Keywords: workgroup-based repetitive scheduling, genetic algorithm, optimization.

The idea of repetitive scheduling originated in the manufacturing industry, in connection with the use of mass production line units. These production line units are identical. Most of the construction repetitive scheduling methods developed so far also maintain the premise that a repetitive project consists of many identical production units. In practice, however, the production units in many repetitive construction projects may not be identical. For instance, the excavation depth and the soil conditions encountered when placing each pile will not be exactly the same in a piling project; the number of manholes and the number of pipe sections will not normally be the same in a pipeline-laying project, which makes the identification of repetitive production units difficult; the interior design of each house may be different in a multi-housing project, and therefore the required workload, as well as the time duration and cost, will differ. Furthermore, even a typical repetitive construction project with many identical production units is very likely to contain portions of work of a non-repetitive nature.

Huang and Sun [1] developed a workgroup-based repetitive scheduling method in 2004. This approach takes the view that a repetitive construction project consists of repeating activities of workgroups. Instead of repetitive production units, workgroups with repetitive or similar activities are identified in a repetitive project and are employed in planning and scheduling. Each workgroup contains activities with the same functional purpose, but possibly different resource usage, construction conditions, time, costs, and so on. In addition, multiple resource crews employing different construction methods, and/or combinations of equipment and labor may perform repetitive activities in the same workgroup, depending on the needs of the project and the market availability of work crews. The workgroup-based method thus adds more flexibility to the planning and scheduling of repetitive construction projects and enhances the effectiveness of repetitive scheduling.

This work builds on previous research and develops a GA-based optimization model for workgroup-based repetitive scheduling. Our objective is to maximize total project income while conforming to the proper work sequence between workgroups in a repetitive project and maintaining the work continuity of resources. The development of the GA-based optimization model (WoRSM) supplements the workgroup-based scheduling method by providing a capability of finding near-optimal solutions for repetitive project scheduling. A sample case study verifies and validates the WoRSM system. With WoRSM, a repetitive project can be scheduled in such a way that its maximum or near-maximum project net present value obtained. It also facilitates application of the workgroup-based repetitive scheduling method

1

Huang, Rong-yau, and Sun, Kuo-Shun (2004), "Non-UNIT Based Planning and Scheduling of Repetitive Construction Projects.", Proceedings of The 12th Annual Conference for International Group of Lean Construction, IGLC, Denmark, 343-356.

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