Performance And Parameter Optimization Design Of Base-isolated Structures Based On Semi-active Inertial Mass Damper

As an effective building seismic damping technique,base-isolated structure can keep the basic period of the structure far away from the seismic excellence period,thus protecting the building from seismic hazards.However,under the action of large earthquakes,the seismic isolation floor displacement may exceed its design limit.Constructing a hybrid seismic isolation system by adding seismic isolation pad damping or additional damping devices can control the displacement of seismic isolation floor to a certain extent,but may lead to an increase in the acceleration of the superstructure.This paper proposes the concept of the semi-active inertial mass damper(SIMD)and constructs a new base-isolated structure(BIS+SIMD),to achieve effective reduction of both the displacement for the isolation floor and the acceleration for superstructure.The paper analyzes the seismic performance of the base-isolated structure based on serial and parallel semi-active inertial mass damper,proposes an optimal design method for BIS+SIMD,clarifies the influence of soil-structure interaction,control strategies and time lag on the seismic performance of BIS+SIMD.The main contents and research results are as follows.1.The averaging method is used to obtain the analytical solution of the dynamic response of the base-isolated structure based on serial and parallel semi-active inertial mass damper under the control of relative acceleration-relative velocity control strategy,and the effects of the parameters of such combined base-isolated structure on the displacement amplification factors of the isolation floor,the absolute acceleration amplification factors of the superstructure and their peaks are studied in detail,and the optimal damper parameter values of the multidegree-of-freedom BIS+SIMD is proposed using genetic algorithm,and the BIS+SIMD is compared with other different control methods such as traditional base-isolated structure.The results show that compared with the base-isolated structure based on serial semi-active inertial mass damper,the base-isolated structure based on parallel semi-active inertial mass damper has a lower overall amplification factor of the displacement of the isolation floor and the absolute acceleration of the superstructure;the comparative analysis with other different control methods shows that BIS+SIMD can effectively control the displacement of the seismic isolation floor without causing the amplification of the acceleration of the superstructure.2.The influence law of structure-to-soil stiffness ratio,aspect ratio of structure and SIMD parameters(maximum inertance-to-mass ratios,minimum inertance-to-mass ratios and damping ratios)of BIS+SIMD on the seismic performance of the system is analyzed in detail from the perspective of time and frequency domains,the impacts of detuning effect on the control efficiency of different control systems is compared and the optimized design method of BIS+SIMD considering soil-structure interaction is proposed,and BIS+SIMD is compared with other different control methods such as traditional base-isolated structure.The results show that the soil-structure interaction effect will prolong the self-oscillation period of BIS+SIMD,make the overall dynamic amplification factors of the system shift to low frequency,and amplify the first-order dynamic response of BIS+SIMD,weaken the influence of higher-order modes on the system;BIS+SIMD designed by considering soil-structure interaction can improve the seismic isolation effect of the base-isolated structure on soft foundation,and effectively suppress the displacement of the seismic isolation floor and the absolute acceleration of the top floor.3.The dynamics model of BIS+SIMD under the relative acceleration-absolute velocity control strategy is established and the fuzzy controller for BIS+SIMD is designed,and then the dynamic response analysis of BIS+SIMD under different control strategies is further analyzed based on 20 earthquake records.The results show that compared with the relative accelerationrelative velocity control strategy and the relative acceleration-absolute velocity control strategy,the fuzzy control strategy can effectively reduce the maximum displacement of the seismic isolation floor,the maximum absolute acceleration of the seismic isolation floor and the maximum absolute acceleration of the top floor without causing a significant increase in the interfloor displacement of the top floor;on the whole,the BIS+SIMD with relative accelerationrelative velocity control strategy,relative acceleration-absolute velocity control strategy and fuzzy control strategy can simultaneously control the dynamic response of the seismic isolation floor and the superstructure,which can provide effective protection for the base-isolated structure under the strong earthquake.4.The analytical solution of the dynamic amplification factors of BIS+SIMD under the relative acceleration-relative velocity control strategy with time lag effect is derived,and the stability condition of the system is established based on Lyapunov theory,and then the influence law of parameters such as time lag,maximum inertance-to-mass ratios,minimum inertance-tomass ratios and damping ratios on the control effect of the system is studied.The results show that the BIS+SIMD without time lag is always stable,while the BIS+SIMD shows periodic stability after considering the time lag;the time lag has a damping-like effect,which can suppress the system dynamic response and improve the control effect of the BIS+SIMD.