STATIC STRENGTH OF CONCRETE FILLED CIRCULAR CFRP-STEEL TUBULAR STUBS UNDER AXIAL COMPRESSION

The static strength of circular concrete filled steel tubular (C-CFST) stubs strengthened with carbon fiber reinforced polymer (CFRP) is studied theoretically. Based on continuum mechanics, a theoretical model of circular CFRP-concrete filled steel tubular (C-CFRP-CFST) stubs under axial compression is established based on the assumptions that steel tube and concrete are both in a three-dimensional stress state and CFRP is in a uniaxial tensile stress state. The equations for calculating the yield strength and the ultimate strength of C-CFRP-CFST stubs under axial compression are deduced. The theoretical predictions from the presented equations are compared with existing experimental results, and the accuracy of the theoretical predictions is verified. Finally, a parametric study is carried out by the predictions of presented equations. The results from parametric study indicate that increasing the yield strength of a steel tube and the compressive strength of concrete or decreasing the diameter/thickness ratio of a steel tube can both improve the yield strength and the ultimate strength of C-CFRP-CFST stubs. The ultimate strength of C-CFRP-CFST stubs can be also improved by increasing the number of CFRP layers and the circumferential tensile strength of CFRP. However, the number of CFRP layers has little influence on the yield strength of C-CFRP-CFST stubs while the tensile strength of CFRP has no influence on such yield strength.