Lecture 6- Network Scheduling Techniques 315gk

LECTURE 5

Scheduling Techniques

Introduction 

An important part of project planning is determining the logical workflow of the various activities you identified in the WBS.



Network diagrams are used that represent a graphical flow plan of activities that must be accomplished to complete the project.



The diagram illustrates which activities must be performed in sequence.



It also shows the planned sequence of steps, with all dependencies.



Project management software will automatically prepare network diagrams and bar charts.

2

Scheduling techniques    

Gantt or bar charts Milestone charts Line of balance Networks • Program Evaluation and Review Technique (PERT) • Arrow Diagram Method () [Sometimes called the Critical Path Method (M)] • Precedence Diagram Method (PDM) • Graphical Evaluation and Review Technique (GERT)

3

Advantages of Scheduling techniques  Basis for planning and predicting and how to use the resources  Provide visibility to control  Help management evaluate alternatives  Basis for obtaining facts for decision making  Utilize time network analysis  Basic structure for reporting information  Reveal interdependencies of activities  Identify the longest path or critical path  Aid in scheduling risk analysis 4

interdependencies of activities

5

Advantages of Scheduling techniques  Basis for planning and predicting and how to use the resources  Provide visibility to control  Help management evaluate alternatives  Basis for obtaining facts for decision making  Utilize time network analysis  Basic structure for reporting information  Reveal interdependencies of activities  Identify the longest path or critical path  Aid in scheduling risk analysis 6

GANTT Chart 

A Gantt chart is a type of bar chart, illustrate the start and finish dates of the terminal tasks and summary tasks of a project



A Gantt chart is eveloped by Karol Adamiecki in 1896, and independently by Henry Gantt in the 1910s



A Gantt chart is one of the most popular and useful tool of showing activities (tasks or events) displayed against time

7

Gantt Chart Example

Job

Day 1

Day 2

Day 3

Day 4

Day 5

Day 6

Day 7

Day 8

Start of an activity End of an activity

A

Scheduled activity time allowed

B

Maintenance

Actual work progress Nonproduction time

C

Point in time when chart is reviewed Now 8

Milestone schedules  A tool used to mark specific points along a project timeline. They focus on major progress points that must be reached to achieve success.  Project milestone schedules contains information: • • • •

Project start date Project end date Other milestones (review meetings or testing) Data items (deliverables or reports)

 Milestones are a good means to determine if your project is on schedule and a useful tool for reporting to management 9

Milestone schedules

10

Network analyis  The major disadvantage of GANTT and milestone is the inability to show the interdependencies between events and activities  Network analysis can provide valuable information for planning, integration of plans, time studies, scheduling and resource management.  Network are composed of events and acivities  There are two different format diagram • AON: Activities on the node (AIB- Activities in the box) • AOA: Activities on the arrow 11

AON: Activities On the Node

A

C

Order Pipe

Deliver Pipe

D Start

Lay Pipe

Finish

B Dig Trench

Precedence Diagram Method 12

AOA: Activities On the Arrow

ACTIVITY

6

3

3 WEEKS

COMPLETE TESTING

COMPLETE FINAL REPORT

LEGEND EVENT ACTIVITY

Standard PERT Nomenclature

13

AOA: Terminology  Event: equivalent to a milestone indicating when activity starts or finish  Activity: Element of work must be accomplished  Duration: Total time required to complete the activity  Critical path: The longest path thru the network and determines the duration of the project  Dummy activity: showing the precedential relationships between activities and consuming zero time

14

Dependencies

26

31

31

18

18

7

7

BURST POINT

26

SINK 15

Dependencies

a a b

e

d b 1

c

e d

c

Activity c must not precede activity e  Which one is correct? WRONG

RIGHT

16

Simplified PERT Network

3 1

5

2

6

7

8

9

4 LEGEND: (TIME = WEEKS) EVENT ACTIVITY CRITICAL PATH ACTIVITY 17

Dummy Activities D A

PRECEDING ACTIVITY ACTIVITY

DUMMY B

A B C D

B A,B

C 18

Dependencies c

a

b precede d b

d a and b precede c

d

a

a and b precede d

b c

e

a,b, and c precede e

19

Dependencies c

a

d b

e

a

d d depends on a and b e depends on b and c

b c

d depends on a and b c depends only on a e depends only on b

e 20

Constructing the Network a d

a 1 c

a

1

b

b e

e

WRONG

RIGHT d

c 2 a,b,c must precede d, but only a,b precede e d a d 1 1 a precede d

b

e 2

a and b precede d

f 3

4

2 b and c precede d

c

e

b

WRONG

c

f 3

RIGHT 21

Estimating Activity Time  PERT (Program evaluation and review technique): A method to analyze the involved tasks in completing a given project, especially the time needed to complete each task, and to identify the minimum time needed to complete the total project. • Optimistic time (a): the minimum possible time required to accomplish a task • Pessimistic time (b): the maximum possible time required to accomplish a task, • Most likely time (M): the best estimate of the time required to accomplish a task 22

Estimating Activity Time  Expected time (TE): The best estimate of the time required to accomplish a task TE = (a + 4M + b) / 6  Standard deviations of each activities

=(b-a)/6

23

Crashing the Schedule 

If the schedule you develop does not allow the project to complete when desired, you might have to take action to decrease the total project duration.



This is known as crashing the schedule.



You need to look at options in areas such as: • • •



Resources Activities Project Objectives.

Look for options that give the greatest compression at the lowest costs. 24

Schedule Compression  Elimination of some parts of the project  Addition of more resources  Substitution of less time-consuming components or activities  Parallelization of activities  Shortening critical path activities  Shortening early activities  Shortening longest activities 25

Schedule Compression (Continued)  Shortening easiest activities  Shortening activities that are least costly to speed up  Shortening activities for which you have more resources  Increasing the number of work hours per day

26

Resource Leveling  Resource leveling is an attempt to eliminate the manpower peaks and valleys by smoothing out the period-to-period resource requirements.  The ideal situation is to do this without changing the end date. However, in reality, the end date moves out and additional costs are incurred.

27

Resource Allocation  Resource allocation (or resource limited planning) is an attempt to find the shortest possible critical path based upon the available or fixed resources.  The problem with this approach is that the employees may not be qualified technically to perform work on more than one activity in a network.

28

Activity to Construct a Pump Station Activity 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Activity description Start Mobilise Survey Grade site Trench footings Form and pour concrete Cure concrete Concrete and material design Spec prefab metal building Plumbing materials, pump Electrical materials, lights, Install pump Erect structural steel Install roofing and siding Install lights and s Test Pump Paint End

Duration ,days 0 2 1 2 5 5 8 5 4 5 5 7 4 5 3 2 3 0

Immediate Predecessors 1 2 2 3,4 5,8 6 1 1 1 1 7,9,10 7,9,10 13 11,14 12 15 16, 17

29

Classroom Activity 6a



Draw a network diagram using the details in the previous slide.

30

Precedence Network The interrelationships on bar charts MONTHS AFTER GO-AHEAD TASKS

1

2

3

4

5

1 2 3 4 5

31

Types Of Precedence Charts

FINISH FINISH-TO-START

ACTIVITY 1

START

ACTIVITY 2

START START-TO-START

ACTIVITY 1

START

ACTIVITY 2

32

Types Of Precedence Charts

FINISH

FINISH

ACTIVITY 1

FINISH-TO-FINISH

ACTIVITY 2 PERCENT COMPLETE

ACTIVITY 1 50 % 20 %

ACTIVITY 2

33

ACTIVITY INFORMATION

EARLY START 01/06/97

TIME DURATION 2 WORK-WEEKS TOTAL SLACK(TS)

ACTIVITY 4

LATE START 15/06/97

FREE SLACK (FS) COST/PROFIT CENTER 2810

EARLY FINISH 14/06/97

$250,000

LATE FINISH 28/06/97 34

Questions?

35