1. ELC 347 project management
Day 20

2. Agenda
Integrative Project
Part 4 Not corrected (yet)
Part 5 Due Nov 24 (page 342)
Any of the first five sections can be resubmitted for rescoring prior to finals week. The recorded score will the average of the original score and the score on the resubmitted section.
Assignment 6 Graded
3 A’s, 3 B’s, 2 D’s and 1 F
Assignment 7 Posted
Due Nov. 24
Today will discuss Project Scheduling: Lagging, Crashing and Activity Networks

3. Schedule for rest of semester
Nov 13
Chap 10
Nov 17
Chap 11
Nov 20
Group work
Nov 24
Quiz 3
Through Chap 11
IP part 5 Due
Assignment 7 due
Dec 1
Project s 5 & 6
Dec 4
Group Work
Assignment 8 due
Dec 8
Chap 12
IP Part 6 due
Dec 11
Chap 13 & 14
Dec 10 AM
Quiz 4
Through chap 14
IP Project’s due
© 2007 Prentice-Hall, Inc

4. Project Scheduling: Lagging, Crashing and Activity Networks
Chapter 10
© 2007 Pearson Education

6. Lags in Precedence Relationships
The logical relationship between the start and finish of one activity and the start and finish of another activity.
Four logical relationships between tasks
Finish to Start
Finish to Finish
Start to Start
Start to Finish

7. This lag is not the same as activity slack
Finish to Start Lag
Most common type of sequencing
Shown on the line joining the modes
Added during forward pass
Subtracted during backward pass
This lag is not the same as activity slack A
Spec Design 6 B
Design Check 5 C
Blueprinting 7
Lag 4

8. Finish to Finish Lag Two activities share a similar completion point
The mechanical inspection cannot happen until wiring, plumbing, and HVAC installation are complete A
Plumbing 6 B
HVAC 5 C
Inspection 1 D
Wiring

9. Start to Start Lag
Logic must be maintained by both forward and backward pass A
Plumbing 6 B
HVAC 5 C
Inspection 1 D
Wiring
Lag 3

10. Start to Finish Lag Least common type of lag relationship
Successor’s finish dependent on predecessor’s start D
Wiring 6
Lag 3 B
HVAC 5 C
Inspection 1 A
Plumbing 6
fssf.mpp

11. Gantt Charts Establish a time-phased network
Can be used as a tracking tool
Benefits of Gantt charts
Easy to create and comprehend
Identify the schedule baseline network
Allow for updating and control
Identify resource needs

12. Create a Gantt chart based on the activities listed in the table.
Task
Time
Pred Z 8 -- U 3 W Y 5 T 6 V X S 7
U,T 4
Y,X R 9
Task ES EF LS LF Z Y X W V U T S R
gantt.mpp

13. Gantt Chart With Resources in MS Project

14. Principal methods for crashing
Crashing Projects
Accelerating a project by committing more resources than initially planned
Principal methods for crashing
Improving existing resources’ productivity
Changing work methods
Increasing the quantity of resources

15. Example – Calculating the Cost of Crashing
CRASHING ACTIVITIES – AN EXAMPLE
Formula Slope = crash cost – normal cost
normal time – crash time
Example – Calculating the Cost of Crashing
SUPPOSE:
NORMAL ACTIVITY DURATION = 8 WEEKS
NORMAL COST = $14,000
CRASHED ACTIVITY DURATION = 5 WEEKS
CRASHED COST = $23,000
THE ACTIVITY COST SLOPE =
23,000 – 14, or, $9, = $3,000 per week
8 –

17. Managerial Considerations
Determine activity fixed and variable costs
The crash point is the fully expedited activity
Optimize time-cost tradeoffs
Shorten activities on the critical path
Cease crashing when
the target completion time is reached
the crash cost exceeds the penalty cost

18. Project costs Normal Crashed Crash/day activity Duration Cost A 5 10003
1500
250 B 7
700 6
300 C
2500 2
4000 D - E 9
3750
9000
17500 F 4
1600
900 G
2400
3000 H
15000
2000
Total
22450
37500

21. Other costs Previous examples only includes direct costs What about
Indirect costs (overhead)
$ per day overhead
Late penalties
$ per day late

23. What is the lowest cost to complete this project in 53 weeks
What is the lowest cost to complete this project in 53 weeks? Times are in weeks and costs in dollars.
Activity
Pred
Normal Time
Min Time
Normal Cost
Crash Cost A -- 14 9
500
1500 B 5 2
1000
1600 C 10 8
2000
2900 D
B, C
2500 E 6
1900 F
3000 G
E, F 7 4
600
1800 H 15 11
3600
Initial early and late start and finish times
Task ES EF LS LF Slack A B C D E F G H
Project 63
Reduce A by 5 days at $200/week = $1000 Project length is now 58 weeks
Reduce G by 3 days at $400/week = $1200 Project length is now 55 weeks
Reduce C by 2 days at $450/week = $900 Project length is now 53 weeks
Total cost to finish project in 53 weeks is $3100 more than normal cost of $9800
crash.mpp, crash.xls

24. Activity on Arrow Networks
Activities represented by arrows
Widely used in construction
Event nodes easy to flag
Forward and backward pass logic similar to AON
Two activities may not begin and end at common nodes
Dummy activities may be required

26. Project delta Activity Pre Duration A 5 B C 6 D B,C 13 E F 4 G 9 H2

27. Two Succesors
Wrong
Wrong

28. AOA Network

29. Forward Pass

30. Backwards pass

31. Calculate early and late start and finish times for all activities.
Use AOA to sketch the network that represents the project as described in the table.
Calculate early and late start and finish times for all activities.
Activity
Time
Pred A 4 -- F D B 2 G 15 C 10 H 7
E,F,G 3
B,C K 11 E
Task ES EF LS LF A B C D E F G H K

32. Controversies in the Use of Networks
Networks can be too complex
Poor network construction creates problems
Networks may be used inappropriately
When employing subcontractors
The master network must be available to them
All sub-networks must use common methods
Positive bias exists in PERT networks