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Project Scheduling: Lagging, Crashing, and Activity Networks 10-01.

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Presentation on theme: "Project Scheduling: Lagging, Crashing, and Activity Networks 10-01."— Presentation transcript:

1 Project Scheduling: Lagging, Crashing, and Activity Networks 10-01

2 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall Chapter 10 Learning Objectives After completing this chapter, students will be able to: Apply lag relationships to project activities. Construct and comprehend Gantt charts. Recognize alternative means to accelerate projects, including their benefits and drawbacks. Understand the trade-offs required in the decision to crash project activities. Develop activity networks using Activity-on-Arrow techniques. Understand the differences in AON and AOA and recognize the advantages and disadvantages of each technique

3 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall 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 1. Finish to Start 2. Finish to Finish 3. Start to Start 4. Start to Finish 10-03

4 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall Finish to Start Lag Most common type of sequencing Shown on the line joining the modes Added during forward pass Subtracted during backward pass 0 A 6 Spec Design 6 6 B 11 Design Check 5 15 C 22 Blueprinting 7 Lag 4 This lag is not the same as activity slack 10-04

5 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall Finish to Finish Lag Two activities share a similar completion point The mechanical inspection cannot happen until wiring, plumbing, and HVAC installation are complete 10 A 16 Plumbing 6 16 B 21 HVAC 5 21 C 22 Inspection 1 15 D 21 Wiring 6 Lag

6 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall Start to Start Lag Logic must be maintained by both forward and backward pass 31 A 33 Plumbing 6 33 B 36 HVAC 5 36 C 37 Inspection 1 30 D 36 Wiring 6 Lag

7 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall Start to Finish Lag Least common type of lag relationship Successors finish dependent on predecessors start 22 A 28 Plumbing 6 28 B 33 HVAC 5 33 C 34 Inspection 1 30 D 36 Wiring 6 Lag

8 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall Gantt Charts Establish a time-phased network Can be used as a tracking tool Benefits of Gantt charts 1. Easy to create and comprehend 2. Identify the schedule baseline network 3. Allow for updating and control 4. Identify resource needs 10-08

9 FIGURE 10.8 Completed Gantt Chart for Project Delta Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall 10-9

10 FIGURE 10.9 Gantt Chart for Project Delta with Critical Path Highlighted Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

11 FIGURE Gantt Chart with Resources Specified Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

12 FIGURE Gantt Chart with Lag Relationships Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

13 Crashing The process of accelerating a project Principal methods for crashing Improving existing resources productivity Changing work methods Compromise quality and/or reduce project scope Institute fast-tracking Work overtime Increasing the quantity of resources 10-13

14 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall 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 crashing cost exceeds the penalty cost 10-14

15 Project Activities and Costs Table 10.1 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

16 FIGURE Time–Cost Trade-Offs for Crashing Activities Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall 10-16

17 FIGURE Fully Crashed Project Activity Network Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall 10-17

18 FIGURE Relationship Between Cost and Days Saved in a Crashed Project Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall 10-18

19 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall 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

20 FIGURE Notation for Activity-on-Arrow (AOA) Networks Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

21 FIGURE Sample Network Diagram Using AOA Approach Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

22 FIGURE 10.20A Representing Activities with Two or More Immediate Successors(Wrong) Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

23 FIGURE 10.20B Alternative Way to Represent Activities with Two or More Immediate Successors (Wrong) Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

24 FIGURE 10.20C Representing Activities with Two or More Immediate Successors Using Dummy Activities (Better) Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

25 FIGURE Partial Project Delta Network Using AOA Notation Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

26 FIGURE Completed Project Delta AOA Network Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

27 FIGURE Project Delta Forward Pass Using AOA Network Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

28 FIGURE Project Delta Backward Pass Using AOA Network Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

29 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 10-29

30 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall Summary 1. Apply lag relationships to project activities. 2. Construct and comprehend Gantt charts. 3. Recognize alternative means to accelerate projects, including their benefits and drawbacks. 4. Understand the trade-offs required in the decision to crash project activities. 5. Develop activity networks using Activity-on-Arrow techniques. 6. Understand the differences in AON and AOA and recognize the advantages and disadvantages of each technique

31 10-31 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall


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