Axial-flexural mechanism and design method of grouted connection for high-rise modular steel structures: Numerical and theoretical analysis

During long-term service, modular structures are subjected to various loads, and their key components, inter-module connections, experience complex multiaxial stress states. This paper investigates the performance of inter-module grouted connections under combined axial force and bending moment. Building upon previous experimental studies, the compressive-bending failure modes and force transfer mechanisms of the connection are revealed through numerical simulation and theoretical analysis, and corresponding calculation methods are proposed. The numerical model is first validated, followed by a comprehensive parametric study. The results show that increasing the axial compression ratio, grout height, and inner sleeve thickness can all significantly enhance the flexural resistance of the connection, among which the axial compression ratio has the most significant influence on flexural performance. When the axial compression ratio increases from 0 to 0.8, the flexural bearing capacity of the connection increases by 49.7%. The observed failure modes include failure of the grouted connection, simultaneous failure of both the grouted connection and the connected column, and failure of the connected column. In addition, the stiffness characteristics of the grouted connection are analyzed, and the required stiffness for equivalent-stiffness design is theoretically derived. Furthermore, a predictive equation for the compressive-bending resistance of the connection is proposed, and a conservative envelope curve for the compressive-bending resistance is provided. Finally, the recommended dimensions and design guidelines for module columns to achieve equivalent-strength connections using grouted connections are presented.