| The seismic response of mid-to-long period structures located in the near-fault area performed significant when subjected to the strong impulse earthquake.The oil damper was usually selected and installed into the structure to effectively control the seismic response.The pulse characteristic of near-fault ground motion generates a strong destructive effect on the structure.and these pulse characteristics are mainly determined by the key parameters such as the pulse period and peak velocity of the low-frequency pulses.Also the seismic response of the structure controlled by oil damper is closely related to the characteristic parameters of input ground motion.Therefore,based on the key parameters of ground motion,it is of great value to research the rapid and accurate method to predict the seismic response of the structure with nonlinear oil damper for improving the design efficiency.In this paper,the response controlled structure with an additional oil damper was used.And the seismic responses of the structure added with oil dampers under near-fault pulse-like ground motions were predicted on the basis of the prediction model of displacement,velocity,and acceleration response spectra,.The main research contents are as follows:(1)The characteristics of near-fault ground motions and the pulse determination methods were systematically introduced,also the causes of the velocity pulse and the key factors determining the pulse characteristics were analyzed,which lays a theoretical foundation for the subsequent research work of this paper.(2)The relationship between response spectra and pseudo response spectra of impulsive ground motion was studied.Through statistical regression analysis,the empirical formula of the damping modification factor ratio was obtained,meanwhile,the function relationship between the velocity response spectra and pseudo velocity response spectra was also established.Thus,the conversion relation between different response spectra was established.(3)Taking factors such as pulse period,peak ground velocity,structural period,and structural damping ratio into account,a model for predicting the acceleration response spectra was proposed using numerical analysis method.Furthermore,based on the relationship among different response spectra,the prediction models of displacement response spectra and velocity response spectra of pulse-type ground motion were obtained.(4)The single-degree-of-freedom structure with additional nonlinear oil dampers was used as the research object in the study.Based on the prediction model of response spectra subjected to impulsive ground motions,a prediction method for the maximum displacement and maximum damping force of response controlled structure with oil dampers was established using the principle of equivalent linearization.The numerical analysis results show that the method presented in this paper would predict the seismic response of response controlled structure added with oil dampers relatively well when the ratio of structural period to pulse period T/T_p is in the interval of(0.1,5).(5)Aiming at the isolation structure with oil damper installed on the base isolation layer,considering the nonlinear characteristics of the oil damper,a method for establishing an equivalent single degree of freedom system for the base-isolated structure is proposed.Based on the response spectra model and the seismic response evaluation method of the response controlled system with oil damper,the seismic response prediction method of the base-isolated structure with oil damper is established. |
