Pei Qiang, Wu Cong, Cheng Zhi, Ding Yu, Guo Hang
College of Architectural Engineering, Dalian University, Dalian 116622, China.
Department of Construction Engineering Management, Southwest Jiaotong University Hope College, Chengdu 610400, China.
Materials (Basel). 2022 Feb 24;15(5):1704. doi: 10.3390/ma15051704.
In order to improve the deformation energy consumption and self-centering ability of reinforced concrete (RC) frame beam-column joints for main buildings of conventional islands in nuclear power plants, a new type of self-centering joint equipped with super-elastic shape memory alloy (SMA) bars and a steel plate as kernel components in the core area of the joint is proposed in this study. Four 1/5-scale frame joints were designed and manufactured, including two contrast joints (a normal reinforced concrete joint and a concrete joint that replaces steel bars with SMA bars) and two new model joints with different SMA reinforcement ratios. Subsequently, the residual deformation, energy dissipation capacity, stiffness degradation and self-centering performance of the novel frame joints were studied through a low-frequency cyclic loading test. Finally, based on the OpenSees finite element software platform, an effective numerical model of the new joint was established and verified. On this basis, varying two main parameters, the SMA reinforcement ratio and the axial compression ratio, a simulation was systematically conducted to demonstrate the effectiveness of the proposed joint in seismic performance. The results show that replacing ordinary steel bars in the beam with SMA bars not only greatly reduces the bearing capacity and stiffness of the joint, but also makes the failure mode of the joint brittle. The construction of a new type of joint with consideration of the SMA reinforcement and the steel plate can improve the bearing capacity, delay the stiffness degradation and improve the ductility and self-centering capability of the joints. Within a certain range, increasing the ratio of the SMA bars can further improve the ultimate bearing capacity and energy dissipation capacity of the new joint. Increasing or decreasing the axial compression ratio of column ends has little effect on the overall seismic performance of new joints.
为提高核电站常规岛主厂房钢筋混凝土（RC）框架梁柱节点的变形能耗和自复位能力，本研究提出一种新型自复位节点，该节点在节点核心区设置超弹性形状记忆合金（SMA）筋和钢板作为核心部件。设计制作了4个1/5缩尺的框架节点，包括2个对比节点（普通钢筋混凝土节点和用SMA筋代替钢筋的混凝土节点）和2个不同SMA配筋率的新型节点。随后，通过低周反复加载试验研究了新型框架节点的残余变形、耗能能力、刚度退化和自复位性能。最后，基于OpenSees有限元软件平台，建立并验证了新型节点的有效数值模型。在此基础上，通过改变SMA配筋率和轴压比这两个主要参数，系统地进行了模拟，以证明所提节点在抗震性能方面的有效性。结果表明，用SMA筋代替梁中的普通钢筋不仅会大大降低节点的承载力和刚度，还会使节点的破坏模式变脆。考虑SMA配筋和钢板的新型节点的构造可以提高节点的承载力，延缓刚度退化，提高节点的延性和自复位能力。在一定范围内，增加SMA筋的配筋率可以进一步提高新型节点的极限承载力和耗能能力。柱端轴压比的增大或减小对新型节点的整体抗震性能影响不大。
