Lateral Force–Displacement Hysteretic Model for CFRP (Carbon Fiber-Reinforced Polymer)-Retrofitted Square RC Columns

In this study, the lateral force–displacement hysteretic performance of FRP-retrofitted square reinforced concrete (RC) columns was numerically investigated. The finite element (FE) model for CFRP-retrofitted square RC columns was established by utilizing software OpenSees 3.7.1 A nonlinear force-based beam–column element with a fiber section was employed to simulate the RC column. Specifically, a self-developed stress–strain model was adopted to represent the confined concrete within the FRP-retrofitted region. After verifying the accuracy of the numerical simulation analysis results, parametric analysis was conducted to comprehend the influences of key parameters such as section size, axial compression ratio, shear/span ratio, number of layers of FRP wrap, steel reinforcement ratio, and concrete strength on the characteristic points of the lateral force–displacement curve of retrofitted columns. Subsequently, a lateral force–displacement hysteretic model for CFRP-retrofitted square RC columns was proposed. The proposed model consists of a trilinear skeleton curve and an unloading/reloading rule. By comparing it with the test results, it is shown that the proposed hysteretic model has a relatively high level of accuracy.