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.

中文翻译：

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聚氯乙烯-碳纤维增强聚合物约束混凝土柱与钢筋混凝土梁连接用芯钢管约束节点芯受压性能

本研究研究了一种新型节点的轴压行为，其中核心混凝土由核心钢管约束，外部混凝土由环形箍筋约束。这种连接核心用于连接聚氯乙烯-碳纤维增强聚合物-约束钢筋混凝土柱和钢筋混凝土梁。分析了破坏过程和结构参数对关节芯力学行为的影响。结果表明，混凝土在接缝核心处的破碎是所有试件的主要破坏模式。裂纹发展速度与试件高度和芯钢管配筋率有关。箍筋比不会显着影响裂纹发展速度，但可以在试样破碎过程中部分支配裂纹扩展路径。此外，节点核心的极限承载力随着试件高度的降低而增加，而随着核心钢管的箍筋率或配筋率的降低而降低。此外，基于与数值模拟相关的尺寸分析，提出了用于预测由核心钢管约束的节点核心的极限承载力的公式。预计这项研究将为促进结构系统的这种连接接头芯提供初步指导。而随着核心钢管箍筋率或配筋率的减小而减小。此外，基于与数值模拟相关的尺寸分析，提出了用于预测由核心钢管约束的节点核心的极限承载力的公式。预计这项研究将为促进结构系统的这种连接接头芯提供初步指导。而随着核心钢管箍筋率或配筋率的减小而减小。此外，基于与数值模拟相关的尺寸分析，提出了用于预测由核心钢管约束的节点核心的极限承载力的公式。预计这项研究将为促进结构系统的这种连接接头芯提供初步指导。