Finite Element Simulation Of Isolation Performance Of Restrained Rubber Bearing

People often set protection devices or other methods to protect the isolation layer,in order to prevent the structure under rare or extremely rare earthquake damage due to the horizontal displacement of the isolation layer overrun failure.Moreover,the edge bearing of isolation layer is prone to tension under overturning moment or structural torsion.In some projects,we also need to consider vertical isolation.Therefore,in this paper,the finite element simulation analysis is carried out for a new type of rubber bearing with tensile,limit and damping to analyze its seismic isolation performance.Under the shear load,the constraint plate of the rubber bearing can play the effect of limit and damping.Because the constrained rubber bearing has the advantages of good seismic isolation performance,simple process,tensile resistance,limit,damping,etc.,it has a wide range of engineering application conditions.Taking the constrained rubber bearing as the research object,this paper completed the following work :（1）This paper summarizes the methods of prevention and control failure design of isolation bearing : setting limit block in isolation layer,prevention and control through composite isolation bearing and metal cable.The authors discussed the mechanical characteristics of different vertical isolation and limit devices,and introduced the structure and research significance of a new type of constrained rubber bearing with limit and tensile properties.（2）I use ABAQUS software to simulate the vertical stiffness,vertical bearing capacity and horizontal stiffness of the constrained rubber bearing,so as to analyze the stress and strain of the rubber layer,steel plate layer and constraint plate of the constrained rubber bearing under vertical compression and compression shear.Compared with the thick rubber bearing,the author found that the constrained rubber bearing has higher vertical stiffness and vertical bearing capacity.The influence of the number of steel plates and the hardness of rubber materials on the vertical stiffness and vertical bearing capacity of the constrained rubber bearing was discussed.By simulating the horizontal shear state of the bearing,we studied and analyzed the horizontal stiffness of the constrained rubber bearing,and the simulation results were in good agreement with the theoretical formula.（3）The seismic performance of isolated frame structure based on constrained rubber bearings is analyzed.The nonlinear numerical models of isolated structures were established in the finite element software ETABS and Open Sees,respectively,and the elastoplastic seismic response analysis was carried out.The modal,maximum story drift angle,base shear and other parameters of the structural models established in different softwares were compared and verified.According to the structure,site conditions and other information,I selected three ground motions to compare the dynamic response of frame structure before and after isolation design under frequent and rare earthquakes.The results show that the parameters of the isolated frame structure based on the constrained rubber bearing meet the requirements of the seismic code,and the isolation performance of the constrained rubber bearing is verified.（4）Taking the base-isolated frame structure based on constrained rubber bearings as an example,a total of 75 natural ground motions were selected from 15 sites in each category to analyze the influence of different site conditions on the seismic response of the structure.The relationship between the first period spectral value S_a（T₁） of structural acceleration response spectrum and the peak value S_amax of structural acceleration response spectrum is established,and the peak value S_amax of structural acceleration response spectrum is used as the seismic parameter index.The structural seismic probability demand parameters of superstructure and isolation layer are the maximum inter-story drift angle（θ）and ratio（δ/ d）of horizontal displacement of support（δ）to diameter（d）.Considering the site conditions,the structural probability demand model under the same ground motion parameter index is established.