Experimental and numerical investigation on flexural-torsional buckling of Q460 steel beams

High strength steel is increasingly used in current engineering structures, because of its high structural efficiency. However, the current design method of the ultimate capacity of lateral-torsional buckling of steel beams is based on the research achievement of normal strength steels. To investigation the lateral-torsional buckling behavior of high strength steel beams, an experimental and numerical study on the ultimate bearing capacity of welded I-section beam with a nominal yield stress of 460 MPa in bending was carried out. The flange width-to-thickness ratios of 5 and 9 and member slenderness ratio of 95 and 155 were adopted in the test. A nonlinear FE model was established with the consideration of initial geometric imperfection and residual stress. The ultimate flexural resistances predicted by FE models agree well with those obtained from the test, which validated the FE model. A series of parametric study with considering various steel grades, cross-sectional dimensions, member slenderness ratio and initial imperfections were taken into account to the influence on flexural-torsional buckling behavior of the beams. The applicability of current design codes for the ultimate capacity of high strength steel I-section beams was evaluated by comparing with experimental and numerical results. The comparison shows that American National Standard (AISC 360–16) can provide an accurate perdition of the flexural resistance of beams fabricated from Q460 steel, while EN1993-1-1 is more conservative than Chinese Standard (GB50017–2017).