Analysis and design of cold-formed steel channels subjected to combined bending and web crippling

The channel failures due to combined bending and web crippling may occur at the highly concentrated interior loading when there is no load stiffener in cold-formed thin-walled steel beams. This paper presents accurate finite element models to predict the behavior and ultimate strengths of cold-formed steel channels subjected to pure bending as well as combined bending and web crippling. Both geometric and material nonlinearities are considered in the finite element analysis. The nonlinear finite element models are verified against experimental results of cold-formed steel channels subjected to pure bending as well as combined bending and web crippling. The finite element analytical results show a good agreement with the experimental results in terms of the ultimate loads and moments, failure modes and web load-deformation curves thus validating the accuracy of the finite element models. The verified finite element models are then used for an extensive parametric study of different channel dimensions. The channel strengths predicted from the parametric study are compared with the design strengths calculated from the North American Specification for cold-formed steel structures. It is shown that the design rules in the North American Specification are generally conservative for channel sections with unstiffened flanges having the web slenderness ranged from 7.8 to 108.5 subjected to combined bending and web crippling. It is demonstrated that the nonlinear finite element analysis by using the verified finite element models against test results is an effective way to predict the ultimate strengths of cold-formed thin-walled steel members.