1 / 63

Project Planning and Control

Project Planning and Control. Jay Sounderpandian University of Wisconsin - Parkside. Part I. INTRODUCTION. Historical Note. Until the 1940’s the Gantt Chart was the only tool available for Project Planning and Control.

cindy
Download Presentation

Project Planning and Control

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Project Planning and Control Jay Sounderpandian University of Wisconsin - Parkside

  2. Part I INTRODUCTION

  3. Historical Note • Until the 1940’s the Gantt Chart was the only tool available for Project Planning and Control. • During the 40’s, managers at Du Pont and (independently) engineers in the US Military invented the PERT/CPM method. • In the 90’s we have sophisticated computer programs for almost all aspects of Project Management. Sounderpandian

  4. A Gantt Chart Project Title Week 1 Week 2 Week 3 Week 4 Week 5 W Task 1 Task 2 Task 3 Task 4 Sounderpandian

  5. Gantt Chart Refinements Project Title Now Week 1 Week 2 Week 3 Week 4 Week 5 W Task 1 Task 2 Task 3 Task 4 Sounderpandian

  6. Another Refinement Project Title Week 1 Week 2 Week 3 Week 4 Week 5 W Task 1 Task 2 Task 3 Task 4 Sounderpandian

  7. Gantt Chart Limitations • Showing the interdependencies of tasks is cumbersome in a Gantt Chart. • If the chart is not computer driven, • Critical tasks are not readily identified. • Rescheduling and monitoring are difficult. • The amount of slack in the schedule of a task is difficult to calculate. Sounderpandian

  8. The POLARIS Project • It had numerous tasks with intricate interdependencies. • It needed ready identification of critical tasks. • It needed close monitoring with frequent rescheduling. • No computer was available. Sounderpandian

  9. Part II Project Network Diagrams

  10. Task on Node (TON) Task on Arrow (TOA) A C B A C B Two Graphical Representations Sounderpandian

  11. Advantages of TOA over TON • An arrow denotes passage of time and therefore is better suited (than a node) to represent a task. • Scheduling (manually) on a TOA diagram is easier than on a TON diagram. • In general, TOA needs fewer arrows than TON and therefore will be more clear. Sounderpandian

  12. A Disadvantage of TOA • A TOA diagram often requires the use of dummy arrows, which represent dummy activities artificially introduced into the project. • Consider the project: • It needs a dummy arrow. Sounderpandian

  13. C A End Start D B The need for Dummy Arrows • Consider the project: • The only way to draw a TOA diagram for it is: Dummy Sounderpandian

  14. C A End Start D B The use of dummy arrows The dummy (broken) arrow is to be considered an additional (dummy) activity which takes zero time. It starts after A is finished. Since D starts after the end of B and the dummy activity, it has to wait, in effect, for A and B to be over. That is exactly the prerequisite for D. Sounderpandian

  15. More on dummy arrows • Dummy arrows introduce additional tasks into the project and thus add complexity. • Therefore one should minimize the number of dummy arrows used in any project diagram. • Unfortunately, (and interestingly,) minimizing the number of dummy arrows is a very difficult problem. To wit, in a project with a large number of tasks, it may not be possible to know the minimum number of dummy arrows needed. Sounderpandian

  16. TOA vs TON • Despite the difficulty with dummy arrows, the TOA diagram is better suited than the TON for manual work, because of its manual scheduling advantages. • Computer programs use the TON diagram, because of the trouble with dummy arrows. Sounderpandian

  17. Steps in drawing a TOA diagram • 1. List all the activities in the project • 2. List all the precedence relationships among the tasks. • A precedence relationship may be due to resource constraint or due to a physical necessity. • 3. Estimate the duration of all the tasks. • 4. Draw the TOA diagram observing all conventions. Sounderpandian

  18. Conventions in a TOA diagram • The length of an arrow need not be indicative of the task duration. • At most one arrow between any two nodes. • Exactly one Start node and one End node. • Avoid unnecessary dummy arrows. • Nodes are numbered such that every arrow goes from a smaller to a larger number. • Arrows go from left to right. Sounderpandian

  19. Exercise 1 Draw a TOA diagram for the project: Sounderpandian

  20. Exercise 2 Draw a TOA diagram for the project: Sounderpandian

  21. Exercise 3 Draw a TOA diagram for the project: Sounderpandian

  22. Exercise 4 Draw a TOA diagram for the project: Sounderpandian

  23. Exercise 5 Draw a TOA diagram for the project: (Tricky!) Sounderpandian

  24. Exercise 6 Draw a TOA diagram for the project: Sounderpandian

  25. Part III Project Scheduling

  26. Event Scheduling • The easiest way to schedule a project is by scheduling the events. Recall that events are represented by nodes in TOA diagrams. • While scheduling an event we will be interested in two things, namely, • the Earliest Time the event can occur assuming everything goes according to plan. • the Latest Time the event can occur without delaying the completion of the project. Sounderpandian

  27. Earliest Time Estimate 10 + 9 = 19 13 + 5 = 18 8 + 14 = 22 Max = 22 10 22 9 13 5 14 8 Sounderpandian

  28. Earliest Time Estimate • Assign time zero to start event (1). • Go to the next event (2, 3, ...). • Consider all incoming arrows. • Calculate the completion time of each arrow. • Pick the maximum. • Continue until all events are scheduled. Sounderpandian

  29. Latest Time Estimate 25 - 5 = 20 28 - 14 = 14 23 - 13 = 10 Min = 10 25 5 10 28 14 13 23 Sounderpandian

  30. Latest Time Estimate • Set the latest time equal to the earliest for the Finish event (n). • Go to the previous event (n-1, n-2, ...). • Consider all outgoing arrows. • Calculate the start time of each arrow. • Pick the minimum. • Continue until all events are scheduled. Sounderpandian

  31. Critical Event • An event whose earliest and latest time estimates are equal is a Critical Event. • If there is a delay in a critical event, then the project completion will be delayed. Sounderpandian

  32. Slack 5 10 23 29 13 Slack = 29 - 5 - 13 = 11 Sounderpandian

  33. Critical Task • A task with zero slack is a Critical Task. • If a critical task is delayed, it would delay the project completion. • If a non-critical task is expedited, it would not expedite project completion. It would simply increase the slack of that task. Sounderpandian

  34. Part IV The Critical Path

  35. Exercise 7 Identify the critical path(s). 4 18 14 7 2 22 5 16 17 12 5 1 4 8 20 Start End 15 19 3 8 6 Sounderpandian

  36. Critical Path • The critical path is the longest path from Start to Finish. • Its length is the project duration. • It consists of all and only the critical tasks and passes through all and only the critical events. • A project can have more than one critical path. Sounderpandian

  37. When a critical task is expedited.. • The project duration may or may not decrease. • The critical path may cease to be critical, and a new critical path may emerge. • If another critical path already exists, it will remain critical. • The slack on any other task can only decrease or stay the same. Sounderpandian

  38. When a critical task is delayed... • The project duration will increase. • The task will continue to be critical and its critical path will continue to be critical. • Another critical path may cease to be critical because it may not be one of the longest paths any more. • The slack on any other task can only increase or stay the same. Sounderpandian

  39. If a non-critical task is delayed ... • As long as the delay is less than the slack: • the project duration would not increase • no changes would occur in critical path(s). • there could be some cost saving. • When the delay equals or exceeds the slack: • the task will become critical • changes in critical path(s) will occur • project cost may increase Sounderpandian

  40. Exercise 8 • Refer to the project in Exercise 7. • 1. By how many days can the task 2-7 be delayed before it becomes critical? • 2. If the task 2-7 is delayed by 20 days what will be the new project duration? • 3. If a task has a slack of x days and is delayed by x + y days, what is the delay in the project? Sounderpandian

  41. Exercise 9 • Refer to the project in Exercise 7. By how many days can the task 5-6 be expedited before the critical path changes? Note: This question is harder than those in the previous exercise because the new critical path can be any one of a number of possibilities. Sounderpandian

  42. Part IV Expediting

  43. Expediting a Project • When a project needs to be completed sooner, it needs to be expedited. • Expediting is beneficial (only) as long as the benefit exceeds the cost. • Sometimes a precedence relationship due to resource constraint can be removed by getting additional resources. That could greatly reduce project duration. Sounderpandian

  44. Expediting a Project • In order to expedite a project, the lengths of all the critical paths need to be reduced. That is, if two parallel critical paths exist, then both paths need to be shortened. • An annoying complication is that critical path could change as some critical tasks are expedited. Thus, it has to be a trial-and-error process. Sounderpandian

  45. Exercise 10 The figure shows the critical paths and expediting cost per day for each critical task. 8 $ 180 $ 210 $ 680 $ 520 1 4 15 18 Start End $320 $ 360 11 Assuming that no other task becomes critical, what is the least cost plan to expedite the project by 1 day? Sounderpandian

  46. Exercise 10 Continued Assuming that no other task becomes critical, what is the least cost plan to expedite the project by 2 days? The assumption in the above question is crucial. If other tasks become critical, the problem becomes much harder. Sounderpandian

  47. Exercise 11 Here is a whole project with critical path in red. Duration and crashing cost per day are shown for each task.. 2 $ 180 $ 210 7 14 5 1 4 End $50 Start 11 10 $ 360 $320 3 Find the minimum cost crashing plan for reducing the project duration by i) 1 day ii) 2 days. Sounderpandian

  48. Part V PERT

  49. PERT • PERT stands for Program Evaluation and Review Technique. • PERT is a refinement on CPM. It accommodates uncertainties in task durations. • In practice, almost all task durations are uncertain, and therefore PERT is useful and popular. Sounderpandian

  50. Beta Distribution • Research shows that task durations follow a Beta distribution, which is right skewed. • To simplify the estimation of the distribution, a three-time estimate is used. The three estimates are: • the optimistic duration (a) • the most likely duration (m) • the pessimistic duration (b) Sounderpandian

More Related