Axial-Flexural Interactions of GFRP-CFFT Columns with and without Reinforcing GFRP Bars

This study presents the results of an experimental program and analytical modeling for axial-flexural interactions of concrete-filled glass fiber–reinforced polymer tube (GFRP-CFFT) columns with and without reinforcing glass fiber–reinforced polymer (GFRP) bars. The experimental program included four steel RC specimens, four GFRP-CFFT specimens, and four GFRP bar–reinforced GFRP-CFFT specimens with an outer diameter of 205–206 mm and a height of 800–812 mm. The specimens were tested under concentric and 25- and 50-mm eccentric axial loads and four-point load. The experimental results showed that GFRP bar–reinforced GFRP-CFFT specimens sustained higher peak axial loads, axial and lateral deformations at peak axial load, and flexural loads than GFRP-CFFT specimens without reinforcing GFRP bars and steel RC specimens. Axial load and bending moment (P-M) interactions of GFRP-CFFT specimens with and without reinforcing GFRP bars and steel RC specimens were analytically modeled. A parametric study was conducted to evaluate the effects of actual confinement ratio and GFRP bar reinforcement ratio on P-M interactions of GFRP-CFFT specimens. The P-M interactions were found to be significantly affected by both actual confinement ratio and GFRP bar reinforcement ratio.