Post-Buckling; Strength and Design of Cold-Formed Steel-Lipped Channel; Hat-Section and Zed-Section Columns Affected by Local-Distortional Interaction

This work reports the latest results of an ongoing investigation on the post-buckling behavior, strength and design of cold-formed steel columns affected by local-distortional interaction, aimed at extending findings recently obtained for lipped channels to other cross-section shapes. Initially, the paper compares the elastic and elastic-plastic post-buckling and strength behaviors of hat-section, zed-section and lipped channel fixed-ended columns sharing cross-section dimensions (web, flange and lip widths) and lengths that lead to virtually identical local and distortional buckling loads, i.e., to a high susceptibility to localdistortional mode interaction − note that the three columns exhibit the same local and distortional buckling behaviors. Then, the paper presents and discusses the results of an extensive parametric study, carried out by means of ABAQUS shell finite element analyses, aimed at determining the “exact” ultimate loads of 210 pairs of initially imperfect hat-section and zed-section columns with various geometries, all of them associated with strong local-distortional interaction − the cross-section dimensions and lengths of these column pairs are those exhibited by fixed-ended lipped channel columns that were analyzed in previous investigations. Finally, the ultimate strength data gathered are used to assess the performance of a recent design approach, based on the Direct Strength Method (DSM) and developed/validated in the context of cold-formed steel fixed-ended lipped channel columns undergoing local-distortional interaction, in order to assess whether it can be successfully applied to hat and zed-section columns under the same conditions.

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