project network

pm

1. Project Network

2. Project “A project is a series of activities directed to accomplishment of a desired objective.” Plan your work first…..then work your plan

3. Network analysis Introduction Network analysis is the general name given to certain specific techniques which can be used for the planning, management and control of projects. One definition of a project: “A project is a temporary endeavour undertaken to create a "unique" product or service”

4. 4 Graphical portrayal of activities and event Shows dependency relationships between tasks/activities in a project Clearly shows tasks that must precede (precedence) or follow (succeeding) other tasks in a logical manner Clear representation of plan – a powerful tool for planning and controlling project NETWORK

5. CPM - Critical Path Method Definition: In CPM activities are shown as a network of precedence relationships using activity-on-node network construction Single estimate of activity time Deterministic activity times USED IN : Production management - for the jobs of repetitive in nature where the activity time estimates can be predicted with considerable certainty due to the existence of past experience.

6. PERT - Project Evaluation & Review Techniques Definition: In PERT activities are shown as a network of precedence relationships using activity-on-arrow network construction Multiple time estimates Probabilistic activity times USED IN : Project management - for non-repetitive jobs (research and development work), where the time and cost estimates tend to be quite uncertain. This technique uses probabilistic time estimates.

7. Originated by H.L.Gantt in 1918 Gantt chart Advantages - Gantt charts are quite commonly used. They provide an easy graphical representation of when activities (might) take place. Limitations Do not clearly indicate details regarding the progress of activities Do not give a clear indication of interrelation ship between the separate activities

8. CPM/PERT These deficiencies can be eliminated to a large extent by showing the interdependence of various activities by means of connecting arrows called network technique. Overtime CPM and PERT became one technique ADVANTAGES: Precedence relationships large projects more efficient

9. NETWORK TECHNIQUES PERT CPM Program Evaluation and Review Technique developed by the US Navy with Booz Hamilton Lockheed on the Polaris Missile/Submarine program 1958 Critical Path Method Developed by El Dupont for Chemical Plant Shutdown Project- about same time as PERT Both use same calculations, almost similar Main difference is probabilistic and deterministic in time estimation Gantt Chart also used in scheduling

10. 10 BENEFITS OFCPM / PERT NETWORK Consistent framework for planning, scheduling, monitoring, and controlling project.   Shows interdependence of all tasks, work packages, and work units. Helps proper communications between departments and functions. Determines expected project completion date. Identifies so-called critical activities, which can delay the project completion time.  

11. 11 Identified activities with slacks that can be delayed for specified periods without penalty, or from which resources may be temporarily borrowed Determines the dates on which tasks may be started or must be started if the project is to stay in schedule. Shows which tasks must be coordinated to avoid resource or timing conflicts. Shows which tasks may run in parallel to meet project completion date BENEFITS OFCPM / PERT NETWORK (cont.)

12. Questions Answered by CPM & PERT Completion date? On Schedule? Within Budget? Critical Activities? How can the project be finished early at the least cost?

13. 13 Example of Simple Network – Survey

14. 14 DEFINITION OF TERMS IN A NETWORK Activity : any portions of project (tasks) which required by project, uses up resource and consumes time – may involve labor, paper work, contractual negotiations, machinery operations Activity on Arrow (AOA) showed as arrow, AON – Activity on Node Event : beginning or ending points of one or more activities, instantaneous point in time, also called ‘nodes’ Network : Combination of all project activities and the events ACTIVITY PRECEEDING SUCCESSOR EVENT

15. 15 Emphasis on Logic in Network Construction Construction of network should be based on logical or technical dependencies among activities Example - before activity ‘Approve Drawing’ can be started the activity ‘Prepare Drawing’ must be completed

16. Activity on Node & Activity on Arrow Activity on Node - A completion of an activity is represented by a node Activity on Arrow - An arrow represents a task, while a node is the completion of a task - Arrows represent order of events

17. Activity Slack Each event has two important times associated with it : Earliest time , Te , which is a calendar time when a event can occur when all the predecessor events completed at the earliest possible times Latest time , TL , which is the latest time the event can occur with out delaying the subsequent events and completion of project. Difference between the latest time and the earliest time of an event is the slack time for that event Positive slack : Slack is the amount of time an event can be delayed without delaying the project completion

18. Critical Path Is that the sequence of activities and events where there is no “slack” i.e.. Zero slack Longest path through a network minimum project completion time

19. 19 Example 1- A simple network Consider the list of four activities for making a simple product: Activity Description Immediate predecessors A Buy Plastic Body - B Design Component - C Make Component B D Assemble product A,C Immediate predecessors for a particular activity are the activities that, when completed, enable the start of the activity in question.

20. 20 Sequence of activities Can start work on activities A and B anytime, since neither of these activities depends upon the completion of prior activities. Activity C cannot be started until activity B has been completed Activity D cannot be started until both activities A and C have been completed. The graphical representation (next slide) is referred to as the PERT/CPM network

21. 21 Network of Four Activities 1 3 4 2 A B C D Arcs indicate project activities Nodes correspond to the beginning and ending of activities

22. 22 Example 2 Develop the network for a project with following activities and immediate predecessors : Activity Immediate predecessors A - B - C B D A, C E C F C G D,E,F Try to do for the first five (A,B,C,D,E) activities

23. 23 Network of first five activities 1 3 4 2 A B C D 5 E We need to introduce a dummy activity

24. 24 Note how the network correctly identifies D, E, and F as the immediate predecessors for activity G. Dummy activities is used to identify precedence relationships correctly and to eliminate possible confusion of two or more activities having the same starting and ending nodes Dummy activities have no resources (time, labor, machinery, etc) – purpose is to PRESERVE LOGIC of the network Network of Seven Activities 1 3 4 2 A B C D 5 E 7 6 F G dummy

25. 25 1 1 2 2 3 3 4 a d b e c f a d b e f c WRONG!!! RIGHT!!! a precedes d. a and b precede e, b and c precede f (a does not precede f)

26. 26 Scheduling with activity time Activity Immediate Completion predecessors Time (week) A - 5 B - 6 C A 4 D A 3 E A 1 F E 4 G D,F 14 H B,C 12 I G,H 2 Total …… 51 This information indicates that the total time required to complete activities is 51 weeks. However, we can see from the network that several of the activities can be conducted simultaneously (A and B, for example).

27. Activity Relationships Activity Relationship AOA AON Figure 4.1

28. Activity Relationships Activity Relationship S precedes T, which precedes U. AOA AON 1 2 S 3 T 4 U S T U Figure 4.1

29. Activity Relationships Activity Relationship S and T must be completed before U can be started. AOA AON S T U 1 2 3 T S 4 U Figure 4.1

30. Activity Relationships Activity Relationship T and U cannot begin until S has been completed. AOA AON T U S 3 4 1 T U 2 S Figure 4.1

31. Activity Relationships Activity Relationship U and V cannot begin until both S and T have been completed. AOA AON 1 2 4 5 U V S T 3 S T U V Figure 4.1

32. Activity Relationships Activity Relationship U cannot begin until both S and T have been completed; V cannot begin until T has been completed. AOA AON S T U V 1 3 Dummy 5 2 4 6 S U T V Figure 4.1

33. Activity Relationships Activity Relationship T and U cannot begin until S has been completed; V cannot begin until both T and U have been completed. AOA AON 1 2 4 3 S T 5 V U Dummy S T V U Figure 4.1