Capacity and Behavior of Sheathed Cold-Formed Steel Stud Walls under Outward Flexural Loading

This paper reports on an experimental investigation of the out-of-plane bending behavior and capacity of cold-formed steel (CFS) stud walls sheathed with wood-based boards [oriented strand board (OSB) or plywood] by means of four-point bending tests on a series of 10 specimens. The tests simulated outward wind loading (suction), which subjects the free flange of the studs to compression. The key design parameters were systematically varied in the test program, including the material type and thickness of the boards, the thickness of the studs and tracks, the stud spacing, and the presence or absence of longitudinal seams, noggins and track sections. Material coupon tests and subassembly tests on the stud-to-board connections were also conducted. The observed failure mode typically consisted of lateral buckling of the compressed stud flange, partially restrained by the rotational stiffness of the screwed connections with the boards and accompanied by significant cross-sectional distortion, with superimposed local buckling. A comparative analysis of the flexural responses of stud walls under inward and outward loading was also carried out, using additional data from a previously conducted experimental campaign.