Abstract
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.
Highlights
Introduction published maps and institutional affilAt present, nuclear power plants have adopted higher seismic design criteria according to the seismic hazard evaluation of the site
The bearing capacity of the cause the Young’s modulus of the shape memory alloy (SMA) bars (65.4 GPa) is much smaller t new joint PSJD-1 is relatively stable after yield and can withstand relatively larger the steel bars deformation, indicating that the built-in super-elastic SMA reinforcement-steel end plate can yield delay the yield the of theyield joint todisplacement a certain extent and improve the ductility
In order to further study the new frame joints to further optimize the design, considering that the PSJD-2 joints failed earlier in the test and failed to fully reflect the influence of SMA reinforcement ratio on the related performance of the new joints, based on the verified finite element analysis model, the parameters such as the reinforcement ratio and the axial compression ratio of the built-in SMA bars in the new joints were simulated and analyzed to further quantify their effects on the mechanical properties, such as hysteretic performance, energy dissipation, and the self-centering ability of the new joints
Summary
Factured, including two self-centering new beam-to-column joint models nu longitudinal reinforcement plus hybrid joints wi diameters of beam-to-column. Four frame joints withand a scale ratio of 1:5 were designed manufactured, including two self-centering new beam-to-column models numbered by crete beam-to-column joints numbered by PJD-1, joint. The geometric dimensions of each specimen were the sam diameters of SMA reinforcement) and two comparative joints The fixe crete beam-to-column joints numbered by PJD-1, SMA reinforced beam-to-column joints requiredbyinSJD-1). This The experiment of played the role ofthe connecting shape me numbered geometric dimensions each specimen were same and were made to the currentthe concrete specifications inreinforcement.
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