Flexural buckling performance of concrete-filled aluminium alloy tubular columns

Abstract

The use of aluminium alloys as a structural material has recently increased because of their advantageous properties such as high strength-to-weight ratio and corrosion resistance. However, due to their low Modulus of Elasticity, instability is a major concern for aluminium alloy structural members subjected to compression. One of the ways to improve the performance of aluminium alloy hollow sections on this count is to have concrete infill within them. Past research studies have demonstrated the potential of concrete-filled aluminium tubular (CFAT) stub columns and beams to have improved structural performance, but there is still no reported research on CFAT slender columns. This paper presents an experimental and numerical investigation on the structural response of square and rectangular CFAT members under axial compression. A series of 18 tests were carried out, including 9 CFAT and 9 bare aluminium tubular (BAT) columns for reference purpose. The columns had pin-ended boundary conditions allowing rotation about the minor axis. The tubes were made of 6082-T6 heat-treated aluminium alloy and filled with concrete. The experimental failure modes, ultimate strengths and load versus mid-height lateral displacement curves are reported. Finite element models were developed and validated against the test results. A parametric study was subsequently conducted to study the buckling behaviour for a range of cross-sections and concrete strengths. The test and numerical results were utilised to assess Eurocode design equations for Class A aluminium alloy columns. It was shown that the current codified equations underestimate the actual strength of BAT slender columns and a new buckling curve improving the design accuracy is proposed. In absence of design provisions for CFAT columns, the design methodology of European standards for composite steel-concrete members with the material properties of steel replaced by those of aluminium is adopted. Finally, on the basis of the results of this study a design buckling curve suitable for CFAT columns is proposed.