Compression–Shear Hysteretic Performance of Circular Section Members Strengthened with CFRP-Wrapped Steel Tube Confined Concrete

A multi-faceted research framework integrating experimental tests, finite element (FE) simulations, and parametric analysis was adopted to investigate the compression–shear hysteretic performance of CFRP-confined concrete-filled steel tubes (CFRP-CFST). Nine circular specimens were designed, with the axial compression ratio and transverse CFRP confinement coefficient as key variables, to conduct material performance tests, laying a foundation for subsequent research. Displacement-controlled cyclic loading was applied in the tests to obtain hysteretic curves, observe the failure process, and calculate stiffness degradation and strength degradation. FE models were established using the constitutive relationships of corresponding materials and material parameters derived from tests (e.g., concrete plastic damage coefficients), and their reliability was verified by comparing simulation results with experimental data. Further stress analysis throughout the loading process was performed to reveal the stress distribution and evolution laws of concrete, steel tubes, and CFRP during loading. Finally, parametric analysis was carried out to explore the effects of material strength, transverse CFRP layers, and axial compression ratio on the hysteretic performance of the members. The results indicate that the specimens exhibit a stable four-stage mechanical response and typical failure modes, including steel tube shear fracture, CFRP tensile fracture, and concrete shear fracture. The established FE models can reliably predict the hysteretic characteristics and failure mechanisms of the specimens. While material strength, CFRP layers, and axial compression ratio significantly enhance the peak bearing capacity, they have little impact on the initial elastic stiffness or the overall trend of the skeleton curve. In addition, the steel tube and CFRP maintain effective synergy, improving the ductility and energy dissipation capacity of the members.