Finite Element Modeling and Experimental Verification of CFRP-Confined CFST Columns Under Compression

This study develops and evaluates a three-dimensional nonlinear finite element (FE) framework for carbon fiber-reinforced polymer (CFRP)-confined concrete-filled steel tube (CFST) short columns subjected to concentric axial compression. The concrete core is represented using C3D8R solid elements, and the steel tube and CFRP jacket using S4R shell elements. Concrete is modeled with the concrete damage plasticity (CDP) formulation, the steel tube with an elastic–plastic constitutive law, and the CFRP jacket with an orthotropic elastic law. The FE framework is evaluated against the 72-column experimental database reported previously comprising 18 unwrapped CFST specimens and 54 CFRP-confined specimens. The database covers steel tube thicknesses of 1.8–3.8 mm, measured concrete strengths of 19.3–39.8 MPa, and 0–3 CFRP layers. No constitutive parameter was fitted to the 72 ultimate-load results; the comparison therefore represents validation against a previously published experimental database rather than blind validation after database-specific calibration. The ratio of experimental to numerical ultimate load ranges from 0.83 to 1.08, with a mean of 0.952, a standard deviation of 0.045, RMSE of 68.2 kN, MAPE of 6.10%, and R2 = 0.937. A factorial evaluation of the validated matrix shows that additional CFRP layers increase peak load and deformation capacity, while concrete strength and steel tube thickness also exert strong effects. Stress contours indicate that CFRP confinement limits outward deformation and redistributes stresses, although these mechanistic conclusions remain conditional on the idealized perfect-bond interfaces and elastic CFRP representation. The framework is therefore suitable for trend-oriented studies within the investigated range, but it should not be extrapolated to cases involving different geometries, loading conditions, or explicit CFRP/interface failure without further validation.