Experimental and numerical study on overall buckling behavior of Q460 high-strength steel continuous beams with welded singly symmetric I-section

In order to study the overall buckling behavior of continuous beams with welded singly symmetric I-section for Q460 high strength steel (HSS), experiments and numerical simulations were conducted on nine continuous beams with various strengthened top flange section forms and span ratio. The initial geometric imperfections and cross-sectional residual stresses of specimens were also measured in the test. The finite element model consid-ering the material nonlinearity, initial geometric imperfections and welding residual stresses was developed and verified against experimental results. The validated model which reasonably agreed with experimental results was employed for parametric analysis to investigate the effect of span ratio, height to width ratio, width and thickness of the strengthened top flange on the overall buckling capacity of continuous beams with welded singly symmetric I-section for Q460 HSS. According to the calculation formulas of elastic lateral-torsional buckling moment for simply supported beams in GB50017-2017, the calculation formulas of elastic lateral-torsional buckling moment for continuous beams with singly symmetric I-section were proposed. The buckling design curve was obtained by substituting the proposed elastic lateral-torsional buckling moment of continuous beams into the formula for the buckling coefficient of continuous beams given in JGJ/T483-2020. By using the vali-dated FEA models, the data obtained from parametric studies were compared with the current codes of JGJ/ T483-2020, Eurocode 3-2005, ANSI/AISC360-2016 and GB50017-2017. It was found that the design method of JGJ/T483-2020 and Eurocode 3-2005 yield conservative predictions (with an average over 21.7 %) of the overall buckling capacity of Q460 HSS continuous beams with singly symmetric I-section. ANSI/AISC360-2016 and GB50017-2017 underestimate the overall buckling capacity (with an average below 13.7 %) of Q460 HSS continuous beams with singly symmetric I-section. Finally, recommendations were proposed which is more suitable for design of Q460 HSS continuous beams with singly symmetric I-section.