Formalizing Construction Sequencing Constraints for Rapid Generation of Schedule Alternatives

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Abstract: Construction planners typically rely on CPM (Critical Path Method) based schedules to schedule and coordinate the work of the multiple disciplines on a project. During the course of a project, planners frequently need to modify activity sequences to meet changing demands. In particular, planners need to coordinate multiple trades often working in limited workspaces to ensure that intermediate milestones are met and that components are installed in a timely manner to maximize the workflow of follow-on work. To determine an appropriate sequence of activities for trades to work, planners need to develop and evaluate different sequencing alternatives. When developing sequencing alternatives, planners need to determine the physical or technical impact or "role" an activity has on following activities. They also need to determine which activities may or may not be delayed. Distinguishing the role and "status" (i.e., whether an activity may be delayed) of activities in turn requires planners to understand the rationale and flexibility of constraints between activities. However, the current CPM framework only represents the temporal aspect of constraints using precedence relationships (e.g., FS, SS etc.). In addition, existing schedule acceleration techniques such as time-cost trade-off assume that activity sequences are fixed and hence are not applicable for developing sequencing alternatives. Consequently, identifying and developing sequencing alternatives using CPM-based schedules is currently an error-prone and time-consuming process. The anticipated contributions of this research focus on formalizing the rationale and flexibility of constraints in CPM schedules and on leveraging such a formalized representation to determine the role and status of activities. This work should enable construction planners to identify and develop sequencing alternatives correctly and rapidly, which in turn should help reduce the time and cost to complete constructed facility.