Strong Seismic Motion Observation And Seismic Response Analysis Of Aid-wenchuan Isolated Structures

In recent years,there have been many major earthquakes in China,which have caused great losses to the lives and property of the people.With the maturity of research and development of isolation technology in China,more and more building use it to improve the safety of buildings.Strong earthquake observation system and the response of the isolated building in the actual earthquake has become an important reference and basis for the effectiveness of the isolation technology in the actual engineering application.However,at present,in China,there are few research results based on the monitoring of isolated buildings in the actual earthquakes and the observation records of strong seismic motion are rare.The research team arrange a strong seismic motion observation system in three isolated buildings built after the Wenchuan earthquake.Wenchuan No.2 Primary School and Yingxiu Resettlement House are isolated structures.Wenchuan No.2 Primary School is a reinforced concrete structure,which the isolation layer is arranged with lead rubber bearings and elastic slide plate bearings.Yingxiu Resettlement House is a masonry structure with new simple isolation bearings.Therefore,this paper will study the seismic response of the isolation building in the strong seismic motion collected by the observation system in recent years.In this paper,8 seismic data observed in Wenchuan No.1 and No.2 primary schools are analyzed.By comparing the acceleration response of the structure,we can see that the peak acceleration magnification of upper and lower bearings of Wenchuan No.2 Primary School decreases with the increase of seismic intensity,and the magnification is less than Wenchuan No.1 Primary School.There is little correlation between peak acceleration magnification of superstructure of isolated building and seismic motion intensity.In Wenchuan No.1 Primary School,the correlation between peak acceleration magnification and seismic motion intensity is small,and the overall magnification is much larger than that of Wenchuan No.2 Primary School.Through comparison,the isolation structure shows good isolation effect in earthquake.In addition,the modal parameters of strong seismic motion observation data from Wenchuan No.2 Primary School are identified in this paper.The results of modal identification show that the modal frequency of Wenchuan No.2 Primary School decreases with the increase of seismic intensity,which indicates that the period of isolated structure increases with the increase of seismic intensity,which is consistent with the expected isolation effect.Then,Refined finite element simulation of Wenchuan No.2 Primary School based on modal parameter identification results Superstructure of finite element model is modified by adding non-structural members,fit the parameters of the isolation layer of the finite element model with the measured acceleration time history data,obtain finite element model of structure in different seismic motion.The results of numerical simulation show that that the initial stiffness of isolation layer of isolation structure is different in different seismic motions.With the increase of seismic intensity,the initial stiffness of isolation layer decreases gradually until it breaks through the yield point and enters non-linearity.Based on the measured data,the three working conditions of fixed,non-isolated and isolated obtained from refined simulation are compared.The results show that the inter-story displacement angle shear force and acceleration time histories of isolated structures are much smaller than those of non-isolated and fixed structures,and it prove the effectiveness and superiority of isolation structure in earthquake.Five observation data of resettlement houses in Yingxiu are also selected for the study.Because the observed seismic motion intensity is small,the correlation between peak acceleration magnification of isolation layer,superstructure and whole structure and seismic motion intensity is low.The first and second modal frequencies of the structure are 5.6 Hz and 4.33 Hz by using modal parameter identification method.With the increase of earthquake intensity,the modal frequencies of the structure decrease slightly.Five observation data are used to establish the finite element model of the village isolated structure.Based on the observation data,we modified the parameters such as the stiffness of the isolation layer The results of numerical simulation show that the initial stiffness of isolation layer is different in various seismic motion.In the case of small earthquake amplitude,the initial stiffness of the new simple isolation bearing is very large,which makes the structure closer to the fixed structure and basically consistent with the expected isolation design goal.The dynamic performance analysis of Yingxiu resettlement house proves that the performance of isolation structure will be better than that of non-isolation structure in the case of frequent earthquakes.