Plastic hinge characteristics of RC rectangular columns with Fiber Reinforced Polymer (FRP)

This study is based on extending the previous research work entitled Fiber reinforced polymers (FRP) confined columns that published by the authors. The modeling characteristics for plastic hinges of RC columns have been determined in FEMA 356. However, for evaluating a retrofitted member, there are no parameters for one. This issue is an important deficiency of the mentioned code. The main purpose of this study is to introduce the plastic hinge parameters for the RC rectangular columns that are retrofitted by FRP. These characteristics of plastic hinges can be used in a nonlinear static analysis, instead of nonlinear dynamic one. In order to analytical simulation of RC column behavior and also accuracy of acquired results, at first using LS-DYNA software including 3D nonlinear finite element modeling, a RC column studied in the literature has been verified. The obtained results are showed a good match between both Finite element model and experimental test and there are reasonable correlations between ones. Moreover in the next stage, in order to evaluate the robustness of the proposed method 20 reinforced concrete columns which supposed to be fixed at one end, have been retrofitted using FRP in the plastic hinge zone. The columns have been simulated under a constant compressive load and lateral cyclic displacement that the hysteresis curves have been drawn for obtaining the plastic hinge parameters. Numerical results demonstrate that the plastic hinge parameters have averagely been increased after retrofitting with a thickness of CFRP about 0.165 mm.