Study of flexural-torsional buckling behaviour of 6061-T6 aluminium alloy unequal-leg angle columns

Unequal-leg angles can be used to provide more efficient design in specific cases, but the behaviour of unequal-leg angles has received much less attention than equal-leg angles. This paper studies the flexural and torsional buckling modal participation and investigates the structural behaviour of aluminium alloy unequal-leg angle columns. The experimental programme, which was carried out on two unequal-leg angle cross-sections, included material coupon tests, initial geometric imperfection measurements and a total of eight column tests. The test setup, procedure and results are fully reported. Following the experimental investigation, numerical models were developed and validated against the test results. Upon validation, a series of parametric studies were carried out to analyse the influence of width-to-thickness ratio and aspect ratio on the flexural and torsional buckling modal participation. The ultimate resistances obtained from simulations were used to assess the accuracy of the current design provisions given in the European standard for aluminium alloy structures. The result comparison shows that the existing design provisions yield inaccurate predictions for unequal-leg angle columns. Considering mode interaction, a more accurate and convenient design method was proposed for unequal-leg angle columns.