Behaviour of concrete-filled circular TIG-welded aluminium alloy tubes under axial compression

Concrete-filled aluminium alloy tubes (CFATs) are an effective solution to enhance the stiffness and load-bearing capacity of aluminium alloy members. However, the existing research primarily focuses on the CFATs without welding seams, and there are no investigations on the effects of the welding process on the mechanical behaviour of CFATs. This study aims to investigate the basic axial compressive behaviour of concrete-filled circular welded aluminium alloy tubular (CFWAT) columns. Eight circular stub specimens are tested, comprising two main test variables of the thicknesses of aluminium alloy tubes and welding types. The failure modes, axial load-deformation responses and ductility have been carefully analysed. A refined finite element analysis has been developed with consideration of the heat-affected effects during the welding process. Parametric analysis has been conducted to further analyse the influence of residual stresses, welding types, widths of heated-affected zones, material strengths, and tube thicknesses. Finally, the typical existing design methods for the axial-load bearing capacity of CFATs have been examined, and then a new design method for the CFWATs has been proposed.