Research On Hysteretic Behaviors Of FRP-PVC Tube Confined Reinforced Concrete Beam-columns

To study the seismic behaviors of circular reinforced concrete columns confined by FRP-PVC tubes under low-cyclic reversed loading, a total of six specimens were prepared and tested under cyclic reversed loading. The experimental parameters included the axial force ratio, the layers and the types of FRP. The failure modes, hysteretic characteristics, ductility, energy dissipation, and rigidity degradation were also studied.On the basis of the fiber model at OpenSEES (Open System for Earthquake Engineering Simulation), a nonlinear numerical procedure was developed by adopting appropriate geometric model and material model, which is used to analyze the hystereic performance. After the numerical model was validated by the experimental results, parameter analyses were conducted using the verified numerical model. It was found that the constraint stress of FRP (f1), the level of axial load, concrete strength, and slenderness ratio were the key factors. The longitudinal reinforcement ratio (ps) had significant influence on the horizontal bearing capacity and energy dissipation, however, little effect on the ductility.On basis of stress-strain relationship of FRP-PVC tube confined concrete, the carrying-capacity formula of FRP-PVC tube confined reinforced concrete columns under axial load and moment was developed. Based on hysteresis curves of FRP-PVC tube confined reinforced concrete columns, skeleton curves characteristics and unloading stiffness degradation rules were summarized. On the basis of the theoretical analysis, the moment-curvature hysteresis model and load-displacement hysteresis model for FRP-PVC tube confined reinforced concrete columns were established, and the validity was testified by experimental and simulation results.