FEM simulations and rotation capacity evaluation for RHS temper T4 aluminium alloy beams

The aim of this work is the development of an empirical relationship for evaluating the rotation capacity of RHS temper T4 aluminium alloy beams subjected to non-uniform bending. The proposed relationships are based on the numerical results coming from an extensive parametric analysis performed by means of FE code ABAQUS, which gains insight into the influence of all the geometrical and mechanical parameters affecting the ultimate behaviour of aluminium alloy beams. In particular, the influence of the flange slenderness, the influence of the web restraining effect related to the flange-to-web slenderness ratio and the influence of the moment gradient are investigated. The modelling of the material is carried out by adopting the constitutive law proposed by Eurocode 9, based on the Ramberg-Osgood model whose shape factor characterises the hardening behaviour of the material. The investigations concern these factors considered separately as well as their interaction. The results are herein reported with reference to temper T4, i.e. an alloy characterised by a significant hardening behaviour, and show the importance of some of the investigated parameters on the maximum flexural resistance, corresponding to the complete development of local buckling of compressed flange, and on the rotation capacity of aluminium alloy beams. Successively, by means of monovariate and multivariate non linear regression analyses, empirical relationships are provided in order to predict both the ultimate bending resistance and the rotation capacity of RHS temper T4 aluminium alloy beams starting from their geometrical and mechanical properties.