Flexural behavior of concrete-filled aluminum alloy circular hollow section tubes

This paper presents an experimental investigation on flexural behavior of concrete-filled aluminum alloy circular hollow section (CHS) tubes under pure in-plane bending. A total of 28 circular concrete-filled aluminum alloy tubes (CFAT) with nominal concrete cube strengths of 30 MPa and 50 MPa were tested. The flexural strengths, failure modes, flexural stiffness, ductility, bending moment versus mid-span deflection curves, overall vertical deflection curves, bending moment versus longitudinal strain curves and longitudinal strain distribution curves of circular CFAT beams are reported. It is demonstrated that the comparatively large wall thickness of aluminum alloy CHS tube enhanced the bearing capacity, the bending deformation capacity and the ductility of circular CFAT beams. Whereas, the concrete strength generally has insignificant influence on the flexural strength, flexural stiffness and ductility of circular CFAT beams. The current design specifications for the CFST are generally inappropriate for circular CFAT beams under pure in-plane bending with high scatter of predictions. Further research is still required to propose accurate design rules for circular CFAT beams.