Experimental And Numerical Investigation On The Interaction Of Overall And Local Buckling Of High Strength Aluminum Alloy Columns

Aluminum alloy was widely used as a structure material for its advantages such as the high strength-to-weight ratio, lightness, corrosion resistance and ease of production. However, the stability of structure components is predominant due to the low value of the elastic modulus of aluminum alloy. Experimental and numerical studies of columns extruded from aluminum alloy of 6082-T6 under concentric compression were performed. A design approach account for the local-overall interaction buckling was proposed in this research.The material properties were obtained from 26 tensile tests and the stress-strain relationship was discribed using Ramberg-Osgood constitutive model. Experimental study of 32 pin-ended column specimens extruded from aluminum alloy of 6082-T6 was presented in this research. The specimens consists of 17 I-section and 15 box-section columns and were loaded in concentric compression. 32 specimens were observed to fail mainly by flexural buckling and several box-section columns were failed by the interaction of local and overall buckling.A numerical investigation of aluminum alloy columns of I-section and box-section in concentric compression were conducted by using finite element (FE) analysis software ABAQUS, and the simulation results were compared with experiments of 32 specimens extruded from aluminum alloy of 6082-T6. A fine finite element model with 4-node shell element and Ramberg-Osgood expression for stress-strain relationship was developed, and factors influencing simulation results including mesh size, thickness of end plates, initial geometric imperfection and material parameters were analyzed. The simulation results show that the calibrated FE model provides accurate predictions of failure modes, buckling load and deformation of specimens; mesh size and thickness of end plates have negligible influence on FE results; the increase of initial geometric imperfection will lead to a decline in ultimate loads, especially for regularized slenderness around 1.0; the buckling loads of intermediate columns with slenderness ratio ranging from 26.33 to 78.98 are very sensitive to the non-dimensional 0.2% proof stress and slightly influenced by parameter n from Ramberg-Osgood constitutive model.Parameter studies were performed using the FE model to investigate the local-overall interaction buckling. 3 I-secion and 4 box-section with an amount of 119 columns were presented in the parameter studies. A design approach for aluminum alloy members under concentric compression, which combines the Chinese code for design of aluminum alloy and the North American specification for cold-formed steel structural members, was proposed and compared with results of tests, FE analysis, American, European and Chinese specifications for aluminum structures. It shows that the proposed method is able to accurately predict the ultimate load of aluminum alloy columns under concentric compression. The mean value of proposed approach-to-FEA results ratios ranging from 0.998 to 1.064 with the corresponding coefficient of variation (COV) ranging from 0.019 to 0.074. The proposed approach is much more convenient than the American, European and Chinese specification for aluminum structure members, and takes into account of the assembly effect of the folded cross-section. Besides, the proposed approach was developed based on Chinese code for design of aluminum alloy thus can be applied conveniently in China.