Behaviors and design method for distortional buckling of thin-walled irregular-shaped aluminum alloy struts under axial compression

Since an aluminum alloy structural component can be manufactured through extrusion technology, the cross section can easily comprise various longitudinal stiffeners to strengthen the thin wall and to hold the partition wall panel. In this paper, experimental and numerical investigations on distortional buckling behaviors of thin-walled irregular-shaped aluminum alloy stub columns under axial compression were carried out. Initial geometric imperfections of six extruded aluminum alloy columns were measured using LVDT. The ultimate strength, failure deformation, out-of-plane displacement and strain development of six test specimens were recorded and used to verify a Finite Element Model (FEM) developed by the finite element software ABAQUS. The open plates in the irregular-shaped section had low distortional buckling resistance, which causes the premature failure of the studied columns. 117 columns with different length and plate thickness were numerically simulated by the verified FEM to reveal the influences of plate thickness on column distortional buckling behaviors. The Direct strength method (DSM) was applied and it was essential to determine column distortional buckling stress before performing DSM to calculate column ultimate strength. A modified calculation method for distortional buckling stress of the irregular-shaped aluminum alloy columns was proposed. Distortional buckling stresses of 81 aluminum alloy columns with different plate thickness were analyzed by the FEM to evaluate the modified calculation method. It was accurate and more efficient to use the modified calculation method to calculate distortional buckling stress of the irregular-shaped aluminum alloy columns in DSM.