Buckling behavior of large-section and 420MPa high-strength angle steel columns

Large-section and high-strength angle steel (LHS) columns have been increasingly used in steel structures in recent years, however existing corresponding design methods were mostly based on studies of mild carbon steels with normal-size sections. In order to investigate the buckling behavior of LHS columns, an experimental study, involving 90 Q420 (420MPa) specimens under axial compression was conducted. The experimental buckling strengths were compared with corresponding design values in current specifications. Non-linear finite element (FE) models considering residual stress, actually measured geometric imperfections and stress-strain curves obtained from tension coupon tests were developed and validated, and then used to perform an extensive parametric study. Effects of hardening progress in Q420 stress-strain curves were investigated and discussed. Theoretical dimensionless buckling strengths for slenderness from 30 to 120 were obtained through FE analysis and then compared with current design column curves. It is concluded that, the degree of conservative of current codes decreased when slenderness increased, and none of the compared curves was in good agreement with theoretical results, while design curves in GB 50017-2003 and Eurocode3 can be used conservatively. Finally, based on the parametric studies a new column curve was proposed to predict the buckling strengths of LHS columns.