Optimization model for construction project durations using a multistage decision process

The optimization of project duration is often performed during the planning stage of a construction project. Though there are four types of activity time–cost functions used in the optimization of project duration, most of the methods used in the optimization of project duration are only appropriate for a particular type of activity time–cost function. In order to overcome this limitation, this paper constructs an analytical model for optimizing project duration which is applicable to various types of activity time–cost functions. Based on the concept of a multistage decision process, the objective function and the expressions of both serial recurrence and parallel recurrence are established. In addition, the computation algorithms for both recurrence expressions which can reduce the computer memory space used and unnecessary computation are also developed. Finally, every optimal combination of project duration and its corresponding minimum project cost can be computed efficiently. The optimal allocation of activity time and its corresponding cost from each recurrence stage for the specific project duration can also be obtained.