Cyclic Tests and Modeling of CFS Structures with CFRP-Toughened Screws and Special Shape Built-Up End Studs

Abstract

Cracking of wallboards near screw connections (SCs) and buckling of end studs are typical failure modes of cold-formed steel (CFS) shear walls, which results in strength degradation of CFS structures. This paper proposes the use of carbon fiber reinforced plastic (CFRP) to toughen wallboards near screw connections (CFRP-SCs) and T-shaped end studs (T-BUCs) to enhance the buckling capacity of CFS structures. Six full-scale shear walls strengthened with CFRP-SCs or T-BUCs were designed and tested under cyclic loads. Then, numerical models of these walls were developed considering the nonlinear behaviors of CFRP-SCs and T-BUCs on the basis of component-level tests, and the numerical results were validated by cyclic tests. Finally, nonlinear dynamic analysis of 5-story CFS structures is performed considering the hysteretic behavior of those shear walls. The results showed that CFRP-SCs alleviated cracking at wallboard corners while improving energy dissipation by 115.1%. Adding T-BUCs to CFRP-toughened walls further reduced the relative slip between the CFS frame and wallboards, accompanied by an 11.8% increase in shear strength. The simulated results for the cyclic tests closely matched the experimental data, with errors not exceeding 18%. The nonlinear dynamic analysis results of these CFS structures indicated that the CFRP-SCs and T-BUCs were effective in strengthening the shear wall system and reducing the seismic response.