Experimental and Numerical Studies on Lateral-Torsional Buckling of GJ Structural Steel Beams Under a Concentrated Loading Condition

GJ structural steel has been applied in many high-rise buildings and large-span structures, such as New CCTV Building and Beijing Olympic Stadium (Birds Nest). However, the design methods of GJ structural steel members are not covered by the current design codes. This paper describes the lateral-torsional buckling behavior of welded sections based on a series of flexural tests performed on H-sections fabricated from GJ structural steel plates. Six steel beams were tested under a concentrated loading condition. It was observed from the experimental tests that lateral-torsional buckling controlled the final failure modes. Numerical simulations of the experimental tests were conducted as well. The numerical simulation results agreed well with the test data. Parametric study was conducted after the validation of the numerical model. Finally, both the experimental test and parametric study results were compared with multiple design codes, including Chinese steel structure design codes (GB50017-2003, GB50017-201X), Eurocode (EC3) and American code (ANSI/AISC360-10). The comparisons indicate that GB50017-201X can predict appropriate flexural strengths of GJ structural steel beams. Also, it is found that the predictions of EC3 are too conservative, while for certain cases ANSI/AISC360-10 predictions are too high for the design flexural strength of GJ structural steel beams.