For each link on a beam there are two load combinations created (as described in 15.6a). These combinations are then used to determine if the beam (outside of the link) is adequate to resist the forces that would ensure link yielding before beam failure. Note: The code stipulates that the beam capacity (outside of the link) can be increased by Ry. In RAM Frame the program implements this provision by reducing the demand (load factor in the combination) by Ry. All the above mentioned parameters are shown on the report. §15.6d – The brace connection forces are taken as the maximum forces at the top of the brace, generated by the load combination(s) created according to 15.6a. The design of a column according to load combinations A4 and A5 is not performed as part of the seismic provisions, but rather as a part of the code check performed in standard provision mode. In seismic mode RAM Frame identifies all beams that frame into an EBF column and determines if they are EBF beams. If so, the links are identified and, similar to §15.6a, load combinations are generated that would result in the appropriate force being generated in the links and the column in consideration. In the event that there are non-EBF beams ed on the column the will be given a warning. The warning is to let the consider the fact that there may be a loading condition that would result in the non-EBF frame beam causing controlling loads on the column, prior to the EBF link beams yielding. This is most likely to be a consideration when the non-EBF beam frames into the column perpendicular to the EBF beams.

6.2.5 AISC 1997 – LRFD Limitations A few individual checks are not performed. When a check is necessary and is not performed by the program it will be indicated in the output.

§3. Seismic Design Categories The is not required to assign a seismic category. If the engineer selects to use this code then all the provisions are assumed to be applicable.

§4. Loads, Load Combinations, and Nominal Strengths Where standard provision load combinations are referred to (such as in Section 4.1 in regard to the applicable building code), RAM Frame will use the current load combinations from the standard provision mode. The engineer is responsible for ensuring that an appropriate set of loads and combinations are defined in the standard provision mode prior to switching to special seismic mode and performing a code check. Amplified Seismic load combinations as referenced in Section 4.1 are generated within this mode. The provisions of AISC 2002 are written for consistency with load combinations given in ASCE 7 (ASCE 2002) and IBC (ICC 2000). While AISC 2002 refers to the applicable building code as the source of the load combinations they should be consistent with the codes above to be applicable to the design


146


Steel Seismic Provisions Technical Notes Code Check provisions. Refer to the Section C4 in the commentary of the AISC 2002 specification for more information. Nominal strengths are based on Load and Resistance Factor Design Specification for Structural Steel Buildings (December 27, 1999), published by the American Institute of Steel Construction in Manual of Steel Construction - Load and Resistance Factor Design (3rd Edition).

§6. Materials §6.1 Material Specification No steel grade is specified in RAM Frame and as such the engineer is responsible for ensuring compliance with this provision.

§6.2 Material Properties for Determination of Required Strength of Connections or Related The Ry values according to Table I-6-1 have been implemented. Note that all Hollow Structural Sections (HSS and TS) are assigned a Ry of 1.3. For other rolled sections Ry is based on the engineer specified yield strength.

§8.Columns All columns, of all frame types, are subject to the requirements of this section. Pu is taken as the maximum axial tension and compression force on the column from all the selected standard provision load combinations.

§9. Special Moment Frames (SMF) §9.2 Beam-to-Column ts and Connections Refer to the specification for information regarding testing procedures for special moment resisting frame connections. Note that at the time of this printing the web site http://quiver.eerc.berkeley.edu:8080/design/conndbase/index.html contains a database of all the tested connections. When calculating the shear (Vu) based on 1.2D + 0.5L + 0.2S + 2Mpe/L, all combinations of 1.2D, 0.5L, and 0.2S are calculated so as to determine the maximum shear load on the beam from the gravity loads. This is added to the contribution of 2Mpr/L. L is taken as the distance between reduced beam sections, if they exist, otherwise L is the distance between the face of the columns ing the beams. Mpr is the ultimate strength of the beam in bending at the reduced beam section, if it exists, otherwise it is from the full beam section.

§9.3 -Zone of Beam-to-Column Connections Per supplement no 2, the required shear strength of the -zone is determined from the summation of moments at the column faces as determined by projecting the expected moments at the plastic hinge locations to the column faces. Also the material factor ϕv is taken as 1.0 in all cases. Pu is taken as the maximum axial load on the column at the t from all standard provision load combinations.


147


Steel Seismic Provisions Technical Notes Code Check If the beams frame into the flange of the column at some angle other than parallel to the column web, then the component of the beam force parallel to the column web is used. Zone shear is calculated as the moment divided by the distance between the center of the beam flanges.

§9.4 Beam and Column Limitations The Pu used to calculate the limiting width-to-thickness ratio is taken as the maximum axial compressive force from all standard provision load combinations. The calculation of the b/t, d/t and h/t ratios are based on the AISC LRFD 3rd specification. Per supplement no. 2, columns will be checked to comply with λp in Table I-9-1 when Equation 9-3 is less than 2.0, else they will be checked against LRFD Table B5.1.

§9.6 Column-Beam Moment Ratio Per supplement No. 2, The calculation of ΣM×pb is determined by summing the projections of the expected beam flexural strength(s). If the beams frame into the flange of the column at some angle other than parallel to the column web, then the component of the beam force parallel to the column web is used to calculate M×pb If no reduced beam section is specified on a member than the capacity of the full member is utilized. To calculate the design shear strength of a story, the component of the major axis shear strength, of all the columns in the direction of the column under consideration, is added together. All columns, not only those columns of the special moment frame type, are considered.

§9.7 Beam-To-Column Connection Restraint Per supplement No. 2, a column will be assumed to remain elastic only if the ratio from Equation 9-3 is greater than 2.0. A t is considered restrained if contained within a deck, is a beam frames into the weak axis of the column, or by the specifying that the column is braced. If the indicates that the minor axis of the t column is unbraced then the physical bracing (deck or beams) is ignored and the t is considered unrestrained. The deck is only considered to brace the t at the elevation of the top flange of the beams framing into the flanges of the column. If a beam is determined to frame into the minor axis of the column at the t, then RAM Frame assumes that the t is restrained at the elevation of both the top and bottom flanges of the framing beams.

§9.8 Lateral of Beams Beams framing into the side of a lateral girder are assumed to brace both the top and bottom flange of the girder. Joists framing into the side of a lateral girder are assumed to brace only the top flange of the girder. If required the engineer can assign brace points to all lateral beams to meet this provision. The brace points should represent actual physical bracing to be provided on the constructed beam.


148



§10. Intermediate Moment Frames (IMF) Per Supplement 2, Intermediate moment frames no longer need comply with modified SMF requirements. The following information is provided to facilitate design of IMF structures.

§10.2 Beam-to-Column ts and Connections The required shear strength of the connection (Vu) is provided for the load combination 1.2D + 0.5L + 0.2S + 2.0 x (1.1 Ry Fy Z) / L. The maximum shear from load combination 4-1 is also provided.

§11. Ordinary Moment Frames (OMF) §11.2 Beam-to-Column ts and Connections The required shear strength of the connection (Vu) is provided for the load combination 1.2D + 0.5L + 0.2S + 2.0 x (1.1 Ry Fy Z) / L.

§11.3 Continuity Plates The engineer should provide continuity plates equal in dimension to the ed beam flanges unless tests prove they are not required per AISC Supplement No. 2.

§13. Special Concentric Braced Frames (SCBF) §13.2 Bracing The unbraced length of a brace is considered to be the length between the nodes at the brace ends. To perform the lateral force distribution checks on SCBFs, the engineer is required to assign the same frame number to all the braces in the same line of bracing. Also, the Use Frame Nos. to Designate a Frame Line option must be selected in the Seismic Code Dialog obtained by selecting the CriteriaCodes command.

§13.2d Width-Thickness Ratios Per Supplement No. 2 the b/t ratios of stiffened and unstiffened elements are checked against the compactness requirements in LRFD specification Table B5.1. Also, b/t of angles are not allowed to exceed 52/√fy, I-Shaped and channels will be checked with λp in Table I-9-1.

§14. Ordinary Concentrically Braced Frames (OCBF) Per supplement no 2, Requirements of AISC 1997 – Section 14.2 – 14.5 have been replaced with the following:

§14.2 Strength The required strength of is based on load combinations 4-1 and 4-2. To facilitate connection design the brace strength (Ry Fy Ag) is reported. Chevron (V or inverted V) brace frames are not allowed to have braces with Kl/r larger than 720/√Fy.


149



§15. Eccentrically Braced Frames (EBF) The following frame configurations are considered valid EBF frames by the RAM Structural System.


§15.2 Links §15.2e – The maximum axial force in the link is taken as the maximum axial load from all the standard provision load combinations. §15.2f – The axial force (Pu) in the link is the same as that calculated for 15.2e. §15.2g – The link rotation angle is taken as the largest calculated link rotation from all seismic load cases. The program uses the approximate link rotation angle calculation described in the commentary. The formulae provided in the commentary are modified as follows to for unsymmetrical geometry. Note that the frame displacement (Delta) is calculated as the net difference in horizontal displacement of the column top node relative to the column bottom node, projected into the plane of the original frame. The story ht (h) is calculated as the node to node distance from the beam-column t down the column to the next braced level. The link length (e) is the clear length (from face of column if at a ). EBF beams are required to span between two steel, lateral columns.


150



Δ1

e γ

h θp L


θp = h γ=

θ p(L − e) e


Δ1

a

e

b

γ2 γ1

h θp1

θp2 L

γ1 = θ p1 +


151

θ p2b + θ p1a e



γ2 = θ p2 +

θ p2b + θ p1a e


Δ1

γ1 e1

a

b

e2

Δ2 γ2

h θp1

θp2 L

γ1 = γ2 =

(θ p1 + θ p2) (e1 + a) 2

e1

(θ p1 + θ p2) (e2 + b) 2

e2

Figure 18: Configuration 3 The calculated angle is then multiplied by the Cd value provided by the engineer in the Codes dialog box, to produce the plastic link rotation angle. This magnified rotation angle is then compared to the code prescribed limits. The calculated plastic link rotation angle in conservatively not reduced by the elastic link rotation angle. For the central EBF configuration, where two different rotation angles are calculated, the larger angle is reported. Note: No additional consideration is given to the calculations for sloped beams, that is, the link displacement is assumed to be perpendicular to the link. Also, no consideration is given for rigid body translation and rotation that may exist in an EBF frame in the upper stories of a tall structure.

§15.3 Link Stiffeners Link Stiffeners are detailed in the output with a schematic diagram (not-to-scale) similar to that shown inf the following figure. In the output the table below the schematic provides details on the stiffener numbers and dimensions. The table contains the following columns. Link


e



152


Steel Seismic Provisions Technical Notes Code Check #


X


WxT End


WxT Int



e # Equal Spc


§15.4 Link-To-Column Connections §15.4a – Link-to-column connection design should be based on test results and are not designed in RAM Frame. §15.4b – If the beam-to-column connection is reinforced so as to preclude yielding over a length of the link the engineer is responsible for determining the applicability of the RAM Frame results. This situation is not currently considered in the EBF design performed by RAM Frame.

§15.6 Diagonal Brace and Beam Outside of Link The design of Eccentric Braced Frames are sensitive to the geometric configuration of the braces (and link length). In particular the ability to get the beam outside the link to meet code specification may require a change in the geometry of the brace rather than an increase or decrease in beam size. The engineer is referred to the AISC website for references (Steel Tips) regarding efficient EBF brace configurations. §15.6a – To perform the diagonal brace capacity provision the link beam at the top of the brace is located and the link capacity (1.25 Ry Vn) is calculated. The analyzed load case that produces the largest shear in the identified link is also determined. The brace is then designed for a load combination that consists of a single term (load factor x load case). The combination factor is taken as the ratio of the link capacity to the maximum link shear force. The load case in the combination is that which produced the maximum link shear force. This load combination should thus produce the desired shear force (equal in magnitude to the link capacity) in the link. For example, if a link capacity is 100 kip, and the maximum shear in the link is 40 kip from load case S1, then the generated load combination is 100/40 S1 = 2.5 S1


153


Steel Seismic Provisions Technical Notes Code Check (both positive and negative combinations are considered). All the above-mentioned parameters are shown on the report. §15.6b – The design of the beam outside the link is performed in a similar fashion to §15.6a. That is, the link(s) on a beam are identified and load combinations are generated based on the ratio of the link shear to link capacities. For each link on a beam there are two load combinations created (as described in 14.6a). These combinations are then used to determine if the beam (outside of the link) is adequate to resist the forces that would ensure link yielding before beam failure. Note: The code stipulates that the beam capacity (outside of the link) can be increased by Ry. In RAM Frame the program implements this provision by reducing the demand (load factor in the combination) by Ry. All the above mentioned parameters are shown on the report. §15.6d – The brace connection forces are taken as the maximum forces at the top of the brace, generated by the load combination(s) created according to §15.6a. – The design of a column according to load combinations A4 and A5 is not performed as part of the seismic provisions, but rather as a part of the code check performed in standard provision mode. In seismic mode RAM Frame identifies all beams that frame into an EBF column and determines if they are EBF beams. If so, the links are identified and, similar to §15.6a, load combinations are generated that would result in the appropriate force being generated in the links and the column in consideration. In the event that there are non-EBF beams ed on the column the will be given a warning. The warning is to let the consider the fact that there may be a loading condition that would result in the non-EBF frame beam causing controlling loads on the column, prior to the EBF link beams yielding. This is most likely to be a consideration when the non-EBF beam frames into the column perpendicular to the EBF beams.

FEMA 350 The requirements of FEMA 350 are based substantially on those of the AISC 1997 Seismic Provisions for Structural Steel Buildings. The engineer has the option of performing the FEMA 350 provision checks for all the seismic provision codes (UBC and AISC). The FEMA 350 provisions are only applicable to Steel Moment Frame structures as indicated in this section. The FEMA 350 provisions take the place or are in addition to some of the requirements of the selected seismic provision code. In all detailed output both the current code section, and the FEMA 350 section that replaces it, are displayed. Note that the June 18, 2001 errata have been incorporated where required.

§2.9 Frame Design §2.9.1 Strength of Beams and Columns Strong Column-Weak Beam should satisfy Equation 9-3 of the AISC 1997, Except that M*pb is based on the requirements of Section 3.2.6 in FEMA 350. Note that r is always taken equal to 1.2 for this check.

§2.9.2 Lateral Bracing of Column Flanges Lateral bracing of column flanges should be provided whenever the following equation is not satisfied: ΣM * pc ΣMc

≥ 2.0

where M*pc Mc


= =

per Section 9.6 of AISC 1997 as indicated in Section 3.2.6 of the FEMA 350 Requirements

154



§2.9.3 Zone Strength The zone check is per Section 3.3.3.2 of FEMA 350. In that section the thickness of the zone required is determined from the following equation:

t=

h − db h (0.9)0.6F yc R yc dc (db − t fb) C yM c

In RAM Frame this equation is represented by the capacity and the demand side as follows:

()

0.9 0.6F yc R yc dc t = Σ

h − db h db − t fb

C yM c

This allows us to determine the zone demand from the beams at both sides of the column and design an appropriate web plate to carry the demand. Refer the FEMA 350 for an explanation of the parameters shown above. Note that r is always taken equal to 1.2 for this check.

§2.9.4 Section Compactness Requirements Beams should conform to the requirements of AISC Seismic Provisions. Per FEMA 350 Section 3.3.1.1 in the case of a beam with a reduced beam section the program considers the bf/2tf to occur at the ends of the center two-thirds of the reduced beam section (RBS). For this reason the engineer is required to input three dimensions to define the RBS, the distance face-of-column to start of RBS (a), the length of RBS (b), and the cut of the flange each side of beam (c). Refer to the v7.0 manual for more details on asg reduced beam sections to in the model. For columns FEMA 350 stipulates that they should be compact unless a non-linear analysis shows that they do not yield. All of the building codes already require that the column is compact and as such no additional FEMA 350 compactness checks are performed for columns.

§2.9.5 Beam Lateral Bracing Similar to AISC 1997 the unbraced length between s of the beam flanges is not permitted to exceed 2500 ry/Fy.

§3.5.5 Reduced Beam Section Connections Several items of the data required for the design procedure of the pre-qualified Reduced Beam Section Connections (FEMA 350 Section 3.5.5) are reported. In the t output for moment frames with reduced beam sections the Mf (using r = 1.15), Vg and Vf values are all printed. Note that for sloped beams Vg is reported perpendicular to the longitudinal axis of the beam but Vf is always given in the vertical (along column flange) direction. The ratio of Mf /RyZbFy is reported and a value greater than 1.0 is considered unacceptable. All the parameters mentioned here are defined in section 3.5.5 of FEMA 350.

6.2.6 UBC97 – ASD Limitations The eccentric brace frame type is not implemented (it is for AISC 1997).


155


Steel Seismic Provisions Technical Notes Code Check A few individual checks are not performed. When a check is necessary and is not performed by the program it will be indicated to the engineer. In most of the automatically calculated load combinations in RAM Frame the standard provision mode load factors are reduced by one-third for load combinations with seismic load. Several checks in the special seismic provisions require that the stress of columns be determined based on standard load combinations. Where the seismic load combinations are considered the member stress will be smaller than required based on the third decrease in the load factors. It is suggested that in RAM Frame all standard provision load combinations with lateral load be copied and pasted as custom load combinations. The load factors of these combinations should be changed to 1.0 from 0.75 for all the load cases. These load combinations should only be selected prior to proceeding into the special provision mode. Note that if the UBC 1997 ASD automatic load generator is used in the standard provision mode then the seismic load combinations are not reduced by one-third. As such the load factor modifications described above do not need to be performed.

§2213 – Seismic Provisions for Structural Steel Buildings in Seismic Zone 3 and 4 The seismic zone is selected in the code dialog displayed by selecting the Criteria-Codes command. The seismic provisions performed are dependent on the selected zone as specified in the UBC 1997 – ASD specification.

§2213.4 Materials §2213.4.2 Member Strength Member strengths are as specified in Section 2213.4.2. where = Ms Zfy = Vs 0.55Fydt = Psc 1.7FaA = Pst FyA

§2213.5 Column Requirements Where standard provision load combinations are referred to (such as in exception 2 of Section 2213.5.1), RAM Frame will use the current load combinations from the standard provision mode. The engineer is responsible for ensuring that an appropriate set of loads and combinations are defined in the standard provision mode prior to switching to special seismic mode and performing a code check. Load Combinations 1.0DL + 0.7LL ± ΩoE and 0.85DL ± ΩoE are generated within this mode.

§2213.6 Ordinary Moment Frame (OMF) Detailing information is only provided for fully restrained ts Per section 2213.7.1 the plastic bending moment of each beam (Mp), and where appropriate the moment resulting from the zone shear strength (Mpz) are reported. Mpz is calculated independently for each beam as Vn ( zone strength) x Beam Depth (distance between center of flanges). The Mpz reported is the component of the zone moment in the direction that the beam frames into the column flange (less than the full -zone moment if the beam is not parallel to the column web). If no zone value can be calculated or the beam frames into the column web then no value is shown for Mpz in the output.


156


Steel Seismic Provisions Technical Notes Code Check When calculating the zone check (from the reference to Section 2213.7.1.1 (2)) the capacity is calculated for the column web without any doubler. This is because the zone check of 2213.7.2.1 is not required for ordinary moment frames.

§2213.7 Special Moment Frame (SMF) Refer to previous section for discussion of section 2213.7.1.

§2213.7.2 Zone The moment strength of a member is calculated as Ms = Z x Fy, no over-strength is applied to the beams. Load combination 1.0D + 1.0L + 1.85E is created internally to RAM Frame to perform this check. The shear in the column above the t is considered when calculating the zone shear force using the above generated load combination. zone strength is a function of the beam depth. Where one zone capacity is reported it is based on the deepest beam framing into the column flange (which provides the smallest capacity). When calculating the zone strength per (13-1) the contribution of the web plate is added to that of the column web. The doubler capacity is calculated independent of the column web using its own yield strength value. The depth of the web plate (doubler) is taken as the clear distance between column flanges.

§2213.7.3 Width Thickness Ratio The axial value used to calculate the web d/tw limit for I-Sections based on Section 2251N7 is the maximum axial load from all standard provision load combinations. As this is a plastic capacity check the axial load used to perform this check should be the result of a factored load combination. Per AISC 9th, page 5-184, RAM Frame calculates the largest factored axial load on the member by multiplying the standard provision load combinations force by 1.7 if there are no lateral load case, and by 1.3 if there are lateral load cases. The width to thickness ratio of girders is checked against the compact member limits of the AISC ASD specification, except as modified in 2213.7.2.

§2213.7.4. Continuity Plates Stiffeners are only designed for flange bending requirement of chapter K in AISC ASD 9th Edition. The required area of the stiffeners is calculated as the difference in the design force (Pbf) and the flange capacity (Rn) divided by the stiffener yield strength.

§2213.7.5. Strength Ratio Mpz is calculated as the zone shear capacity multiplied by the deepest beam section framing into the column flange. When calculating the shear capacity of a story for exception 2, all lateral steel columns, not only those columns of the special moment frame type, are considered. Only the major axis shear capacity of the member is considered.


157



§2213.7.7 Girder-Column t Restraint §2213.7.7.1 Restrained t – A t is considered restrained if contained within a deck, is a beam frames into the weak axis of the column, or by the specifying that the column is braced. If the indicates that the minor axis of the t column is unbraced then the physical bracing (deck or beams) is ignored and the t is considered unrestrained. The deck is only considered to brace the t at the elevation of the top flange of the beams framing into the flanges of the column. If a beam is determined to frame into the minor axis of the column at the t, then RAM Frame assumes that the t is restrained at the elevation of both the top and bottom flanges of the framing beams.

§2213.8.2.3. Lateral-Force Distribution The lateral-force distribution check of Section 2213.8.2.3 is only performed if the indicates that frame numbers are to be used to define a line of bracing (refer to Criteria-Codes dialog). When performing the lateral-force distribution check of Section 2213.8.2.3, RAM Frame only accumulates loads for those braces with the same frame numbers.

§2213.8.2.5. Compression Elements in Braces The flat wall dimension per the AISC-ASD is used to calculate the width-thickness ratio for tube sections when checking §2213.8.2.5.

§2213.8.4.2 K-Type Bracing K-Type frames are only allowed if the indicates to apply one and two story exceptions in the Criteria-Codes dialog. All the of the structure designated as type K-Frame will be required to meet the requirements of §2213.8.5.

§2213.8.5. One- and Two- Story Buildings Section 2213.8.5 requires that the strength of all braces meet the increased strength demands. RAM Frame only performs this check if all the braces of the frame type have pinned connections (i.e. axial only load). This is because the specification provides no indication of how to calculate the bending “strength” of a member that may fail in an elastic fashion (e.g. due to lateral torsional buckling).

6.2.7 UBC 1997 – LRFD Limitations The eccentric brace frame type is not implemented (it is for AISC 1997) A few individual checks are not performed. When a check is necessary and is not performed by the program it will be indicated in the output.


158


Steel Seismic Provisions Technical Notes Code Check Reduced beam sections are not considered except for zone and strong-column weak-beam calculations if the engineer specifies FEMA 350.

§6 Column Requirements §6.1 Column Strength The standard provision load combinations are used to calculate Pu in Section 6.1. Where Pu/ϕPn exceeds 0.5 then the extreme axial loads from all the Special Seismic load combinations are used to calculate axial load in 6.1a and 6.1b.

§6.2 Column Splices The axial force calculated for column splices per 6.2 is calculated as the maximum from both the standard provision and the special provision load combinations.

§7 Ordinary Moment Frames §7.1 Scope No standard provision checks are performed in seismic provision mode. The engineer is responsible for confirming that all the are capable of resisting the standard provision load combinations, in standard provision mode. Only the “added provisions” are performed in this special seismic mode.

§7.2 t Requirements Detailing information is only provided for fully restrained ts Per Section 8.2 the plastic bending moment of each beam (Mp), and where appropriate the moment resulting from the zone shear strength (Mpz) are reported. Mpz is calculated independently for each beam as Vn ( zone strength) x Beam Depth (distance between center of flanges). The Mpz reported is the component of the zone moment in the direction that the beam frames into the column flange (less than the full -zone moment if the beam is not parallel to the column web). If no zone value can be calculated or the beam frames into the column web then no value is shown for Mpz in the output. The minimum of Mp (beam moment strength) and Mpz ( zone strength at the t under consideration) is used to calculate the required shear strength per §8.2b (1.2D + 0.5L + 0.2S + 2M/L). Where D is the dead load, M/L is the positive live load and S is snow load if it exists. Mpz is only considered if it has a positive magnitude.

§8 Special Moment Frames §8.1 Scope No standard provision checks are performed in seismic provision mode. The engineer is responsible for confirming that all the are capable of resisting the standard provision load combinations, in standard provision mode. Only the “added provisions” are performed in this special seismic mode.


159



§8.2 t Requirements The plastic bending moment of each beam (Mp), and for beams framing into the flange, the moment resulting from the zone shear strength (Mpz) are reported. Mpz is calculated independently for each beam as Vn ( zone strength) x Beam Depth (distance between center of flanges). The Mpz reported is the component of the zone moment in the direction that the beam frames into the column flange (less than the full zone moment if the beam is not parallel to the column web). If no zone value can be calculated or the beam frames into the column web then no value is shown for Mpz in the output. The minimum of Mp (beam moment strength) and Mpz ( zone strength at the t under consideration) is used to calculate the required shear strength per 8.2b (1.2D + 0.5L + 0.2S + 2M/L). Where D is the dead load, L is the positive live load and S is snow load if it exists. Mpz is only considered if it has a positive magnitude.

§8.3 Zone of Beam-to-Column Connections The shear in the column above the t is considered when calculating the zone shear force using the above generated load combination. The zone strength is the minimum value calculated for all the beams framing into the column flanges. Where a web plate (doubler) is provided its capacity is added to that of the column web when calculating the t capacity. The depth of the web plate is taken as the clear height between the flanges of the column.

§8.4 Beam and Column Limitations Round hollow structural section columns are limited to the compact width-thickness ratio from Table B5 in the AISC-LRFD specification. The Pu value used in Table 8-1 is the maximum compression load on the element from all standard provision load combinations.

§8.5. Continuity Plates Stiffeners are only designed for flange bending requirement of chapter K in LRFD 3rd Edition. The required area of the stiffeners is calculated as the difference in the design force and the flange capacity (Rn) divided by the stiffener yield strength.

§8.6 Column-Beam Moment Ratio Nominal strength of zone is taken as the value calculated in section 8.3. The db value is taken as the average depth of all the fixed, steel lateral beams framing into the t. When calculating the shear capacity of a story for exception 2, all columns, not only those columns of the special moment frame type, are considered.


160



§9 Concentrically Braced Frames §9.2. Bracing To perform the lateral force distribution checks on braced frames per Section 9.2c, the engineer is required to assign the same frame number to all the braces in the same line of bracing. Also, the Use Frame Nos. to Designate a Frame Line option must be selected in the Seismic Code Dialog obtained by selecting the Criteria-Codes command. Note: The force distribution requirement for §9.2c is performed on a per story basis. If the distribution on a single story exceeds the lateral distribution limit, then the braces of that story are checks for compliance with the exception. Note that the full strength of the braces (excluding phi factor) is used to check compliance with the exception. The web of a HSS (Tube) section for special concentric braced frame is checked in accordance with the Stiffened Webs in Combined Axial and Bending provision of LRFD Table B5.1. This is true even if no bending exists on the member as the tube is required to be Compact per 12.2d (for SCBF) and pure compression does not have a compact limit in Table B5.1. In §9.2d, the h/t and b/t limits are calculated in accordance with the AISC-LRFD specification. For HSS sections b = Flange Width – 3 x Web Thickness and h = Depth – 2 x Flange Thickness.

§9.4. Special Bracing Configuration Requirements Per Section 9.4.a.1. The chevron braces are checked for all the loads from standard provision load combinations that include a seismic load case.

§9.5 Low Buildings The low building exception is applied if the indicates to apply the one and two story exceptions (refer to Criteria–Codes command), or if the member is at the top most lateral story.


161





162


Steel Seismic Provision Reports

7

A number of reports are available in Steel-Seismic Provision Mode. Many of these have already been described in Chapter 4. The reports presented below are those that are not described in the above referenced section and are specific to the Steel Seismic Provision Mode. Many of the reports are based on load combinations (member forces, reactions etc). In Steel – Seismic Provision Mode these reports are all based on the seismic load combinations (generated and custom) from this mode only. The reports available in the Steel-Seismic Provision mode are for the most part identical to those available in the Steel – Standard Provision mode. Only those reports in which the content changed are described below. Refer to Chapter 4, for all other reports not described below. Note that all reports that use load combinations will show results for the load combinations (generated and custom) that are created in the seismic provision mode. Load Combinations

The Load Combinations report is a listing of the analyzed load cases of which the combinations are comprised, the program-generated load combinations, and the -defined load combinations from this mode only. Note that the standard provision load combinations play an important part in the checks performed in the steel seismic mode. The engineer should switch to the Steel – Standard Provision mode to print the standard provision load combinations.

Member Code Check

The Member Code Check report lists detailed results of the currently selected Seismic Code Specifications check for individual . The report includes member information, design parameters, and the results of all the checks performed on each member. Member Code Check reports can be printed for a single frame member, all frame included in a fenced area, all of a selected frame, all frame shown in the current view or for every frame member in the model.

t Code Check

The Member Code Check report shows detailed results of the currently selected Seismic Code Specification checks for individual moment frame ts. The report includes member information, design parameters, and the results of all the checks performed on each t. t Code Check reports can be printed for a single frame member, all t included in a fenced area, all ts of a selected frame, all frame ts shown in the current view or for every frame t in the model.

Member Check Summary

The Member Code Check Summary report lists each seismic check performed on a member, and the result of each check. The report is the same as the list of checks and results displayed in the member view-update dialog

t Check Summary

The t Code Check Summary report lists each seismic check performed on a t, and the result of each check. The report is the same as the list of checks and results displayed in the t view-update dialog.


163


Steel Seismic Provision Reports Load Combinations Star Seismic Summary

The Star Seismic Summary lists each Star Seismic BRB result of the currently selected Seismic Code Specification. The report includes member information, design parameters, and the results of all the checks performed on each brace.

7.1 Load Combinations The Load Combinations report lists the combinations used in the seismic provision steel code checks. The report includes the Roof Live Load criteria, which affects the generated load combinations. The load cases included in the load combinations are listed along with the generated and -specified load combinations, as well as which of the combinations are selected to be used in the code check. For generated combinations the Code specified as the basis of the generation is indicated. For example, “AISC 1997” indicates that the generated combinations are for AISC 1997 design, based on the combinations specified by the AISC 1997 design specification. The Omega value on which the load combinations are based is also displayed.

7.2 Member Code Check The Member reports generated vary depending on the currently selected seismic code, the options selected for that code (Zone, One Story Exceptions etc) and the frame type being checked. To show all the possible variations on the reports is impractical. All reports will display some fundamental information on the member properties (Yield Strength, Size etc), the story number, frame number, and the frame type. If seismic checks are required then the report will clearly show which code checks were performed (referencing the code section directly) and the results of each of these checks. The engineer is encouraged to refer directly to the section (as shown in the output) in the currently selected seismic code when reviewing the results.

7.3 Member Check Summary Due to the nature of the seismic provision checks (being one of multiple detailing and design checks), no single output line would suffice to report the result of a code check. As such the summary results report a single line for each check performed on a member, along with the result for that check (if the check is a design requirement and not simply a detailing requirement). For a single member that means several lines of output. Each line should clearly state the member, story, frame number and for each check the code reference (section) and the result.


164


Steel Seismic Provision Reports t Check Summary

7.4 t Code Check The t reports generated vary depending on the currently selected seismic code, the options selected for that code (Zone etc) and the frame type being checked. To show all the possible variations on the reports is impractical. All reports will display some fundamental information on the t’s properties (Yield Strength, Size etc), the story number, frame number, and the frame type. If seismic checks are required then the report will clearly show which code checks were performed (referencing the code section directly) and the results of each of these checks. The engineer is encouraged to refer directly to the section (as shown in the output) in the currently selected seismic code when reviewing the results. Note that code checks are only performed for valid moment frame ts as described in Section 3.3.1, Assumptions and Limitations.

7.5 t Check Summary Due to the nature of the seismic provision checks (being one of multiple detailing and design checks), no single output line would suffice to report the result of a code check. As such the summary results report a single line for each check performed on a t, along with the result for that check (if the check is a design requirement and not simply a detailing requirement). For a single t that means several lines of output. Each line should clearly state the t, story, frame number and for each check the code reference (section) and the result. Note that code checks are only performed for valid moment frame ts as described in Section 3.3.1, Assumptions and Limitations.


165


Steel Seismic Provision Reports t Check Summary



166


Index A

AISC member code check 100 AISC - ASD 9th local web yielding 87 AISC -AISD 9th t code check 87 AISC -ASD 9th zone checks 87 stifener design 87 web crippling 87 AISC 1997 - LRFD code check 146 columns 147 eccentrically braced frames 150, 152, 153 FEMA 350 154 intermediate moment frames 149 limitations 146 materials 147 ordinary concentrically braced frames 149 ordinary moment frames 149 seismic design categories 146 special concentric braced frames 149 special moment frames 147, 148 AISC 2002 (ANSI 341-02) LRFD code check 137 eccentrically braced frames 142, 144, 145 intermediate moment frames 141 limitations 137 materials 138 138, 139


ordinary concentrically braced frames 141 ordinary moment frames 141 seismic design categories 138 special concentric braced frames 141 special moment frames 139, 140 special truss moment frames 141 AISC 2002 (ANSI 341-02) LRFD) load combinations 138, 146 loads 138, 146 nominal strengths 138, 146 AISC 2005 (ANSI 341-05) - ASD and LRFD buckling restrained braced frame 136, 137 eccentrically braced frames 132, 134, 135 general seismic design requirements 124 intermediate moment frames 129, 130 limitations 124 load combinations 124 loads 124 materials 125 125, 126 nominal strengths 124 ordinary concentrically braced frames 132 ordinary moment frames 130 special concentric braced frames 131 special moment frames 126–129

167

special truss moment frames 131 AISC 2005 (ANSI 341-05) – ASD and LRFD code check 124 AISC 360 t code check 87 local web yielding 88 zone check 88 stiffener design 88 web crippling 88 AISC 360 - ASD and LRFD buckling restrained braces 52 connector spacing for double angles 52 direct analysis method 45 error messages 52 K-factor 52 load combinations 50 member code check 45 notional loads 48 reduced stiffness 49 second order analysis 45 AISC 360 direct analysis validation design code 98 notional loads 99 reduced stiffness 99 second-order analysis 98 steel standard provisions reports 98 stiffener design t code check 105 web plate details t code check 105 AISC ASD critera column moments 16 AISC ASD criteria axial slenderness limits 17 B1 Factors 15


B2 Factors 15 design criteria 15 flange bracing 16 ts 17 K-Factor 16 sidesway 16 aligning notional load cases with a specific direction BS5950:1990 59 BS5950:2000 59 allowable strength design combinations load combinations 50 allowable stress design combinations ASD 9th 54 LRFD 3rd 54 amplified first order analysis second order analysis 46 amplified sway factor Kamp BS5950:1990 63 BS5950:2000 63 amplified sway method BS5950:1990 63 BS5950:2000 63 analysis method AS 4100-98 75 second order analysis by amplified first order analysis 77 δ factors 78 δb factors 77 AS load combinations 79 AS 410-98 second order effects 75 AS 4100-98 analysis method 75 connector spacing for double angles 81 design assumptions 81 design yield strength 79 effective length with Kefactor 80 error messages 82 t code check 92, 93 load combinations 79


local flange bending tension 92 member code check 75, 101 notional loads 78 second order analysis by geometric stiffness method 77 stiffener design 92 web bearing yielding tension and compression 92 web buckling - compression 92 web shear 92 ASCE 7-05 load combinations 50 ASD criteria 112 ASD 9th allowable stress design combinations 54 buckling restrained braces 56 connector spacing for double angles 55 design yield strength 55 error messages 56 IBC 2000 53 IBC 2003 53 K-factor 55 load and resistance factor design combinations 54 load combinations 53 member code check 53 round bar slenderness limits 55 steel standard provisions technical notes 53 unbraced bending length 64 assign menu beams 27 braces 30 changing modes 35 columns 26 design process 34 exiting modes 35

168

frame numbers 32, 113 frame types 113 horizontal braces 29 t view 33 member view 33 process menu 32 sidesway 31 steel seismic provisions post-processors 113 steel standard provisions post-processors 26 sway-sensitive design method 31 update 33 assumptions code check 123 assumptions and limitations t code check 82 Australia AS4100 criteria column moments 25 effective length factors 25 flange bracing 25 ts 25 reduced beam sections 26 sidesway 25 steel standard provisions post-processors 24 axial slenderness limits AISC ASD criteria 17 CAN 22 CSA S16-01 22 LRFD criteria 17

B

B1 factor second order analysis 47 B1 Factors AISC ASD criteria 15 LRFD criteria 15 B2 factor second order analysis 48 B2 Factors AISC ASD criteria 15 LRFD criteria 15 beams assign menu 27


effective lengths 28 flange bracing 28 reduced beam sections 29 unbraced lengths 28 beams - Lu for axial minor axis bracing 42 beams - Lu for bending minor axis bracing 43 beams with end connections CAN 20, 22 CSA S16-01 20, 22 bending capacity BS5950:1990 64 BS5950:2000 64 CAN 68 CSAS16-01 68 Eurocode 73 braces assign menu 30 effective lengths 30 size 30 unbraced lengths 31 BS 5950 member code check 101 BS 5950 - draft amend, April 1998 t code check 105 BS 5950-1:1990 BS5950:1990 64 BS5950:2000 64 BS5950 column moments 24 design 24 effective lengths 23 flange bracing 24 ts 24 reduced beam sections 24 sidesway 23 steel standard provisions post-processors 22 BS5950 - draft amend, April 1998 final design 105 results 105 stiffener design 106 BS5950 Part 1:1990 t code check 88


stiffener design 89 web buckling 89 web shear 89 web tensile force 89 BS5950-1:2000 final design 105 t code check 105 results 105 stiffener design 106 BS5950-1:2000 specific BS5950:1990 67 BS5950:2000 67 BS5950:1900 moment amplification 62 BS5950:1990 aligning notional load cases with a specific direction 59 amplified sway factor Kamp 63 amplified sway method 63 bending capacity 64 BS 5950-1:1990 64 BS5950-1:2000 specific 67 calculating sway state per load combination 58 calculating λcr per load combination 58 cross section classification 56 design yield strength 64 effective length method 63 effective lengths 60, 61 error messages 66 load combinations 57, 67 member code check 56 non-sway sensitive 57 notional loads in load combinations 58 P-delta 63 section capacity BS5950-1:1990 65 section capacity BS5950-1:2000 65 sway sensitive 57 unbraced bending length 55

169

web shear interaction BS5950-1:2000 66 BS5950:2000 aligning notional load cases with a specific direction 59 amplified sway factor Kamp 63 amplified sway method 63 bending capacity 64 BS 5950-1:1990 64 BS5950-1:2000 specific 67 calculating sway state per load combination 58 calculating λcr per load combination 58 cross section classification 56 design yield strength 64 effective length method 63 effective lengths 60, 61 load combinations 57, 67 member code check 56, 57 moment amplification 62 notional loads in load combinations 58 P-delta 63 section capacity BS5950-1:1990 65 section capacity BS5950-1:2000 65 unbraced bending length 55 web shear interaction BS5950-1:2000 66 BS5950:Part 1 1990 web bearing – tension and compression 89 BS5950:Part 1:1990 BS5950:Part 1:2000 89 BS5950:Part 1:2000 BS5950:Part 1:1990 89 buckling restrained braced frame AISC 2005 (ANSI 341-05) ASD and LRFD 136, 137 buckling restrained braces


AISC 360 - ASD and LRFD 52 ASD 9th 56 LRFD 3rd 56

C

calculating sway state per load combination BS5950:1990 58 BS5950:2000 58 calculating λcr per load combination BS5950:1990 58 BS5950:2000 58 CAN axial slenderness limits 22 beams with end connections 20, 22 bending capacity 68 column moments 22 compression 21.3 90 connector spacing for double angles 69 design yield strength 68 effective length 67 flange bracing 22 ts 22 K-Factor 22 member code check 67, 68 zone - web shear 90 section capacity 69 steel standard provisions post-processors 21 tension 21.3 90 CAN/CSA S16-01 error messages 69 t code check 90 CAN/CSA S16-09 bending capacity 71 connector spacing 71 design yield strength 70 effective length 70 error messages 71 load combinations 70 unbraced bending length 70 changing modes assign menu 35


steel seismic provisions post-processors 119 cocde check criteria steel standard provisions reports 97 code check AISC 1997 - LRFD 146 AISC 2002 (ANSI 341-02) LRFD 137 AISC 2005 (ANSI 341-05) – ASD and LRFD 124 assumptions 123 limitations 123 reduced beam section check 123 steel seismic provisions 123 UBC97 - ASD 155 code check criteria member check summary 102 codes criteria 111 design criteria 15 column moments AISC ASD critera 16 Australia AS4100 criteria 25 BS5950 24 CAN 22 CSA S16-01 22 Eurocode criteria 21 LRFD criteria 16 minor axis bracing 44 column requirements UBC97 - ASD 156 UBS 1997 - LRFD 159 columns AISC 1997 147 assign menu 26 effective length factors 26 flange bracing 27 size 26 unbraced lengths 27 columns - unbraced length minor axis bracing 43 compression 21.3 CAN 90 CSA S16-01 90

170

compression flange bracing steel standard provisions technical notes 41 concentrically braced frames UBC 1997 - LRFD 161 connector spacing for double angles AISC 360 - ASD and LRFD 52 AS 4100-98 81 ASD 9th 55 CAN 69 CSAS16-01 69 LRFD 3rd 55 criteria AISC ASD 15 ASD 112 codes 111 design 15 Eurocode 20 t code check 103 LFRD 112 LRFD 15 member check summary 102 steel seismic provisions post-processors 111 cross section classification BS5950:1990 56 BS5950:2000 56 steel standard provisions technical notes 40 CSA S16-01 axial slenderness limits 22 beams with end connections 20, 22 column moments 22 compression 21.3 90 flange bracing 22 ts 22 K-Factor 22 zone - web shear 90 steel standard provisions post-processors 21 tension 21.3 90 CSA/CAN S16-09 section capacity 71 CSAS16-01


bending capacity 68 connector spacing for double angles 69 design yield strength 68 effective length 67 member code check 67, 68 section capacity 69 custom load combinations load combinations 14, 111

D

design BS5950 24 design assumptions AS 4100-98 81 design code AISC 360 direct analysis validation 98 design criteria AISC ASD criteria 15 codes 15 Eurocode criteria 20 LRFD criteria 15 steel standard provisions post-processors 15 design process assign menu 34 steel seismic provisions post-processors 117 design yield strength AS 4100-98 79 ASD 9th 55 BS5950:1990 64 BS5950:2000 64 CAN 68 CSAS16-01 68 Eurocode 72 LRFD 3rd 55 direct analysis method AISC 360 - ASD and LRFD 45 direct analysis validation report load combinations 51

E

eccentrically braced frames


AISC 1997 - LRFD 150, 152, 153 AISC 2002 (ANSI 341-02) LRFD 142, 144, 145 AISC 2005 (ANSI 341-05) ASD and LRFD 132, 134, 135 effective length CAN 67 CSAS16-01 67 Eurocode 72 effective length factors Australia AS4100 criteria 25 columns 26 Eurocode criteria 21 horizontal braces 29 effective length method BS5950:1990 63 BS5950:2000 63 effective length with Ke-factor AS 4100-98 80 effective lengths beams 28 braces 30 BS5950 23 BS5950:1990 60, 61 BS5950:2000 60 elastic critical moment Eurocode 73 error messages AS 4100-98 82 ASD 9th 56 BS5950:1990 66 BS5950:2000 66 CAN/CSA S16-01 69 CAN/CSA S16-09 71 Eurocode 75 LRFD 3rd 56 Eurocode bending capacity 73 design yield strength 72 effective length 72 elastic critical moment 73 error messages 75 load combinations 72 member code check 100 unbraced bending length 72

171

Eurocode 3 BS EN 1993-1-8:2005 design 106 Eurocode 3:BS EN 1993-1-8 resistance of compression zone (web bearing) 91 Eurocode 3:BS EN 1993-1-8:2005 t code check 90, 106 zone - web shear 90 resistance of tension zone (flange bending) 91 resistance of tension zone (web bearing) 91 stiffener design 91, 106 Eurocode criteria column moments 21 design criteria 20 effective length factors 21 flange bracing 21 ts 21 reduced beam sections 21 sidesway 20 exiting modes assign menu 35 steel seismic provisions post-processors 119

F

FEMA 350 AISC 1997 - LRFD 154 frame design 154, 155 reduced beam section connections 155 final design BS5950 - draft amend, April 1998 105 BS5950-1:2000 105 t code check 103 flange bracing Australia AS4100 criteria 25 beams 28 BS5950 24 CAN 22 columns 27


CSA S16-01 22 Eurocode criteria 21 horizontal braces 30 flexural-torsional buckling of tees minor axis bracing 44 forces ts 18 frame design FEMA 350 154, 155 frame numbers assign menu 32, 113 frame types assign menu 113

G

general steel standard provisions technical notes 37 general seismic design requirements AISC 2005 (ANSI 341-05) ASD and LRFD 124 generated load combinations load combinations 14, 110 geometric stiffness method second order analysis 46 geometry ts 17

H

horizontal braces assign menu 29 effective length factors 29 flange bracing 30 minor axis bracing 44 size 29 unbraced lengths 30

I

IBC 2000 ASD 9th 53 LRFD 3rd 53 IBC 2003 ASD 9th 53


LRFD 3rd 53 IBC 2006 load combinations 50 IBS 2009 load combinations 50 intermediate moment frames AISC 1997 - LRFD 149 AISC 2002 (ANSI 341-02) LRFD 141 AISC 2005 (ANSI 341-05) ASD and LRFD 129, 130 introduction 11

J

t check summary steel seismic provision reports 165 t code check AISC -AISD 9th 87 AISC 360 87 stiffener design 105 web plate details 105 AS 4100-98 92, 93 assumptions and limitations 82 BS 5950 - draft amend, April 1998 105 BS5950 Part 1:1990 88 BS5950-1:2000 105 CAN/CSA S16-01 90 CAN/CSA S16-09 90 criteria 103 Eurocode 3:BS EN 1993-1-8:2005 90, 106 final design 103 t data 103 t design 86 t forces 84 t number 103 LRFD 3rd 87 material properties 103 process menu 34, 116 results 103

172

steel seismic provision reports 164 steel standard provisions reports 102 steel standard provisions technical notes 82 story number 102 t data t code check 103 t design t code check 86 t forces t code check 84 t number t code check 103 t view assign menu 33 t view/update process menu 115 ts AISC ASD criteria 17 Australia AS4100 criteria 25 BS5950 24 CAN 22 CSA S16-01 22 Eurocode criteria 21 forces 18 geometry 17 LRFD criteria 17 materials 17 optimization 19

K

k factor CAN/CSA 70 K-factor AISC 360 - ASD and LRFD 52 ASD 9th 55 LRFD 3rd 55 K-Factor AISC ASD criteria 16 CAN 22 CSA S16-01 22 LRFD criteria 16 kinked column equivalent uniform moment


minor axis bracing 45

L

LFRD criteria 112 limitations AISC 1997 - LRFD 146 AISC 2002 (ANSI 341-02) LRFD 137 AISC 2005 (ANSI 341-05) ASD and LRFD 124 code check 123 UBC97 - ASD 155 UBS 1997 - LRFD 158 load and resistance factor design combinations ASD 9th 54 load combinations 51 LRFD 51 LRFD 3rd 54 load cases aligning, with a specific direction 59 load combinations AISC 2002 (ANSI 341-02) LRFD 138, 146 AISC 2005 (ANSI 341-05) ASD and LRFD 124 AISC 360 - ASD and LRFD 50 allowable strength design combinations 50 AS 79 AS 4100-98 79 ASCE 7-05 50 ASD 9th 53 BS5950:1990 57, 67 BS5950:2000 57, 67 calculating sway state per 58 calculating λcr per 58 custom load combinations 14, 111 direct analysis validation report 51 Eurocode 72


generated load combinations 14, 110 IBC 2006 50 IBS 2009 50 load and resistance factor design combinations 51 LRFD 51 LRFD 3rd 53 member check summary 102 notional loads in 58 NZS 1170 79 steel seismic provision reports 164 steel seismic provisions post-processors 109 steel seismic provisions technical notes 122 steel standard provisions post-processors 14 steel standard provisions reports 97 steel standard provisions technical notes 39 loads AISC 2002 (ANSI 341-02) LRFD 138, 146 AISC 2005 (ANSI 341-05) ASD and LRFD 124 local flange bending - tension AS 4100-98 92 local web yielding AISC - ASD 9th 87 AISC 360 88 LRFD 3rd 88 LRFD 3rd allowable stress design combinations 54 buckling restrained braces 56 connector spacing for double angles 55 design yield strength 55 error messages 56 IBC 2000 53

173

IBC 2003 53 t code check 87 K-factor 55 load and resistance factor design combinations 54 load combinations 53 local web yielding 88 member code check 53 zone check 88 round bar slenderness limits 55 steel standard provisions technical notes 53 stiffener design 88 unbraced bending length 64 web crippling 88 LRFD criteria axial slenderness limits 17 B1 Factors 15 B2 Factors 15 column moments 16 design criteria 15 flange bracing 16 ts 17 K-Factor 16 sidesway 16

M

major axis bracing steel standard provisions technical notes 41 material properties t code check 103 materials AISC 1997 - LRFD 147 AISC 2002 (ANSI 341-02) LRFD 138 AISC 2005 (ANSI 341-05) ASD and LRFD 125 ts 17 UBC97 - ASD 156 member check summary code check criteria 102 criteria 102 load combinations 102


steel seismic provision reports 164 steel standard provisions reports 102 summary results 102 member code check AISC 100 AISC 360 - ASD and LRFD 45, 52 AS 4100-98 75, 101 ASD 9th 53 BS 5950 101 BS5950:1990 56 BS5950:2000 56 CAN 67, 68 CAN/CSA S16-01 100 CSAS16-01 67, 68 Eurocode 100 LRFD 3rd 53 process menu 33, 115 steel seismic provision reports 164 steel standard provisions reports 100 steel standard provisions technical notes 45 member force summary steel standard provisions reports 107 member forces steel standard provisions reports 106 member forces envelope steel standard provisions reports 107 member view assign menu 33 process menu 114 AISC 2002 (ANSI 341-02) LRFD 138, 139 AISC 2005 (ANSI 341-05) ASD and LRFD 125, 126 memeber code check Eurocode 72 minor axis bracing


beams - Lu for axial 42 beams - Lu for bending 43 column moments 44 columns - unbraced length 43 flexural-torsional buckling of tees 44 horizontal braces 44 kinked column equivalent uniform moment 45 steel standard provisions technical notes 42 assigned unbraced length 43 model status steel standard provisions post-processors 13 models saving 13 modes changing 119 exiting 119 steel seismic provisions post-processors 109 steel standard provisions post-processors 13 moment amplification BS5950:1900 62 BS5950:2000 62

notional loads in load combinations BS5950:1990 58 BS5950:2000 58 NZS 1170 load combinations 79

O

OCCS 131 optimization ts 19 ordinary cantilever column system 131 ordinary concentrically braced frames AISC 1997 - LRFD 149 AISC 2002 (ANSI 341-02) LRFD 141 AISC 2005 (ANSI 341-05) ASD and LRFD 132 ordinary moment frames AISC 1997 - LRFD 149 AISC 2002 (ANSI 341-02) LRFD 141 AISC 2005 (ANSI 341-05) ASD and LRFD 130 UBC 1997 - LRFD 159 UBC97 - ASD 156

P

N

NDy, NDx, NLx, NLy 59 nominal strengths AISC 2002 (ANSI 341-02) LRFD 138, 146 AISC 2005 (ANSI 341-05) ASD and LRFD 124 non-sway sensitive BS5950:1990 57 BS5950:2000 57 notional loads AISC 360 - ASD and LRFD 48 AISC 360 direct analysis validation 99 AS 4100-98 78

174

P-delta BS5950:1990 63 BS5950:2000 63 design Eurocode 3 BS EN 1993-1-8:2005 106 zone - web shear CAN 90 CSA S16-01 90 Eurocode 3:BS EN 1993-1-8:2005 90 zone check AISC 360 88 LRFD 3rd 88 zone checks AISC -ASD 9th 87


process menu assign menu 32 t code check 34, 116 t view/update 115 member code check 33, 115 member view 114 steel seismic provisions post-processors 114 update 114 update result icon 116 view result icon 116

R

reduced beam section check code check 123 reduced beam section connections FEMA 350 155 reduced beam sections Australia AS4100 criteria 26 beams 29 BS5950 24 Eurocode criteria 21 reduced stiffness AISC 360 - ASD and LRFD 49 AISC 360 direct analysis validation 99 resistance of compression zone (web bearing) Eurocode 3:BS EN 1993-1-8 91 resistance of tension zone (flange bending) Eurocode 3:BS EN 1993-1-8:2005 91 resistance of tension zone (web bearing) Eurocode 3:BS EN 1993-1-8:2005 91 results BS5950 - draft amend, April 1998 105 BS5950-1:2000 105 t code check 103 round bar slenderness limits ASD 9th 55


LRFD 3rd 55

S

saving the model steel standard provisions post-processors 13 sccs 131 second order analysis AISC 360 - ASD and LRFD 45 B1 factor 47 B2 factor 48 by amplified first order analysis 46 by geometric stiffness method 46 second order analysis by amplified first order analysis analysis method 77 second order analysis by geometric stiffness method AS 4100-98 77 second order effects AS 410-98 75 second-order analysis AISC 360 direct analysis validation 98 section capacity CAN 69 CSAS16-01 69 section capacity BS5950-1:1990 BS5950:1990 65 BS5950:2000 65 section capacity BS5950-1:2000 BS5950:1990 65 BS5950:2000 65 seismic design categories AISC 1997 - LRFD 146 AISC 2002 (ANSI 341-02) LRFD 138 seismic provisions for structural steel buildings in seismic zone 3 UBC97 - ASD 156

175

seismic provisions for structural steel buildings in seismic zone 4 UBC97 - ASD 156 sidesway AISC ASD criteria 16 assign menu 31 Australia AS4100 criteria 25 BS5950 23 Eurocode criteria 20 LRFD criteria 16 single angles CAN/CSA S16-09 71 size braces 30 columns 26 horizontal braces 29 sloping beams steel standard provisions technical notes 39 special cantilever column systems 131 special concentric braced frames AISC 1997 - LRFD 149 AISC 2002 (ANSI 341-02) LRFD 141 AISC 2005 (ANSI 341-05) ASD and LRFD 131 special moment frame UBC97 - ASD 157, 158 special moment frames AISC 1997 - LRFD 147, 148 AISC 2002 (ANSI 341-02) LRFD 139, 140 AISC 2005 (ANSI 341-05) ASD and LRFD 126–129 UBS 1997 - LRFD 159, 160 special truss moment frames AISC 2002 (ANSI 341-02) LRFD 141 AISC 2005 (ANSI 341-05) ASD and LRFD 131 steel design codes steel standard provisions technical notes 37


steel seismic provision reports t check summary 165 t code check 164 load combinations 164 member check summary 164 member code check 164 steel seismic provisions postprocessors assign menu 113 changing modes 119 criteria 111 design process 117 exiting modes 119 load combinations 109 modes 109 process menu 114 steel seismic provisions technical notes load combinations 122 UBC 1997 LRFD 158 steel shapes steel standard provisions technical notes 38 steel standard provision postprocessors 13 steel standard provisions postprocessors assign menu 26 Australia AS4100 criteria 24 BS5950 22 CAN 21 CSA S16-01 21 design criteria 15 load combinations 14 model status 13 modes 13 saving the model 13 steel standard provisions reports AISC 360 direct analysis validation 98 cocde check criteria 97 t code check 102 load combinations 97 member check summary 102


member code check 100 member force summary 107 member forces 106 member forces envelope 107 steel standard provisions technical notes ASD 9th 53 compression flange bracing 41 cross section classification 40 general 37 t code check 82 load combinations 39 LRFD 3rd 53 major axis bracing 41 member code check 45 minor axis bracing 42 sloping beams 39 steel design codes 37 steel shapes 38 tension capacity 41 torsion 41 stifener design AISC -ASD 9th 87 stiffener design AISC 360 88 AS 4100-98 92 BS5950 - draft amend, April 1998 106 BS5950 Part 1:1990 89 BS5950-1:2000 106 Eurocode 3:BS EN 1993-1-8:2005 91, 106 LRFD 3rd 88 story number t code check 102 summary results member check summary 102 sway-sensitive design method assign menu 31 BS5950:2000 only 31

176

T

tension 21.3 CAN 90 CSA S16-01 90 tension capacity steel standard provisions technical notes 41 torsion steel standard provisions technical notes 41

U

UBC 1997 - LRFD concentrically braced frames 161 ordinary moment frames 159 UBC 1997 LRFD steel seismic provisions technical notes 158 UBC97 - ASD code check 155 column requirements 156 limitations 155 materials 156 ordinary moment frames 156 seismic provisions for structural steel buildings in seismic zone 3 156 seismic provisions for structural steel buildings in seismic zone 4 156 special moment frame 157, 158 UBS 1997 - LRFD column requirements 159 limitations 158 special moment frames 159, 160 unbraced bending length ASD 9th 64 BS5950:1990 55 BS5950:2000 55


Eurocode 72 LRFD 3rd 64 unbraced lengths beams 28 braces 31 columns 27 horizontal braces 30 update assign menu 33 process menu 114 update result icon process menu 116 assigned unbraced length minor axis bracing 43

V

view result icon


process menu 116

W

web bearing – tension and compression BS5950:Part 1 1990 89 web bearing yielding - tension and compression AS 4100-98 92 web buckling BS5950 Part 1:1990 89 web buckling - compression AS 4100-98 92 web crippling AISC -ASD 9th 87 AISC 360 88 LRFD 3rd 88

177

web shear AS 4100-98 92 BS5950 Part 1:1990 89 web shear interaction BS5950-1:2000 BS5950:1990 66 BS5950:2000 66 web tensile force BS5950 Part 1:1990 89



178


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