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# Crashing and Updating.ppt

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# Crashing and Updating.ppt

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### Crashing and Updating.ppt

1. 1. 8-1 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall Chapter 5 Crashing
2. 2. 8-2 2 Project Crashing Basic Concept In last lecture, we studied on how to use CPM and PERT to identify critical path for a project problem Now, the question is: Question: Can we cut short its project completion time? If so, how!
3. 3. 8-3 3 Project Crashing Solution! Yes, the project duration can be reduced by assigning more resources to project activities. But, doing this would somehow increase our project cost! How do we strike a balance? ■ Project crashing is a method for shortening project duration by reducing one or more critical activities to a time less than normal activity time.
4. 4. 8-4 4 Trade-off concept Here, we adopt the “Trade-off” concept  We attempt to “crash” some “critical” events by allocating more resources to them, so that the time of one or more critical activities is reduced to a time that is less than the normal activity time.  How to do that:  Question: What criteria should it be based on when deciding to crashing critical times?
5. 5. 8-5 5 Example – crashing (1) The critical path is 1-2-3, the completion time =11 How? Path: 1-2-3 = 5+6=11 weeks Path: 1-3 = 5 weeks Now, how many days can we “crash” it? 1 3 2 5 (1) 6(3) 5(0) Normal weeks Max weeks can be crashed
6. 6. 8-6 6 Example – crashing (1) 1 3 2 5 (1) 6(3) 5(0) The maximum time that can be crashed for: Path 1-2-3 = 1 + 3 = 4 Path 1-3 = 0 Should we use up all these 4 weeks?
7. 7. 8-7 7 Example – crashing (1) 1 3 2 5 (1) 6(3) 5(0) If we used all 4 days, then path 1-2-3 has (5-1) + (6-3) = 7 completion weeks Now, we need to check if the completion time for path 1-3 has lesser than 7 weeks (why?) Now, path 1-3 has (5-0) = 5 weeks Since path 1-3 still shorter than 7 weeks, we used up all 4 crashed weeks Question: What if path 1-3 has, say 8 weeks completion time? 4(0) 3(0)
8. 8. 8-8 8 Example – crashing (1) 1 3 2 5 (1) 6(3) 8(0) Such as Now, we cannot use all 4 days (Why?) Because path 1-2-3 will not be critical path anymore as path 1-3 would now has longest hour to finish Rule: When a path is a critical path, it will not stay as a critical path So, we can only reduce the path 1-2-3 completion time to the same time as path 1-3. (HOW?)
9. 9. 8-9 9 Example – crashing (1) 1 3 2 5 (1) 6(3) 8(0) Solution: We can only reduce total time for path 1-2-3 = path 1-3, that is 8 weeks If the cost for path 1-2 and path 2-3 is the same then We can random pick them to crash so that its completion Time is 8 weeks
10. 10. 8-10 10 Example – crashing (1) 1 3 2 5 (1) 6(3) 8(0) Solution: 1 2 3 5 (1) 6(3) 8(0) OR 4(0) 4(1) 3(0) Now, paths 1-2-3 and 1-3 are both critical paths
11. 11. 8-11 Project Crashing and Time-Cost Trade-Off Example Problem (2 of 5) Figure 8.20 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall Crash cost & crash time have a linear relationship: \$2000 5 \$400 / Total Crash Cost Total Crash Time weeks wk  
12. 12. 8-12 Project Crashing and Time-Cost Trade-Off General Relationship of Time and Cost (2 of 2) Figure 8.23 The Time-Cost Trade-Off Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall
13. 13. 8-13 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall
14. 14. 8-14 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall
15. 15. 8-15 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall
16. 16. 8-16 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall
17. 17. 8-17 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall
18. 18. 8-18 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall
19. 19. 8-19 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall