Experimental Investigation of Nonlinear Cyclic Flexural Behavior of Hollow and Concrete-Filled Aluminium Beams

This study presents an experimental program to characterize, for the first time, the nonlinear cyclic flexural behavior of hollow and concrete-filled aluminium tubular beams at large rotation levels up to 0.08 rad. Particularly, four different tubular cross sections, fabricated from two grades of structural aluminium alloys–6082-T6 and 6063-T6–with various cross-sectional slenderness were tested with and without concrete infill to establish their hysteretic flexural behavior. All tested specimens showed hysteretic loops without significant gradual strength and stiffness degradation under cyclic loading. The influence of aluminium alloy type, cross-sectional slenderness, and presence of concrete infill on the plastic hinge deformation, ultimate strength, failure mode, secant stiffness degradation, and energy dissipation capacity is thoroughly investigated. Analysis of the in-plane strain measurements from digital image correlation (DIC) suggest that under large cyclic loads the examined members can develop an average plastic hinge length equal to 1.5 times the largest cross-sectional dimension measured from the fixed end of the members. Overall, the experimental results demonstrate that hollow and concrete-filled aluminium beam members can sustain large deformations without any structural damage under large rotation levels.