Local buckling analysis of axially compressed welded box-section stub columns using Q420-Q960 steel

Considering the broad applications of high-strength steel (HSS) in civil engineering and addressing the dearth of reliable research on current engineering specifications, axial compression tests were conducted on 12 HSS welded box-section stub columns made of Q420-Q960 grade steels; moreover, their local buckling behaviour was studied. In addition, a parametric analysis was performed using a finite element model (FEM). Prior to the tests, the initial geometric imperfections and material properties of the specimens were measured to ensure their adherence to relevant engineering specifications. The local buckling process, axial deformation, and strain of the specimens were analysed. As observed, the utilisation rate of steel strength decreased as the width-thickness ratio and yield strength increased. More importantly, the results revealed that the post-buckling strength of the axially compressed HSS welded box-section stub columns with slender sections cannot be neglected. Accordingly, a finite element analysis was conducted to verify the accuracy of the FEM that considered the initial geometric imperfections and welding residual stress. For the Q420-Q960 steel welded box-section stub columns, a parametric analysis was performed using the verified FEM to evaluate the limits of the width-thickness ratio and the ultimate bearing capacity. A new formula for the limit of the plate width-thickness ratio is proposed. To enable the application of the EN 1993-1-5 and ANSI/AISC 360-16 guidelines as well as the Chinese codes GB 50017-2017 and JGJ/T 483-2020, the modification factors are also provided for the ultimate bearing capacity.