Diagonal bars anchored in beams have been proven to be an effective reinforcement detail for reinforced concrete interior beam-column joints (BCJs) in mitigating the congestion of conventional stirrups without compromising their seismic performance. This paper investigates the effects of bonding condition and diameter of diagonal bars on the seismic performance of interior BCJs. Four interior BCJ specimens, including one control specimen reinforced with conventional stirrups and three others reinforced with diagonal bars, were fabricated and tested under cyclic loading. The results show that the control specimen fails with plastic hinges formed at the beam-joint interfaces, while all other specimens fail with relocated plastic hinges on the beams. The two BCJ specimens reinforced with bonded and debonded diagonal bars show similar improvement over the control specimen in terms of joint damage level, loading capacity, energy dissipation, stiffness degradation, and bonding condition of beam longitudinal reinforcement. For instance, the BCJ specimens reinforced with bonded and debonded diagonal bars possess 9% and 12% higher loading capacity, and 13% and 7% higher energy dissipation than the control specimen. Debonding the diagonal bars can slightly reduce joint cracks but has marginal effect on the overall performance of BCJs. In addition, the debonding treatment weakens the contribution of the diagonal bars to joint shear resistance, as evidenced by the increased strain in joint stirrups. Furthermore, increasing the diameter of debonded diagonal bars enhances the ductility and energy dissipation of the BCJ specimens since this improves their buckling resistance after concrete spalling. In addition, finite element models for BCJs were developed and validated for parametric study. The simulation results indicate that insufficient diagonal bars can lead to unsuccessful relocation of plastic hinges in BCJs, which decreases the loading capacity and accelerates the load degradation. With similar total sectional area, reducing the number of diagonal bars deteriorates their anchorage in beams. This consequently weakens the flexural capacity at beam ends, leading to unsuccessful plastic hinge relocation and poor seismic performance of BCJs.

中文翻译：

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斜筋钢筋混凝土梁柱节点试验与数值研究：粘接条件和直径的影响

锚固在梁上的对角钢筋已被证明是钢筋混凝土内部梁柱接头 (BCJ) 的有效加固细节，可减轻传统箍筋的拥堵，同时又不影响其抗震性能。本文研究了粘结条件和斜筋直径对内部BCJ抗震性能的影响。制作了四个内部 BCJ 试件，其中包括一个用传统箍筋加固的对照试件和另外三个用斜杆加固的试件，并在循环载荷下进行了测试。结果表明，控制试件因梁-接头界面处形成的塑性铰链而失效，而所有其他试件因梁上重新定位的塑性铰链而失效。用粘结和脱粘斜筋加固的两个 BCJ 试件在接头损伤水平、承载能力、能量耗散、刚度退化和梁纵向钢筋的粘结条件方面与对照试件相比显示出类似的改进。例如，用粘合和脱粘斜筋加固的 BCJ 试件的承载能力比对照试件高 9% 和 12%，能量耗散分别高 13% 和 7%。对角钢筋脱粘可以稍微减少接头裂纹，但对 BCJ 的整体性能影响有限。此外，脱粘处理削弱了对角钢筋对接头抗剪力的贡献，接头箍筋应变的增加证明了这一点。此外，增加脱粘斜杆的直径可以增强 BCJ 样本的延展性和能量耗散，因为这可以提高混凝土剥落后的抗屈曲能力。此外，还开发并验证了 BCJ 的有限元模型以进行参数研究。仿真结果表明，斜杆不足会导致BCJ中塑料铰链的重新定位失败，从而降低承载能力并加速载荷退化。在总截面积相似的情况下，减少对角钢筋的数量会降低其在梁中的锚固力。这会削弱梁端的抗弯能力，导致塑性铰重新定位不成功，BCJ 的抗震性能较差。