Seismic performance and shear capacity of modular steel frames infilled with cold-formed steel walls with openings

Abstract

Door and window openings, which universally exist in the external load bearing walls of module units, significantly impact the seismic performance and shear capacity of cold-formed steel walls (CFSWs). In this study, we conducted cyclic loading tests on three full-scale specimens to investigate the seismic performance of a single frame of modular steel structures infilled with cold-formed steel walls (MSS-CFSWs). The CFSW of two specimens had window and door openings, while that of the remaining specimen did not have any openings. Test results indicated that the failure mode of the specimens had two stages; the self-drilling screw connection of the CFSW failed first, followed by plastic hinges formation at the beam end of the steel frame. We observed 45° inclined cracks on the wallboards on both sides of the CFSW with openings. The window and door openings reduced the initial lateral stiffness by 24.4% and 28.7% and shear capacity by 3.8% and 15.5%, respectively, compared with those of the specimen without openings. Both the CFSW and steel frame contributed to the shear capacity of the MSS-CFSW. Furthermore, the irregular wallboard units were divided into rectangular wallboard units. Based on the modified global analysis method and the failure mode of the plastic hinges formed at the beam end, we developed a calculation method for the shear capacity of the specimen. We verified the accuracy of the proposed method by comparing the theoretical and test values. The results of this study are expected to serve as a reference for engineering design.