Project Scheduling: Lagging, Crashing, and Activity Networks
10-01 Slide 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. 10-02 Slide 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 Slide 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 Slide 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 3 10-05 Slide 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 3 10-06 Slide 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 3 10-07 Slide 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 Slide 9 FIGURE 10.8 Completed Gantt
Chart for Project Delta Copyright 2013 Pearson Education, Inc.
Publishing as Prentice Hall 10-9 Slide 10 FIGURE 10.9 Gantt Chart
for Project Delta with Critical Path Highlighted 10-10 Copyright
2013 Pearson Education, Inc. Publishing as Prentice Hall Slide 11
FIGURE 10.10 Gantt Chart with Resources Specified 10-11 Copyright
2013 Pearson Education, Inc. Publishing as Prentice Hall Slide 12
FIGURE 10.11 Gantt Chart with Lag Relationships 10-12 Copyright
2013 Pearson Education, Inc. Publishing as Prentice Hall Slide 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 Slide 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 Slide
15 Project Activities and Costs 10-15 Table 10.1 Copyright 2013
Pearson Education, Inc. Publishing as Prentice Hall Slide 16 FIGURE
10.14 TimeCost Trade-Offs for Crashing Activities Copyright 2013
Pearson Education, Inc. Publishing as Prentice Hall 10-16 Slide 17
FIGURE 10.15 Fully Crashed Project Activity Network Copyright 2013
Pearson Education, Inc. Publishing as Prentice Hall 10-17 Slide 18
FIGURE 10.16 Relationship Between Cost and Days Saved in a Crashed
Project Copyright 2013 Pearson Education, Inc. Publishing as
Prentice Hall 10-18 Slide 19 Copyright 2013 Pearson Education, Inc.
Publishing as Prentice Hall 10-19 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 Slide 20 FIGURE 10.18 Notation for
Activity-on-Arrow (AOA) Networks 10-20 Copyright 2013 Pearson
Education, Inc. Publishing as Prentice Hall Slide 21 FIGURE 10.19
Sample Network Diagram Using AOA Approach 10-21 Copyright 2013
Pearson Education, Inc. Publishing as Prentice Hall Slide 22 FIGURE
10.20A Representing Activities with Two or More Immediate
Successors(Wrong) 10-22 Copyright 2013 Pearson Education, Inc.
Publishing as Prentice Hall Slide 23 FIGURE 10.20B Alternative Way
to Represent Activities with Two or More Immediate Successors
(Wrong) 10-23 Copyright 2013 Pearson Education, Inc. Publishing as
Prentice Hall Slide 24 FIGURE 10.20C Representing Activities with
Two or More Immediate Successors Using Dummy Activities (Better)
10-24 Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall Slide 25 FIGURE 10.21 Partial Project Delta Network Using AOA
Notation 10-25 Copyright 2013 Pearson Education, Inc. Publishing as
Prentice Hall Slide 26 FIGURE 10.22 Completed Project Delta AOA
Network 10-26 Copyright 2013 Pearson Education, Inc. Publishing as
Prentice Hall Slide 27 FIGURE 10.23 Project Delta Forward Pass
Using AOA Network 10-27 Copyright 2013 Pearson Education, Inc.
Publishing as Prentice Hall Slide 28 FIGURE 10.24 Project Delta
Backward Pass Using AOA Network 10-28 Copyright 2013 Pearson
Education, Inc. Publishing as Prentice Hall Slide 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 Slide 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. 10-30 Slide 31
10-31 Copyright 2013 Pearson Education, Inc. Publishing as Prentice
Hall
