Constraint programming approach to optimizing project schedules under material logistics and crew availability constraints

With increasing implementation of off-site prefabrication and modular construction technologies, the complexity of material supply chain management on construction projects has grown substantially. However, research on construction scheduling has yet to take dynamic material logistics as an explicit constraint in analytically deriving construction schedules and addressing impacts of uncertainties in material supply on project budget. This study proposes a two-step analytical approach to tackle the identified problem. First, a constraint programming-based scheduling optimization model is developed to derive project schedules subject to variable material delivery times and finite crew resource availability. The second step is to take advantage of the valid optimization model for evaluating the impact of different input settings of material logistics on project budget. An example project adapted from the literature is used to illustrate the effectiveness of the proposed optimization model in coping with variable material delivery times. Based on the same case, the delivery date of a particular material is singled out as the risk factor of interest in order to derive the complex relationship between material delivery date and total project cost. In addition, a case study based on a bridge girder fabrication project is presented to demonstrate the applicability of the proposed optimization model on projects of practical size. In conclusion, this study adds to the body of knowledge by developing an analytical methodology that factors material supply constraints into the resource-constrained scheduling optimization model so as to analyze the impact of uncertainties in material deliveries on project budget.