1. OPMA 5364 Project Management Part 5 Project Scheduling

2. Topic Outline: Project Scheduling
Identifying relationships among activities
Project network diagrams
Identifying critical paths and critical activities
Determining activity slack times
Gantt charts
Project scheduling exercise
Microsoft Project example
Other precedence relationships
Management of project schedules
Part 5 - Project Scheduling

3. Identifying Activity Relationships
In addition to estimating activity time duration and cost, relationships among activities must also be identified
Relationships:
What task immediately precedes this task?
What task immediately follows this task?
What tasks can be done concurrently?
These are referred to as precedence relationships
The main relationship for scheduling is ‘what task immediately precedes the current task,’ which is referred to as the immediate predecessor task
Part 5 - Project Scheduling

4. Project Network Diagrams
Network diagrams show the precedence relationships among activities
It’s easier to understand these relationships graphically
Network diagrams help to understand the flow of work in a project
Network diagrams are a useful tool for project planning and control, as well as for scheduling
One (perhaps exaggerated) claim is that the network represents ¾ of the planning process
Part 5 - Project Scheduling

5. 2 Versions of Network Diagrams
Activity-on-Arrow (AOA) networks
also called Arrow Diagramming Method (ADM)
simpler for projects with many dependencies
emphasizes events; milestones can be easily flagged
sometimes requires dummy activities
Activity-on-Node (AON) networks
also called Precedence Diagramming Method (PDM)
easier to draw for simple projects
emphasizes activities
no dummy activities
Part 5 - Project Scheduling

6. Part 5 - Project Scheduling
Activities vs. Events
Activity – a chunk of work that is part of the project; an activity may be broken down into multiple subactivities
Event – a significant point in time during the project, such as a milestone event; an event could be the time at which an activity is completed or the time at which related concurrent activities have all completed
Dummy Activity – an artificial activity with zero time duration that only shows a precedence relationship among activities
Part 5 - Project Scheduling

7. Activity-on-Arrow (AOA) Networksb c d e f g k j or
Dashed lines are called dummy activities k j
Activity Predecessor m n r s _
m, n
Part 5 - Project Scheduling

8. Project Network for House Construction1 2
Excavate & pour footings
Pour foundation
Install drains
Project Network for House Construction
(AOA network) 3 6 7 4 8 9 5 10 11 12 16 18 13 17 15 14
Install rough
electrical & plumbing
Pour
basement
floor
Install
cooling &
heating
Erect
frame & roof
Lay
brickwork
storm
drains
drywall
flooring
finished
plumbing
kitchen
equipment
Paint
Finish
roof
drainage
grading
floors
walks;
Landscape
electrical
work
carpeting
Part 5 - Project Scheduling

9. Project Network Example
Task Pred. Dur. Task Pred. Dur.
a g c,d
b h e
c a i f
d a j e,g
e b k h,i
f b
Draw AOA and AON networks
Part 5 - Project Scheduling

10. Activity-on-Arrow (AOA or ADM) Network
(Initial Network)
Part 5 - Project Scheduling

11. Activity-on-Arrow (AOA or ADM) Network
(Final Network) c d a g j b e h k f i
Part 5 - Project Scheduling

12. Activity-on-Node (AON or PDM) Network
Part 5 - Project Scheduling

13. Project Network Example
A project has the following activities and precedence relationships:
Predecessor Predecessor
Activity Activities Activity Activities
a f c,e
b a g b
c a h b,d
d a i b,d
e b j f,g,h
Draw AOA and AON networks
Part 5 - Project Scheduling

14. Activity on Arrow (Initial Network)
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15. Activity on Arrow (Final Network)b c d e f g h i j
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16. Part 5 - Project Scheduling
Activity on Node
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17. Part 5 - Project Scheduling
Critical Path
path – any route along the network from start to finish
Critical Path – path with the longest total duration
This is the shortest time in which the project can be completed.
Critical Activity – an activity on the critical path
*If a critical activity is delayed, the entire project will be delayed. Close attention must be given to critical activities to prevent project delay. There may be more than one critical path.
Part 5 - Project Scheduling

18. Part 5 - Project Scheduling
Critical Path
Brute force approach to finding critical path:
identify all possible paths from start to finish
sum up durations for each path
largest total indicates critical path
(This approach is inefficient, but is instructive)
Part 5 - Project Scheduling

19. Part 5 - Project Scheduling1 2 6 4 7 5 3
b = 2
d = 4
g = 9
h = 9
f = 8
c = 5
a = 6
k = 6
j = 7
i = 4
e = 3
Part 5 - Project Scheduling

20. Part 5 - Project Scheduling
Slack Times
EST—Earliest Start Time
Largest EFT of all predecessors
EFT—Earliest Finish Time
EST + duration for this task
LFT—Latest Finish Time
Smallest LST of following tasks
LST—Latest Start Time
LFT – duration for this task
Slack—LFT – EFT or LST – EST
Part 5 - Project Scheduling

21. Part 5 - Project Scheduling
Computing Slack Times
Task = duration
slack = xxxx
EST
EFT
LST
LFT
Part 5 - Project Scheduling

22. Part 5 - Project Scheduling
Slack Times Example
Task Pred. Dur. Task Pred. Dur.
a g c,d
b h e
c a i f
d a j e,g
e b k h,i
f b
For each task, compute ES, EF, LF, LS, Slack
Part 5 - Project Scheduling

23. Part 5 - Project Scheduling
Start
Finish
a=4
slack=
b=3
c=3
d=2
e=6
f=4
g=1
h=4
i=5
j=6
k=1
Task=dur
slack=xxx
EST
EFT
LFT
LST
Part 5 - Project Scheduling

24. Part 5 - Project Scheduling
Gantt Charts
The main purpose of a Gantt chart is to display the schedule of activities
They are easy to understand
They are flexible in that you can also show other information on the chart, such as resources required, who is responsible, critical activities, percent complete, etc.
All project management software packages will create Gantt charts
Part 5 - Project Scheduling

25. Part 5 - Project Scheduling
Gantt Chart
Activity a b c d e f g h i
Time (weeks)
Part 5 - Project Scheduling

26. Project Scheduling Exercise
DynaTech Equipment Corp. case
Divide into small groups
Read case (5 minutes)
Assignment: (40 minutes)
List the immediate predecessors and WBS number for each activity
Draw project network diagram (lowest level)
Draw Gantt chart
Determine project completion time
Part 5 - Project Scheduling

27. Microsoft Project Example
Part 5 - Project Scheduling

28. Microsoft Project Example
Part 5 - Project Scheduling

29. Microsoft Project Example
Part 5 - Project Scheduling

30. Other Precedence Relationships
The typical precedence relationship between two activities is that when the first activity has finished, then the second activity can start. In this case the first activity is called the immediate predecessor of the second activity.
This is referred to as a Finish-to-Start linkage.
Other precedence relationships, or linkages, are also possible.
Lead and lag times are also possible.
Part 5 - Project Scheduling

31. Other Precedence Relationships
Finish-to-Start
Linkage (FS)
Start-to-Start
Linkage (SS)
Finish-to-Finish
Linkage (FF)
Start-to-Finish
Linkage (SF)
Activity 1
Activity 2
Lead and Lag Times
Lead (-) and Lag (+) times are expressed as part of the immediate predecessor notation. So 1FS+3 listed for the immediate predecessor of Activity 2 means that Activity 1 is the predecessor with a Finish-to-Start linkage and a 3-day lag time after Activity 1 finishes before Activity 2 can start.
1FS-3 means that Activity 2 can start 3 days before Activity 1 finishes.
1FF+3; 1SF-5; 1SS+4
Part 5 - Project Scheduling

32. Management of Project Schedules
Meeting project deadlines is often the most important goal in project management
Careful scheduling of project activities is critical to meeting the project due date
Effective project managers should have a good understanding of the issues involved in activity scheduling
Part 5 - Project Scheduling

33. Ineffective Scheduling
Notice:
As of tomorrow, employees will only be able to access the building using individual security cards. Pictures will be taken next Wednesday, and employees will receive their cards in two weeks.
Part 5 - Project Scheduling