Day 19 ELC 347/BUS 348/PSA 347

Agenda Questions? IP Part 4 IP Part 5 Assignment 6 Corrected Missing .mmp file with costs update IP Part 5 Due Nov 18 Developing a Project Schedule Assignment 6 Corrected 3 A’s and 1 B Assignment 7 Posted Only one more Exam 2 Corrected 2 A’s, 1 B and 1 C Finish Critical Chain Project Scheduling

Finals Rescheduling Do IP Project presentation on Dec 12 Exam 3 done asynchronously via Blackboard on Dec 16 Final IP Project Due Dec 18

Project Scheduling: Lagging, Crashing, and Activity Networks Chapter 10 Project Scheduling: Lagging, Crashing, and Activity Networks

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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.

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 Finish to Start Finish to Finish Start to Start Start to Finish

Finish to Start Lag Most common type of sequencing Shown on the line joining the modes Added during forward pass Subtracted during backward pass This lag is not the same as activity slack 0 A 6 Spec Design 6 6 B 11 Design Check 5 15 C 22 Blueprinting 7 Lag 4

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 Lag 3

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 Lag 3

Start to Finish Lag Least common type of lag relationship Successor’s finish dependent on predecessor’s start 30 D 36 Wiring 6 Lag 3 22 A 28 Plumbing 6 28 B 33 HVAC 5 33 C 34 Inspection 1

Gantt Charts Establish a time-phased network Can be used as a tracking tool Benefits of Gantt charts Easy to create and comprehend Identify the schedule baseline network Allow for updating and control Identify resource needs

Create a Gantt chart based on the activities listed in the table. Task Time Pred Z 8 -- U 3 W Y 5 T 6 V X S 7 U,T 4 Y,X R 9 Task ES EF LS LF Z 0 8 0 8 Y 8 13 11 16 X 8 16 8 16 W 16 20 16 20 V 20 25 20 25 U 20 23 28 31 T 25 31 25 31 S 31 38 31 38 R 38 47 38 47 gantt.mpp

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

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

Gantt Chart with Resources Specified FIGURE 10.10   Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Gantt Chart with Lag Relationships FIGURE 10.11   Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Gantt Chart with Lag Relationships

Principal methods for 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

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

Formula Slope = crash cost – normal cost normal time – crash time CRASHING ACTIVITIES – AN EXAMPLE   Formula Slope = crash cost – normal cost normal time – crash time Example – Calculating the Cost of Crashing SUPPOSE: NORMAL ACTIVITY DURATION = 8 WEEKS NORMAL COST = $14,000 CRASHED ACTIVITY DURATION = 5 WEEKS CRASHED COST = $23,000 THE ACTIVITY COST SLOPE = 23,000 – 14,000 or, $9,000 = $3,000 per week 8 – 5 3

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

FIGURE 10.14 Time–Cost Trade-Offs for Crashing Activities Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Project costs Pre Normal Crashed Crash/day Days Gained activity Duration Cost A 5 1000 3 1500 250 2 B 7 700 6 300 1 C 2500 4000 D - E C,D 9 3750 9000 1750 F 4 1600 900 G 2400 3000 H E,F,G 15000 2000 Total 22450 37500

Normal Netw0rk 7 4 3 5 9 9 5 6 Project time = 28 days Project Cost = $22450

Fully Crashed Netw0rk Project time = 19 days Project Cost = $37,500

Partially Crashed Netw0rk 7 4 3 6 Project time = 19 days Project Cost = $34,200 (save $3,300)

FIGURE 10.16  Relationship Between Cost and Days Saved in a Crashed Project Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Other costs Previous examples only includes direct costs What about Indirect costs (overhead) $ per day overhead Late penalties $ per day late

What is the lowest cost to complete this project in 53 weeks What is the lowest cost to complete this project in 53 weeks? Times are in weeks and costs in dollars. Activity Pred Normal Time Min Time Normal Cost Crash Cost A -- 14 9 500 1500 B 5 2 1000 1600 C 10 8 2000 2900 D B, C 2500 E 6 1900 F 3000 G E, F 7 4 600 1800 H 15 11 3600 Initial early and late start and finish times Task ES EF LS LF Slack A 0 14 0 14 0 B 14 19 19 24 5 C 14 24 14 24 0 D 24 32 24 32 0 E 32 38 35 41 3 F 32 41 32 41 0 G 41 48 41 48 0 H 48 63 48 63 0 Project 63 Reduce A by 5 days at $200/week = $1000 Project length is now 58 weeks Reduce G by 3 days at $400/week = $1200 Project length is now 55 weeks Reduce C by 2 days at $450/week = $900 Project length is now 53 weeks Total cost to finish project in 53 weeks is $3100 more than normal cost of $9800 crash.mpp, crash.xls

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

Notation for Activity-on-Arrow (AOA) Networks FIGURE 10.18 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Project delta Activity Pre Duration A 5 B C 6 D B,C 13 E F 4 G 9 H 2

Sample Network Diagram Using AOA Approach FIGURE 10.19   Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

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

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

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

Partial Project Delta Network Using AOA Notation FIGURE 10.21   Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Completed Project Delta AOA Network FIGURE 10.22   Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Project Delta Forward Pass Using AOA Network FIGURE 10.23 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Project Delta Backward Pass Using AOA Network FIGURE 10.24   Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Calculate early and late start and finish times for all activities. Use AOA to sketch the network that represents the project as described in the table. Calculate early and late start and finish times for all activities. Activity Time Pred A 3 -- F 4 D B 5 G 2 C 7 H E,F,G B,C E Task ES EF LS LF A 0 4 0 4 B 4 6 12 14 C 4 14 4 14 D 14 17 14 17 E 6 21 21 36 F 17 21 32 36 G 17 32 17 32 H 32 39 36 43 K 32 43 32 43

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

Summary 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.

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