Aluminum alloy circular hollow section beam-columns

An experimental investigation was performed on aluminum alloy circular hollow sections in combined axial compression and bending. The test program consists of four series of beam-column tests as well as pure bending tests. The test specimens were fabricated by extrusion using 6061-T6 heat-treated aluminum alloy. The beam-column specimens were compressed between pined ends at different eccentricities in order to obtain an interaction curve for each series of test. The lengths of the beam-column specimens were either 500 or 1000 mm. Pure bending tests were conducted for each test series to determine the bending capacities of the specimens. Overall initial geometric imperfections of the specimens were measured. Material properties were obtained from tensile coupon tests. The observed failure modes of the beam-column tests included flexural buckling and material yielding in the heat-affected zone. A comparison of the test strengths with the design strengths obtained using the American, Australian/New Zealand and European specifications for aluminum structures has been presented. Axial load versus moment interaction curves were plotted for each test series. It is shown that the bending capacities and beam-column design strengths predicted by the three specifications are generally conservative.