Strain-hardening dependent cross-sectional slenderness limits for the plastic resistance of steel beams

Cross-sectional classification forms a relevant preliminary condition for the selection of appropriate resistance models in design structural steel elements. It is thus important that cross-sections are correctly classified, as this determines their utilisation. The focus paper lies on analysis transition point between cross-sectional classes 2 (compact) and 3 (elastic sections) typical cross-section shapes. In particular, it studies how various degrees strain hardening ratios ultimate yield strength influence point, which defines whether plastic moment section can be exploited. Based numerical simulations short beams, calibrated against full-scale tests, three independent cases were investigated i) outstand flanges similar elements supported along one longitudinal edge loaded pure compression, ii) webs other internal two edges, bending iii) compression. first eigenform retrieved from lateral buckling (LBA) was used initial imperfection geometric material non-linear (GMNIA). results analysed: maximum achieved compared with theoretical resistance. From these analyses, generalised observations could made reached or not consequently should assigned to class 3. Consequently, limit slenderness values determined correlations behaviour found integrated into corresponding formulas.