Post-Buckling Behavior of Thin-Walled Regular Polygonal Tubular Columns Undergoing Local-Distortional Interaction

This work presents and discusses numerical results of an ongoing investigation concerning the elastic post-buckling behavior and imperfection sensitivity of regular convex polygonal cross-section (RCPS) tubular columns affected by local-distortional (L-D) interaction. This investigation is conducted by means of geometrically non-linear Generalized Beam Theory (GBT) analyses, extending the knowledge on the "pure" local and distortional post-buckling behaviors of RCPS tubes recently reported by the authors (Martins et al. 2018a). Due to their inherent modal nature, the GBT analyses make it possible to acquire in-depth knowledge on the structural behavior of RCPS tubes and also to include, in a straightforward fashion, arbitrary member initial geometrical imperfections. Columns with distortional-to-local critical buckling load ratios (i) close to 1 ("true L-D interaction" -- the most trivial L-D interaction type) and (ii) significantly above 1 ("secondary-distortional bifurcation L-D interaction" -- the most relevant L-D interaction type) are investigated. Local/distortional critical-mode initial geometrical imperfections and (linear) combinations of both are considered in the former columns, while only local initial imperfections are dealt with in the latter ones -- several amplitudes are dealt with to assess the imperfection sensitivity. For comparison and validation purposes, ABAQUS shell finite element analysis results are also reported.

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