Behaviour and design of aluminium CHS in compression and bending

This study presents an experimental investigation of extruded aluminium circular hollow sections (CHS) subjected to compression and bending, with emphasis on local buckling and the design of slender sections. Nine stub column and seven four-point bending tests were conducted on aluminium CHS made of alloys 6063-T66, 6063-T6, 6082-T6, 6061-T6, covering outer diameter-to-thickness D/t ratios from 16.60 to 62.73. Validated finite element models were used to generate 64 simulations, extending the database to a wider range of cross-sectional slenderness. The experimental and numerical results were used to assess the local buckling provisions of EN 1999-1-1:2007, EN 1999-1-1:2023 and the Continuous Strength Method (CSM). Attention was given to the revised local buckling coefficient for CHS in compression introduced in EN 1999-1-1:2023, whereby k 0 was increased from 3 to 6, substantially increasing the number of sections classified as Class 4. Two approaches for Class 4 were assessed: the effective-thickness method specified in EN 1999-1-1:2023 and the shell buckling provisions of EN 1999-1-5:2023. Reliability analyses in accordance with EN 1990 demonstrate that the EN 1999-1-1:2023 provides reliability levels closest to the target value for compression, whereas the combined EN 1999-1-1:2023 and EN 1999-1-5:2023 approach generally is generally more conservative. For bending, a simplified design method for Class 4 sections is proposed that avoids the complexity of EN 1999-1-5:2023 while achieving comparable reliability and design efficiency. The results demonstrate that the statistical characterisation of aluminium material properties influences reliability-based calibration and highlight the need for further experimental data, particularly for Class 4 sections in bending.