Strength and ductility of concrete cylinders confined with FRP composites

Based on results from more than 300 specimens of fiber reinforced polymer (FRP) confined concrete cylinders covering a wide range of parameters, the confinement effect and failure mechanisms are analyzed. Special attention is given to predict whether FRP-confined concrete cylinder has a strain-hardening or a strain-softening response. In the case of FRP-confined concrete cylinder with a strain-hardening response, it is found that the ultimate Poisson’s ratio of FRP-confined concrete trends to an asymptotic value. Through calculation of the ultimate Poisson’s ratio, and according to strain compatibility, the ultimate strain of FRP-confined concrete can be predicted. Moreover, by comparing with a lot of existing experimental data, the proposed models are quite simple and still accurate enough, which can be applied to the concrete cylinders confined with various types of FRP composites. Besides, for the case of FRP-confined concrete cylinder with a strain-softening response, equations for predicting the maximum strength, peak strain, ultimate strength and ultimate strain are suggested in this paper.