Seismic performance and risk mitigation of CFS shear walls with CFRP-reinforced screw connections and special-shape L-section end studs

Abstract

Cracking damage of screw connections and buckling of end studs always resulted in performance degradation of cold-formed steel (CFS) shear walls. To improve the seismic performance and to avoid the brittle failure of CFS shear walls, two methods for strengthening CFS walls are proposed in this paper: carbon fiber reinforced plastic (CFRP) toughened screw connections (CFRP-SC) and special-shape built-up end studs with L-shaped sections (SBC-L). A total of 5 full-scale strengthened CFS walls with CFRP-SC or SBC-L were tested to examine the performance, and simplified numerical models of strengthened CFS walls and 5-story CFS buildings were developed and validated. Nonlinear dynamic analyses are performed to investigate the effects of those two methods on seismic responses and risks of CFS buildings, and the risk mitigation of CFS buildings is then discussed. The results show that the CFS shear walls with CFRP-SC can mitigate the damage to screw connections and wallboards nearby those connections, especially for the connections at the corners of the walls. The connections could continually dissipate the earthquake energy due to large loading and deformation capacities. The SBC-L can effectively delay the buckling failure of end studs, thus enhancing the shear resistance of CFS walls. Due to the two methods, the collapse probability of the CFS building with CFRP-SC in service life is reduced by almost 40.8%, and that of the building with CFRP-SC and SBC-L is reduced by almost 59.7%.