Strength model for concrete columns reinforced with fiber-reinforced polymer bars and ties

Few studies are available on members reinforced internally with fiber-reinforced polymer (FRP) bars and subjected to compressive axial load; therefore, the behavior of FRP internally reinforced concrete columns has not been well established. In this paper, experimental results of 23 nearly full-scale square concrete columns reinforced transversally with glass FRP (GFRP) and carbon FRP (CFRP) ties, and longitudinally with GFRP, CFRP, and steel bars, and subjected to concentric monotonic axial compression were used to develop a strength model. Experimental results showed that FRP ties significantly increased concrete strength and ductility. The proposed confinement model for this new FRP application takes into consideration transverse reinforcement volumetric ratio, strength, spacing, and configuration, as well as longitudinal bar distribution. The proposed strength model provides good predictions of stress and strain with respect to the experimental results. © 2014, American Concrete Institute.