Study on shear bearing capacity of PVC-CFRP confined concrete column-RC beam exterior joint with core steel tube

In this study, a method of strengthening polyvinyl chloride (PVC)-carbon fiber reinforced polymer (CFRP) confined concrete (PCCC) column-reinforced concrete (RC) beam exterior joint with core steel tube (CST) is proposed. The joints connected by CST can improve the seismic performance without increasing the size of the specimen and have the advantage of easy construction. Eleven PCCC column-RC beam exterior joints were prepared and tested with low cyclic loading to measure the shear capacity of the novel joints. Five factors were considered: the steel ratio of the CST, stirrup ratio of the joint, axial compression ratio, longitudinal reinforcement ratio of the beam, and CFRP strips spacing. The results show that the CST can significantly enhance the stiffness and energy dissipation capacity of the joints, which makes the joints exhibit excellent seismic performance. In addition, the longitudinal reinforcement ratio of the RC beam and CFRP strips spacing had less effect on the shear bearing capacity than the steel ratio of the CST, stirrup ratio of the joint, and axial compression ratio. The shear mechanism of the joints was revealed through experimental studies. Then, it was found that the shear bearing capacity of the joint can be roughly equated to the superposition of the shear forces supported by the concrete diagonal compression truss, stirrups, and CST based on the truss-diagonal compression member model theory and superposition principle. Finally, the formula for calculating the shear bearing capacity of the joints was established.