MECHANICS OF DISTORTIONAL-GLOBAL INTERACTION IN FIXED-ENDED LIPPED CHANNEL COLUMNS

This work reports the results of a numerical investigation concerning the elastic post-buckling behaviour of fixed-ended thin-walled lipped channel columns affected by distortional-global (D-G) interaction. The columns analysed (i) exhibit cross-section dimensions and lengths ensuring simultaneous distortional and global critical buckling loads, and (ii) contain critical-mode initial geometrical imperfections (linear combinations of D and G buckling modes). For comparison and clarification purposes, the post-buckling behaviour of columns buckling in an "isolated" distortional mode and containing "pure" distortional and global (flexural-torsional) initial geometrical imperfections are also analysed. The results presented and discussed are obtained through geometrically non-linear Generalised Beam Theory (GBT) analyses and provide the evolution, along given equilibrium paths, of the column deformed configuration (expressed in GBT modal form), relevant displacement profiles and modal participation diagrams, making it possible to acquire in-depth knowledge on the column D-G interaction mechanics. Finally, particular attention is paid to interpreting the differences exhibited by the several aforementioned column post-buckling behaviours.