Effect of Confinement on High-Strength Concrete Circular Columns Reinforced with GFRP Bars and Spirals

Abstract

The differences in the mechanical properties between steel and glass fibre-reinforced polymer (GFRP) reinforcement, in terms of tensile strength, compressive strength, and stress–strain relationship, necessitate developing independent code provisions for the design of FRP-reinforced concrete (RC) structures. Moreover, due to the lack of experimental data on GFRP-RC circular columns in general and those constructed with high-strength concrete (HSC), in particular, the design provisions remain in need of further research and development. In this study, three full-scale HSC columns with 60 MPa concrete compressive strength were constructed and tested to failure under eccentric loading. One specimen was reinforced with steel as a control specimen, while the other two were constructed using GFRP longitudinal and spiral reinforcement. The test variable was the pitch of the spiral reinforcement, which varied between 50 and 85 mm. The specimens had a diameter of 350 mm, a length of 1,750 mm, and 1.23% longitudinal reinforcement ratio. The results showed that a spiral pitch of 85 mm was adequate to confine the concrete core of the column under eccentric load.