Study of buckling behavior for 7A04-T6 aluminum alloy rectangular hollow columns

A series of eccentric load tests on aluminum alloy columns with square and rectangular hollow sections, fabricated by extrusion using 7A04-T6 aluminum alloy, were conducted in this paper. The initial geometric imperfections were measured prior to compression tests to investigate their impact on ultimate strength. The relevant load-displacement and load-strain curves acquired from testing reacted to the buckling behavior of columns subjected to combined axial load and bending, and the failure modes observed included overall buckling and the combination of local and overall buckling. Finite element models were developed and validated in conjunction with the experimental conditions and results. Then, an expanded parametric study was performed to explore the effect of the stability performance for columns over a wide range of normalized slenderness ratios and load eccentricity ratios. The experimental and numerical results were compared to the design strength provided by the current Chinese code, European code, American specification, and the Australian/New Zealand standard, as well as optional design approaches, the direct strength method and continuous strength method. The comparisons revealed that the majority of the current design provisions and methods presented relatively conservative predictions of ultimate strength for 7A04-T6 aluminum alloy columns under combined loading. A formula based on the Chinese code was proposed, with several parameters modified, to more accurately predict the ultimate strength of 7A04-T6 aluminum alloy columns.