Moment-curvature restoring force model of PVC-CFRP confined concrete column-RC ring beam joint

To accurately characterize the nonlinear mechanical behavior of polyvinyl chloride-carbon fiber reinforced polymer (PVC-CFRP) confined concrete column-reinforced concrete (RC) ring beam joints under low cyclic loading, 11 ring beam joints are designed based on the principle of "strong members and weak joints" and subsequently fabricated. Various parameters, including the ring beam reinforcement ratio, ring beam width, CFRP strip spacing, axial compression ratio, and frame beam reinforcement ratio, are considered. Generally, as the ring beam reinforcement ratio, ring beam width, axial compression ratio, and frame beam reinforcement ratio increased, the moment-curvature curves of the joint specimens demonstrated improved seismic performance. Subsequently, a simplified model of the moment-curvature skeleton curve is proposed based on the experimental results. Utilizing the simplified model, along with Clough tri-linear degradation model, the hysteretic behavior rules of the joints are formulated, the moment-curvature restoring force model is then developed to simulate the hysteretic behavior, which agrees well with the experimental data.