Steel Design Final Project - Tradeoffs For All Structural 5m3v
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CHAPTER I - PROJECT BACKGROUND 1.2 The Project The project is a seminary whose structure is made up of steel. It is intended to be built in Antipolo, Rizal. Building a seminary is important for the Antipoleneos since the city contains the National Shrine of the Philippines, and thus needs training areas for students who want to become priests someday. The seminary contains all the necessary rooms for the residents of the building.
Figure 1. Perspective of the Proposed Seminary
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As seen in Figure 1, the building has five floors with a flat roof, and is rectangular in shape. It has a total floor area of 700 sq. m with dimensions of 50 m x 14 m. The first floor contains the refectory (dining), chapel, lobby, infirmary (clinic), recreation area, kitchen and staff room. The second and third floors contain class rooms, laboratories, library, and offices. The fourth and fifth floor contain the study area and dormitories. It has a main stair, fire exit, ramps, and an elevator. The height of each floor is 3 m having a total of 15 m.
1.3 Project Location The project area is located in Antipolo City, Rizal, which is included in the areas under seismic zone 4. The address of the area lot is Lot 6 Blk.1, Sampaguita St. Bermuda Hts. Subd., Brgy. San Luis, Antipolo City. Figures 2 and 3 show the vicinity map of the area and its distance from the nearest fault line which is the Makati Valley Fault System, respectively.
Figure 2. Vicinity Map of the Seminary 2
1.4 Project Objectives The main objective of this project is to analyse and design a steel structure in accordance with the principles written in NS 2001. Other objectives of the project are as follows: a. To design a five-story steel seminary main building that will have an acceptable probability of performing satisfactorily during its intended life time. b. To provide all the necessary architectural plans, structural plans, and the estimate of the building cost. c. To plan the structure considering balanced constraints, trade-offs and standards on the design.
1.5 The Client The client of this structure is a set of religious people led by Mrs. Sharon Umayam. She is a businesswoman and at the same time the president of the lectors in Our Lady of Peace and Good Voyage Church (National Shrine of the Philippines).
1.6 Project Scope and Limitation The following were the scope covered by the design project: 1.) The project was designed in accordance to the National Building Code of The Philippines and the National Structural Code of the Philippines applying the Allowable Strength Design (ASD). 2.) Structural analysis was done manually and was checked through STAAD. 3.) All the needed architectural plans and structural plans of the building were provided.
The following were the limitations of the design project: 1.) Only the main structure (includes beams, columns, and connections) were considered in the design. 2.) The cost estimates for the mechanical, plumbing and architectural plan were not included. 3.) The plumbing and electrical plans are not included in this design. 4.) The interior design of the structure was not considered.
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1.7 Project Development
PLANNING/CONCEPTUALIZATION
IDENTIFICATION OF DESIGN STANDARDS AND PARAMETERS
PRESENTATION OF ARCHITECTURAL AND STRUCTURAL PLANS WITH INITIAL ESTIMATE
IDENTIFICATION OF DESIGN CONSTRAINTS, TRADE-OFF
LOAD IDENTIFICATION, STRUCTURAL ANALYSIS, AND FINAL DESIGN
Figure 4. Project Development Process Figure 3. Project Development Process The project development process started with the planning/conceptualization. In this stage, the identification of client was the most important so as to know the structure to be build. In this case, the structure requested by the client was a seminary. It also included the identification of the location where the structure was intended to be built. The next stage was the identification of design standards. Knowing the structure to be constructed, the next part was to know the specific design standards that are required before coming up to the design (i.e., minimum dimension of a classroom, minimum size of an elevator shaft, etc.). These will set the parameters in the creation of the architectural and floor plans which is the next stage in the process. 4
In the third stage, the plans will be presented to the client so that alterations could be made. After all has been settled, constraints can now be identified, which is the next stage. In this, the constraints that were projected will then be classified as either qualitative or quantitative. Knowing the quantitative tradeoffs will pave the way to the determination of the trade-offs for the structure. In the last stage, the geometric design, computation, and final estimation for each trade-offs will be made. Then, all of these will be presented to the client. The client will then rate each trade-off. The one which has the most favorable rating among all will then be chosen for the design of the structure.
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CHAPTER 2: DESIGN INPUTS 2.1 Description of the Structure The structure contains five floors with each floor having different function from the other. The structure has two access stairs, a set of ramps, and an elevator. The structure has special moment resisting frames in the longitudinal axis, and special braced frames (X-bracing) in the transverse axis. Figure 5 shows the geometric model of the structure.
Figure 4. Geometric Model of the Structure
Figure 5. Wire frame Perspective View 6
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Table 1 shows the total floor area and the different areas of the rooms contained in each floor. Table 1. Total Floor Areas and Functions per Floor FUNCTION
AREA (m2)
1ST Floor Ramps and Elevator
49
Stairs
25
C.R.
22.5
Chapel
168
Refectory
168
Staff Room
63
Clinic
49
Lobby
70
Kitchen
63
Hallway
22.5
TOTAL
700 2nd Floor
Ramps and Elevator
49
Stairs
25
C.R.
22.5
Offices
3(45)
Class Rooms & Laboratories
4(63)
Other Rooms
32.5
Lounge
35
Hallway
79
TOTAL
700 3rd Floor
Ramps and Elevator
49
Stairs
25 8
C.R.
22.5
Offices
45
Class Room
2(63)
Other Rooms
133
Faculty Room
65
Library
94.5
Hallway
73.5
Sisters’ Room
66.5
TOTAL
700 4th Floor
Ramps and Elevator
49
Stairs
12.5
C.R.
22.5
Study Area
178.5
Dormitory
255.5
Vice Rector’s and Prefect’s Room
66.5
Toilet & Bath
59.5
Laundry
28
Hallway
28
TOTAL
700 5th Floor
Ramps and Elevator
49
Stairs
25
Hallway
28
Dormitory (1)
201
Dormitory (2)
196
Toilet & Bath
2(59.5)
Laundry
28
Rector’s Room
66.5 9
TOTAL
700
TOTAL FLOOR AREA
3500
2.2 Classification of the Structure Using the National Structural Code of the Philippines (NS) 2010, the designer was able to classify and determine the classifications and parameters of the structure. 2.2.1 Seismic Load Parameters Since the structure is a seminary, the occupancy category of the building is classified as an Essential Facility, whose value of importance factor (I) is equal to 1.50. For the site geology, the soil profile type was considered as SD because the soil properties of the area was not known. Since the area is in Region IV-A, the structure is included in the areas under seismic zone 4, with seismic zone factor (Z) of 0.4.
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As Figure 7, the nearest
to
Figure 6. Distance of the Nearest Fault Line to the Proposed Seminary
seen
in
fault
line
the area is
the Makati Valley Fault System which is 16 km away. The seismic source type is considered as Type C since this fault line is not prone on producing large magnitude of earthquakes. With these data, the near source factors Na and Nv are both 1.0. The values of Ca and Cv are now determined as 0.44 and 0.64 respectively. Since the building is rectangular, it is a regular structure. Special Moment Resisting Frame System (SMRF) was utilized in the longitudinal, and special steel concentric braces frame was utilized in the transverse axis, thus, the seismic response coefficient (R) is 7. Static force procedure was utilized for the determination of the seismic forces acting on the strcture.
2.2.2 Wind Load Parameters In this part, the parameters for the determination of the wind loads will be presented, but those which are presented already in the seismic part will not be repeated. As the area is included in the zone 4, it has a basic wind speed (V) of 200 kph. The structural type of the building is a Main Wind Resisting Force System, thus, the value of Directionality Factor (K d) is 0.85. The surface roughness of the building is B because it is intended to be built in an urban area. The seminary is a medium rise building and an enclosed structure. The gust effect factor is considered as 0.85. Other parameters such as topographic factor (k zt) and velocity pressure exposure coefficients (k z) will be 11
computed. These values are those needed in the determination of the wind pressure acting on the structure.
2.2.3 Dead Loads and Live Loads The minimum design for dead loads and live loads used in the structure is presented in this part. For the live loads and dead loads (includes ceiling, floors and floor finishes) of the structure, the materials and their respective uniform load are in shown In Table 2
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Table 2. Dead Loads and Live Loads of the Structure DEAD LOADS Component
Load (kPa) Ceiling
Gypsum Board Mechanical Duct Allowance Wood Furring Suspension System Floor and Floor Finishes Cement Finish on Stone Concrete Fill Ceramic Quarry Tile Masonry For Plastering (both sides)
0.008 0.2 0.12 1.53 1.1 0.24
LIVE LOADS Basic Floor Area
1.9
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2.3 Architectural Plans
Figure 7. Firs Floor Plan of the Seminary
Figure 8. Second Floor Plan of the Seminary
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Figure 9. Third Floor Plan of the Seminary
Figure 10. Fourth Floor Plan of the Seminary
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Figure 11. Fifth Floor Plan of the Seminary
Figure 12. Front Elevation of the Seminary
Figure 13. Side View of the Seminary
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CHAPTER 3: DESIGN CONSTRAINTS, TRADE-OFFS, AND STANDARDS 3.1 Design Constraints Constraint based design takes the parameters associated with a design problem and links them to the attributes of the formal components and relationships of a solution. The forms that compose a building are defined by a set of attributes. Constraints have to be managed effectively throughout the decision making process, and also could be reduced or eliminated. In this project, there are specific constraints and general constraints. The specific constraints will serves as the criteria for ranking. The general constraints are the basis of the tradeoffs which will be ranked. The specific constraints were divided into two types, namely, quantitative and qualitative constraints. Quantitative constraints are those constraints that can be measured using engineering methods (estimation, direct counting, etc.). The qualitative constraints are those which cannot be measured but are ranked through the designer’s perception and experience (unranked in this project). The next sections present the specific constraints selected among all others that will have a significant impact in the design of the structure. 3.1.1 Quantitative Constraints 1. Economic (Cost). The design of the building will comprise steel for the structural framing as specified by the client. The tradeoffs presented in the next section are compared so as to determine which of those could be the cheaper choice. Davison (2003) noted that frame in the steel building has a greater percentage in the entire budget of the structural design. The components of the steel structure (beams and columns) can consist 30% in the total cost of construction. Total cost outcome of the tradeoffs in sections and connections will be considered in this design. The cost of the structure is highly significant both to the designer and the client. 2. Constructability (Duration). In this constraint, the designer thought on the process of manufacturing of structural sections is considered for the tradeoff in sections. For the tradeoffs in connections, the designer considered the construction time in ing the beams and columns. The tradeoffs to be presented would be compared so as to know which among the tradeoffs will require lesser amount of man-hour for construction. 17
3. Safety (Deflection). The designer considered the safety of the structure with respect to its vertical axis. Having considered the constructability of structure either using rolled or built-up sections, it is also reasonable to look at the safety of the structure. This must be capable to withstand the gravity loads. 4. Strength (Capacity). The designer considered the capacity of a connection to resist the possible failures such as failure in bearing, shearing (double or single), tensile, block shear. Knowing the capacity of the bolt would lead the designer to know how serviceable the structure is. The designer also measured the tensile capacity that the tension can resist, and the axial capacity that columns can carry. 3.1.2 Qualitative Constraints 1. Aesthetics. The beauty of the structure lies upon its final output. This constraint depends on the taste of a person therefore it is considered as a qualitative constraint. It depends on a person’s perception which design is more presentable. 2. Social. People are very influential when it comes to ideas and other things. In this project, the friends and relatives of the client might give him an idea which might alter the work of the designer. Demands from these people might affect the decision of the client and the designer. 3. Health and Safety. Different areas surrounding commercial building might affect the people that might use the commercial building. Smoke from the cars using the roads and cigarettes, smell from the nearby canal, laundry areas, restaurants, etc., are examples of these hazardous odor that might affect health and safety of the people in the building.
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CONSTRAINTS
SPECIFIC
QUALITATIVE
GENERAL
QUANTITATIVE
TENSION BEAMS COLUMNS
HEALTH AND SAFETY
ECONOMIC
SOCIAL
CONSTRUCTABILITY
AESTHETICS
SAFETY
BOLTED CONNECTIONS WELDED CONNECTIONS
STRENGTH
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3.2 Tradeoffs Design trade-off strategies are always present in the design process. Considering design constraints, trade-offs that have a significant effect on the structural design of the structure was provided by the designer. As a trade-off, the designer will have to evaluate which of the two is more effective considering each constraint. The following are the tradeoffs that were chosen by the designer because they are the most fitted to the said constraints. Tradeoffs in Beams and Columns. The first part of the project is to determine which section is more effective for a structural member (beams and columns). The designer utilized the rolled sections (W Shapes) and built up sections (BW Shapes) as tradeoffs for the structural . Considering both tradeoffs to be effective and efficient in the design, the designer sought to find out which section will have greater performance considering the constraints; economic, constructability, safety, and strength.
Figure 14. Actual (left) and Theoretical (right) Built Up Sections
Tradeoffs in Tension . The tension for the structure are the x-bracing. The designer chose the tradeoffs to be the section of the tension member, namely single angle with equal legs,
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and single angle with unequal legs. The designer would like to know if there will be difference in the performance of the two sections. Tradeoffs in Bolted Connections. Bolted connections are widely used in almost every mechanical and structural system due to the added flexibility of assembly and disassembly of sub-systems for inspection, replacement, and routine maintenance. The designer utilized bolted connections in the bracing of the structure. The tradeoffs for bolted connections is the bolt hole that will be used, namely standard hole dimensions and oversized hole dimensions. The designer would like to know if there will be alterations in the performance of the connection when these two are applied.
Tradeoffs in Welded Connections. Welded connections are ts connected through welding. The designer planned that the beams and columns of the structure will be connected through welding. The tradeoffs chosen by the designer for the welded connections are the electrodes that will be used in welding. COLUMNS
The electrodes are namely E70XX and E60XX.
TRADEOFF IN SECTION
BEAMS
TRADEOFFS
TENSION
TRAFEOFF IN TYPE OF BOLT
BOLTED CONNECTIONS CONNECTIONS
21 WELDED CONNECTIONS TRADEOFF IN TYPE OF WELDING EQUIPMEN
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3.2.3 Ranking Scale The ranking scale that will be used in this design is based on the model on tradeoff strategies formulated by Otto and Antonsson (1991). The importance factors in each constraint is scaled from 0 to 5, while the ability to satisfy the constraint is scaled from -5 to 5, 5 being the highest for both. After obtaining the results, the product of the importance and ability to satisfy the criteria will be summed of from each constraint. The result will then be the overall ranking of the tradeoff.
Figure 3.7 Ranking Scale for Importance Factor
Figure 3.8. Ranking Scale for Satisfactory Factor
Computation of ranking for ability to satisfy criterion of materials:
Difference( )=
Higher value−Lower value ×100( ) Lower value
Subordinate rank =Governing rank −(
difference ) 10
Equation 1 Equation 2
The above equations will be used for the manipulation of the rankings of each constraint given to the tradeoffs. The governing rank is the highest possible value set by the designer. The subordinate rank in second equation is a variable that corresponds to its percentage difference from the governing rank along the ranking scale.
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3.3 Initial Estimate, Ranking Computation, and Raw Designer’s Ranking For the first part of the project, choosing between the rolled section and built-up section, two sections from each tradeoff was assumed. The designer assumed each to have the same areas. To determine which of these two is more economic, the price per unit weight of each section were multiplied by the quantity (with respect to length) of the each section. To measure the serviceability constraint, the deflections of the assumed sections were computed and compared. All assumed values and the estimates were shown in Appendix C. BEAMS INITIAL ESTIMATED VALUES Criteria Economic Constructability Safety
Tradeoffs Rolled Php 20,596,736 74 days 0.30%
Built Up Php 16,529,336 84 days 0.22%
INITIAL RANKING COMPUTATION FOR BEAMS To Determine the Ranking of the Values, Difference (%) = [(Higher - Lower)/Higher]*100 Subordinate Rank = Governing Rank - (Difference (%)/10) Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 20,596,736 16,529,336 5 19.75 3
CRITERIA Constructability N/A N/A 5 N/A 2
Safety 0.297 0.222 5 25.09 2
For the economic constraint, initial cost estimate is provided in the Appendix. To make an initial cost estimate, the designer considered the two tradeoffs to have the same area, and due to their different weights, the 24
tradeoffs will have different cost. To compute the rank of each tradeoff, the designer used the formula formerly enumerated. For the constructability constraint, the designer considered the manufacturability of each section. In this constraint, the designer gave a rank of 5 to Rolled Sections, and 2 fof Built Up sections. The main reason is that the rolled sections is manufactured as one, considering only the molding and curing time of the whole member, while built up section are rolled sections combined together to form another section, thus, aside from molding and curing time, we also consider the stiffening of the section. For the safety of the member, the designer considered the deflection per unit of length, of the same shapes used in the economic section. The deflection was presented in of percentage of the allowable deflection. Like in economic constraint, the rank for each tradeoff was computed.
COLUMNS INITIAL ESTIMATED VALUES Criteria Economic
Tradeoffs Rolled Php 20,596,736
Built Up Php 16,529,336
INITIAL RANKING COMPUTATION FOR COLUMNS Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 9,957,151 9,351,936 5 6.08 4
CRITERIA Constructability N/A N/A 5 N/A 2
Strength N/A N/A 5 N/A 4
For the economic constraint, initial cost estimate is provided in the Appendix. To make an initial cost estimate, the designer considered the two tradeoffs to have the same area, and due to their different weights, the tradeoffs will have different cost. To compute the rank of each tradeoff, the designer used the formula formerly enumerated. For the constructability constraint, the designer considered the manufacturability of each section. In this constraint, the designer gave a rank of 5 to Rolled Sections, and 2 fof Built Up sections. The main 25
reason is that the rolled sections is manufactured as one, considering only the molding and curing time of the whole member, while built up section are rolled sections combined together to form another section, thus, aside from molding and curing time, we also consider the stiffening of the section. For the strength of the member, values cannot be assumed since axial capacity of columns can only be measured after analyzing the whole structure. Therefore, the designer sought a way to rank this constraint. The designer gave a higher rank to the rolled beam sections because considering same area of cross sections, they always give lower value of weight. Thus, they can still carry greater amount of load to be sum up with their selfweights. Thus, the designer gave a rank of 5 to rolled sections, and 4 for built up sections. TENSION INITIAL ESTIMATED VALUES Criteria Economic
Tradeoffs Rolled Php 77,520
Built Up Php 119,321
INITIAL RANKING COMPUTATION FOR TENSION
Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 119,321 77,520 5 35.03 1
CRITERIA Constructability N/A N/A 5 N/A 4
Safety N/A N/A 5 N/A 3
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For the economic constraint, initial cost estimate is provided in the Appendix. To make an initial cost estimate, the designer considered the two tradeoffs to have the same area, and due to their different weights, the tradeoffs will have different cost. To compute the rank of each tradeoff, the designer used the formula formerly enumerated. For the constructability constraint, the designer considered the manufacturability of each section. In this constraint, the designer gave a rank of 5 to Single Angle with Equal Legs because there is equal distribution in the period of time in both legs, unlike in unequal legs, ranked as 4, because they can have variation of manufacturing, especially in curing time. For the strength of the member, In this part, values cannot be assumed since axial capacity of columns can only be measured after analyzing the whole structure. Therefore, the designer sought a way to rank this constraint. The designer gave a higher rank of 5 to the single angle with unequal legs because the axial load is possibly higher since the fasteners are placed in the longer leg, unlike in the single angle with equal legs ranked as 3, both have same dimensions thus giving high possibly of having lesser leg than that of single angle with unequal legs. Comparing the longer legs is necessary because there will be computation of gross area and net area, where the axial capacity of the tension member will depend.
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WELDED CONNECTIONS INITIAL ESTIMATED VALUES Criteria
Tradeoffs
Economic
E70XX Php 291,600
Constructability Safety
174.96 man-hrs 485
E60XX Php 264,600 158.76 manhrs 415
INITIAL RANKING COMPUTATION FOR BEAMS To Determine the Ranking of the Values, Difference (%) = [(Higher - Lower)/Higher]*100 Subordinate Rank = Governing Rank - (Difference (%)/10) Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 291600 264600 5 9.26 4
CRITERIA Constructability 175 159 5 9.21 4
Safety 485.000 415.000 5 14.43 4
To have an initial cost estimate in welded connections, the designer assumed equal length of weld but different thickness. The designer assumed that E70XX will result to thinner weld size, but is more costly. For constructability, the designer considered that material cost and the labor cost that will be resolved from the cost estimate. And finally for the strength, E70XX obviously got higher rank because it has greater strength than the other.
Bolted Connections 28
INITIAL ESTIMATED VALUES Criteria Economic Constructability
Tradeoffs Standard Oversized 9,900 11,200 51.48 44.8
INITIAL RANKING COMPUTATION FOR TENSION To Determine the Ranking of the Values, Difference (%) = [(Higher - Lower)/Higher]*100 Subordinate Rank = Governing Rank - (Difference (%)/10) Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 11,200 9,900 5 11.61 4
CRITERIA Constructability 51 45 5 12.98 4
Safety N/A N/A 5 N/A 3
To have an initial cost estimate in bolted connections, the designer based his estimate on the bolt hole area. The designer assumed the same number of bolts, but the oversized hole still got higher rank because it is more costly than the standard. For constructability, it comes the other way around where the oversized won. And finally for the strength, the designer gave rank of 5 into the oversized because the holes lessen the load that is transmitted.
3.4 Raw Designer’s Ranking and Assessment After making an initial estimate of the structure considering the constraints, the design came up with the raw rankings on the one-way slab and two-way slab. The values computed in the latter section is tabulated. BEAMS Criterion
Importance
Ability to Satisfy the Criterion Hot Rolled Built-Up 29
Economic (Cost) Constructability (Manufacturability) Safety (Deflection) Overall Ranking
5 4 4
3 5 2 43
5 2 5 53
As for economic constraint, it turned out that the rough cost estimate for the rolled sections is cheaper than the rolled sections. As for constructability, rolled up sections are easier to manufacture than the built up sections. As for the serviceability constraint, the deflection of the critical beam in the built-up section is lesser than that of the rolled section. Overall, it turned out that the built up section tradeoff outranked the rolled section for the raw designer’s ranking in beams.
COLUMNS Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Strength (Axial Capacity) Overall Ranking
5 4 4
Ability to Satisfy the Criterion Hot Rolled Built-Up 4 5 5 2 4 5 56 53
As for economic constraint, it turned out that the rough cost estimate for the built up sections is cheaper than the rolled sections. As for constructability, rolled up sections are easier to manufacture than the built up sections. As for the strength of the member, the axial capacity of the built up columns was hypothesized to be greater than that of rolled columns. Overall, it turned out that the rolled section tradeoff outranked the built up section for the raw designer’s ranking in columns.
TENSION Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Strength (Axial Capacity) Overall Ranking
5 4 4
Ability to Satisfy the Criterion SA Equal Legs SA Unequal Legs 5 1 5 4 3 5 57 41
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As for economic constraint, it turned out that the rough cost estimate for the single angle with equal legs is cheaper than single angle with unequal legs. As for constructability, the former is easier to manufacture than the latter. As for the strength of the bracing member, the axial capacity of the equal legs was hypothesized to be greater than that of the unequal legs rolled columns. Overall, it turned out that the single angle with equal legs tradeoff outranked single angle with equal legs tradeoff for the raw designer’s ranking in tension . WELDED CONNECTIONS Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Strength (Ultimate) Overall Ranking
5 4 4
Ability to Satisfy the Criterion E70XX E60XX 4 5 4 5 5 4 56 61
As for economic constraint, it turned out that the rough cost estimate for the welding electrode E60XX will result to cheaper price of welding connections compared to welding electrode E70XX. For constructability constraint, the designer considered the amount of man-hour that the welding connections will incur. To get an initial estimate, the designer used the economic cost to get the percentage of the labor cost required for the construction (welding), which resulted to number of hours the process will be finished. For the strength, the designer considered the ultimate tensile strength of two electrodes, which is their main difference. The E70XX basically has higher strength than E60XX. Overall, it turned out that the E60XX tradeoff outranked E70XX tradeoff for the raw designer’s ranking in welded connections. BOLTED CONNECTIONS RAW DESIGNER'S RANKING Criterion
Importance
Economic Constructability Strength Overall Ranking
5 4 4
Ability to Satisfy the Criterion Standard Oversized 5 4 5 4 3 5 57 56
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*Reference: Otto, K. N. and Antonsson, E. K., (1991). Trade-off strategies in engineering design. Research in Engineering Design, volume 3, number 2, pages 87-104.Retrieved from http://www.design.caltech.edu/Research/Publications/90e.pdf on January 27, 2016 As per economic constraint, the standard bolt hole is cheaper than the oversized. One reason is that it is the used by many company, unlike the oversized. Also, the standard bolt hole got higher rank in constructability. But regarding the strength, the designer gave a rank of 5 into oversized, and 3 to standard, because the transmission of force is not directly into the bolt. These tabulated values are just subjective, especially the importance factors. These values will still go on with the validation after making a final estimate and final ranking.
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3.9 Design Standards The design standards used are taken from the following codes and standards: 1. 2. 3. 4. 5.
National Structural Code of the Philippines (NS) vol. 1-2001 edition (PD1096) National Building Code of the Philippines ASTM (American Society for Testing and Materials) ASEP Steel Handbook 2004 vol. 1 Steel Designers’ Manual of the Steel Construction Institute 6th Edition
1. The National Structural Code of the Philippines 2001.This structural code provides minimum requirements for building structural systems using prescriptive and performance-based provisions. It is founded on broad-based principles that make possible the use of new materials and new building designs. It is also designed to meet these needs through various model codes/regulations, to safeguard the public health and safety nationwide. This is the main reference for the design procedure of the structure. Material Strength. Materials conforming specifications of NS 6th edition 2010 were used in the design of the project. Loadings. Dead loads, live loads and environmental loads (wind and earthquake) are the forces acting on the structure. Dead loads are consists of the weight of all materials of construction and partition loads that are presented in the next chapter. Live loads shall be the maximum loads expected by the occupancy; these loads are attached in chapter 4 as well. The required lateral loads due to wind and earthquake forces shall be separately calculated. Wind Loads. The wind load is calculated in STAAD Pro using specifications adopted in American Society of Civil Engineers ASCE7-05 and based on procedure as stated in NS 2010, section 207. Seismic Loads. The structure shall be designed and constructed to resist the effect of seismic ground motion as provided in section 208 of NS 6th edition (2010). Load Combinations. Steel sections shall be designed using the “Allowable Stress Design” method using the following combination DL + LL DL + 0.75 LL DL + WL DL + 0.7 EL 33
DL + 0.75 WL + 0.75 LL 0.6 DL + WL : 0.6 DL + 0.7 E Deformation Limits. Structures or structural shall be checked such that the maximum deformation does not exceed the following: a. Beams and Girders. Beams and girders ing floors and roof shall be proportioned with due regard to the deflection produced by the design loads. Considering then the total deflection, which is due to the additional live loads, occurring after attachment of non-structural elements shall not exceed L/360. 2. The National Building Code of the Philippines (PD 1096).The National Building Code of the Philippines, also known as Presidential Decree No. 1096 was formulated and adopted as a uniform building code to embody up-to-date and modern technical knowledge on building design, construction, use, occupancy and maintenance. The Code provides for all buildings and structures, a framework of minimum standards and requirements to regulate and control
location, site, design, and quality of materials,
construction, use, occupancy, and maintenance. A. Loading
: UBC 97, ASCE 7-05
B. Steel
: A36 3. Association of Structural Engineers of the Philippines (ASEP) Steel Handbook, 3rd
Edition, Volume 1. This provide the civil and structural engineering practitioners with a handy reference to locally available rolled shapes, built-up shapes, cold-formed steel sections and light gage steel sections. a. Hot-rolled Sections Dimensions and Properties b. Built-up Sections Dimensions and Properties
34
CHAPTER IV: STRUCTURAL ANALYSIS AND DESIGN 4.1 Design Methodology The design was done in accordance with the codes and standards appropriate for a reinforced concrete structure. The figure below shows the step by step process of the design of the building. FRAMING PLANS
STRUCTURAL PLANS
NS NB
DESIGN SPECIFICATIONS
MATERIAL PROPERTIES
MODULUS OF ELASTICITY STRUTURAL MEMBER DIMENSIONS
GEOMETRIC MODELING
STRUCTURAL MODEL
LOAD MODELS
DEAD AND LIVE LOAD SEISMIC AND WIND LOAD LOAD COMBINATIONS
STRUCTURAL ANALYSIS
SHEAR DIAGRAMS MOMENT DIAGRAMS REACTIONS AND DEFLECTIONS
STRUCTURAL DESIGN
DESIGN SCHEDULES DETAILING
Figure 15. Design Methodology 35
The first process in design methodology was the creation of structural plans. The structural plans included the foundation plans of the two trade-offs. The next step was to know the design specifications. These specifications are the codes and standards needed for the structure’s classification and description. The National Building Code and National Structural Code of the Philippines are the main references used for design specifications. The third step in the process was the identification of the material properties. The compressive stresses and modulus of elasticity of the concrete and steel to be used were determined. Also, the structural member dimensions (b, d, etc.) were assumed. The fourth step was the creation of the structural model. These models included geometric modelling, which showed the positioning of the structural (beams, columns, slabs) in 3D form. The fifth step was the presentation of load models. In this part, the loads acting on the structure were computed. These loads were the dead load, live load, wind load, and seismic (earthquake) load, applying also the load combinations. After computing for these loads, load models was presented also in 3D form. The sixth step was the structural analysis. In structural analysis, member (beams and columns) forces and reactions were determined. The member forces included were the axial force, shear force, and moment acting on the member. The last part was the structural design. The structural design did not include the design of footings. The values from the structural analysis was utilized to design the structural of the structures, mainly the beams and columns. The maximum moment acting on a beam was used to design the beam, and the maximum value of the axial force acting on a column was used to design the column. To design the slab, the total load on the floors was utilized.
36
4.1.1 Structural Plans
Figure 16. Second – Fifth Floor Framing Plan
37
4.1.2 Design Specifications The all the design specifications coming from NB and NS for the structure is stated Appendix A of the project.
4.1.3 Material Properties
Material Properties conforming to specifications of NS 6th Edition (2010) were used in the design of the structure using rolled sections. The properties for rolled sections were based on rolled section of Association of Structural Engineers of the Philippines, Inc. (2004).Steel Handbook, Dimensions and Properties. Philippines. ASEP. Locally produced rolled shapes were applicable only for structural steel whose minimum yield stress is 230 MPa. In this structure, the designers used A36 for rolled sections with minimum yield stress of 248 MPa and tensile strength of 400-551 MPa. The following material properties were used in the design:
38
4.1.4 Structural Models
Figure 17. Geometric Modelling of Structure
4.1.5 Load Models The loads considered in this project are the dead load, live load, wind load and seismic loads. Load combinations were also applied to these loads. The load combinations that were utilized were those that are written in Section 203 of NS 2010. The highlighted row shows the governing load combination.
39
Table 3. Load Combinations Load Case Combinations (UBC 1997) – STAAD Pro Load Case Dead Live Wind Seismic LC 1 1.4 1.4 LC 2 1.2 1.2 LC 3 1.2 1.2 0.8 LC 4 1.2 1.2 1.3 LC 5 1.2 1.2 1 LC 6 1.2 1.2 1 LC 7 0.9 0.9 1 LC 8 0.9 0.9 1.3
40
Figure 18. Dead Loads of the Structure
Figure 19. Live Loads of the Structure 41
Figure 20. Wind Loads Acting in the Structure
Figure 21. Seismic Loads Acting the Structure
42
4.1.6 Structural Analysis For the structural analysis of the , the results considered are those that came from the load combination which gave the maximum values of member forces and reactions, namely load combination 1 (1.4L + 1.4LL).
Figure 22. Axial Forces Acting on the Structure
A summary of values of the member forces is presented in the appendices. The following figures show the results of the structural analysis done through the software STAAD.
43
Figure 23. Moment Forces Acting on the Structure (Y-Axis)
4.1. 7 Structural Design The flowchart below shows the step by step process on how the designer designed each member present in the structure.
44
45
46
47
48
49
50
51
52
53
TENSION - SINGLE ANGLE WITH EQUAL LEGS DESIGN FOR ALL TENSION Given Fy Fu L P
248 415 3.807887 24.591
MPa MPa m kN RESULTS
Part 1. Determine the Trial Section rmin = L/300 Ag = P/(.6*Fy) *Select a Trial Section based on the 3
Part 2. Determine the Capacity of the Member
Ag
12.69295 52 165.2620 97
mm mm 2
Trial Section Used L 40 x 40 x5 rx
11.97
mm
ry
11.97
mm mm 2 mm
rmin
According to Net Area Pt = 0.5Fu*U*An *Assume Reduction Coefficient U = 0.85
A t
378.86 5
L w
40 40
An = Ag - Σholes
M
2.87
According to Gross Area Pt = 0.6Fy*Ag Governing Pt is smaller of the two
Net Area U Φbolt An
Part 3. Check the Capacity *If Pt < P, Reselect another section
0.85 22 268.86
mm mm kg/ m
mm mm 2
Capacity Pt
47.42018 25 SAFE
kN
54
TENSION - SINGLE ANGLE WITH UNEQUAL LEGS DESIGN FOR ALL TENSION
Given Fy Fu L P
248 415 3.807887 24.591
MPa MPa m kN RESULTS
Part 1. Determine the Trial Section 12.6929 6 165.262 1
mm mm 2
rx
15.46
mm
ry
8.44
A t L
426.72 5 50
mm mm 2 mm mm
w
40
M
3.35
rmin = L/300
rmin
Ag = P/(.6*Fy) *Select a Trial Section based on the 2
Ag Trial Section Used L 50 x 40 x5
Part 2. Determine the Net Area *Assume Reduction Coefficient U = 0.85 An = Ag - Σholes Part 3. Check the Capacity based on An Pt = 0.5*Fu*U*An *If Pt < P, Reselect another section
Net Area U Φbolt n An
0.85 22 3
mm kg/ m
316.72
mm pcs mm 2
55.8614 9
kN
Capacity Pt
55
SAFE
56
WELDED CONNECTIONS - TRADEOFF 1 (E70XX) CORNER COLUMN - EXTERIOR LONGITUDINAL BEAM CONNECTION (C1-B1) Given
Beam
Column
A bf tf
12323 192.8 19.1
mm2 mm mm
P Fy
200 248
kN MPa
A bf tf
Fu 30581 356.1 27.4
mm2 mm mm
E60 E70 E80 E90 E100 E110 E120
Part 1. Select the Welding Electrode to be used *Each eletrode corresponds to different stress Part 2. Determine the Capacity of the attached member Base on Gross Area T = 0.6FyAg Based on Net Area T = 0.5*Fu*U*Ag where U is to Reduction Factor
Electrode
E70
Fu
485
MPa
12323 1833.66 2
mm2
Capacity Gross Area Ag T Net Area U
If 1.5W > L > W, U = 0.75
T Governing T
*Lower Tensile Capacity Governs Part 3. Check the Tensile Capacity If T < P, the connections is safe
MPa MPa MPa MPa MPa MPa MPa
RESULTS
If L > 2W, U = 1 If 2W > L > 1.5W, U = 0.87
*Since weld is only in longitudinal, we use U = 0.75
415 485 550 620 690 760 825
kN
0.75 2241.24 6 1833.66 2 SAFE
Dimensions of Weld Min t
8
mm 57
else, Redesign Part 4. Determine the size of weld Min Thickness Thicker Material Min t <6mm 3 >6-12mm 5 >12-20mm 6 >20-38mm 8 >38-57mm 10 >57-150mm
12
>150mm
16
Max t t (used) L
17.5 12.75 152.488 6
mm mm mm
Max Thickness Attached Material <6mm te = t >6mm te = t - 1.6 Part 4. Compute for the Length of Weld T = 0.707tL*0.3Fu, solve for L
58
WELDED CONNECTIONS - TRADEOFF 2 (E60XX) EXTERIOR TRANSVERSE BEAM - COLUMN CONNECTION Given
Beam
Column
A
12323
bf tf
192.8 19.1
mm 2 mm mm
P Fy
200 248
kN MPa
A bf tf
Fu 3058 1 356.1 27.4
E60
415
MPa
mm2
E70
485
MPa
mm mm
E80 E90 E100 E110 E120
550 620 690 760 825
MPa MPa MPa MPa MPa
Part 1. Select the Welding Electrode to be used *Each eletrode corresponds to different stress Part 2. Determine the Capacity of the attached member Base on Gross Area T = 0.6FyAg Based on Net Area T= 0.5*Fu*U*Ag where U is to Reduction Factor If L > 2W, U = 1 If 2W > L > 1.5W, U = 0.87 If 1.5W > L > W, U = 0.75 *Since weld is only in longitudinal, we use U = 0.75 Lower Tensile Capacity Governs
RESULTS Electrode
E60
Fu
415
MPa
Ag
12323
mm2
T
1833.662 4
kN
Capacity Gross Area
Net Area U T Governing T
0.75 1917.766 9 1833.662 4 SAFE
59
Part 3. Check the Tensile Capacity If T < P, the connections is safe else, Redesign Part 4. Determine the size of weld Min Thickness Thicker Material Min t <6mm 3 >6-12mm 5 >12-20mm 6 >20-38mm 8 >38-57mm 10 >57-150mm 12 >150mm 16
Dimensions of Weld Min t
8
mm
Max t
17.5
mm
t (used)
12.75 178.2095 8
mm
L
mm
Max Thickness Attached Material <6mm te = t >6mm
te = t - 1.6
Part 4. Compute for the Length of Weld T = 0.707tL*0.3Fu, solve for L
60
WELDED CONNECTIONS - TRADEOFF 2 (E60XX) CORNER COLUMN - TRANSVERSE BEAM CONNECTION (C1-B34) Given
Beam
Column
A
12323
bf tf
192.8 19.1
mm 2 mm mm
P Fy
200 248
kN MPa
E60
Fu 415
MPa
A
8710
mm2
E70
485
MPa
bf tf
153.9 8.1
mm mm
E80 E90 E100 E110 E120
550 620 690 760 825
MPa MPa MPa MPa MPa
Part 1. Select the Welding Electrode to be used *Each eletrode corresponds to different stress Part 2. Determine the Capacity of the attached member Base on Gross Area T = 0.6FyAg Based on Net Area T = 0.5*Fu*U*Ag where U is to Reduction Factor If L > 2W, U = 1 If 2W > L > 1.5W, U = 0.87 If 1.5W > L > W, U = 0.75 *Since weld is only in longitudinal, we use U = 0.75 Lower Tensile Capacity Governs Part 3. Check the Tensile Capacity If T < P, the connections is
RESULTS Electrode
E60
Fu
415
MPa
12323 1833.662 4
mm2
Capacity Gross Area Ag T Net Area U T Governing T
kN
0.75 1917.766 9 1833.662 4 SAFE
Dimensions of Weld Min t
5
mm 61
safe else, Redesign Part 4. Determine the size of weld Min Thickness Thicker Material Min t <6mm 3 >6-12mm 5 >12-20mm 6 >20-38mm 8 >38-57mm 10 >57-150mm 12 >150mm 16
Max t t (used) L
17.5 11.25 201.9708 6
mm mm mm
Max Thickness Attached Material <6mm te = t >6mm
te = t - 1.6
Part 4. Compute for the Length of Weld T = 0.707tL*0.3Fu, solve for L
62
BOLTED CONNECTION - TRADEOFF 1 (STANDARD BOLT HOLES) P t Φbolts bolt hole
24.591 5 16 18
kN mm mm mm
RESULTS Fu
Part 1. Get the required number of bolts considering shear in the bolts Pu = AvFv, solve for n (number of bolts) where Av = n*pi*(Φ^2)/4 Fv = 0.30Fu Part 2. Get the required number of bolts considering bearing in the bolts Pu = AbFb, solve for n (number of bolts) where Ab = n*Dt Fb = 1.2Fu *Choose the greater amount of n
MPa
254.469 62.1 2
mm2 MPa pcs
Ab Fb n
90 248.4 2
mm2 MPa pcs
n (governs) s Le
2 24 32
pcs mm mm
Block Shear Av At Fv Ft Pt
190 155 62.1 103.5 27.8415
mm2 mm2 MPa MPa kN
Shear in Bolts Av per bolt Fv n
Bearing of Bolts
Pary 4. Check for Block Shear Pt = FvAv + FtAt where Fv = 0.3*Fu Ft = 0.5*Fu Av = Shear Area At = Tension Area *If Pt < P, Reselect another section else, the section chosen is SAFE Part 3. Determine the spacing of bolt
207
Le
SAFE
and edge distance s = 1.5*Φbolt Le = 2*Φbolt
63
64
BOLTED CONNECTION - TRADEOFF 1 (OVERSIZED BOLT HOLE) P t Φbolts bolt hole
24.591 5 16 20
kN mm mm mm
RESULTS Fu
Part 1. Get the required number of bolts considering shear in the bolts Pu = AvFv, solve for n (number of bolts) where Av = n*pi*(Φ^2)/4 Fv = 0.30Fu Part 2. Get the required number of bolts considering bearing in the bolts Pu = AbFb, solve for n (number of bolts) where Ab = n*Dt Fb = 1.2Fu *Choose the greater amount of n Pary 4. Check for Block Shear Pt = FvAv + FtAt where Fv = 0.3*Fu Ft = 0.5*Fu Av = Shear Area At = Tension Area *If Pt > P, Reselect another section else, the section chosen is SAFE Part 3. Determine the spacing of bolt and edge distance s = 1.5*Φbolt Le = 2*Φbolt
207
MPa
314.15927 62.1 2
mm2 MPa pcs
Ab Fb n
100 248.4 1
mm2 MPa pcs
n (governs) s Le
2 24 32
pcs mm mm
180 150 62.1
mm2 mm2 MPa
103.5 26.703
MPa kN
Shear in Bolts Av per bolt Fv n
Bearing of Bolts
Block Shear Av At Fv Ft Pt SAFE
65
4.3 Validation of Trade-offs This portion will testify if the ranking made in Chapter 3 is against or similar to the results of the final design and final cost estimates.
4.3.1 Final Estimate and Ranking Computation Beams FINAL ESTIMATED VALUES Criteria Economic Constructability Safety
Tradeoffs Rolled Php 12135424 74 days 7.41 mm
Built Up Php 14,785,004 84 days 5.67 mm
FINAL RANKING COMPUTATION FOR BEAMS CRITERIA Economic Constructability 14,785,004 84 12,135,424 74 5 5 21.83 13.32 3 4
Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Safety 7.41 5.67 5 30.69 2
Columns FINAL ESTIMATED VALUES Criteria Economic
Tradeoffs Rolled Php 7,533,312
Built Up Php 7,606,979 66
Constructability Strength
47 days 6385.42 kN
53 days 6762.8 kN
FINAL RANKING COMPUTATION Summary
Economic 7,606,979 7,533,312 5 0.97 4
Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
CRITERIA Constructability 53 47 5 11.11 4
Strength 2264.896667 2203.336061 5 2.72 4
Tension FINAL ESTIMATED VALUES Tradeoffs
Criteria Economic Constructability Strength
Single Angle (Equal) Php 44,765 7 days 47.42 kN
Single Angle (Unequal) Php 52,252 9 days 55.86 kN
FINAL RANKING COMPUTATION CRITERIA
Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 52,252 44,765 5 14.33 4
Constructability 9 7 5 21.08 3
Strengt h 55.860 47.420 5 15.11 3
WELDED CONNECTIONS INITIAL ESTIMATED VALUES 67
Criteria
Tradeoffs
Economic
E70XX Php 291,600
Constructability Safety
174.96 man-hrs 485
E60XX Php 264,600 158.76 manhrs 415
INITIAL RANKING COMPUTATION FOR BEAMS To Determine the Ranking of the Values, Difference (%) = [(Higher - Lower)/Higher]*100 Subordinate Rank = Governing Rank - (Difference (%)/10)
Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 291600 264600 5 9.26 4
CRITERIA Constructabilit y 175 159 5 9.21 4
Safety 485.000 415.000 5 14.43 4
BOLTED CONNECTIONS
Criteria Economic Constructability Strength
Tradeoffs Standard Oversized 4,800 6,400 24.96 30.72 27.84 26.7
INITIAL RANKING COMPUTATION FOR BOLTED CONNECTIONS Summary Higher Value Lower Value Governing Rank
Economic 6,400 4,800 5
CRITERIA Constructability 25 31 5
Safety 27.840 26.703 5 68
Difference (%) Subordinate Rank
25.00 3
23.08 3
4.08 4
4.3.2 Final Designer’s Ranking and Assessment BEAMS
Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Safety (Deflection) Overall Ranking
5 4 4
Ability to Satisfy the Criterion Hot Rolled Built-Up 5 3 5 4 2 5 53 51
The result of the final ranking and assessment for beams validates that the initial ranking is correct, although in the final ranking, the hot rolled beams with 53, and built up beams with 51, got very close rank. COLUMNS
Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Strength (Axial Capacity) Overall Ranking
5 4 4
Ability to Satisfy the Criterion Hot Rolled Built-Up 5 4 5 4 4 5 61 56
The result of the final ranking and assessment for columns validates that the initial ranking is correct. The hot rolled beams with 61, and built up beams with 56. TENSION
Criterion
Importance
Economic Constructability Strength Overall Ranking
5 4 4
Ability to Satisfy the Criterion SA Equal Legs SA Unequal Legs 5 4 5 3 3 5 57 52 69
The result of the final ranking and assessment for columns validates that the initial ranking is correct. The table below shows the difference of the two ranks. In the initial, the equal angle got 15 points higher than unequal, but in the final, only 5 points is the margin, with each having 57 and 52 respectively..
WELDED CONNECTIONS Ability to Satisfy the Criterion E70XX E60XX Economic (Cost) 5 3 5 Constructability (Manufacturability) 4 3 5 Safety (Deflection) 4 5 4 Overall Ranking 47 61 Same as the other three, the welded connections is also correct. As seen in the raw ranking, they only have Criterion
Importance
5 points deficit, but in the final, their diminished value is 14 points. The E70XX got 47, while E60XX got 61 points. BOLTED CONNECTIONS
Criterion
Importance
Economic 5 Constructability 4 Strength 4 Overall Ranking
Ability to Satisfy the Criterion Standard Oversized 5 3 5 3 5 4 65 43
In bolted connections, all criteria was won by the standard holes unlike before that the strength criteria was given to the oversized holes. The standard got 65 while oversized got 43 for a difference of 12 points. Overall, all the assumptions of the designer on each member are correct. Some methods are really reliable to come up with an initial estimate of value.
4.4 Influence of Multiple Constraints, Tradeoffs and Standards in the Final Design 70
Economic, constructability, and safety, and strength are among the constraints which influenced the design process of all the alternatives studied by the designer. The charts below show the differences between all of the tradeoffs. Economic Constraint The figure below shows the difference in the economic cost between the two tradeoffs in each structural member. Knowing the total cost of the structure is essential both for the designer and the client, so that one can easily choose between which tradeoff to take. The winning tradeoff in each might have a very large discrepancy against the losing tradeoff, but sometimes have a very small difference, which can change the mind of the client to pick the losing tradeoff, considering the other constraints in the design.
ECONOMIC CONSTRAINT
Winning Tradeoff
Losing Tradeoff
Figure 24. Economic Constraint Comparison
Constructability Constraint
71
The figure below shows the difference in the constructability between the two tradeoffs in each structural member. Knowing the total duration of the structure is essential both for the designer and the client, so that one can easily choose between which tradeoff to take. The winning tradeoff in each might have a very large discrepancy against the losing tradeoff, but sometimes have a very small difference, which can change the mind of the client to pick the losing tradeoff, considering the other constraints in the design.
CONSTRUCTABILITY CONSTRAINT
Winning Tradeoff
Losing Tradeoff
Figure 25. Constructability Constraint Comparison
Safety Constraint The figure below shows the difference in the safety between the two tradeoffs in the beams of the structure. Although only one structural part was designed with this kind of constraint, it is still necessary to look at the outcome. Having a beam with a very much large possible deflection is very dangerous, that’s why the designer really need to consider this constraint.
72
SAFETY CONSTRAINT
Winning Tradeoff
Losing Tradeoff
Strength Constraint The figure below shows the difference in the strength between the two tradeoffs in each structural member. Knowing the difference in the strength of the two would pave the way for the designer to choose which of the two is better.
STRENGTH CONSTRAINT
Winning Tradeoff
Losing Tradeoff
Figure 26. Constructability Constraint Comparison
73
CHAPTER 5: FINAL DESIGN
After all the processes done by the designer, he came up to the final design of the structure. Summing up all the results of the design, the winning tradeoffs are enumerated as follows: 1. 2. 3. 4. 5.
The beams of the structure will be designed using hot rolled sections. The columns of the structure will be designed using hot rolled sections. The tension (X-bracing) will be designed using single angle with equal legs. The welded connections will be designed using E60XX The bolted connections will be designed using standard bolt holes.
The tables below show the final design schedule of the project.
BEAMS BEAMS AT 2ND FLR Transverse W 18 x 65 Interior Longitudinal W 16 x 40 Exterior Longitudinal W 12 x 30 BEAMS AT 3RD FLR Transverse W 18 x 65 Interior Longitudinal W 16 x 40 Exterior Longitudinal W 12 x 30 BEAMS AT 4TH FLR Transverse W 18 x 65 Interior Longitudinal W 16 x 40 Exterior Longitudinal W 12 x 30 BEAMS AT 5TH FLR Transverse W 18 x 65 Interior Longitudinal W 16 x 40 Exterior Longitudinal W 12 x 30 BEAMS ATROOF FLR Transverse W 18 x 65
COLUMNS COLUMNS AT GRD - 2ND FLR Interior W 27 x 161 Exterior
W 21 x 83
Corner W 18 x 46 COLUMNS AT 2ND - 3RD FLR Interior W 27 x 161 Exterior
W 21 x 83
Corner
W 18 x 46
COLUMNS AT 3RD - 4TH FLR Interior
W 27 x 161
Exterior
W 21 x 83
Corner W 18 x 46 COLUMNS AT 4TH - 5TH FLR Interior W 27 x 161 Exterior
W 21 x 83
Corner W 18 x 46 COLUMNS AT 5TH - ROOF FLR Interior W 27 x 161
74
Interior Longitudinal Exterior Longitudinal
W 16 x 40
Exterior
W 21 x 83
W 12 x 30
Corner
W 18 x 46
TENSION ALL
L 40 X 40 X5
75
APPENDIX A: CODES AND STANDARDS
76
APPENDIX B: RESULTS OF STRUCTURAL ANALYSIS
77
APPENDIX C: INITIAL ESTIMATE OF VALUES
78
APPENDIX D: FINAL ESTIMATE OF VALUES
79
APPENDIX E: MANUAL COMPUTATION OF BEAMS
80
APPENDIX F: DESIGN COMPUTATION OF COLUMNS
81
APPENDIX G. DESIGN COMPUTATION OF TENSION
82
APPENDIX H: BEAM – DESIGN OF COLUMN INTERACTION
83
APPENDIX I: DESIGN COMPUTATION OF COLUMN BASE PLATE
84
APPENDIX J: DESIGN OF WELDED CONNECTIONS
85
APPENDIX K: DESIGN OF BOLTED CONNECTIONSAppendix K: References
Arda, T. S. and Yardımcı, N. (1989). Çelik Yapıda Öngerme, 4. Çelik Yapılar Semineri, Nov.27-Dec.2, ĐTÜ Vakfı ve Đnşaat Fakültesi, Đstanbul. Calado L. Non-linear cyclic model of top and seat with web angle for steel beam-to-column connections, Engineering Structures, 2003; 25:1189-1197
Davison, O. (2006). Experimental investigation on built-up columns, Journal of Constructional Steel research 62: 1325-1332. Hart, A. (1992). Multi-storey Buildings, Steel Designer’s Manual, ed. G. W. Owens and P. R. Knowles, Blackwell Scientific, Oxford. Otto, K. N. and Antonsson, E. K., (1991). Trade-off strategies in engineering design. Research in Engineering Design, volume 3, number 2 Schollar, T. (1993). Chapter 21: Structural Connections for Steelwork, Architecture and Construction in Steel, ed. Blanc A., McEvoy M., Plank R., pub. E & FN Spon, London.
86
Figure 1. Perspective of the Proposed Seminary
1
As seen in Figure 1, the building has five floors with a flat roof, and is rectangular in shape. It has a total floor area of 700 sq. m with dimensions of 50 m x 14 m. The first floor contains the refectory (dining), chapel, lobby, infirmary (clinic), recreation area, kitchen and staff room. The second and third floors contain class rooms, laboratories, library, and offices. The fourth and fifth floor contain the study area and dormitories. It has a main stair, fire exit, ramps, and an elevator. The height of each floor is 3 m having a total of 15 m.
1.3 Project Location The project area is located in Antipolo City, Rizal, which is included in the areas under seismic zone 4. The address of the area lot is Lot 6 Blk.1, Sampaguita St. Bermuda Hts. Subd., Brgy. San Luis, Antipolo City. Figures 2 and 3 show the vicinity map of the area and its distance from the nearest fault line which is the Makati Valley Fault System, respectively.
Figure 2. Vicinity Map of the Seminary 2
1.4 Project Objectives The main objective of this project is to analyse and design a steel structure in accordance with the principles written in NS 2001. Other objectives of the project are as follows: a. To design a five-story steel seminary main building that will have an acceptable probability of performing satisfactorily during its intended life time. b. To provide all the necessary architectural plans, structural plans, and the estimate of the building cost. c. To plan the structure considering balanced constraints, trade-offs and standards on the design.
1.5 The Client The client of this structure is a set of religious people led by Mrs. Sharon Umayam. She is a businesswoman and at the same time the president of the lectors in Our Lady of Peace and Good Voyage Church (National Shrine of the Philippines).
1.6 Project Scope and Limitation The following were the scope covered by the design project: 1.) The project was designed in accordance to the National Building Code of The Philippines and the National Structural Code of the Philippines applying the Allowable Strength Design (ASD). 2.) Structural analysis was done manually and was checked through STAAD. 3.) All the needed architectural plans and structural plans of the building were provided.
The following were the limitations of the design project: 1.) Only the main structure (includes beams, columns, and connections) were considered in the design. 2.) The cost estimates for the mechanical, plumbing and architectural plan were not included. 3.) The plumbing and electrical plans are not included in this design. 4.) The interior design of the structure was not considered.
3
1.7 Project Development
PLANNING/CONCEPTUALIZATION
IDENTIFICATION OF DESIGN STANDARDS AND PARAMETERS
PRESENTATION OF ARCHITECTURAL AND STRUCTURAL PLANS WITH INITIAL ESTIMATE
IDENTIFICATION OF DESIGN CONSTRAINTS, TRADE-OFF
LOAD IDENTIFICATION, STRUCTURAL ANALYSIS, AND FINAL DESIGN
Figure 4. Project Development Process Figure 3. Project Development Process The project development process started with the planning/conceptualization. In this stage, the identification of client was the most important so as to know the structure to be build. In this case, the structure requested by the client was a seminary. It also included the identification of the location where the structure was intended to be built. The next stage was the identification of design standards. Knowing the structure to be constructed, the next part was to know the specific design standards that are required before coming up to the design (i.e., minimum dimension of a classroom, minimum size of an elevator shaft, etc.). These will set the parameters in the creation of the architectural and floor plans which is the next stage in the process. 4
In the third stage, the plans will be presented to the client so that alterations could be made. After all has been settled, constraints can now be identified, which is the next stage. In this, the constraints that were projected will then be classified as either qualitative or quantitative. Knowing the quantitative tradeoffs will pave the way to the determination of the trade-offs for the structure. In the last stage, the geometric design, computation, and final estimation for each trade-offs will be made. Then, all of these will be presented to the client. The client will then rate each trade-off. The one which has the most favorable rating among all will then be chosen for the design of the structure.
5
CHAPTER 2: DESIGN INPUTS 2.1 Description of the Structure The structure contains five floors with each floor having different function from the other. The structure has two access stairs, a set of ramps, and an elevator. The structure has special moment resisting frames in the longitudinal axis, and special braced frames (X-bracing) in the transverse axis. Figure 5 shows the geometric model of the structure.
Figure 4. Geometric Model of the Structure
Figure 5. Wire frame Perspective View 6
7
Table 1 shows the total floor area and the different areas of the rooms contained in each floor. Table 1. Total Floor Areas and Functions per Floor FUNCTION
AREA (m2)
1ST Floor Ramps and Elevator
49
Stairs
25
C.R.
22.5
Chapel
168
Refectory
168
Staff Room
63
Clinic
49
Lobby
70
Kitchen
63
Hallway
22.5
TOTAL
700 2nd Floor
Ramps and Elevator
49
Stairs
25
C.R.
22.5
Offices
3(45)
Class Rooms & Laboratories
4(63)
Other Rooms
32.5
Lounge
35
Hallway
79
TOTAL
700 3rd Floor
Ramps and Elevator
49
Stairs
25 8
C.R.
22.5
Offices
45
Class Room
2(63)
Other Rooms
133
Faculty Room
65
Library
94.5
Hallway
73.5
Sisters’ Room
66.5
TOTAL
700 4th Floor
Ramps and Elevator
49
Stairs
12.5
C.R.
22.5
Study Area
178.5
Dormitory
255.5
Vice Rector’s and Prefect’s Room
66.5
Toilet & Bath
59.5
Laundry
28
Hallway
28
TOTAL
700 5th Floor
Ramps and Elevator
49
Stairs
25
Hallway
28
Dormitory (1)
201
Dormitory (2)
196
Toilet & Bath
2(59.5)
Laundry
28
Rector’s Room
66.5 9
TOTAL
700
TOTAL FLOOR AREA
3500
2.2 Classification of the Structure Using the National Structural Code of the Philippines (NS) 2010, the designer was able to classify and determine the classifications and parameters of the structure. 2.2.1 Seismic Load Parameters Since the structure is a seminary, the occupancy category of the building is classified as an Essential Facility, whose value of importance factor (I) is equal to 1.50. For the site geology, the soil profile type was considered as SD because the soil properties of the area was not known. Since the area is in Region IV-A, the structure is included in the areas under seismic zone 4, with seismic zone factor (Z) of 0.4.
10
As Figure 7, the nearest
to
Figure 6. Distance of the Nearest Fault Line to the Proposed Seminary
seen
in
fault
line
the area is
the Makati Valley Fault System which is 16 km away. The seismic source type is considered as Type C since this fault line is not prone on producing large magnitude of earthquakes. With these data, the near source factors Na and Nv are both 1.0. The values of Ca and Cv are now determined as 0.44 and 0.64 respectively. Since the building is rectangular, it is a regular structure. Special Moment Resisting Frame System (SMRF) was utilized in the longitudinal, and special steel concentric braces frame was utilized in the transverse axis, thus, the seismic response coefficient (R) is 7. Static force procedure was utilized for the determination of the seismic forces acting on the strcture.
2.2.2 Wind Load Parameters In this part, the parameters for the determination of the wind loads will be presented, but those which are presented already in the seismic part will not be repeated. As the area is included in the zone 4, it has a basic wind speed (V) of 200 kph. The structural type of the building is a Main Wind Resisting Force System, thus, the value of Directionality Factor (K d) is 0.85. The surface roughness of the building is B because it is intended to be built in an urban area. The seminary is a medium rise building and an enclosed structure. The gust effect factor is considered as 0.85. Other parameters such as topographic factor (k zt) and velocity pressure exposure coefficients (k z) will be 11
computed. These values are those needed in the determination of the wind pressure acting on the structure.
2.2.3 Dead Loads and Live Loads The minimum design for dead loads and live loads used in the structure is presented in this part. For the live loads and dead loads (includes ceiling, floors and floor finishes) of the structure, the materials and their respective uniform load are in shown In Table 2
12
Table 2. Dead Loads and Live Loads of the Structure DEAD LOADS Component
Load (kPa) Ceiling
Gypsum Board Mechanical Duct Allowance Wood Furring Suspension System Floor and Floor Finishes Cement Finish on Stone Concrete Fill Ceramic Quarry Tile Masonry For Plastering (both sides)
0.008 0.2 0.12 1.53 1.1 0.24
LIVE LOADS Basic Floor Area
1.9
13
2.3 Architectural Plans
Figure 7. Firs Floor Plan of the Seminary
Figure 8. Second Floor Plan of the Seminary
14
Figure 9. Third Floor Plan of the Seminary
Figure 10. Fourth Floor Plan of the Seminary
15
Figure 11. Fifth Floor Plan of the Seminary
Figure 12. Front Elevation of the Seminary
Figure 13. Side View of the Seminary
16
CHAPTER 3: DESIGN CONSTRAINTS, TRADE-OFFS, AND STANDARDS 3.1 Design Constraints Constraint based design takes the parameters associated with a design problem and links them to the attributes of the formal components and relationships of a solution. The forms that compose a building are defined by a set of attributes. Constraints have to be managed effectively throughout the decision making process, and also could be reduced or eliminated. In this project, there are specific constraints and general constraints. The specific constraints will serves as the criteria for ranking. The general constraints are the basis of the tradeoffs which will be ranked. The specific constraints were divided into two types, namely, quantitative and qualitative constraints. Quantitative constraints are those constraints that can be measured using engineering methods (estimation, direct counting, etc.). The qualitative constraints are those which cannot be measured but are ranked through the designer’s perception and experience (unranked in this project). The next sections present the specific constraints selected among all others that will have a significant impact in the design of the structure. 3.1.1 Quantitative Constraints 1. Economic (Cost). The design of the building will comprise steel for the structural framing as specified by the client. The tradeoffs presented in the next section are compared so as to determine which of those could be the cheaper choice. Davison (2003) noted that frame in the steel building has a greater percentage in the entire budget of the structural design. The components of the steel structure (beams and columns) can consist 30% in the total cost of construction. Total cost outcome of the tradeoffs in sections and connections will be considered in this design. The cost of the structure is highly significant both to the designer and the client. 2. Constructability (Duration). In this constraint, the designer thought on the process of manufacturing of structural sections is considered for the tradeoff in sections. For the tradeoffs in connections, the designer considered the construction time in ing the beams and columns. The tradeoffs to be presented would be compared so as to know which among the tradeoffs will require lesser amount of man-hour for construction. 17
3. Safety (Deflection). The designer considered the safety of the structure with respect to its vertical axis. Having considered the constructability of structure either using rolled or built-up sections, it is also reasonable to look at the safety of the structure. This must be capable to withstand the gravity loads. 4. Strength (Capacity). The designer considered the capacity of a connection to resist the possible failures such as failure in bearing, shearing (double or single), tensile, block shear. Knowing the capacity of the bolt would lead the designer to know how serviceable the structure is. The designer also measured the tensile capacity that the tension can resist, and the axial capacity that columns can carry. 3.1.2 Qualitative Constraints 1. Aesthetics. The beauty of the structure lies upon its final output. This constraint depends on the taste of a person therefore it is considered as a qualitative constraint. It depends on a person’s perception which design is more presentable. 2. Social. People are very influential when it comes to ideas and other things. In this project, the friends and relatives of the client might give him an idea which might alter the work of the designer. Demands from these people might affect the decision of the client and the designer. 3. Health and Safety. Different areas surrounding commercial building might affect the people that might use the commercial building. Smoke from the cars using the roads and cigarettes, smell from the nearby canal, laundry areas, restaurants, etc., are examples of these hazardous odor that might affect health and safety of the people in the building.
18
CONSTRAINTS
SPECIFIC
QUALITATIVE
GENERAL
QUANTITATIVE
TENSION BEAMS COLUMNS
HEALTH AND SAFETY
ECONOMIC
SOCIAL
CONSTRUCTABILITY
AESTHETICS
SAFETY
BOLTED CONNECTIONS WELDED CONNECTIONS
STRENGTH
19
3.2 Tradeoffs Design trade-off strategies are always present in the design process. Considering design constraints, trade-offs that have a significant effect on the structural design of the structure was provided by the designer. As a trade-off, the designer will have to evaluate which of the two is more effective considering each constraint. The following are the tradeoffs that were chosen by the designer because they are the most fitted to the said constraints. Tradeoffs in Beams and Columns. The first part of the project is to determine which section is more effective for a structural member (beams and columns). The designer utilized the rolled sections (W Shapes) and built up sections (BW Shapes) as tradeoffs for the structural . Considering both tradeoffs to be effective and efficient in the design, the designer sought to find out which section will have greater performance considering the constraints; economic, constructability, safety, and strength.
Figure 14. Actual (left) and Theoretical (right) Built Up Sections
Tradeoffs in Tension . The tension for the structure are the x-bracing. The designer chose the tradeoffs to be the section of the tension member, namely single angle with equal legs,
20
and single angle with unequal legs. The designer would like to know if there will be difference in the performance of the two sections. Tradeoffs in Bolted Connections. Bolted connections are widely used in almost every mechanical and structural system due to the added flexibility of assembly and disassembly of sub-systems for inspection, replacement, and routine maintenance. The designer utilized bolted connections in the bracing of the structure. The tradeoffs for bolted connections is the bolt hole that will be used, namely standard hole dimensions and oversized hole dimensions. The designer would like to know if there will be alterations in the performance of the connection when these two are applied.
Tradeoffs in Welded Connections. Welded connections are ts connected through welding. The designer planned that the beams and columns of the structure will be connected through welding. The tradeoffs chosen by the designer for the welded connections are the electrodes that will be used in welding. COLUMNS
The electrodes are namely E70XX and E60XX.
TRADEOFF IN SECTION
BEAMS
TRADEOFFS
TENSION
TRAFEOFF IN TYPE OF BOLT
BOLTED CONNECTIONS CONNECTIONS
21 WELDED CONNECTIONS TRADEOFF IN TYPE OF WELDING EQUIPMEN
22
3.2.3 Ranking Scale The ranking scale that will be used in this design is based on the model on tradeoff strategies formulated by Otto and Antonsson (1991). The importance factors in each constraint is scaled from 0 to 5, while the ability to satisfy the constraint is scaled from -5 to 5, 5 being the highest for both. After obtaining the results, the product of the importance and ability to satisfy the criteria will be summed of from each constraint. The result will then be the overall ranking of the tradeoff.
Figure 3.7 Ranking Scale for Importance Factor
Figure 3.8. Ranking Scale for Satisfactory Factor
Computation of ranking for ability to satisfy criterion of materials:
Difference( )=
Higher value−Lower value ×100( ) Lower value
Subordinate rank =Governing rank −(
difference ) 10
Equation 1 Equation 2
The above equations will be used for the manipulation of the rankings of each constraint given to the tradeoffs. The governing rank is the highest possible value set by the designer. The subordinate rank in second equation is a variable that corresponds to its percentage difference from the governing rank along the ranking scale.
23
3.3 Initial Estimate, Ranking Computation, and Raw Designer’s Ranking For the first part of the project, choosing between the rolled section and built-up section, two sections from each tradeoff was assumed. The designer assumed each to have the same areas. To determine which of these two is more economic, the price per unit weight of each section were multiplied by the quantity (with respect to length) of the each section. To measure the serviceability constraint, the deflections of the assumed sections were computed and compared. All assumed values and the estimates were shown in Appendix C. BEAMS INITIAL ESTIMATED VALUES Criteria Economic Constructability Safety
Tradeoffs Rolled Php 20,596,736 74 days 0.30%
Built Up Php 16,529,336 84 days 0.22%
INITIAL RANKING COMPUTATION FOR BEAMS To Determine the Ranking of the Values, Difference (%) = [(Higher - Lower)/Higher]*100 Subordinate Rank = Governing Rank - (Difference (%)/10) Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 20,596,736 16,529,336 5 19.75 3
CRITERIA Constructability N/A N/A 5 N/A 2
Safety 0.297 0.222 5 25.09 2
For the economic constraint, initial cost estimate is provided in the Appendix. To make an initial cost estimate, the designer considered the two tradeoffs to have the same area, and due to their different weights, the 24
tradeoffs will have different cost. To compute the rank of each tradeoff, the designer used the formula formerly enumerated. For the constructability constraint, the designer considered the manufacturability of each section. In this constraint, the designer gave a rank of 5 to Rolled Sections, and 2 fof Built Up sections. The main reason is that the rolled sections is manufactured as one, considering only the molding and curing time of the whole member, while built up section are rolled sections combined together to form another section, thus, aside from molding and curing time, we also consider the stiffening of the section. For the safety of the member, the designer considered the deflection per unit of length, of the same shapes used in the economic section. The deflection was presented in of percentage of the allowable deflection. Like in economic constraint, the rank for each tradeoff was computed.
COLUMNS INITIAL ESTIMATED VALUES Criteria Economic
Tradeoffs Rolled Php 20,596,736
Built Up Php 16,529,336
INITIAL RANKING COMPUTATION FOR COLUMNS Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 9,957,151 9,351,936 5 6.08 4
CRITERIA Constructability N/A N/A 5 N/A 2
Strength N/A N/A 5 N/A 4
For the economic constraint, initial cost estimate is provided in the Appendix. To make an initial cost estimate, the designer considered the two tradeoffs to have the same area, and due to their different weights, the tradeoffs will have different cost. To compute the rank of each tradeoff, the designer used the formula formerly enumerated. For the constructability constraint, the designer considered the manufacturability of each section. In this constraint, the designer gave a rank of 5 to Rolled Sections, and 2 fof Built Up sections. The main 25
reason is that the rolled sections is manufactured as one, considering only the molding and curing time of the whole member, while built up section are rolled sections combined together to form another section, thus, aside from molding and curing time, we also consider the stiffening of the section. For the strength of the member, values cannot be assumed since axial capacity of columns can only be measured after analyzing the whole structure. Therefore, the designer sought a way to rank this constraint. The designer gave a higher rank to the rolled beam sections because considering same area of cross sections, they always give lower value of weight. Thus, they can still carry greater amount of load to be sum up with their selfweights. Thus, the designer gave a rank of 5 to rolled sections, and 4 for built up sections. TENSION INITIAL ESTIMATED VALUES Criteria Economic
Tradeoffs Rolled Php 77,520
Built Up Php 119,321
INITIAL RANKING COMPUTATION FOR TENSION
Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 119,321 77,520 5 35.03 1
CRITERIA Constructability N/A N/A 5 N/A 4
Safety N/A N/A 5 N/A 3
26
For the economic constraint, initial cost estimate is provided in the Appendix. To make an initial cost estimate, the designer considered the two tradeoffs to have the same area, and due to their different weights, the tradeoffs will have different cost. To compute the rank of each tradeoff, the designer used the formula formerly enumerated. For the constructability constraint, the designer considered the manufacturability of each section. In this constraint, the designer gave a rank of 5 to Single Angle with Equal Legs because there is equal distribution in the period of time in both legs, unlike in unequal legs, ranked as 4, because they can have variation of manufacturing, especially in curing time. For the strength of the member, In this part, values cannot be assumed since axial capacity of columns can only be measured after analyzing the whole structure. Therefore, the designer sought a way to rank this constraint. The designer gave a higher rank of 5 to the single angle with unequal legs because the axial load is possibly higher since the fasteners are placed in the longer leg, unlike in the single angle with equal legs ranked as 3, both have same dimensions thus giving high possibly of having lesser leg than that of single angle with unequal legs. Comparing the longer legs is necessary because there will be computation of gross area and net area, where the axial capacity of the tension member will depend.
27
WELDED CONNECTIONS INITIAL ESTIMATED VALUES Criteria
Tradeoffs
Economic
E70XX Php 291,600
Constructability Safety
174.96 man-hrs 485
E60XX Php 264,600 158.76 manhrs 415
INITIAL RANKING COMPUTATION FOR BEAMS To Determine the Ranking of the Values, Difference (%) = [(Higher - Lower)/Higher]*100 Subordinate Rank = Governing Rank - (Difference (%)/10) Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 291600 264600 5 9.26 4
CRITERIA Constructability 175 159 5 9.21 4
Safety 485.000 415.000 5 14.43 4
To have an initial cost estimate in welded connections, the designer assumed equal length of weld but different thickness. The designer assumed that E70XX will result to thinner weld size, but is more costly. For constructability, the designer considered that material cost and the labor cost that will be resolved from the cost estimate. And finally for the strength, E70XX obviously got higher rank because it has greater strength than the other.
Bolted Connections 28
INITIAL ESTIMATED VALUES Criteria Economic Constructability
Tradeoffs Standard Oversized 9,900 11,200 51.48 44.8
INITIAL RANKING COMPUTATION FOR TENSION To Determine the Ranking of the Values, Difference (%) = [(Higher - Lower)/Higher]*100 Subordinate Rank = Governing Rank - (Difference (%)/10) Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 11,200 9,900 5 11.61 4
CRITERIA Constructability 51 45 5 12.98 4
Safety N/A N/A 5 N/A 3
To have an initial cost estimate in bolted connections, the designer based his estimate on the bolt hole area. The designer assumed the same number of bolts, but the oversized hole still got higher rank because it is more costly than the standard. For constructability, it comes the other way around where the oversized won. And finally for the strength, the designer gave rank of 5 into the oversized because the holes lessen the load that is transmitted.
3.4 Raw Designer’s Ranking and Assessment After making an initial estimate of the structure considering the constraints, the design came up with the raw rankings on the one-way slab and two-way slab. The values computed in the latter section is tabulated. BEAMS Criterion
Importance
Ability to Satisfy the Criterion Hot Rolled Built-Up 29
Economic (Cost) Constructability (Manufacturability) Safety (Deflection) Overall Ranking
5 4 4
3 5 2 43
5 2 5 53
As for economic constraint, it turned out that the rough cost estimate for the rolled sections is cheaper than the rolled sections. As for constructability, rolled up sections are easier to manufacture than the built up sections. As for the serviceability constraint, the deflection of the critical beam in the built-up section is lesser than that of the rolled section. Overall, it turned out that the built up section tradeoff outranked the rolled section for the raw designer’s ranking in beams.
COLUMNS Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Strength (Axial Capacity) Overall Ranking
5 4 4
Ability to Satisfy the Criterion Hot Rolled Built-Up 4 5 5 2 4 5 56 53
As for economic constraint, it turned out that the rough cost estimate for the built up sections is cheaper than the rolled sections. As for constructability, rolled up sections are easier to manufacture than the built up sections. As for the strength of the member, the axial capacity of the built up columns was hypothesized to be greater than that of rolled columns. Overall, it turned out that the rolled section tradeoff outranked the built up section for the raw designer’s ranking in columns.
TENSION Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Strength (Axial Capacity) Overall Ranking
5 4 4
Ability to Satisfy the Criterion SA Equal Legs SA Unequal Legs 5 1 5 4 3 5 57 41
30
As for economic constraint, it turned out that the rough cost estimate for the single angle with equal legs is cheaper than single angle with unequal legs. As for constructability, the former is easier to manufacture than the latter. As for the strength of the bracing member, the axial capacity of the equal legs was hypothesized to be greater than that of the unequal legs rolled columns. Overall, it turned out that the single angle with equal legs tradeoff outranked single angle with equal legs tradeoff for the raw designer’s ranking in tension . WELDED CONNECTIONS Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Strength (Ultimate) Overall Ranking
5 4 4
Ability to Satisfy the Criterion E70XX E60XX 4 5 4 5 5 4 56 61
As for economic constraint, it turned out that the rough cost estimate for the welding electrode E60XX will result to cheaper price of welding connections compared to welding electrode E70XX. For constructability constraint, the designer considered the amount of man-hour that the welding connections will incur. To get an initial estimate, the designer used the economic cost to get the percentage of the labor cost required for the construction (welding), which resulted to number of hours the process will be finished. For the strength, the designer considered the ultimate tensile strength of two electrodes, which is their main difference. The E70XX basically has higher strength than E60XX. Overall, it turned out that the E60XX tradeoff outranked E70XX tradeoff for the raw designer’s ranking in welded connections. BOLTED CONNECTIONS RAW DESIGNER'S RANKING Criterion
Importance
Economic Constructability Strength Overall Ranking
5 4 4
Ability to Satisfy the Criterion Standard Oversized 5 4 5 4 3 5 57 56
31
*Reference: Otto, K. N. and Antonsson, E. K., (1991). Trade-off strategies in engineering design. Research in Engineering Design, volume 3, number 2, pages 87-104.Retrieved from http://www.design.caltech.edu/Research/Publications/90e.pdf on January 27, 2016 As per economic constraint, the standard bolt hole is cheaper than the oversized. One reason is that it is the used by many company, unlike the oversized. Also, the standard bolt hole got higher rank in constructability. But regarding the strength, the designer gave a rank of 5 into oversized, and 3 to standard, because the transmission of force is not directly into the bolt. These tabulated values are just subjective, especially the importance factors. These values will still go on with the validation after making a final estimate and final ranking.
32
3.9 Design Standards The design standards used are taken from the following codes and standards: 1. 2. 3. 4. 5.
National Structural Code of the Philippines (NS) vol. 1-2001 edition (PD1096) National Building Code of the Philippines ASTM (American Society for Testing and Materials) ASEP Steel Handbook 2004 vol. 1 Steel Designers’ Manual of the Steel Construction Institute 6th Edition
1. The National Structural Code of the Philippines 2001.This structural code provides minimum requirements for building structural systems using prescriptive and performance-based provisions. It is founded on broad-based principles that make possible the use of new materials and new building designs. It is also designed to meet these needs through various model codes/regulations, to safeguard the public health and safety nationwide. This is the main reference for the design procedure of the structure. Material Strength. Materials conforming specifications of NS 6th edition 2010 were used in the design of the project. Loadings. Dead loads, live loads and environmental loads (wind and earthquake) are the forces acting on the structure. Dead loads are consists of the weight of all materials of construction and partition loads that are presented in the next chapter. Live loads shall be the maximum loads expected by the occupancy; these loads are attached in chapter 4 as well. The required lateral loads due to wind and earthquake forces shall be separately calculated. Wind Loads. The wind load is calculated in STAAD Pro using specifications adopted in American Society of Civil Engineers ASCE7-05 and based on procedure as stated in NS 2010, section 207. Seismic Loads. The structure shall be designed and constructed to resist the effect of seismic ground motion as provided in section 208 of NS 6th edition (2010). Load Combinations. Steel sections shall be designed using the “Allowable Stress Design” method using the following combination DL + LL DL + 0.75 LL DL + WL DL + 0.7 EL 33
DL + 0.75 WL + 0.75 LL 0.6 DL + WL : 0.6 DL + 0.7 E Deformation Limits. Structures or structural shall be checked such that the maximum deformation does not exceed the following: a. Beams and Girders. Beams and girders ing floors and roof shall be proportioned with due regard to the deflection produced by the design loads. Considering then the total deflection, which is due to the additional live loads, occurring after attachment of non-structural elements shall not exceed L/360. 2. The National Building Code of the Philippines (PD 1096).The National Building Code of the Philippines, also known as Presidential Decree No. 1096 was formulated and adopted as a uniform building code to embody up-to-date and modern technical knowledge on building design, construction, use, occupancy and maintenance. The Code provides for all buildings and structures, a framework of minimum standards and requirements to regulate and control
location, site, design, and quality of materials,
construction, use, occupancy, and maintenance. A. Loading
: UBC 97, ASCE 7-05
B. Steel
: A36 3. Association of Structural Engineers of the Philippines (ASEP) Steel Handbook, 3rd
Edition, Volume 1. This provide the civil and structural engineering practitioners with a handy reference to locally available rolled shapes, built-up shapes, cold-formed steel sections and light gage steel sections. a. Hot-rolled Sections Dimensions and Properties b. Built-up Sections Dimensions and Properties
34
CHAPTER IV: STRUCTURAL ANALYSIS AND DESIGN 4.1 Design Methodology The design was done in accordance with the codes and standards appropriate for a reinforced concrete structure. The figure below shows the step by step process of the design of the building. FRAMING PLANS
STRUCTURAL PLANS
NS NB
DESIGN SPECIFICATIONS
MATERIAL PROPERTIES
MODULUS OF ELASTICITY STRUTURAL MEMBER DIMENSIONS
GEOMETRIC MODELING
STRUCTURAL MODEL
LOAD MODELS
DEAD AND LIVE LOAD SEISMIC AND WIND LOAD LOAD COMBINATIONS
STRUCTURAL ANALYSIS
SHEAR DIAGRAMS MOMENT DIAGRAMS REACTIONS AND DEFLECTIONS
STRUCTURAL DESIGN
DESIGN SCHEDULES DETAILING
Figure 15. Design Methodology 35
The first process in design methodology was the creation of structural plans. The structural plans included the foundation plans of the two trade-offs. The next step was to know the design specifications. These specifications are the codes and standards needed for the structure’s classification and description. The National Building Code and National Structural Code of the Philippines are the main references used for design specifications. The third step in the process was the identification of the material properties. The compressive stresses and modulus of elasticity of the concrete and steel to be used were determined. Also, the structural member dimensions (b, d, etc.) were assumed. The fourth step was the creation of the structural model. These models included geometric modelling, which showed the positioning of the structural (beams, columns, slabs) in 3D form. The fifth step was the presentation of load models. In this part, the loads acting on the structure were computed. These loads were the dead load, live load, wind load, and seismic (earthquake) load, applying also the load combinations. After computing for these loads, load models was presented also in 3D form. The sixth step was the structural analysis. In structural analysis, member (beams and columns) forces and reactions were determined. The member forces included were the axial force, shear force, and moment acting on the member. The last part was the structural design. The structural design did not include the design of footings. The values from the structural analysis was utilized to design the structural of the structures, mainly the beams and columns. The maximum moment acting on a beam was used to design the beam, and the maximum value of the axial force acting on a column was used to design the column. To design the slab, the total load on the floors was utilized.
36
4.1.1 Structural Plans
Figure 16. Second – Fifth Floor Framing Plan
37
4.1.2 Design Specifications The all the design specifications coming from NB and NS for the structure is stated Appendix A of the project.
4.1.3 Material Properties
Material Properties conforming to specifications of NS 6th Edition (2010) were used in the design of the structure using rolled sections. The properties for rolled sections were based on rolled section of Association of Structural Engineers of the Philippines, Inc. (2004).Steel Handbook, Dimensions and Properties. Philippines. ASEP. Locally produced rolled shapes were applicable only for structural steel whose minimum yield stress is 230 MPa. In this structure, the designers used A36 for rolled sections with minimum yield stress of 248 MPa and tensile strength of 400-551 MPa. The following material properties were used in the design:
38
4.1.4 Structural Models
Figure 17. Geometric Modelling of Structure
4.1.5 Load Models The loads considered in this project are the dead load, live load, wind load and seismic loads. Load combinations were also applied to these loads. The load combinations that were utilized were those that are written in Section 203 of NS 2010. The highlighted row shows the governing load combination.
39
Table 3. Load Combinations Load Case Combinations (UBC 1997) – STAAD Pro Load Case Dead Live Wind Seismic LC 1 1.4 1.4 LC 2 1.2 1.2 LC 3 1.2 1.2 0.8 LC 4 1.2 1.2 1.3 LC 5 1.2 1.2 1 LC 6 1.2 1.2 1 LC 7 0.9 0.9 1 LC 8 0.9 0.9 1.3
40
Figure 18. Dead Loads of the Structure
Figure 19. Live Loads of the Structure 41
Figure 20. Wind Loads Acting in the Structure
Figure 21. Seismic Loads Acting the Structure
42
4.1.6 Structural Analysis For the structural analysis of the , the results considered are those that came from the load combination which gave the maximum values of member forces and reactions, namely load combination 1 (1.4L + 1.4LL).
Figure 22. Axial Forces Acting on the Structure
A summary of values of the member forces is presented in the appendices. The following figures show the results of the structural analysis done through the software STAAD.
43
Figure 23. Moment Forces Acting on the Structure (Y-Axis)
4.1. 7 Structural Design The flowchart below shows the step by step process on how the designer designed each member present in the structure.
44
45
46
47
48
49
50
51
52
53
TENSION - SINGLE ANGLE WITH EQUAL LEGS DESIGN FOR ALL TENSION Given Fy Fu L P
248 415 3.807887 24.591
MPa MPa m kN RESULTS
Part 1. Determine the Trial Section rmin = L/300 Ag = P/(.6*Fy) *Select a Trial Section based on the 3
Part 2. Determine the Capacity of the Member
Ag
12.69295 52 165.2620 97
mm mm 2
Trial Section Used L 40 x 40 x5 rx
11.97
mm
ry
11.97
mm mm 2 mm
rmin
According to Net Area Pt = 0.5Fu*U*An *Assume Reduction Coefficient U = 0.85
A t
378.86 5
L w
40 40
An = Ag - Σholes
M
2.87
According to Gross Area Pt = 0.6Fy*Ag Governing Pt is smaller of the two
Net Area U Φbolt An
Part 3. Check the Capacity *If Pt < P, Reselect another section
0.85 22 268.86
mm mm kg/ m
mm mm 2
Capacity Pt
47.42018 25 SAFE
kN
54
TENSION - SINGLE ANGLE WITH UNEQUAL LEGS DESIGN FOR ALL TENSION
Given Fy Fu L P
248 415 3.807887 24.591
MPa MPa m kN RESULTS
Part 1. Determine the Trial Section 12.6929 6 165.262 1
mm mm 2
rx
15.46
mm
ry
8.44
A t L
426.72 5 50
mm mm 2 mm mm
w
40
M
3.35
rmin = L/300
rmin
Ag = P/(.6*Fy) *Select a Trial Section based on the 2
Ag Trial Section Used L 50 x 40 x5
Part 2. Determine the Net Area *Assume Reduction Coefficient U = 0.85 An = Ag - Σholes Part 3. Check the Capacity based on An Pt = 0.5*Fu*U*An *If Pt < P, Reselect another section
Net Area U Φbolt n An
0.85 22 3
mm kg/ m
316.72
mm pcs mm 2
55.8614 9
kN
Capacity Pt
55
SAFE
56
WELDED CONNECTIONS - TRADEOFF 1 (E70XX) CORNER COLUMN - EXTERIOR LONGITUDINAL BEAM CONNECTION (C1-B1) Given
Beam
Column
A bf tf
12323 192.8 19.1
mm2 mm mm
P Fy
200 248
kN MPa
A bf tf
Fu 30581 356.1 27.4
mm2 mm mm
E60 E70 E80 E90 E100 E110 E120
Part 1. Select the Welding Electrode to be used *Each eletrode corresponds to different stress Part 2. Determine the Capacity of the attached member Base on Gross Area T = 0.6FyAg Based on Net Area T = 0.5*Fu*U*Ag where U is to Reduction Factor
Electrode
E70
Fu
485
MPa
12323 1833.66 2
mm2
Capacity Gross Area Ag T Net Area U
If 1.5W > L > W, U = 0.75
T Governing T
*Lower Tensile Capacity Governs Part 3. Check the Tensile Capacity If T < P, the connections is safe
MPa MPa MPa MPa MPa MPa MPa
RESULTS
If L > 2W, U = 1 If 2W > L > 1.5W, U = 0.87
*Since weld is only in longitudinal, we use U = 0.75
415 485 550 620 690 760 825
kN
0.75 2241.24 6 1833.66 2 SAFE
Dimensions of Weld Min t
8
mm 57
else, Redesign Part 4. Determine the size of weld Min Thickness Thicker Material Min t <6mm 3 >6-12mm 5 >12-20mm 6 >20-38mm 8 >38-57mm 10 >57-150mm
12
>150mm
16
Max t t (used) L
17.5 12.75 152.488 6
mm mm mm
Max Thickness Attached Material <6mm te = t >6mm te = t - 1.6 Part 4. Compute for the Length of Weld T = 0.707tL*0.3Fu, solve for L
58
WELDED CONNECTIONS - TRADEOFF 2 (E60XX) EXTERIOR TRANSVERSE BEAM - COLUMN CONNECTION Given
Beam
Column
A
12323
bf tf
192.8 19.1
mm 2 mm mm
P Fy
200 248
kN MPa
A bf tf
Fu 3058 1 356.1 27.4
E60
415
MPa
mm2
E70
485
MPa
mm mm
E80 E90 E100 E110 E120
550 620 690 760 825
MPa MPa MPa MPa MPa
Part 1. Select the Welding Electrode to be used *Each eletrode corresponds to different stress Part 2. Determine the Capacity of the attached member Base on Gross Area T = 0.6FyAg Based on Net Area T= 0.5*Fu*U*Ag where U is to Reduction Factor If L > 2W, U = 1 If 2W > L > 1.5W, U = 0.87 If 1.5W > L > W, U = 0.75 *Since weld is only in longitudinal, we use U = 0.75 Lower Tensile Capacity Governs
RESULTS Electrode
E60
Fu
415
MPa
Ag
12323
mm2
T
1833.662 4
kN
Capacity Gross Area
Net Area U T Governing T
0.75 1917.766 9 1833.662 4 SAFE
59
Part 3. Check the Tensile Capacity If T < P, the connections is safe else, Redesign Part 4. Determine the size of weld Min Thickness Thicker Material Min t <6mm 3 >6-12mm 5 >12-20mm 6 >20-38mm 8 >38-57mm 10 >57-150mm 12 >150mm 16
Dimensions of Weld Min t
8
mm
Max t
17.5
mm
t (used)
12.75 178.2095 8
mm
L
mm
Max Thickness Attached Material <6mm te = t >6mm
te = t - 1.6
Part 4. Compute for the Length of Weld T = 0.707tL*0.3Fu, solve for L
60
WELDED CONNECTIONS - TRADEOFF 2 (E60XX) CORNER COLUMN - TRANSVERSE BEAM CONNECTION (C1-B34) Given
Beam
Column
A
12323
bf tf
192.8 19.1
mm 2 mm mm
P Fy
200 248
kN MPa
E60
Fu 415
MPa
A
8710
mm2
E70
485
MPa
bf tf
153.9 8.1
mm mm
E80 E90 E100 E110 E120
550 620 690 760 825
MPa MPa MPa MPa MPa
Part 1. Select the Welding Electrode to be used *Each eletrode corresponds to different stress Part 2. Determine the Capacity of the attached member Base on Gross Area T = 0.6FyAg Based on Net Area T = 0.5*Fu*U*Ag where U is to Reduction Factor If L > 2W, U = 1 If 2W > L > 1.5W, U = 0.87 If 1.5W > L > W, U = 0.75 *Since weld is only in longitudinal, we use U = 0.75 Lower Tensile Capacity Governs Part 3. Check the Tensile Capacity If T < P, the connections is
RESULTS Electrode
E60
Fu
415
MPa
12323 1833.662 4
mm2
Capacity Gross Area Ag T Net Area U T Governing T
kN
0.75 1917.766 9 1833.662 4 SAFE
Dimensions of Weld Min t
5
mm 61
safe else, Redesign Part 4. Determine the size of weld Min Thickness Thicker Material Min t <6mm 3 >6-12mm 5 >12-20mm 6 >20-38mm 8 >38-57mm 10 >57-150mm 12 >150mm 16
Max t t (used) L
17.5 11.25 201.9708 6
mm mm mm
Max Thickness Attached Material <6mm te = t >6mm
te = t - 1.6
Part 4. Compute for the Length of Weld T = 0.707tL*0.3Fu, solve for L
62
BOLTED CONNECTION - TRADEOFF 1 (STANDARD BOLT HOLES) P t Φbolts bolt hole
24.591 5 16 18
kN mm mm mm
RESULTS Fu
Part 1. Get the required number of bolts considering shear in the bolts Pu = AvFv, solve for n (number of bolts) where Av = n*pi*(Φ^2)/4 Fv = 0.30Fu Part 2. Get the required number of bolts considering bearing in the bolts Pu = AbFb, solve for n (number of bolts) where Ab = n*Dt Fb = 1.2Fu *Choose the greater amount of n
MPa
254.469 62.1 2
mm2 MPa pcs
Ab Fb n
90 248.4 2
mm2 MPa pcs
n (governs) s Le
2 24 32
pcs mm mm
Block Shear Av At Fv Ft Pt
190 155 62.1 103.5 27.8415
mm2 mm2 MPa MPa kN
Shear in Bolts Av per bolt Fv n
Bearing of Bolts
Pary 4. Check for Block Shear Pt = FvAv + FtAt where Fv = 0.3*Fu Ft = 0.5*Fu Av = Shear Area At = Tension Area *If Pt < P, Reselect another section else, the section chosen is SAFE Part 3. Determine the spacing of bolt
207
Le
SAFE
and edge distance s = 1.5*Φbolt Le = 2*Φbolt
63
64
BOLTED CONNECTION - TRADEOFF 1 (OVERSIZED BOLT HOLE) P t Φbolts bolt hole
24.591 5 16 20
kN mm mm mm
RESULTS Fu
Part 1. Get the required number of bolts considering shear in the bolts Pu = AvFv, solve for n (number of bolts) where Av = n*pi*(Φ^2)/4 Fv = 0.30Fu Part 2. Get the required number of bolts considering bearing in the bolts Pu = AbFb, solve for n (number of bolts) where Ab = n*Dt Fb = 1.2Fu *Choose the greater amount of n Pary 4. Check for Block Shear Pt = FvAv + FtAt where Fv = 0.3*Fu Ft = 0.5*Fu Av = Shear Area At = Tension Area *If Pt > P, Reselect another section else, the section chosen is SAFE Part 3. Determine the spacing of bolt and edge distance s = 1.5*Φbolt Le = 2*Φbolt
207
MPa
314.15927 62.1 2
mm2 MPa pcs
Ab Fb n
100 248.4 1
mm2 MPa pcs
n (governs) s Le
2 24 32
pcs mm mm
180 150 62.1
mm2 mm2 MPa
103.5 26.703
MPa kN
Shear in Bolts Av per bolt Fv n
Bearing of Bolts
Block Shear Av At Fv Ft Pt SAFE
65
4.3 Validation of Trade-offs This portion will testify if the ranking made in Chapter 3 is against or similar to the results of the final design and final cost estimates.
4.3.1 Final Estimate and Ranking Computation Beams FINAL ESTIMATED VALUES Criteria Economic Constructability Safety
Tradeoffs Rolled Php 12135424 74 days 7.41 mm
Built Up Php 14,785,004 84 days 5.67 mm
FINAL RANKING COMPUTATION FOR BEAMS CRITERIA Economic Constructability 14,785,004 84 12,135,424 74 5 5 21.83 13.32 3 4
Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Safety 7.41 5.67 5 30.69 2
Columns FINAL ESTIMATED VALUES Criteria Economic
Tradeoffs Rolled Php 7,533,312
Built Up Php 7,606,979 66
Constructability Strength
47 days 6385.42 kN
53 days 6762.8 kN
FINAL RANKING COMPUTATION Summary
Economic 7,606,979 7,533,312 5 0.97 4
Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
CRITERIA Constructability 53 47 5 11.11 4
Strength 2264.896667 2203.336061 5 2.72 4
Tension FINAL ESTIMATED VALUES Tradeoffs
Criteria Economic Constructability Strength
Single Angle (Equal) Php 44,765 7 days 47.42 kN
Single Angle (Unequal) Php 52,252 9 days 55.86 kN
FINAL RANKING COMPUTATION CRITERIA
Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 52,252 44,765 5 14.33 4
Constructability 9 7 5 21.08 3
Strengt h 55.860 47.420 5 15.11 3
WELDED CONNECTIONS INITIAL ESTIMATED VALUES 67
Criteria
Tradeoffs
Economic
E70XX Php 291,600
Constructability Safety
174.96 man-hrs 485
E60XX Php 264,600 158.76 manhrs 415
INITIAL RANKING COMPUTATION FOR BEAMS To Determine the Ranking of the Values, Difference (%) = [(Higher - Lower)/Higher]*100 Subordinate Rank = Governing Rank - (Difference (%)/10)
Summary Higher Value Lower Value Governing Rank Difference (%) Subordinate Rank
Economic 291600 264600 5 9.26 4
CRITERIA Constructabilit y 175 159 5 9.21 4
Safety 485.000 415.000 5 14.43 4
BOLTED CONNECTIONS
Criteria Economic Constructability Strength
Tradeoffs Standard Oversized 4,800 6,400 24.96 30.72 27.84 26.7
INITIAL RANKING COMPUTATION FOR BOLTED CONNECTIONS Summary Higher Value Lower Value Governing Rank
Economic 6,400 4,800 5
CRITERIA Constructability 25 31 5
Safety 27.840 26.703 5 68
Difference (%) Subordinate Rank
25.00 3
23.08 3
4.08 4
4.3.2 Final Designer’s Ranking and Assessment BEAMS
Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Safety (Deflection) Overall Ranking
5 4 4
Ability to Satisfy the Criterion Hot Rolled Built-Up 5 3 5 4 2 5 53 51
The result of the final ranking and assessment for beams validates that the initial ranking is correct, although in the final ranking, the hot rolled beams with 53, and built up beams with 51, got very close rank. COLUMNS
Criterion
Importance
Economic (Cost) Constructability (Manufacturability) Strength (Axial Capacity) Overall Ranking
5 4 4
Ability to Satisfy the Criterion Hot Rolled Built-Up 5 4 5 4 4 5 61 56
The result of the final ranking and assessment for columns validates that the initial ranking is correct. The hot rolled beams with 61, and built up beams with 56. TENSION
Criterion
Importance
Economic Constructability Strength Overall Ranking
5 4 4
Ability to Satisfy the Criterion SA Equal Legs SA Unequal Legs 5 4 5 3 3 5 57 52 69
The result of the final ranking and assessment for columns validates that the initial ranking is correct. The table below shows the difference of the two ranks. In the initial, the equal angle got 15 points higher than unequal, but in the final, only 5 points is the margin, with each having 57 and 52 respectively..
WELDED CONNECTIONS Ability to Satisfy the Criterion E70XX E60XX Economic (Cost) 5 3 5 Constructability (Manufacturability) 4 3 5 Safety (Deflection) 4 5 4 Overall Ranking 47 61 Same as the other three, the welded connections is also correct. As seen in the raw ranking, they only have Criterion
Importance
5 points deficit, but in the final, their diminished value is 14 points. The E70XX got 47, while E60XX got 61 points. BOLTED CONNECTIONS
Criterion
Importance
Economic 5 Constructability 4 Strength 4 Overall Ranking
Ability to Satisfy the Criterion Standard Oversized 5 3 5 3 5 4 65 43
In bolted connections, all criteria was won by the standard holes unlike before that the strength criteria was given to the oversized holes. The standard got 65 while oversized got 43 for a difference of 12 points. Overall, all the assumptions of the designer on each member are correct. Some methods are really reliable to come up with an initial estimate of value.
4.4 Influence of Multiple Constraints, Tradeoffs and Standards in the Final Design 70
Economic, constructability, and safety, and strength are among the constraints which influenced the design process of all the alternatives studied by the designer. The charts below show the differences between all of the tradeoffs. Economic Constraint The figure below shows the difference in the economic cost between the two tradeoffs in each structural member. Knowing the total cost of the structure is essential both for the designer and the client, so that one can easily choose between which tradeoff to take. The winning tradeoff in each might have a very large discrepancy against the losing tradeoff, but sometimes have a very small difference, which can change the mind of the client to pick the losing tradeoff, considering the other constraints in the design.
ECONOMIC CONSTRAINT
Winning Tradeoff
Losing Tradeoff
Figure 24. Economic Constraint Comparison
Constructability Constraint
71
The figure below shows the difference in the constructability between the two tradeoffs in each structural member. Knowing the total duration of the structure is essential both for the designer and the client, so that one can easily choose between which tradeoff to take. The winning tradeoff in each might have a very large discrepancy against the losing tradeoff, but sometimes have a very small difference, which can change the mind of the client to pick the losing tradeoff, considering the other constraints in the design.
CONSTRUCTABILITY CONSTRAINT
Winning Tradeoff
Losing Tradeoff
Figure 25. Constructability Constraint Comparison
Safety Constraint The figure below shows the difference in the safety between the two tradeoffs in the beams of the structure. Although only one structural part was designed with this kind of constraint, it is still necessary to look at the outcome. Having a beam with a very much large possible deflection is very dangerous, that’s why the designer really need to consider this constraint.
72
SAFETY CONSTRAINT
Winning Tradeoff
Losing Tradeoff
Strength Constraint The figure below shows the difference in the strength between the two tradeoffs in each structural member. Knowing the difference in the strength of the two would pave the way for the designer to choose which of the two is better.
STRENGTH CONSTRAINT
Winning Tradeoff
Losing Tradeoff
Figure 26. Constructability Constraint Comparison
73
CHAPTER 5: FINAL DESIGN
After all the processes done by the designer, he came up to the final design of the structure. Summing up all the results of the design, the winning tradeoffs are enumerated as follows: 1. 2. 3. 4. 5.
The beams of the structure will be designed using hot rolled sections. The columns of the structure will be designed using hot rolled sections. The tension (X-bracing) will be designed using single angle with equal legs. The welded connections will be designed using E60XX The bolted connections will be designed using standard bolt holes.
The tables below show the final design schedule of the project.
BEAMS BEAMS AT 2ND FLR Transverse W 18 x 65 Interior Longitudinal W 16 x 40 Exterior Longitudinal W 12 x 30 BEAMS AT 3RD FLR Transverse W 18 x 65 Interior Longitudinal W 16 x 40 Exterior Longitudinal W 12 x 30 BEAMS AT 4TH FLR Transverse W 18 x 65 Interior Longitudinal W 16 x 40 Exterior Longitudinal W 12 x 30 BEAMS AT 5TH FLR Transverse W 18 x 65 Interior Longitudinal W 16 x 40 Exterior Longitudinal W 12 x 30 BEAMS ATROOF FLR Transverse W 18 x 65
COLUMNS COLUMNS AT GRD - 2ND FLR Interior W 27 x 161 Exterior
W 21 x 83
Corner W 18 x 46 COLUMNS AT 2ND - 3RD FLR Interior W 27 x 161 Exterior
W 21 x 83
Corner
W 18 x 46
COLUMNS AT 3RD - 4TH FLR Interior
W 27 x 161
Exterior
W 21 x 83
Corner W 18 x 46 COLUMNS AT 4TH - 5TH FLR Interior W 27 x 161 Exterior
W 21 x 83
Corner W 18 x 46 COLUMNS AT 5TH - ROOF FLR Interior W 27 x 161
74
Interior Longitudinal Exterior Longitudinal
W 16 x 40
Exterior
W 21 x 83
W 12 x 30
Corner
W 18 x 46
TENSION ALL
L 40 X 40 X5
75
APPENDIX A: CODES AND STANDARDS
76
APPENDIX B: RESULTS OF STRUCTURAL ANALYSIS
77
APPENDIX C: INITIAL ESTIMATE OF VALUES
78
APPENDIX D: FINAL ESTIMATE OF VALUES
79
APPENDIX E: MANUAL COMPUTATION OF BEAMS
80
APPENDIX F: DESIGN COMPUTATION OF COLUMNS
81
APPENDIX G. DESIGN COMPUTATION OF TENSION
82
APPENDIX H: BEAM – DESIGN OF COLUMN INTERACTION
83
APPENDIX I: DESIGN COMPUTATION OF COLUMN BASE PLATE
84
APPENDIX J: DESIGN OF WELDED CONNECTIONS
85
APPENDIX K: DESIGN OF BOLTED CONNECTIONSAppendix K: References
Arda, T. S. and Yardımcı, N. (1989). Çelik Yapıda Öngerme, 4. Çelik Yapılar Semineri, Nov.27-Dec.2, ĐTÜ Vakfı ve Đnşaat Fakültesi, Đstanbul. Calado L. Non-linear cyclic model of top and seat with web angle for steel beam-to-column connections, Engineering Structures, 2003; 25:1189-1197
Davison, O. (2006). Experimental investigation on built-up columns, Journal of Constructional Steel research 62: 1325-1332. Hart, A. (1992). Multi-storey Buildings, Steel Designer’s Manual, ed. G. W. Owens and P. R. Knowles, Blackwell Scientific, Oxford. Otto, K. N. and Antonsson, E. K., (1991). Trade-off strategies in engineering design. Research in Engineering Design, volume 3, number 2 Schollar, T. (1993). Chapter 21: Structural Connections for Steelwork, Architecture and Construction in Steel, ed. Blanc A., McEvoy M., Plank R., pub. E & FN Spon, London.
86
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