Compact cross-sections of mild and high-strength steel hollow-section beams

The Eurocode 3 rules for the high-strength steel (HSS: f_y > 460 MPa) limit the analysis of beams to elastic global analysis and grades up to S700. In order to fully exploit the potential to design lightweight and sustainable steel structures, plastic analysis and the use of higher steel grades with f_y > 700 MPa are desirable. The main concern is the low ultimate-to-yield strength ratio requirement for HSS, f_u/f_y > 1·05 according to BS EN 1993-1-12. Its influence on the resistance and rotation capacity of HSS square and rectangular hollow-section beams (SHS and RHS) is investigated in this study. The available results of four-point bending experiments on hollow-section beams are validated by finite-element analysis with special attention given to imperfections. Parametric study of steel grades S355–S960 indicates that the slenderness limits given in Eurocode 3 need to be reduced both for the mild steels and HSS.