Experimental Investigation of Aluminum Alloy Thin-Walled Tubular Members in Combined Compression and Bending

This paper presents a test program on aluminum alloy thin-walled square and rectangular hollow sections in combined axial compression and minor axis bending. A total of six series of tests was conducted that included 27 beam-column and 4 pure bending tests. The test specimens were manufactured by extrusion using 6061-T6 heat-treated aluminum alloy in three different cross sections having the clear width-to-thickness ratio ranged from 31.3 to 81.3. The beam-column specimens were compressed between pinned ends at different eccentricities in order to obtain an interaction curve for each series of tests. Pure bending tests were conducted for each test series to determine the bending capacities of the specimens. Local and 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 local buckling, flexural buckling, interaction of local and flexural buckling, and material yielding in the heat-affected zone. The test strengths were compared with the design strengths calculated using the American, Australian/New Zealand, and European specifications for aluminum structures. Beam-column interaction curves were plotted for each test series. It is shown that the beam-column design strengths and bending capacities predicted by the three specifications are generally conservative.