Investigation on Axial Capacity of Cold-Formed Aluminium Alloy Built-Up Columns

The objective of this study is to use finite element analysis (FEA) to investigate the axial strength of built-up sections made from cold-formed aluminium alloy. The built-up columns considered are made by joining two lipped channel sections in a back–back configuration using screw connections. The finite element model considers factors like initial imperfection, material and geometric nonlinearity, contact modelling at the interface of channel sections and incorporation of screws by means of tie constraints at specific locations. Nonlinear FEA is initially validated by analysing and comparing the experimental data sourced from previous literature. A parametric study is performed by incorporating triangular and rectangular stiffeners in the individual flanges of channel of the built-up cross section. The influence of the length of specimen and screw spacing used on various specimens are also studied. The study observes that the incorporation of rectangular stiffeners in flanges is much more effective with an average strength enhancement of 10.25%. The variation in screw spacing in the longitudinal direction has a minor influence on strength for all the models considered. A comparison is made between the finite element results and the ultimate strength of members determined through direct strength method (DSM), and concluded that DSM results are comparable for cross sections with lengths less than 2000 mm.