Performance of longitudinally reinforced concrete-filled FRP tube columns under various parametric conditions

Purpose This study develops and validates a nonlinear finite element analysis (NLFEA) framework for predicting circular concrete-filled fibre-reinforced polymer (FRP) tube (CFFT) columns under concentric and eccentric axial loading. The framework covers both short and slender columns reinforced with fiber-reinforced polymers (FRP) or steel bars, providing a unified assessment beyond the limited conditions considered in previous studies. It also identifies the key parameters governing column response. Design/methodology/approach NLFEA models were developed and calibrated against experimental results from 17 CFFT column specimens covering different material properties, geometries, slenderness ratios, reinforcement types, and loading eccentricities. Concrete was modeled using the concrete damaged plasticity model, while Hashin’s failure criteria were employed to simulate damage and failure in the FRP tubes. Steel reinforcement was modeled using a bilinear elastoplastic constitutive model, whereas FRP bars were represented as linear elastic materials. Findings The calibrated models accurately reproduced the experimental load-deflection behavior and principal failure patterns of the CFFT columns, demonstrating their capability to capture the nonlinear response of both short and slender columns under concentric and eccentric axial loading. The validated models were subsequently used to conduct a systematic parametric study of FRP tube thickness, load eccentricity, longitudinal FRP reinforcement ratio, and column slenderness ratio. Originality/value The main contribution is a validated NLFEA framework that captures the combined effects of column slenderness, load eccentricity, FRP tube thickness, and reinforcement. Validated against 17 specimens and supported by a systematic parametric study, the framework provides broader insight into CFFT column behavior and supports their assessment and preliminary design.