GBT-based first-order analysis of elastic-plastic thin-walled steel members exhibiting strain-hardening

This paper addresses the development and illustrates the application of a generalised beam theory (GBT) formulation intended to perform first-order elastic-plastic analyses of thin-walled members made of isotropic non-linear materials exhibiting strain-hardening. After presenting an overview of the main concepts and procedures involved in the above GBT formulation, its application is illustrated through the analysis of (i) simply supported Z-section beams and (ii) fixed-ended lipped channel beams. In both cases, a bilinear elastic-plastic material model is adopted, which exhibits three strain-hardening levels, namely Esh = 0 (perfectly plastic model), Esh = E/100 and Esh = E/50. The results presented and discussed consist of equilibrium paths, modal participation diagrams, displacement profiles, beam deformed configurations and stress diagrams and contours. For validation purposes, most of the GBT results are compared with values obtained from shell finite element analyses − with a few relatively minor exceptions, a very good correlation is always found. Finally, the paper closes with some remarks concerning the influence of the strain-hardening slope on the structural behaviour of thin-walled steel beams.