Experimental investigation on local buckling behaviors of stiffened closed-section thin-walled aluminum alloy columns under compression

• Stress–strain curves of aluminum alloy were obtained from tests.
• Compression tests on thin-walled aluminum alloy members were carried out.
• Local buckling behaviors of thin-walled aluminum alloy members were studied.
• Current design codes overestimated strength of closed-section aluminum alloy columns.

Six aluminum alloy tensile coupon tests were carried out and stress–strain curves obtained from tests were compared with a Ramberg–Osgood model. Comparison showed that the Ramberg–Osgood model can precisely describe stress–strain relationship of 6063-T5 aluminum alloy. Totally, 10 axial compression tests on thin-walled aluminum alloy members with four stiffened closed-section were carried out. Local buckling occurred in all specimens eventually. The axial displacement, lateral deflection, strain development and failure modes of the tested specimens were recorded. A finite element method (FEM) model was presented to simulate local buckling behaviors of the tested columns under axial load. The ultimate strength, strain development and failure modes obtained from FEM agreed well with the test results. Current design codes on aluminum alloy structures, such as the American aluminum design manual (AA), the European code (EC9), Chinese design specifications for aluminum structures (GB50429), the North American Specification for the design of cold-formed steel structural members (AISI) and the direct strength method (DSM), were used to calculate the ultimate strength of the tested columns. Comparison showed that current design codes overestimated the ultimate strength of stiffened closed-section thin-walled aluminum alloy columns under axial compression loads.