Scheduling Systems Cost Integration

When developing or evaluating the effectiveness of a planning and scheduling program, the following are generally the major considerations:

1) Size of planning and scheduling program (level of detail)

2) Manual or computer program (CPM method), or combination

3) If a CPM program:

a) What type of network (precedence or arrow diagram) Number of activities

4) Degree of integration of cost control system with scheduling

Figure 3-28. Worked Example Using Trapezoidal/Density Method.

Figure 3-28. Worked Example Using Trapezoidal/Density Method.

For CPM/computer programs, there are two basic approaches. Large or small networks. Each approach has significant advantages and disadvantages.

Figure 3-29 outlines the essentials of the large and small network approach and lists major advantages and disadvantages of each approach.

It is the author's judgment that even for mega size projects, the small networks (3,000/5,000 activities) approach will provide a more efficient and cost effective program. There is the mistaken concept that greater level of detail provides more accuracy and increases quality of schedules, as follows: At a great level of detail (10,000/ 20,000 activities), there can be many options for the critical path logic and durations of short-term activities can vary greatly. Also, activity logical dependency can significantly increase, resulting in a requirement for many restraints or dummies, further complicating the network.

The jobsite working environment is extremely volatile, so that constant adjustment and revision of the networks may be required. The larger the size of the network, the greater is the potential for change. The "small network " approach is, therefore, strongly recommended. On large projects, the small network is mainly used to plan the project. Lower level/short-term schedules and manpower resourcing can be developed manually. Progress is evaluated through work quantity measurement and budget unit assessment. Scope is constantly assessed with quantity takeoffs of construction issue drawings. Expended manhours are collated and a comparison with the budgeted manhours (quantities multiplied by budget work units) results in productivity measurement. The lack of scope verification and productivity assessment is a significant deficiency of a large activity network program.

Finally, greater integration with the cost control program is achieved through the scope/quantity control program. If the quan-can be accurately determined, then the labor cost is a matter of productivity and wage rate. The complete integration of cost and scheduling at a detailed "code of accounts" level is rarely cost effec-

Figure 3-29. Scheduling Systems - Cost Integration moject u*aicn hcheoxe

Figure 3-29. Scheduling Systems - Cost Integration moject u*aicn hcheoxe

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