Research On The Torsional Buckling Behavior Of Q460 Welded I-section Simply Supported Beams

Compared with ordinary steel,high strength steel(HSS)has many advantages,such as high yield and tensile strength,good performance of resistance to brittle failure and high reliability of structures.In recent years,HSS beam has gradually been employed in practical engineering.In this study,a series of experimental tests and parametric analyses were conducted to investigate the lateral-torsional buckling behavior and capacity of welded Q460 steel beams.An effective loading system,which can release the lateral constraint of loading point,was developed.A total of eight welded beams with lateral restrains at end supports were tested under a concentrated load at the mid-span.Among these eight welded beams,one Q235 beam was tested to compare with other Q460 beams,the flange width-to-thickness ratio ranged from 4.6 to 9.6,the web width-to-thickness ratio was from 28.75 to 47.50,and the span of beam changed from 3m to 5m.In addition,the finite element model considering initial geometric imperfections is established by using the finite element analysis software ABAQUS.Considering material non-linearity and geometric non-linearity,the results of finite element analysis are compared with the experimental results and the results show that they are in good agreement.Based on the finite element model,a series of parametric analyses were carried out to evaluate the effects of key parameters on the lateral-torsional buckling behavior of Q460 steel beams.Moreover,the experimental and numerical results were compared with the design buckling curves from Chinese steel structure design codes(GB50017-201X),Australia code(AS4100) and Eurocode 3(EC3).It is demonstrated that the current design codes are underestimated(GB50017-201 X,AS4100 and EC3 for general sections)or unsafe(GB50017-2017 and EC3 for rolled and equivalent welded sections)for evaluating the lateral-torsional buckling capacity of HSS beams.Based on experiments and numerical simulations,modified design equations are presented in this study,which is more appropriate for predicting the lateral-torsional buckling capacity of Q460 steel beams and can provide reference for engineering application and academic research.