Identification of material parameters for Drucker-Prager plasticity model for FRP confined circular concrete columns

Existing research works have established that Drucker-Prager (DP) plasticity model is capable of modeling stress-strain behavior of confined concrete. However, accuracy of the model largely depends on adequate evaluation of its parameters that determine the yield criterion, hardening/softening rule and flow rule. Through careful analytical studies of test results of FRP confined concrete columns under theoretical framework of the DP model, it is found that: (1) the hardening/softening rule is governed by plastic strains and the FRP stiffness ratio; (2) the friction angle decreases slightly with an increase in plastic deformation; and (3) the plastic dilation angle is a function of both axial plastic strain and the FRP stiffness ratio. Explicit models for these properties are developed from analytical studies. By implementing the proposed models in ABAQUS, finite element analyses can well predict stress-strain responses of FRP confined concrete columns.