Evaluation of Axial Strength of Sheathed Cold-Formed Steel Wall Panels Using Rayleigh-Ritz Method and Direct-Strength Method: Comparative Study

Abstract

Sheathed cold-formed steel (CFS) wall panels comprise studs, tracks, and sheathings on one side or both sides. It has been observed in the literature that sheathing contributes significantly to the axial load carrying capacity of CFS wall panels. Limited studies are available on comparing the efficacies of available design methodologies to evaluate the axial strength of CFS wall panels with sheathing. The present study investigates the efficacy of analytical/semianalytical methods, namely, the Rayleigh–Ritz (R–R) method and direct strength method (DSM), for evaluating the axial load carrying capacity of sheathed CFS panels. In DSM, three elastic buckling loads are evaluated, namely, local, distortional, and global, using an open-source finite strip method based software CUFSM version 4.05. The bracing provided by sheathing to the section is presumed as springs. For the first time, a problem is undertaken to verify the efficacy of both the mathematical models together to evaluate the axial load carrying capacity of sheathed CFS wall panels. The evaluated results by both the models are compared with experimental strengths of sheathed CFS wall studs from the experimental database including the tests conducted by the authors. Results demonstrate that DSM may be used effectively for predicting axial strength of sheathed CFS wall panels, as a substantially lower coefficient of variation (CoV) is obtained for DSM, which is 0.1274, than the R–R method (CoV=0.1897). DSM is suggested over the R–R method for evaluating the axial load carrying capacity of sheathed CFS wall studs as it better takes into account the local buckling and inelastic effects.