Compressive behavior of joint core confined with core steel tube for connection of polyvinyl chloride-carbon fiber reinforced polymer-confined concrete column and reinforced concrete beam

The axial compression behavior of a new type of joint wherein the core concrete is confined by a core steel tube while the external concrete is confined by a ring stirrup is investigated in this study. Such a joint core is intended to connect a polyvinyl chloride-carbon fiber reinforced polymer-confined reinforced concrete column and reinforced concrete beam. The failure process and the effects of structural parameters on the mechanical behavior of the joint core are analyzed. Results indicate that the crushing of concrete in the joint core is the predominant failure modes of all specimens. The crack development speed is related to the specimen height and the reinforcement ratio of the core steel tube. The stirrup ratio does not significantly affect the crack development speed but can dominate the crack growth path partially during the crushing of the specimen. In addition, the ultimate bearing capacity of the joint core increases with the decrease in the specimen height, whereas it decreases as the stirrup ratio or reinforcement ratio of core steel tube decreases. Furthermore, a formula for predicting the ultimate bearing capacity of a joint core confined by a core steel tube is proposed based on dimensional analysis associated with the numerical simulations. This study is expected to provide preliminary guideline to facilitate such connection joint cores for structural systems.