Precast production scheduling in off-site construction: Mainstream contents and optimization perspective

Precast production scheduling (PPS) is a key factor that enables efficient off-site construction (OSC) and has received considerable attention from researchers. However, there is still a lack of systematic analysis and summary of existing PPS-related studies in the OSC domain to identify current research gaps and predict future research directions. Thus, 75 relevant academic publications were selected for this systematic review. The current research status of PPS was analyzed from four aspects (flow shop scheduling, production rescheduling, internal resource constraints, and external supply chain constraints) to explore the mainstream contents and optimization perspectives of PPS research. The research findings showed that (1) research on flow shop scheduling of precast components (PCs) was dominant in the PPS domain, and the genetic algorithm (GA) was the most applied optimization algorithm; (2) worker allocation strategy, mold grouping, and layout planning of production space were the main starting points for optimizing PPS from a resource perspective; and (3) establishing a collaborative scheduling mechanism by integrating various departments of the OSC supply chain to achieve the just-in-time (JIT) delivery strategy was the main idea for optimizing PPS from the supply chain perspective. This study revealed potential future research focuses in the field of PPS, including PC flow shop scheduling based on carbon emission targets, distributed permutation flow shop scheduling of PCs, layout optimization for intelligent production shops, and production scheduling mechanisms based on digital technology. This study provides theoretical guidance to promote the future development of PPS research in the field of OSC and can help precast production practitioners manage production scientifically and efficiently.