Experimental study on local buckling of high-strength Q960 steel columns at elevated temperatures

High-strength steel has been widely used in many engineering structures owing to its enormous economic benefits. A considerable amount of theoretical and experimental research on the fire resistance of high-strength steel structures has been reported. Most of the research has focused on the mechanical properties of steel and the overall buckling behavior of members, but less work has been done on the local buckling behavior, which is often observed in steel structures subjected to actual fires. Moreover, very few design provisions in codes and standards are available for calculating the local buckling capacity of steel columns under high temperatures. In this study, eight welded H-section columns (groups A and B) made of high-strength Q960 steel were tested under axial compression at ambient and elevated temperatures to investigate their local buckling behaviors. By considering different buckling zones, heating temperatures, and heating methods, the load–axial displacement, load–lateral deflection, and local buckling zone of steel columns were recorded. Compared with the ambient temperature test results, the ultimate load of group A specimens at 480 and 632 °C decreased by 26.1% and 57.2%, respectively, and the ultimate load of group B specimens at 472 and 683 °C decreased by 28.5% and 74.2%, respectively. The critical buckling temperature of the columns in transient-state testing was higher than that in steady-state testing under the same load conditions. A finite element model was established using the ABAQUS finite element software and was validated by the test results. The experimental values were compared with the design methods proposed in Eurocode 3 (EC3). The results reveal that EC3 is unsuitable for calculating the local buckling capacity of H-section Q960 steel columns at elevated temperatures. © 2021