Abstract:
Eleven PVC-CFRP confined concrete column-reinforced concrete ring beam exterior joints are tested under low cyclic loading. The effects of the ring beam width, reinforcement ratio of ring reinforcement, spacing of CFRP strips, reinforcement ratio of frame beam and axial compression ratio on the failure mode, hysteretic behaviors and skeleton curves are analyzed. The test results show that the failure of typical specimens experiences four stages, i.e., initial crack, crack penetration, limit and failure. The moment-curvature hysteretic curve consists of elastic stage, elastic-plastic stage and stationary stages. The hysteresis loops are full, indicating that the specimens exhibit excellent seismic behaviors. By considering the effects of the above parameters on the characteristic points of moment-curvature skeleton curves, the simplified formulas for predicting the characteristic points are proposed based on the softening constitutive model of concrete. On the basis of the degenerate trilinear hysteretic model, the calculation formula for unloading stiffness and the hysteretic rule are proposed, and a moment-curvature hysteretic model of the joints is established with high accuracy.