Stress–strain model for FRP-confined concrete under cyclic axial compression

One important application of fibre-reinforced polymer (FRP) composites in construction is as FRP jackets to confine concrete in the seismic retrofit of reinforced concrete (RC) structures, because FRP confinement can enhance both the compressive strength and ultimate strain of concrete. For the safe and economic design of FRP jackets, the stress–strain behaviour of FRP-confined concrete under cyclic compression needs to be properly understood and modelled. This paper presents a stress–strain model for FRP-confined concrete under cyclic axial compression. The model consists of the following major components: (a) a monotonic stress–strain model for FRP-confined concrete developed by the authors in a previous study for predicting the envelope curve; (b) new algebraic expressions for predicting unloading and reloading paths; and (c) predictive equations for determining the permanent strain and stress deterioration, with the effect of loading history duly accounted for. The capability and accuracy of the proposed model in predicting the complete stress–strain history of FRP-confined concrete under cyclic axial compression are demonstrated through comparisons between predictions of the proposed model and test results.