Flexural behavior of GFRP tube reinforced hollow high strength concrete columns

To address the corrosion deterioration and long‐term serviceability of traditional prestressed high‐strength concrete (PHC) piles in marine environments, a novel GFRP tube‐confined reinforced hollow high‐strength concrete (GRHHC) system is proposed. Four‐point bending tests were conducted on three series of GRHHC specimens to investigate their failure modes, load‐deflection responses, and strain distributions. A nonlinear finite element model was established in Abaqus and used to examine the effects of GFRP tube thickness, fiber winding angle, concrete strength, and longitudinal reinforcement ratio on flexural performance. The results showed that the specimens exhibited compression‐governed failure characterized by crushing of the core concrete in the compression zone, while the sectional strain distribution satisfied the plane‐section assumption. Increasing the GFRP tube thickness from 4 mm to 6 mm and 8 mm increased the flexural capacity by 4.3% and 16.9% and the ductility by 17.1% and 39.0%, respectively. Decreasing the winding angle or increasing the longitudinal reinforcement ratio also improved the flexural performance. A GFRP tube thickness of 8–10 mm and a winding angle of 45°–65° are therefore recommended. Based on the observed failure mechanism, a simplified theoretical model was developed using conventional beam theory, and its predictions agreed well with the experimental and finite element results, providing a practical basis for the flexural design of GRHHC members.