Design Strength of Locally Buckling Stub-Lipped Channel Columns

The compressive strength of cold-formed steel (CFS) lipped channel (LC) members may be governed by yielding, local, distortional, or overall buckling, and any possible interaction among these modes. The direct strength method (DSM) has been advanced recently for evaluating the strength of CFS LC beams and columns. Although the DSM is an improvement over other methods in terms of simplicity and accuracy, further improvement by minor modification to the DSM is possible if all the parameters that affect the strength of such members is properly accounted for and understood. In this study, the DSM equations for evaluating the strength of members that fail after experiencing only local buckling are discussed. The strength of such members, according to the DSM, is a function of only the ratio of yield strength of the section ($P_y$) to the elastic local buckling load ($P_{\mathrm{cr\ell }}$) (also equal to the reciprocal of square of the nondimensional local buckling slenderness ratio, $1/{\lambda }_{\ell }^2$). This study indicates that the relative area of the stocky elements of the cross section, which are less vulnerable to elastic local buckling, also influences the strength of such members. Using the experimental results available in the literature and the finite-element analysis data generated in this study, the behavior and strength of stub LC compression members experiencing only local buckling before failure by yielding are evaluated. Simple modifications to the currently available DSM equations are suggested to more accurately evaluate the strength of such members.