Tests of aluminium alloy CHS columns with circular openings

This paper describes a test program on a wide range of aluminium alloy circular hollow section (CHS) columns with circular openings. A total of 27 specimens including 18 perforated CHS columns and 9 CHS columns were tested with uniform axial compression force applied to the pin-ended columns, which were fabricated by extrusion of CHSs using 6061-T6 and 6063-T5 heat-treated aluminium alloys. The influence of the column slenderness ratio, the plate slenderness ratio, the opening size ratio and the number of openings on the strength and behaviour of aluminium alloy CHS columns were carefully evaluated. The ultimate strengths, failure modes, load versus axial shortening curves and strain distributions along the circular openings of test specimens were all obtained from the experimental investigation. The test strengths of aluminium alloy CHS columns were compared with the design strengths predicted using the design rules given in the current design specifications. Furthermore, the test strengths of aluminium alloy CHS columns with circular openings were also compared with the design strengths calculated using the current design rules for perforated cold-formed steel structural members, which were derived based on the effective diameter method and effective area method. It is shown from the comparison that the design rules given in American Design Manual (AA) and Australian/New Zealand Standard (AS/NZS) for limit state design of aluminium alloy structural members are generally appropriate but with comparatively high scatter of predictions; whereas the design rules given in Chinese Code are generally appropriate for the design of aluminium alloy CHS columns. In addition, the current design rules for perforated cold-formed steel structural members based on the effective area method are generally more accurate than those based on the effective diameter method for the design of aluminium alloy CHS columns with circular openings.