Just-in-Time Precast Production Scheduling Using Dominance Rule-Based Genetic Algorithm.

The objective of this study is to provide a model and method to assist fabricators in making appropriate precast production plans, coordinating factories prefabrication and on-site assembly in construction based on the just-in-time (JIT) philosophy. We propose a JIT precast production scheduling model for the precast production of steel box girders in the Hong Kong-Zhuhai-Macau (HZM) bridge construction project. In order to minimize the total early/tardy costs for this JIT scheduling model, we first present a job batching algorithm (JBA) to group series of jobs into several batches. Then, we model the batch cost function as a piecewise linear convex function and derive its optimal solution, which guides us to propose an optimal shifting algorithm (OSA) to locate the optimal starting time of each batch and minimize the batch cost. In order to get the best job sequence for minimizing the total early/tardy costs and improve search efficiency, we introduce a dominance rule for early/tardy scheduling problem and propose a dominance rule-based genetic algorithm (DBGA) embedded with an optimal timing algorithm, which can find the best job sequence as well as the corresponding optimal schedule. The real-world case study of HZM bridge project demonstrates that our proposed model and algorithm can assist construction practitioners to make better decision on precast production scheduling compared to empirical rule in current engineering practice. In addition, numerical studies prove that our proposed algorithm has a better performance on both effectiveness and efficiency due to the dominance rule.