Simplified modeling of inter-module connections with combined load interactions in modular steel construction

This study investigates the mechanical behavior and simplified model for a novel self-locking and rapid-unlocking (SelRU) inter-module connection for modular steel construction (MSC) under various combined loading conditions. A detailed finite element model (FEM) of the SelRU connection was developed and validated against previous experimental results. The validated numerical model was used to investigate the connection response under five combined loading conditions: compression-shear, tension-shear, compression-bending, tension-bending, and bending-shear. Based on the identified load-transfer mechanisms and expanded numerical database, analytical models covering the elastic and plastic stages and corresponding capacity interaction curves were developed for these loading conditions. By assembling the interaction curves, unified capacity interaction surfaces of the SelRU connection under combined compression-bending-shear and tension-bending-shear actions were established. Accordingly, unified nonlinear power-law surfaces were formulated and incorporated into a simplified FEM of a three-storey prototype MSC. Comparisons with the detailed FEM and the simplified model with decoupled connection behavior show that the proposed model incorporating combined connection behavior accurately captures the global structural capacity and plasticity evolution of the MSC, while reducing the computational time from 23.3 h to 242 s. The proposed framework provides an efficient and reliable numerical modeling methodology for inter-module connections in MSCs.