| In the last two decades, the seismic isolation technology has proved to be a very effective aseismic technology, giving rise to many applications for civil buildings, bridges, and industrial buildings. Base isolation technology is a positive aseismic technology that can keep structural basic frequency away from high frequency components of the seismic ground motion, and reduce the superstructure’s seismic action by using isolation bearing having lower lateral stiffness. The isolation bearings are installed at the bottom of the buildings. Thus it can be seen that, isolation technology is very effective under far-field ground motions, which have a large energy distribution especially for medium to high vibration frequencies. However, the effectiveness of the isolation technology is questionable under pulse-like ground motions, which have a long period, large amplitude, and high energy pulse component. Existing studies have shown that near-fault pulse-like ground motions can lead to buckling or rupture of the isolation bearings, and can influence the safety of superstructure. For these above reasons, this paper will study isolator bearing’s displacement demand, dynamic response, energy dissipation mechanism and seismic performance of the vibration reduction device-base isolation hybrid control system, as follows:(1) Existing studies on division of the near-fault region and characteristics of the pulse-like ground motions were summarized, selection rules of the pulse-like ground motions on the basis of those existing studies was established, and pulse-like ground motion records from PEER strong ground motion database were obtained using the selection rules. Frequency characteristics of the pulse-like earthquake records were studied on the basis of power spectrum. Existing studies on ordinary seismic ground motions’synthetic methods and velocity pulse model were summarized, high frequency component was generated by using spectrum matched technology, velocity pulse component was generated by using He-Agrawal model, and pulse-like ground motions were generated through superposition of the high frequency component and velocity component. Reliability of the synthetic method was studied by analyzing power spectrum of the pulse-like ground motions.(2) The estimation method of the isolation bearing’s inelastic displacement demand was studied. The equations of motion that related to base isolated structure’s elastic displacement demand spectrum and inelastic displacement demand spectrum were established. On the basis of these equations, base isolated structure’s elastic displacement demand spectrum, constant yield strength inelastic displacement demand spectrum, and constant yield strength inelastic displacement ratio spectrum using MATLAB were obtained. Spectrum characteristics of the elastic displacement demand spectrum and constant yield strength displacement ratio spectrum were studied, and fitting expressions of the elastic displacement demand spectrum and constant yield strength inelastic displacement ratio spectrum were proposed. Reliability of the fitting expressions was studied by comparing between real spectrum and fitting spectrum. At last, the estimation equation of the constant strength displacement demand spectrum was established, and the displacement demand can be obtained easily by using this equation.(3) The effect of the TMD and viscous damper on the seismic response of the supstructure and isolation bearing was studied. Nonlinear equations of motion for the LRB structure, TMD-LRB system and Dsup-LRB system were established, dynamic response of the structure under pulse-like ground motions were solved, and effect of the TMD and viscous damper on the isolation bearing displacement response, superstructure inter-story drift and acceleration response was analyzed. Moreover, influence of the velocity pulse period, bearing yield force, stiffness ratio, mass ratio, frequency ratio and additional damping ratio on superstructural and isolation bearing displacement response was studied. At last, Energy equilibrium equations of the LRB structure, TMD-LRB system and Dsup-LRB system were established, energy responses were solved, and the cause of the structural response’s reduction was studied from the perspective of energy dissipation.(4) The effect of the viscous damper on seismic performance of the superstructure and isolation bearing was studied. Nonlinear incremental dynamic analysis of the LRB structure and Dsup-LRB system was performed respectively, IDA curves were obtained. Characteristics of the single IDA curve and multiple IDA curves were analyzed.16%,50%and84%fractile IDA curves were obtained through statistical analysis. Seismic performance of the superstructure and isolation bearing was analyzed from the perspective of statistics. Moreover, Seismic fragility analysis of the LRB structure and Dsup-LRB system was conducted, the seismic fragility curves of the superstructure and isolation bearing under different limit states were obtained, and the seismic performance of the superstructure and isolation bearing was assessed from the viewpoint of probabilit. (5) On the basis of shaking table test of the series seismic isolation system, displacement demand of the isolation bearing was studied. The effect of the ground motion intensity on displacement response of the isolation bearing was studied through the comparison between the seismic responses under ground motions that have different intensity. The effect of the pulse-like ground motions on displacement response of the isolation bearing was studied through the comparison between far-field seismic responses and the seismic responses under near-fault pulse-like ground motions. The effect of the viscous damper on displacement demand of the isolation bearing was studied through the comparison between the LRB structural seismic responses and the Dsup-LRB system’s seismic responses. The test results provided a reference for the results of numerical analysis. |
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