Function alteration and revision of seismic design codes require the improvement of seismic performance of existing spatial RC joints. An innovative and practical seismic retrofitting method using steel haunch system is recommended for existing spatial RC joints with the floor slab and the transverse beam. Four spatial RC joints were designed including one control specimen without strengthening, three retrofitted specimens strengthened with only steel haunches, combined steel haunches and carbon fibre-reinforced polymer (CFRP) sheets, and combined steel haunches and bolted side plates (BSP) on beam's sides. All specimens were subjected to low-cycle reversed loading. The effects of different retrofit methods on failure modes, crack patterns, hysteretic behavior, ultimate load capacity, stiffness degradation, ductility factor, and energy dissipation capacity were analyzed. Results showed that hysteretic curves of retrofitted specimens were more stable and plump. The plastic hinge of spatial joints was transferred from the beam end to the zone outside steel haunch after retrofit. The ultimate load capacity, stiffness, ductility and cumulative hysteresis energy were significantly enhanced with a maximum proportion of 63.8%, 315%, 30% and 165%, respectively. Steel haunch can be effectively combined with bolted side plates and CFRP in the strengthening of RC beam-column-slab joints to make full use of material properties. The preload degradation of the bolts used to install the steel haunch reduced the retrofit efficiency. Combined steel haunches and BSP exhibited the best cooperative performance with the spatial joint. The strains demonstrated that the steel haunches were still in the elastic stage and subjected to eccentric loading during the entire loading stage. Finite element models of retrofitted joints were established based on ABAQUS. The load-displacement curves calculated by ABAQUS agreed well with test results. Numerical analysis shows the stress and strain contribution of each component which is helpful to further optimize this retrofit system.

功能变更和抗震设计规范的修订需要提高现有空间钢筋混凝土节点的抗震性能。对现有的楼板和横梁空间钢筋混凝土节点推荐了一种创新实用的抗震加固方法，采用钢拱体系。设计了四个空间钢筋混凝土接头，包括一个没有加强的对照试件，三个仅用钢腰部加强的改造标本，组合钢腰部和碳纤维增强聚合物（CFRP）板，以及组合钢腰部和梁侧螺栓侧板（BSP） . 所有试样均承受低周反向载荷。不同改造方法对失效模式、裂纹模式、滞后行为、极限承载能力、刚度退化、延展系数的影响，和能量耗散能力进行了分析。结果表明，改造后的试件滞后曲线更加稳定、丰满。改造后，空间节点的塑性铰从梁端转移到钢拱外区域。极限承载能力、刚度、延性和累积滞后能显着提高，最大比例分别为63.8%、315%、30%和165%。在钢筋混凝土梁柱板节点的加固中，钢拱肋可以与螺栓连接的侧板和CFRP有效结合，充分利用材料特性。用于安装钢制臀部的螺栓的预载退化降低了改造效率。组合钢臀部和 BSP 与空间关节表现出最佳的协同性能。应变表明钢臀部仍处于弹性阶段，并在整个加载阶段受到偏心加载。基于ABAQUS建立改造节点有限元模型。ABAQUS 计算的荷载-位移曲线与试验结果吻合较好。数值分析显示了每个组件的应力和应变贡献，这有助于进一步优化该改造系统。