This study examines the flexural performance of reinforced concrete (RC) columns strengthened through a seismic jacket technique developed using a prefabricated steel bar unit that forms peripheral closed hoops and supplementary V ties, satisfying the design requirements of the ACI 318-14 seismic provisions. Three RC jacketed columns were prepared with a parameter of axial load levels and tested under a constant concentric axial load and cyclic lateral loads. Analytical approaches were also applied to examine the axial load–moment interaction of the RC jacketed columns when considering the confinement effect provided by the jacket section and to investigate the applicability of the previous performance-based design models proposed for virgin seismic columns. The test results show that the developed jacket technique possesses a good potential in enhancing the flexural stiffness, strength and ductility of deficient columns, even under a high axial load. Reinforced concrete jacketed columns possess a higher ductility than that estimated using the ductility parameter model, regardless of the axial load level. Thus, the jacket section including the seismic details of a transverse reinforcement can be conservatively designed, based on the axial load–moment interaction and ductility parameter model for the moment and ductility enhancements required by deficient columns.

中文翻译：

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不同轴向荷载作用下RC夹套柱的抗震性能

本研究检查了通过地震套管技术加强的钢筋混凝土 (RC) 柱的弯曲性能，该技术使用预制钢筋单元开发，该单元形成外围封闭箍和补充 V 型连接，满足 ACI 318-14 抗震规定的设计要求。三根钢筋混凝土夹套柱以轴向载荷水平为参数，并在恒定的同心轴向载荷和循环横向载荷下进行测试。考虑到夹套截面提供的限制效应时，还应用了分析方法来检查 RC 夹套柱的轴向载荷 - 力矩相互作用，并研究先前为原始抗震柱提出的基于性能的设计模型的适用性。测试结果表明，即使在高轴向载荷下，所开发的夹套技术在提高缺陷柱的抗弯刚度、强度和延展性方面也具有良好的潜力。无论轴向载荷水平如何，钢筋混凝土夹套柱都具有比使用延性参数模型估计的更高的延性。因此，可以根据轴向荷载-力矩相互作用和延性参数模型来保守地设计包括横向钢筋抗震细节的导管架截面，以用于不足柱所需的弯矩和延性增强。与轴向载荷水平无关。因此，可以根据轴向荷载-力矩相互作用和延性参数模型来保守地设计包括横向钢筋抗震细节的导管架截面，以用于不足柱所需的弯矩和延性增强。与轴向载荷水平无关。因此，可以根据轴向荷载-力矩相互作用和延性参数模型来保守地设计包括横向钢筋抗震细节的导管架截面，以用于不足柱所需的弯矩和延性增强。