Previous studies have confirmed the vulnerability of reinforced concrete (RC) knee joints under cyclic loading, however, there remains a lack of studies on their seismic retrofitting. This study proposes a retrofit strategy aimed at enhancing the seismic performance of knee joints by acknowledging their unique behavior. The strategy involves a novel arrangement of steel plates that optimizes the effectiveness of steel haunch and external prestressing methods. To evaluate this approach, six full-scale knee joint specimens—two controls and four retrofitted—were fabricated using nonseismic reinforcement details and subjected to reversed cyclic loading. Vital parameters, including load, displacement, and strain responses along the reinforcement bars and steel plates, were monitored throughout the tests. The specimens retrofitted with this newly proposed strategy demonstrated a significant improvement in seismic performance by effectively distributing the prestressing force to the core of the joint and promoting beam flexural failure. The lateral strength significantly increased, with maximum enhancements of 100 % and 200 % under closing and opening rotations, respectively. Additionally, the retrofitted specimens dissipated at least 100 % more cyclic energy compared to the control specimens. Furthermore, the proposed distribution of the prestressing force within the joint core was instrumental in restraining the expansion of diagonal cracks. Consequently, this study makes a substantial contribution to the body of knowledge on RC knee joints and promotes their practical implementation under different conditions.

中文翻译：

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非延性钢筋混凝土膝关节钢拱外预应力抗震改造策略


以往的研究已经证实了钢筋混凝土（RC）膝关节在循环荷载作用下的脆弱性，但仍缺乏对其抗震加固的研究。这项研究提出了一种改造策略，旨在通过承认膝关节的独特行为来增强其抗震性能。该策略涉及一种新颖的钢板布置，可优化钢腋和外部预应力方法的有效性。为了评估这种方法，使用抗震加固细节制造了六个全尺寸膝关节样本（两个对照样本和四个改装样本），并承受反向循环载荷。在整个测试过程中，对重要参数进行监测，包括沿钢筋和钢​​板的载荷、位移和应变响应。采用这种新提出的策略进行改造的样本通过有效地将预应力分布到节点核心并促进梁弯曲破坏，显示出抗震性能的显着改善。侧向强度显着增加，在闭合和打开旋转下分别最大增强 100% 和 200%。此外，与对照样本相比，改装样本的循环能量消耗至少多 100%。此外，所提出的接头核心内预应力的分布有助于抑制对角裂缝的扩展。因此，这项研究对 RC 膝关节的知识体系做出了重大贡献，并促进了它们在不同条件下的实际实施。