Damage-plasticity model for FRP-confined normal-strength and high-strength concrete

This paper presents a modified damage-plasticity model for fiber-reinforced polymer (FRP)-confined normal-strength and high-strength concrete (NSC and HSC). The proposed model is based on a concrete damage-plasticity model from the literature, which is improved through accurate incorporation of the effects of the confinement level, concrete strength, and nonlinear dilation behavior of FRP-confined concrete. The proposed model uses a new and accurate failure surface and flow rule that were established using a comprehensive and up-to-date experimental test database and it incorporates an analytical rupture strain model for the FRP jacket. Finite-element (FE) models incorporating the proposed damage-plasticity model are developed and validated for concretes having up to 110-MPa compressive strength confined by different types of FRP under a wide range of confining pressures. Comparisons with experimental results show that the model's predictions of (1) axial stress-axial strain, (2) lateral strain-axial strain, (3) axial stress-volumetric strain, (4) plastic volumetric strain-axial plastic strain, and (5) plastic dilation angle-axial plastic strain relations are in good agreement with the test results of FRP-confined NSC and HSC. The accurate predictions of the compressive strength and ultimate axial strain of FRP-confined concrete were achieved by establishing the hardening/softening rule and flow rule based on the level of confining pressure and modeling the failure surface of the confined concrete by incorporating the effect of unconfined concrete strength.