A Multitower Crane Layout Planning Framework for Modular Integrated Construction Considering Material Relay Handling

Transfer zones play a vital role in multitower crane construction sites as they alleviate on-site logistics bottlenecks by facilitating material relay handling. However, lifting operations within these zones are prone to crane collisions, significantly impacting construction efficiency and safety. In modular integrated construction (MiC), large-sized trucks and heavyweight modules further exacerbate such operational challenges. Current studies on multitower crane layout planning (MTCLP) predominantly rely on manual selection of facility locations and focus on independent lifting operations of single cranes, overlooking multicrane relay handling practices. Therefore, this study proposes a MTCLP framework for MiC, with a focus on material relay handling. It comprises three components: (1) a location evaluation algorithm to automatically generate feasible locations for tower cranes, trucks, and transfer zones; (2) a multiobjective optimization engine with eight submodels to autonomously balance lifting efficiency and safety risk; (3) an automated decision-making module integrating the fuzzy-analytic hierarchy process method, improved nondominant sorting genetic algorithm II, and entropy weight-technique for order preference by similarity to an ideal solution method to adaptively evolve Pareto optimal solution sets of layout plans and identify the optimal solution. The framework’s applicability is validated using a real MiC project in Hong Kong. Compared with the original layout plan, the optimal solution achieves a 7.75% improvement in lifting efficiency and a 9.57% reduction in safety risk. This study pioneers the investigation of transfer zones’ characteristics and impacts in MTCLP, and provides intelligent decision support for decision-makers to formulate layout plans more efficiently and objectively.