Keywords: cold-formed steel columns, lipped channel columns, local-distortional interaction, shell finite element analysis, column ultimate strength, local-to-distortional critical stress ratio, yield-to-critical stress ratio, direct strength method design.

The paper reports the results of a numerical (ABAQUS shell finite element analysis) investigation on the relevance of local-distortional interaction on the ultimate strength of cold-formed steel fixed-ended lipped channel columns. These results concern 416 columns with various geometries (cross-section dimensions and length) and yield stresses, selected to ensure a wide variety of combinations of ratios involving (i) distortional and local critical buckling stresses, and (ii) yield and critical buckling stresses. The aim of the work is to identify the combinations of these ratios that lead to relevant local-distortional interaction effects, in the sense of causing a sizeable erosion of the lipped channel column ultimate strength, as well altering their failure mechanisms. This is achieved by comparing the numerical ultimate strength data with their predictions provided by the available expressions prescribed by the direct strength method (DSM) design approach for local, distortional and local-distortional interactive failures: special attention is devoted to the DSM approaches recently developed to account explicitly for local-distortional interaction. The paper closes with some considerations on how the findings of this work may impact on the DSM design of lipped channel columns undergoing different levels of local-distortional interaction.

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