Slender GFRP-RC Circular Columns under Concentric, Eccentric, and Flexural Loads: Experimental Investigation

The experimental results for large-scale slender circular reinforced concrete (RC) columns are presented and discussed in this study. One reference column was reinforced with steel bars and spirals, and five columns were reinforced with glass fiber–reinforced polymer (GFRP) bars and spirals. The columns were tested under axial loads with variable eccentricities or flexural loading configurations. The test variables included reinforcement type (GFRP and steel), loading type (axial and four-point bending), the ratio of eccentricity-to-column diameter, and the slenderness ratio. Test results revealed that as the eccentricity increased, the peak axial load and the axial and lateral stiffness decreased significantly. Similarly, for the same eccentricity, a reduction in the peak load and both axial and lateral stiffnesses was observed when the slenderness ratio increased. In addition, interaction diagrams for circular GFRP-RC short and slender columns were developed from the experimental results and compared to those obtained analytically. Moreover, a simple modification to account for the slenderness effect on the interaction diagram was proposed.