Mechanical behavior of CFRP confined seawater sea-sand recycled concrete-filled circular aluminum-alloy tube columns under axial compression

This paper presents an experimental study and theoretical analysis of the mechanical behavior of CFRP-confined seawater sea-sand recycled concrete-filled circular aluminum-alloy tube short columns (CFRP-CFAT) under axial compression. A total of 12 circular cross-section specimens were tested, including 4 concrete-filled circular aluminum-alloy tube (CFAT) specimens and 8 CFRP-CFAT specimens. The effects of the number of CFRP layers, the thickness of the aluminum tubes, and the strength of the concrete were investigated. The test results indicate that CFRP can effectively delay or even suppress the local buckling of aluminum alloy tubes and significantly improve the ultimate load capacity of the specimens, and the enhancement is approximately linear with the number of CFRP layers. Based on the experimental results, a modified axial strain-lateral strain response model for core concrete is proposed. In addition, a new analysis-oriented model applicable to circular CFRP-CFAT short columns is established and compared with the test results for verification. Meanwhile, the CFRP-CFAT ultimate load-bearing capacity calculation method is proposed based on the superposition theory and the analysisoriented model. The predicted results are in high consistency with the experimental results.