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OPSM 301 Operations Management

Ko ç Un iversity. OPSM 301 Operations Management. Class 27: Project Management: project crashing. Zeynep Aksin zaksin @ku.edu.tr. Trade-Offs And Project Crashing. The project is behind schedule The completion time has been moved forward.

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OPSM 301 Operations Management

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  1. Koç University OPSM 301 Operations Management Class 27: Project Management: project crashing Zeynep Aksin zaksin@ku.edu.tr

  2. Trade-Offs And Project Crashing • The project is behind schedule • The completion time has been moved forward It is not uncommon to face the following situations: Shortening the duration of the project is called project crashing

  3. Factors to Consider When Crashing A Project • The amount by which an activity is crashed is, in fact, permissible • Taken together, the shortened activity durations will enable us to finish the project by the due date • The total cost of crashing is as small as possible

  4. Steps in Project Crashing • Compute the crash cost per time period. For crash costs assumed linear over time: • Using current activity times, find the critical path • If there is only one critical path, then select the activity on this critical path that (a) can still be crashed, and (b) has the smallest crash cost per period. If there is more than one critical path, then select one activity from each critical path such that (a) each selected activity can still be crashed, and (b) the total crash cost of all selected activities is the smallest. Note that the same activity may be common to more than one critical path. • Update all activity times. If the desired due date has been reached, stop. If not, return to Step 2

  5. Time (Wks) Cost ($) Crash Cost Critical Activity Normal Crash Normal Crash Per Wk ($) Path? A 2 1 22,000 22,750 750 Yes B 3 1 30,000 34,000 2,000 No C 2 1 26,000 27,000 1,000 Yes D 4 3 48,000 49,000 1,000 No E 4 2 56,000 58,000 1,000 Yes F 3 2 30,000 30,500 500 No G 5 2 80,000 84,500 1,500 Yes H 2 1 16,000 19,000 3,000 Yes Crashing The Project Table 3.5

  6. Crash and Normal Times and Costs for Activity B (for Yozgat Paper)

  7. A 2 C 2 F 3 0 2 4 7 2 4 2 4 10 13 0 2 Slack = 0 Slack = 0 Slack = 6 E 4 H 2 Start 0 0 4 8 13 15 13 15 0 0 4 8 0 Slack = 0 Slack = 0 B 3 D 4 G 5 0 3 3 7 8 13 4 8 8 13 1 4 Slack = 1 Slack = 1 Slack = 0 Critical Path And Slack Times For Yozgat Paper Figure 3.17

  8. AON Network for Yozgat Paper Manufacturing with Incremental Crashing Costs I=500 F I=750 I=1000 F 4 7 H A C 13 10 0 2 2 4 H H 3 A 2 C 4 0 2 I=1000 I=3000 2 2 E H 4 8 13 15 0 0 H F H H Start 8 4 15 13 0 0 4 2 I=2000 I=1000 0 I=1500 B D G Start B D G 0 3 3 7 8 13 H H H 4 8 13 1 4 8 3 4 5

  9. Look at all paths-as you crash other paths may become critical! • A-C-E-G-H critical 15 days • A-D-G-H 13 days • A-C-F-H 9 days • B-D-G-H 14 days

  10. A has lowest crash cost on critical path-it can be crashed by 1 week • A-C-E-G-H critical 15 days - 14 days • A-D-G-H 13 days  12 days • A-C-F-H 9 days 8 days • B-D-G-H 14 days

  11. A can no longer be crashedNeed to consider both critical paths • A-C-E-G-H critical 15 days - 14 days • A-D-G-H 13 days  12 days • A-C-F-H 9 days 8 days • B-D-G-H 14 days • C is the next cheap activvity to crash • BUT Crashing C will require crashing another activity on th B-D-G-H path • G is common to both paths-just crashing one activity will take care of both paths!

  12. Crashing Yozgat Paper Manufacturing Project • Minimum crashing plan: Activity A by 1 week and Activity G by 1 week Total Cost=$750 + $1500 = $2250 Why didn’t we crash Activity C??

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