Experimental and numerical studies on lateral torsional buckling of welded Q460GJ structural steel beams

With the development of steel structures, high performance GJ steel has been applied in many large scale projects, such as National Olympic Stadium (Birds Nest), new CCTV Headquarters and Canton Tower in China. In this study, a series of experimental tests and numerical modelling were conducted to investigate the global stability behaviour of Q460GJ structural steel beams. A total of eight doubly symmetric welded beams with lateral restraints at the mid-span were tested under a concentrated load. Finite element analysis (FEA) models considering initial geometric imperfections and residual stresses were also established and verified by experimental results. By using the validated FEA models, parametric studies were carried out as well. The data obtained from parametric studies were compared with the design buckling curves from Chinese steel structure design codes (GB50017-2003, GB50017-201X), American code (ANSI/AISC360-10) and Eurocode 3 (EC3). It was found that the global stability design methods in GB50017-2003 and ANSI/AISC360-10 may not be conservative for GJ structural steel beams with lateral restraints at the mid-span. The design methods in GB50017-201X and EC3 for rolled sections or equivalent welded sections are more appropriate for the overall stability design of GJ structural steel beams.