Seismic performance of connection nodes of concrete-frame modular integrated construction

Concrete-framed modular integrated construction (CF-MIC) offers advantages in construction speed and sustainability; however, its unique double-column-double-beam configuration at horizontal inter-module connections presents a significant challenge under seismic loads. The performance and force-transmission mechanisms of these connection points are critical to structural integrity but have not yet been systematically investigated. This paper proposes a novel connection method for CF-MIC in the horizontal direction. We designed two full-scale node specimens and conducted a systematic investigation into damage modes, stiffness, ductility, and energy dissipation across structural configurations, elucidating lateral force-resisting mechanisms.The experimental results indicate that the proposed composite connection increases the load-bearing capacity by 19.62% compared with the connection using only a rotational steel plate. In addition, crack initiation is effectively delayed. Furthermore, we developed a refined finite element model to analyze force transmission mechanisms and quantify the contribution of connections to overall seismic performance. The finite element analysis revealed that the proposed connection enhances the inter-modular shearing force capacity by 41.9%, accounting for a substantial portion of the overall lateral load resistance in the CF-MIC system. We established a simplified mechanical model to examine the shearing force transmission mechanism between module units. Through a simplified mechanical model, we examined shearing force transfer between modules. These results demonstrate that the proposed connection enhances module protection, delays plastic hinge formation in beams, and improves the overall seismic performance of CF-MIC systems.