On the post-buckling behaviour and imperfection sensitivity of regular convex polygonal columns

This paper presents and discusses numerical results concerning the elastic post-buckling behaviour and imperfection sensitivity of Regular Convex Polygonal cross-Section (RCPS) tubes under uniform compression (columns) and affected by interaction between local and distortional buckling. As the authors showed previously, these tubes are characterised by duplicate bifurcation modes (local or distortional) and, for some geometries, local and distortional buckling may occur simultaneously (local-distortional interaction). A particularly efficient Generalised Beam Theory (GBT) non-linear formulation, specialised for RCPS tubes and employed earlier to characterise their bifurcation behaviour, is used to help pinpoint the occurrence of possible coupling phenomena. The post-buckling results presented and discussed concern columns with different ratios between the critical local and distortional buckling loads, and containing critical-mode initial geometrical imperfections. They are obtained through Abaqus shell finite element analyses and make it possible to draw a few conclusions on the post-buckling behaviour of RCPS columns affected by local-distortional interaction.