Study On Parameter Optimization Of Damper Of Viscous Damper-isolator Hybrid System

In the isolated structure,the viscous damper can be used in combination with the isolation bearings for the seismic design of the building structure.The damper can be used to reduce the deformation of the isolation layer.However,what kind of dampers installed in the seismic isolation layer and damping parameters should be considered.At present there are differences in the research conclusions of relevant literature.In this paper,the damper is optimized on the basis of the optimization goal,and the influence mechanism of the damper on the isolation structure is studied.The main contents include:(1)The construction of non-proportional damping matrix.The non-proportional damping matrix of the isolated structure is constructed from the perspective of mode shape analysis.The damping matrixes of the superstructure and substructure are compared with two different circular frequencies respectively.The difference between the vibration mode damping ratios of the system is compared to select a more reasonable damping matrix of the structural system.The Simulink toolbox was used to simulate the restoring force model of isolation bearing and viscous damper,and the influence mechanism of each parameter of the mechanical model was explored by parameter identification.(2)The establishment of the motion equation of seismic isolation structure.Under the action of earthquake,the upper and lower structures of the isolation layer are in elastic state,while the isolation layer is elastic-plastic.In this paper,the Boucwen model is used to simulate the restoring force-deformation behavior of the isolated bearing.The multi-particle model of the isolated structure is adopted.The framework under earthquake action is established and then solved by the fourth-order Runge-Kutta method.The related time history analysis program of MATLAB is compiled.The elastic-plastic time-history analysis of structural system is realized and the earthquake response of the structure is obtained;(3)Multi-objective optimization of viscous damper parameters.Firstly,the concept of Pareto optimal solution set and the principle of non-dominated sorting multi-objective genetic algorithm(NSGA-II)are briefly introduced.Then,an example of seismic isolation structure is selected to determine the parameters of mass stiffness Value.The modal analysis is conducted and the differences of vibration mode and cycle between isolated structure and non-isolated structure are compared;The time-history analysis method and NSGA-? algorithm are combined by MATLAB programming.The total displacement of the isolation layer and superstructure are selected as the objective of optimization.The damping coefficient and damping index of viscous damper are selected as optimization parameters,and then the multi-objective optimization is performed to obtain the Pareto front of each earthquake.At the same time,the optimization process is studied;(4)Parametric Study of Viscous Damper.Based on the Pareto solution set of a series of damper parameters,the parameter distribution of the damper is studied,and the influence of the optimal damper configuration on the seismic response of the structure is discussed in detail,including the peak story displacement,the absolute peak acceleration of each layer and the maximum value of the base shear force.By adjusting the damping effect of the damper,the change of these structural reaponse are discussed respectively.In addition,the restoring force of the isolation layer and the output force of the damper are also studied.(5)Optimization analysis of the optimal viscous damper.In order to study the influence mechanism of the dampers on the isolation structure of the isolation layer,The vibration velocity of the isolation layer is selected for FFT spectrum analysis.The relationship between the linearity of the dampers and the movement characteristics of the isolation layer and the factor about the reduction of the total displacement of the isolation layer are studied.Two different methods are proposed to measure the additional damping ratio of the damper installed at the isolation layer,including frequency analysis and response spectrum analysis.Furthermore,the influence of the additional damping ratio on the structure reaction was studied by using the response spectrum.The energy response of the system was also analyzed.The energy mechanism of the system without and with the damper were explored.(6)Parameter optimization of viscous Damper in base isolated system.Firstly,modal analysis is conducted to study the difference of the self-vibration characteristics between the inter-storey isolated structure and base isolated structure.Different damping ratios and frequency are selected for the construction of damping matrix.The same earthqaukes are selected to get the Pareto solution set.The effectiveness of the damper is also studied.The differences between two completely different model optimization analysis results are compared.The relationship between linearity of the damper and the movement characteristics of the isolation layer is further analyzed.Because of the difference of based isolated structure,the response spectrum analysis method is used to measure the additional damping ratio of dampers.The more comprehensive analysis of the effectiveness of damper in isolated structure is studied.The energy response analysis is also compared.(7)Seismic response analysis of base isolated system under near-fault earthquake.The differences between the time history curves and the response spectra of near-fault earthquake and far-fault earthquake are compared.The energy spectra are also discussed.In view of the influence of near-fault earthquakes on the isolated structure,the influence of near-fault earthquake and far-fault earthquake measured by different stations of the same earthquake on the base-isolated structure is compared.Then the dynamic response of the base-isolated hybrid control system under near-fault earthquake is discussed.The differences of the effectiveness of the damper under near-fault earthquake and far-fault earthquake are also discussed.The effectiveness of damping offered by damper under near-fault earthquake is highlighted.(8)Viscous damper optimization parameter sensitivity analysis.Using the same earthquakes,the change of the horizontal stiffness of isolation layer,the stiffness ratio before and after yielding of lead-rubber bearing and the amplitude of earthquake are studied.The relationship between three design parameters and the effectiveness of damper are studied.(9)Damper selection.In the case of the base isolated structure,the parameter optimization range of the damper is changed,and the optimization target is controlled within the threshold.The damper parameters is selected by optimization of the NSGA-? algorithm and the effectiveness of damper is verified by other earthquake.The design step of damper is discussed.