1

Chapter 6Developing a Project

Plan

2

Developing the Project PlanThe Project Network

A flow chart that graphically depicts the sequence, interdependencies, and start and finish times of the project job plan of activities that is the critical paththrough the network

Provides the basis for scheduling labor and equipmentProvides an estimate of the project’s durationProvides a basis for budgeting cash flowHighlights activities that are “critical” and should not be delayedHelp managers get and stay on plan

2

3

From Work Package to Network

4

From Work Package to Network (cont’d)

3

5

Constructing a Project NetworkTerminology

Activity: an element of theproject that requires time.

Merge activity: an activity that has two or more preceding activities on which it depends.

Parallel (concurrent) activities: Activities that can occur independently and, if desired, not at the same time.

A

C

B D

6

Constructing a Project Network (cont’d)

TerminologyPath: a sequence of connected, dependent activities.

Critical path: the longest path through the activity network that allows for the completion of all project-related activities;the shortest expected time in which the entire project can be completed. Delays on the critical path will delay completion of the entire project.

D

C

A B

(Assumes that minimum of A + B > minimum of C in length of times to complete activities.)

4

7

TerminologyEvent: a point in time when an activity is started or completed. It does not consume time.Burst activity: an activity that has more than one activity immediately following it (more than one dependency arrow flowing from it).

Two ApproachesActivity-on-Node (AON)

Uses a node to depict an activityActivity-on-Arrow (AOA)

Uses an arrow to depict an activity

B

D

A C

Constructing a Project Network (cont’d)

8

Basic Rules to Follow in Developing Project Networks

Networks typically flow from left to right.An activity cannot begin until all of its activities are complete.Arrows indicate precedence and flow and can cross over each other.Identify each activity with a unique number; this number must be greater than its predecessors.Looping is not allowed.Conditional statements are not allowed.Use common start and stop nodes.

5

9

Activity-on-Node Fundamentals

10

Activity-on-Node Fundamentals (cont’d)

6

11

Network Information

12

Koll Business Center—Partial Network

7

13

Koll Business Center—Complete Network

14

Network Computation ProcessForward Pass—Earliest Times

How soon can the activity start? (early start—ES)How soon can the activity finish? (early finish—EF)How soon can the project finish? (expected time—ET)

Backward Pass—Latest Times

How late can the activity start? (late start—LS)How late can the activity finish? (late finish—LF)Which activities represent the critical path?How long can it be delayed? (slack or float—SL)

8

15

Network Information

16

Activity-on-Node Network

9

17

Activity-on-Node Network Forward Pass

18

Forward Pass ComputationAdd activity times along each path in the network (ES + Duration = EF).

Carry the early finish (EF) to the next activity where it becomes its early start (ES) unless…

The next succeeding activity is a merge activity, in which case the largest EF of all preceding activities is selected.

10

19

Activity-on-Node Network Backward Pass

20

Backward Pass ComputationSubtract activity times along each path in the network (LF - Duration = LS).

Carry the late start (LS) to the next activity where it becomes its late finish (LF) unless...

The next succeeding activity is a burst activity, in which case the smallest LF of all preceding activities is selected.

11

21

Determining Slack (or Float)Free Slack (or Float)

The amount of time an activity can be delayed without delaying connected successor activities

Total SlackThe amount of time an activity can be delayed without delaying the entire project

The critical path is the network path(s) that has (have) the least slack in common.

22

Sensitivity of a Network

The likelihood the original critical path(s) will change once the project is initiated.

Function of:The number of critical pathsThe amount of slack across near critical activities

12

23

Activity-on-Node Network with Slack

24

Practical Considerations

Network logic errorsActivity numberingUse of computers to develop networksCalendar datesMultiple starts and multiple projects

13

25

Illogical Loop

FIGURE 6.9

26

Air Control Project

14

27

Air Control Project (cont’d)

28

Extended Network Techniques to Come Close to Reality

LadderingActivities are broken into segments so the following activity can begin sooner and not delay the work.

LagsThe minimum amount of time a dependent activity must be delayed to begin or end

Lengthy activities are broken down to reduce the delay in the start of successor activities.Lags can be used to constrain finish-to-start, start-to-start, finish-to-finish, start-to-finish, or combination relationships.

15

29

Example of Laddering Using Finish-to-Start Relationship

30

Use of Lags

FIGURE 6.13

Finish-to-Start Relationship

Start-to-Start Relationship

16

31

Use of Lags (cont’d)Use of Lags to Reduce Detail

32

New Product Development Process

17

33

Use of Lags (cont’d)

Finish-to-Finish Relationship

Start-to-Finish Relationship

34

Network Using Lags

18

35

Hammock ActivitiesHammock Activity

An activity that spans over a segment of a project

Duration of hammock activities is determined after the network plan is drawn.

Hammock activities are used to aggregate sections of the project to facilitate getting the right amount of detail for specific sections of a project.

36

Hammock Activity Example

19

37

Key Terms (1)Activity: Task(s) of the project that consumes time whilepeople/equipment either work or wait. Activity-on-arrow (AOA): method for drawing projectnetworks. The activity is shown as an arrow.Activity-on-node(AON): method for drawing projectnetworks. The activity is on the node (rectangle).Burst activity: An activity that has more than one activityimmediately following it.Concurrent engineering: Cross-functional teamwork in new-product development projects that provides product design, quality engineering, and manufacturing process engineering all at the same time.

38

Key Terms (2)Critical path: The longest activity path(s) through the network. The critical path can be distinguished by identifyingthe collection of activities that all have the same minimum slack. Gantt chart: A graphic presentation of project activitiesdepicted as a time-scaled bar line (also called a Gantt chart).Hammock activity: A special-purpose, aggregate activity that identifies the use of fixed resources or costs over a segment ofthe project—e.g., a consultant. Derives its duration from the time span between other activities.Lag relationship: The relationship between the start and/or finish of a project activity and the start and/or finish of anotheractivity. The most common lag relationships are (1) finish-to-start, (2) finish-to-finish, (3) start-to-start, and (4) start-to-finish.

20

39

Key Terms (3)

Merge activity: An activity that has more than one activityimmediately preceding it.Network sensitivity: The likelihood that the critical path willchange on a project.Parallel activity: One or more activities that can be carried on concurrently or simultaneously.Slack - total and free: Time an activity can be delayed beforeit becomes critical.