Seismic performance and shear capacity of modular steel structures infilled with cold-formed steel walls using a novel connection system

A reusable connection system between a cold-formed steel wall (CFSW) and modular steel frame was developed to provide effective seismic resistance while ensuring repairability. Three steel frame specimens were cyclically loaded along the lateral direction to study the influence of the CFSW infill and its connection to the frame on seismic performance, thereby exploring the feasibility of the proposed connection configuration. The results indicated that modular steel structures infilled with cold-formed steel walls (MSS-CFSWs) using the proposed connection exhibited the "strong frame, strong connection, and weak infilled wall" failure mode. The use of a CFSW resulted in increments of 149.8%-307.5% and 53.4%-80.2% in the initial lateral stiffness and shear ca-pacity, respectively. Connecting the CFSW to both the frame beams and columns resulted in superior mechanical performance and energy dissipation capacity. No separation between the CFSW and frame was observed, proving that the proposed connection configuration is safe and reliable. Furthermore, the connector plates and angles in the connection exhibited no evident deformation or damage, allowing the replacement of damaged CFSW components and the reuse of frames. The shear capacity of the MSS-CFSW was calculated by considering plastic hinge formation at the beam end as the critical state and using a modified global analysis method to determine the shear capacity of the CFSW. The resulting equation was verified using the test data and was found to be safely conservative. The results of this study can therefore serve as a reference for the design of MSS-CFSWs.