Exact time-cost tradeoff analysis in concurrency-based scheduling

A construction project can be accelerated by overlapping critical activities. This paper presents a computational method called exact time-cost tradeoff (ETCT) in concurrency-based scheduling that identifies exact global overlaps between critical activities. It calculates the rework cost slope and amount by integrating the activities' concurrency attributes, identifies the exact global solution, and computes the probability to complete a project within the project completion time (PCT) and/or the project completion cost (PCC). The study is of value to project schedulers because ETCT identifies the exact global solution (i.e., the set of activities to be overlapped and the exact overlap rates between these activities) expeditiously, and establishes a compressed schedule that satisfies a project's budget and duration constraints. This is also relevant to researchers in that it clearly defines the computational formula to compute the exact solution in detail and facilitates a comparison of the outcome of a schedule under different project objectives, such as minimizing project completion duration and/or project completion cost. The usability and validity of the computational methods was confirmed by performing two test cases.