Buckling behaviors of thin-walled aluminum alloy column with irregular-shaped cross section under axial compression in a fire

• Irregular section thin-walled aluminum alloy column in a fire was studied.
• .Sectional yielding, local and global buckling, and their interaction were presented.
• Design codes underestimated strengths of irregular section aluminum alloy columns.
• Modifications were proposed to predict strength of aluminum alloy column in a fire.

Failure modes of the thin-walled aluminum alloy column with irregular shaped cross section at ambient temperature and elevated temperatures in a fire were studied using a verified finite element model. The studied failure modes included the sectional yielding, interaction of local buckling and sectional yielding, interaction of local and global buckling, and global buckling. The finite element model was verified by experimental results from the ultimate strength, the failure modes and the failure deformation. Deformation shape along the column failed by different failure modes was presented. Stresses development at the middle span section was greatly affected by the failure modes. Ultimate strengths of a series of aluminum alloy columns with different length, cross section dimension were analyzed by the finite element analysis and current design codes at different temperatures in a fire. The current design codes greatly underestimated the ultimate strength of the thin-walled aluminum alloy column with irregular shaped cross section. Design method provided by EN1999-1-2 can give an accurate prediction of the ultimate strength of a short thin-walled aluminum alloy column with irregular shaped cross section at temperatures lower than 250 °C. A modification to the design method in EN1999-1-2 was proposed for predicting the ultimate strength of the aluminum alloy column with length longer than 500 mm and at temperatures higher than 250 °C. Ultimate strength predicted by the modified equation agreed well with finite element analysis results.