Study On The Response Of Equipment-structure Coupled Isolation System Under Near-fault Earthquake

The main structure and equipment of the building are mutually affected under the action of earthquake.There is a great difference in the dynamic interaction between the equipment and the main structure due to the difference in the natural frequency of different equipment.In recent years,it is found that near-fault ground motion has the characteristics of long period and large velocity pulse compared with ordinary far-field earthquake with the depth study of near-fault ground motion,which may cause more serious damage to building structure and equipment,especially for isolated buildings,its impact can not be ignored.The equipment-structure coupled isolation model is established by finite element analysis software to study the difference of dynamic response of isolated structure caused by impulse near-fault ground motion and non-pulse near-fault ground motion,and the influence of the change of equipment natural frequency on the dynamic response of equipment-structure coupled isolation system.50 impulse near-fault ground motions and 50 non-pulsed near-fault ground motions are selected as inputs from the database of the American Pacific earthquake Engineering Research Center.Eight dynamic response parameters,including isolation layer displacement,interlayer displacement,floor acceleration,floor velocity,floor displacement,equipment acceleration,equipment velocity and equipment displacement are quantitatively analyzed.At the same time,by changing the mass and stiffness of the equipment,and then changing the natural frequency of the equipment,the influence of the change of the natural frequency of the equipment on the dynamic response of the isolation system is studied.The PGA amplitudes of 50 impulse near-fault ground motions and 50 non-pulsed nearfault ground motions are defined as 0.07 g,0.20 g and 0.40 g,which are input into the isolation model group by group.Eight dynamic response parameters are obtained,including isolation layer displacement,interlayer displacement,floor acceleration,floor velocity,floor displacement,equipment acceleration,equipment velocity and equipment displacement.The number of impulse near-fault ground motions is significantly higher than that of non-pulsed near-fault ground motions.By changing the mass and stiffness of the equipment in the model,it can be concluded that:(1)With the increase of the equipment mass ratio,the natural frequency of the equipment decreases and gradually approaches the natural frequency of the main structure,and the dynamic response of the isolation system increases with the increase of the equipment mass ratio.(2)With the increase of the equipment stiffness,the natural frequency of the equipment increases,and the difference between the natural frequency of the equipment and the natural frequency of the main structure increases.The dynamic response of the isolation system decreases with the increase of the equipment stiffness.