Flexural behaviour of CFRP strengthened concrete-filled aluminium alloy CHS tubes

•CFRP strengthened concrete-filled aluminium alloy CHS tubes beams were investigated.•Flexural ultimate strength was generally enhanced by reinforcing with the CFRP.•Ductility of beams was generally deteriorated by reinforcing with the CFRP.•Layer of the CFRP had little influence on mechanical behaviour of the CFRP strengthened CFAT.•Design equations were proposed for the CFRP strengthened CFAT.

This paper presents an experimental investigation on flexural behaviour of concrete-filled aluminium alloy circular hollow section (CHS) tubes reinforced by carbon fiber-reinforced polymer (CFRP). A total of 30 specimens including 20 CFRP strengthened concrete-filled aluminium alloy tubes (CFAT) and 10 traditional CFAT were tested under pure in-plane bending. The ultimate strengths, failure modes, flexural stiffness, ductility and longitudinal strains of test specimens are reported. It is demonstrated that the ultimate strength of the CFAT specimens are generally enhanced by reinforcing with the CFRP, but the ductility is generally deteriorated. Furthermore, the layer of the CFRP has little influence on the ultimate strength, flexural stiffness and ductility of the CFRP strengthened CFAT specimens. It can be generally concluded that the design equations given in the current AIJ standard for the flexural stiffness of the concrete-filled steel tubes (CFST) are appropriate for the initial flexural stiffness of the CFAT, and also appropriate for the post-yield flexural stiffness of the CFAT with a proper reduction factor. The design equations are also proposed for the CFRP strengthened CFAT based on the design rules for the CFAT by further considering the flexural stiffness of the CFRP.