New Proposal for the Shear Strength of Unstiffened Cold-formed Steel Beam Webs

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Shear strength of cold-formed steel beam webs is significantly dependent on the end boundary conditions of the shear panels. The North American Specification for the design of cold-formed steel structural members AISI S100-16 Section G2.1 reflects this dependence by recognizing a lower shear capacity for unstiffened shear panels, as low as the elastic shear buckling strength for slender beam webs. This paper presents a series of shear tests on cold-formed steel C-shaped sections with various bolting configurations at the span ends aiming to simulate different degrees of restraint, somewhat close to industry practice. The tests saw a considerable post-buckling shear strength which has not been appreciated by the current Specification. Supported by additional experimental shear strength data from the literature, a new design shear curve is proposed to allow for a higher shear strength of unstiffened panels than the elastic buckling values. Reliability analyses carried out based upon the available test results produce a resistance factor of 0.9 which is consistent with that for bending.