The building's superstructure is made into a whole, and a slip surface is placed between the superstructure and the building foundation, allowing the building to slide horizontally relative to the foundation in the event of an earthquake. Due to the frictional slipping effect, the transmission of the upper part of the earthquake is weakened. At the same time, during the sliding process, the seismic energy is dissipated by the friction, thereby achieving the effect of damping. The vibration isolation layer is composed of a friction sliding mechanism and a damping centripetal mechanism, wherein the friction sliding mechanism functions to isolate the earthquake, and the damping centripet mechanism functions as a limit reset. The damped centripetal mechanism is generally a combination of additional damping and return springs. The stiffness of the return spring has a very significant effect on the isolation effect of the isolation system. In this paper, an example is given to quantitatively analyze the influence of the stiffness of the return spring on the isolation effect of the isolation system, and the reference recommendations for the selection of the return spring stiffness are given. For the linear elastic resilience model. In this way, an overall model of the isolation system as shown can be obtained. 113 The equation of motion equation is under the action of earthquake ground motion, with the change of the ground motion input and the dynamic reaction state, it is in the alternating between the sliding state and the non-sliding state of the base. Therefore, two different sets of motion equations should be used to describe them separately.
Seismic isolation analysis of each layer quality and stiffness layer Story mass P105kgMass stiffness This paper uses Newmark method to calculate the dynamic response, using Fortran90 language to compile the dynamic response time history analysis program of the isolation system, analyze a 6-layer mixed isolation structure The specific parameters of the quality and stiffness of each layer of the structure are listed. The vibration isolation layer of the structure is composed of a horizontal friction mechanism and a centripetal reset mechanism arranged in groups, wherein the friction sliding isolation mechanism adopts a high molecular polymer as a friction material, and the sliding friction coefficient design value of the material is 011, and the damping ratio is also Take 011, the centripetal reset mechanism uses a petal-like coil spring. The construction site is designed according to the seismic intensity of 8 degrees, near earthquake and apes. The input seismic wave is the EICentr wave in the NS direction of 1940.
For ease of study and generality of the problem, the stiffness of the return spring herein is expressed as a multiple of the total weight of the superstructure. Fix other parameters of the isolation structure, change the stiffness of the return spring, calculate the corresponding maximum tip absolute acceleration response, the maximum underlying relative displacement response and the maximum slip of the substrate, and plot the results in and.
It can be seen from the sum, the overall trend of the maximum absolute acceleration response of the top layer and the maximum relative displacement response of the bottom layer is increased with the increase of the stiffness of the spring of the isolation spring of the complex structure, such as Li Hongmei et al. Large, but in the process of increasing, the maximum acceleration response value fluctuates continuously. In general, as the stiffness of the spring of the isolation system increases, the isolation effect of the isolated structure on the peak acceleration response and the peak displacement response will decrease. It can be seen that when the stiffness of the return spring is less than 1 times the total weight of the superstructure, the maximum slip amount of the base changes sharply, and when the stiffness of the return spring increases from 1 times to 10 times the total weight of the superstructure, the base The maximum slip amount changes gently and remains substantially between 418516 cm.
Conclusion Based on the above analysis results, it can be seen that with the increase of the spring stiffness of the isolation system, the isolation effect of the isolation structure will be reduced, but if the stiffness of the return spring is too small, the maximum slippage of the base will increase. Therefore, the above factors should be considered comprehensively, and the stiffness of the return spring should be appropriately selected. It can be seen from the above analysis that if the stiffness of the return spring is 15 times of the total weight of the superstructure, the maximum slip of the base of the isolated structure is not large, and the isolation effect is also ideal.
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