Numerical study of aluminium alloy continuous beams

The aims of this study are to investigate the behaviour of aluminium alloy continuous beams using finite element (FE) analysis and to underpin the development of revised design methods for indeterminate structures. FE analyses of two-span continuous beams (i.e. five-point bending) of square and rectangular hollow sections (SHS and RHS) are presented. The FE model was developed using ABAQUS 6.10-1, and the ultimate loads were determined when either a plastic collapse mechanism was formed or the material fracture strain was reached on the tension flange. Upon validation of the model against available experimental results, an extensive parametric study was performed to assess the effect of key parameters such as the cross-section aspect ratio, cross-section slenderness and the moment gradient on the strength, strain hardening behaviour and moment redistribution characteristics of aluminium alloy continuous beams. A total of 40 numerical results were generated and reported in this paper. The simulated ultimate loads were found to be beyond the theoretical loads that cause the first hinge to form, as well as the theoretical loads that cause the collapse mechanism to occur. A key characteristic of aluminium alloy, namely strain hardening, receives particular attention in the numerical investigation. In addition, the numerical results were also compared to design predictions from the American, Australian/New Zealand and European design standards and the continuous strength method for indeterminate structures. The design strengths predicted by the three specifications are found to be rather conservative, while the predications of the continuous strength method are more precise and consistent. The results reveal that strain hardening at the cross-sectional level and moment redistribution at the global system level have significant influence on the performance of stocky (plastic and compact sections) aluminium alloy structures, and should therefore be accounted for in efficient design.