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

This study develops and experimentally verifies nonlinear finite element models for carbon-fiber-reinforced (CFRP) confined concrete-filled steel tube (CFST) columns under axial compression. ABAQUS- based 3D models represent the steel tube, concrete core and CFRP wrap using C3D8R solid elements and S4R shell elements, respectively, with contact interactions to capture interface behavior. Concrete is modeled with the concrete damage velocity (CDP) model steel and (CFRP) adopt bilinear and orthotropic elastic – plastic/elastic constitutive laws. Validation uses an experimental database of 72 columns (18 CFST,54 CFRP- confined) varying steel thickness (1.8-3.8mm) concrete strength (20-40 MPa), and CFRP layers (0-3). Numerical load- shortening curves, ultimate loads and failure modes closely match tests (Nu, exp/Nu,FEM=0.83-1.08) parametric studies show that increasing CFRP layers raises peak load and ductility and smooths post-peak softening, but concrete strength and steel thickness exert equal or greater influence on axial capacity. Modeled stress field reveal that CFRP delay outward steel deformation, promotes uniform stress distribution and mitigates local buckling. The validated models quantify confinements effects and provide insight in to interaction mechanics among concrete, steel, and CFRP. Results support the use of the FE framework for design-oriented parametric studies and for developing practical predication tools for CFRP- strengthened CFST columns.