Testing, modelling and design of 7A04-T6 high-strength aluminium alloy RHS columns under axial compression

The buckling behaviour and resistances of extruded 7A04-T6 high-strength aluminium alloy rectangular hollow section (RHS) columns under axial compression are reported in this paper. Nineteen RHS columns with member relative slenderness of 0.44–2.70 and cross-sections of Class 2–4 were conducted. Finite element (FE) models were developed and verified against the test failure modes, axial load-end shortening or mid-height lateral displacement curves and buckling resistances, and parametric analyses with a wide range of member and cross-section slenderness were performed. The generated test and FE results of 7A04-T6 high-strength aluminium alloy RHS columns were compared with current design methods specified in Chinese, European, American and Australian/New Zealand codes. The results indicated that the former three standards yielded conservative flexural buckling resistance predictions by about 9%, while slightly unsafe results were found for Australian/New Zealand standard, with all satisfactory reliability level. However, Chinese code resulted in the most conservative local-flexural buckling resistance predictions by about 35%, while conservative results under smaller member slenderness and overestimated ones under larger member slenderness were observed for other three standards, leading to scattered data and failing to reach target reliability indices. A series of improved design approaches shown to be safe and efficient for 7A04-T6 high-strength aluminium alloy RHS columns were suggested and validated by reliability analyses, including modified design curves for RHS columns to flexural buckling on Chinese and American standards, and three ways of proposals to imperfection terms with new coefficients as well as the direct strength method (DSM) in the framework of Chinese standard for RHS columns to local-flexural buckling.