| Mega-sub control system refers to a new structure system in which control instruments are applied between the main structures and substructures. In the past few years, the system has become focus of a number of researchers due to its outstanding controlling properties. However, there are still a lot of problems needed to be solved in this research subject, such as the study of its working mechanism and the parameters optimization, the research of failure patterns, the research of reliability and sensitivity and so on. In this paper, several issues are theoretically analyzed based on massive previous studies in the fields of the study of working mechanism, the parameters optimization and the analysis of energy response, torsion and swing influence and the reliability, sensitivity and vulnerability. and on this basis, shaking table tests are conducted. The main contents are as follows:(1)The working mechanism of the mega-sub control system is studied when themass ratio between the substructure and the main structure is changed from small tolarge. The analysis results show that with increase of the substructure mass, theworking mechanism are changed from a tuned mass damper mechanism to a seismicisolation mechanism, which is different from the previous studies that suggest theworking mechanism of mega-sub control system was a tuned mass dampermechanism. And the working mechanism of the mega-sub control system is alsoillustrated from the point of energy. Finally, by Hilbert-Huang transform, themarginal spectrum of the mega-sub control system is obtained, and numericalsimulation indicates that the marginal spectrum intensity of displacement andacceleration of both the top primary structure and sub-structure are attenuatedsignificantly compared with the traditional mega-sub structure.(2)The optimal parameters of the mega-sub tuned system and mega-sub inter-story isolation system have been studied first, and then the equations of motion of mega-sub control system are established, and the influence of the number and location of isolated substructures on the optimal parameters of mega-sub control system has also been investigated. The results show that the location of the isolated substructures has little effect on the optimal frequency ratio, while it has great effect on the optimal damping ratio, and the number of the isolated has great influence on both the optimal frequency ratio and the optimal damping ratio. Finally, based on the optimal parameters, the damping effect is studied from the perspective of random spectrum analysis and time-history analysis.(3)The influence of the eccentric parameters of the mega-sub control system on its seismic response control system has been studied by using the multi-rigid plates in series model, and the eccentric parameters include the eccentricity and transgenic stiffness ratio of the main structure, the eccentricity and transgenic frequency ratio of the substructure. And the results show that the eccentric parameters of the structure can not only affect the lateral seismic responses but also can affect the the torsional seismic responses of structure, and with the changes of eccentricity parameters, the responses of structure exhibit different trends. The Equation of motion of mega-sub isolated system with swing is established in this paper. The spectral density and time-varying variance of the structural response are obtained by using virtual excitation method when the random excitation is uniformly modulated and non-stationary. Using the equation of motion which consider structure’s swing and the Matlab programming, the analysis is done for the structure. The results show that when the stiffness ratio is less than the boundary stiffness ratio1?, the response of the swing isolated structure is changed significantly compared with the ordinary isolated structure; when the stiffness ratio is greater than the boundary stiffness ratio1?, the response of the swing isolated structure is consistent with the ordinary isolated structure.(4)The reliability sensitivity of the random parameters of the structure to story drift angle is analyzed by the first passage mechanism of random vibration when the ground motion is considered as random excitation and the structure is considered in elastic state. In addition, the sensitivity of the structure response of the structure to the random parameters is studied by the seismic response information on the system. And the results can explain that why the mass ratio, frequency ratio and damping ratio are usually used for performance analysis to mega-sub control system. Considering the uncertainties of stochastic parameters of mega-sub control system, probability density evolution process of the structure is obtained by using the probability density evolution method, and the dynamic responses of the structure can also be analyzed and predicted.(5)Considering with the uncertainties of near-fault and far-fault ground motions characteristics, the performance-based seismic fragility of the traditional anti-seismic structure and mega-sub control structure under near-fault and far-fault earthquake are compared based on the results of incremental dynamic analysis(IDA). Then considering the uncertainties of ground motions characteristics and structures parameters, this paper also proposes a fragility analysis method of mega-sub control system based on RSM(response surface method). Using central composite design method to construct a series of samples for various ground motions and mega-sub control structures, nonlinear dynamic time analysis of the sample model is carried out, and substructures response surface model of mega-sub control structure is built, then the fragility curves are obtained using of Monte Carlo method. The results show that the the failure probability of mega-sub control system under near-field earthquake is greater than that under far-field earthquake, and in the states of slight damage, moderate damage, and serious damage, the failure of the structure is mainly controlled by the substructure, and in the state of collapse damage, the failure of the structure is controlled by the isolation layer.(6)Three different experimental models are produced for shaking table test, one for aseismic structure, the other is called isolated structure,and another is known as isolated-bottom consolidated structure. By applying different load cases, the shaking table tests have been down on a shaking table measures 3m×3m in plan, is 1.2m in height. The test results show that the structural response of the isolated structure and isolated-bottom consolidated structure are smaller than that of the aseismic structure, and the expected effect is achieved.(7)The finite element models of aseismic structure, isolated structure and isolated-bottom consolidated structure are established by the finite element analysis software SAP2000. The actual table measurement is taken as the excitation, and the dynamic characteristics, acceleration response, the interlayer displacement of the mega structure and the substructure, and the interlayer displacement of isolation layer of this three different structural models are compared and analyzed. And then compared with that of shaking table test, so as to verify the accuracy of the shaking table test. |
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