Behavior of GFRP-RC columns under axial compression: Assessment of existing models and a new axial load-strain model

Concrete structures reinforced with fiber-reinforced polymer (FRP) bars (referred to as FRP-RC structures) are becoming increasingly popular, whereas there is a lack of a robust full-range axial load-strain model for FRP-RC columns, which is fundamental for the design and advanced analysis of FRP-RC structures. To this end, a review and assessment of existing confined compressive concrete ultimate axial stress (or strain) models (including models for glass FRP (GFRP) spiral-confined concrete (GFSCC) and models for FRP partially confined concrete (FPCC)) against a newly established database are reported in this paper. The comparisons show that the models of FPCC are applicable to GFSCC. A new design-oriented full-range axial load-strain model is then proposed for GFRP-RC columns of circular cross-section by explicitly considering the behavior of three key components in FRP-RC columns, namely, confined concrete core, FRP longitudinal reinforcement and concrete cover. The novelty of the proposed model is that the constitutive models of the three components in FRP-RC columns can be considered in separation. The proposed model, which is able to capture the strain softening behavior properly, provides satisfactory predictions of the axial load-strain test curves of FRP-RC columns.