Formalizing Construction Sequencing Constraints for Rapid Generation of Schedule Alternatives

Construction planners today use CPM-based schedules to represent the planned logical sequence of activities to perform a project. A construction schedule typically represents the sequence of multiple trades that perform individual work while sharing common workspaces or resources. The logic or "rationale" behind activity sequences of these schedules can include physical relationships between components (e.g., supported by), trade interactions (e.g., workspace competition) or safety and code regulations (e.g., testing). Due to changing project demands, planners frequently need to modify activity sequences during the course of a project. More than one alternative can exist, and hence planners need to develop and evaluate alternative sequences correctly and rapidly to make well-informed decisions.

When developing sequencing alternatives, planners need to understand the physical or technical "role" an activity plays on following activities. They also need to distinguish between activities that may or may not be delayed. Planners infer the role and "status" (i.e., whether an activity may be delayed) of activities based on the initial rationale and flexibility of the constraints between activities. However, the current CPM framework only distinguishes the temporal aspects of constraints (e.g., FS precedence relationship) and only distinguishes the time-criticality of activities. Consequently, determining the role and status of activities can only be performed in the planner's minds. Hence, identifying and developing sequencing alternatives using CPM-based schedules is today an error-prone and time-consuming process.