Construction scheduling using the constraint satisfaction problem method

Construction projects are subject to numerous constraints of various types, including contractual due dates, resource limitations, and safety, financial, and managerial constraints. Most scheduling methods based on the critical path method (CPM) require that all project constraints be comprehensively defined and arranged into a single logical network for developing a project schedule. In real-life situations, however, there could be more than one option of execution, conditions, and/or precautions that may influence the logic of the project network and its outputs. CPM-based methods have been proven inadequate for scheduling in this kind of situation. This paper views construction scheduling as a constraint satisfaction problem (CSP), which is defined by a set of scheduling variables and a set of constraints. A CSP-based scheduling method has been developed to provide a framework for systematic constraint modeling and effective schedule generation. An illustrative real-life case example is presented to demonstrate the applicability of the proposed method. The results indicate that the present method is effective and efficient due to its expressive constraint representations and its ability to provide alternative schedules for multilogic project networks. This resembles more the nature of construction projects in which various types of constraints both conditional and unconditional are involved and many scheduling options can be derived. Comparing with the traditional CPM-based methods, the proposed method has the potential to transform the way construction schedules are generated and managed.