Experimental investigation of the behaviour and capacity of sheathed cold-formed steel stud walls under inward flexural loading

A comprehensive experimental programme was designed and executed with the aim of investigating the out-of-plane bending behaviour and capacity of cold-formed steel (CFS) stud walls sheathed with wood-based boards. The influence of key design variables, including the screw spacing, the board material and thickness, the stud and track thicknesses, the board configuration (single-sheathed, double-sheathed and unsheathed) and the presence/absence of longitudinal seams, noggins and track sections, was investigated and quantified. A total of 15 stud walls sheathed with either Oriented Strand Board (OSB) or plywood were tested under four-point bending. Ancillary material tests, and push-out and pull-out connector tests were also performed. The results revealed a surprising richness in failure modes, given the initial geometric simplicity of the system. Simultaneous crushing of the OSB and distortional buckling failure of the studs, with either full or partial shear interaction, was a commonly observed failure mode. However, rotational and lateral–distortional deformations of the studs, often accompanied by longitudinal cracking of the boards, were also observed as a cause of failure.