Effect of GFRP Reinforcement Ratio on the Strength and Effective Stiffness of High-Strength Concrete Columns: Experimental and Analytical Study

Abstract

This paper reports the axial–flexural test results for 12 high-strength concrete (HSC) columns reinforced with glass fiber-reinforced polymer (GFRP) rebars to evaluate the implication of using HSC. The parameters were the applied eccentricity, the longitudinal GFRP reinforcement ratio, and concrete compressive strength and investigate their influence on the load-carrying capacity, deflection, ductility, strains in the concrete and reinforcement, failure modes, and flexural stiffness. All the columns failed in a compression failure mode due to concrete crushing. The GFRP bars developed higher tensile strains in the HSC due to the axial–flexural load compared to columns made with normal-strength concrete (NSC). A minimum reinforcement ratio of 1% in the case of HSC proved practical. Increasing the reinforcement ratio to 2.5% improved the postpeak behavior and yielded a second peak for specimens tested at eccentricities corresponding to 30%, 40%, and 60% of the cross-sectional depth. This study integrated the results to develop an analytical model able to establish moment–curvature and effective-stiffness relationships. The results were also evaluated for the tested specimens and compared to the theoretical expressions used for NSC.