Author(s): Amelia R Thompson, Nathan J Walker and Sophia L Martinez

Abstract: This study presents a detailed numerical and analytical investigation into the buckling and post-buckling behaviour of cold-formed steel (CFS) columns subjected to axial compression, emphasizing the influence of geometric imperfections, end-restraint conditions, and mode interactions on structural stability. Using nonlinear finite element analysis incorporating geometric and material nonlinearity, lipped channel columns of varying slenderness ratios (? = 40-120) and thicknesses (1.2-2.0 mm) were analyzed to evaluate their critical and ultimate load capacities. The results indicate that while global buckling governs slender members, local and distortional modes, often coupled in intermediate sections, contribute significantly to post-buckling reserve strength. Columns with fixed-pinned supports demonstrated higher ultimate loads compared to pinned-pinned configurations, reflecting the critical role of boundary conditions in delaying global instability. The study al revealed that the inclusion of realistic imperfection amplitudes, modeled from eigenmode shapes, enhances the prediction accuracy of post-buckling response and residual stiffness. Comparin with the Direct Strength Method (DSM) showed good overall correlation but highlighted systematic underestimation of strength for members exhibiting strong mode interactions. Regression analysis between the finite element (FE) ultimate load and elastic buckling load yielded an R² > 0.95, confirming the fundamental dependence of post-buckling strength on elastic buckling behaviour. The proposed refined approach bridges the gap between traditional DSM design curves and actual nonlinear performance, offering valuable guidance for practical design optimization. The findings underscore the necessity for design standards to integrate post-buckling reserve effects, realistic imperfection modeling, and improved interaction parameters for enhanced accuracy and safety in CFS structures.

Pages: 19-23 | Views: 7 | Downloads: 4

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