Precedence Networks

Over the past ten years there has been an explosion in project management software packages. Small packages may sell for a few thousand dollars, whereas the price for larger packages may be $70,000. Computerized project management can provide answers to such questions as:

• How will the project be affected by limited resources?

• How will the project be affected by a change in the requirements?

• What is the cash flow for the project (and for each WBS element)?

• What is the impact of overtime?

• What additional resources are needed to meet the constraints of the project?

• How will a change in the priority of a certain WBS element affect the total project?

11 See Gary E. Whitehouse, "Project Management Techniques," Industrial Engineering, March 1973, pp. 2429, for a description of the technique.

12 Ellery B. Block, "Accomplishment/Cost: Better Project Control," Harvard Business Review, May-June 1971, pp. 110-124. Copyright © 1971 by the President and Fellows of Harvard College; all rights reserved.

The more sophisticated packages can provide answers to schedule and cost based on:

• Adverse weather conditions

• Weekend activities

• Unleveled manpower requirements

• Variable crew size

• Splitting of activities

• Assignment of unused resources

Regardless of the sophistication of computer systems, printers and plotters prefer to draw straight lines rather than circles. Most software systems today use precedence networks, as shown in Figure 12-22, which attempt to show interrelationships on bar charts. In Figure 12-22, task 1 and task 2 are related because of the solid line between them. Task 3 and task 4 can begin when task 2 is half finished. (This cannot be shown easily on PERT without splitting activities.) The dotted lines indicate slack. The critical path can be identified either by putting an asterisk (*) beside the critical elements, by making the critical connections in a different-colored ink, or by making the critical path a boldface type.

The more sophisticated software packages display precedence networks in the format shown in Figure 12-23. In each of these figures, work is accomplished during the activity. This is sometimes referred to as the activity-on-node method. The arrow represents the relationship or constraint between activities.

MONTHS AFTER GO AHEAD TASKS 1 2 3 4 S

MONTHS AFTER GO AHEAD TASKS 1 2 3 4 S

WfflffflA

Figure 12-22. Precedence network.

WfflffflA

Figure 12-22. Precedence network.

Figure 12-23. Typical precedence relationships.

tARLV START 6/1 «4

TIME OUHATÍON 2 WEEKS

EARLY FINISH

TASK 4

S70000

LATE START 6/15/34

RESPONSIBILITY COST CENTER

2010

LATE FINISH S»fl/S4

Figure 12-24. Computerized information flow.

GENERAL;

ACTIVITYONARROW

ACTIVlTY'ON -NODE

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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Responses

  • linda
    What is a precedence network industrial engineering?
    3 months ago

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