Flexural Capacity of Fiber-Reinforced Polymer-Confined Concrete Column–Ring Beam Exterior Joints under Low Cyclic Loading

Abstract

In this research, low cyclic loading tests were conducted on 10 polyvinyl chloride (PVC) carbon fiber–reinforced polymer (CFRP)-confined concrete column–ring beam exterior joints (PCRBEJs) and one PVC tube-confined concrete column–ring beam exterior joint. The effects of ring beam reinforcement ratio (ρr), CFRP strip spacing (sf), ring beam width (b), frame beam longitudinal reinforcement ratio (ρb), and axial compression ratio (n) on seismic behavior were examined. The test results demonstrated that the specimens with a low ρb value failed in flexure in frame beams. In contrast, specimens with a high ρb value were damaged by shear failure in ring beam joints. The increase in ρr, b, or n augmented the cracking and peak loads, whereas the impacts of sf and ρb on these loads were marginal. The effects of the investigated variables on the strains in ring reinforcement, ring beam stirrups, and frame beam longitudinal reinforcement were analyzed in detail. Considering the effect of b, the yields nonuniformity coefficients of ring reinforcement and ring beam stirrups (ωrs and ωss, respectively) were introduced, and a formula for conveniently estimating the flexural capacity of PCRBEJs under low cyclic loading was proposed. The formula was validated by the good agreement between its results and experimental data.