Research On Seismic Isolation Of Rubber Bearing With Initial Rotation In Steel Grid Structure

Rubber isolation is regarded as one of the important isolation technologies and is widely used in long-span steel grid structure.However,the initial rotation of the bearing will be affected by the mechanical state of the internal members of the grid structure and external factors in practical engineering application.The mechanical properties of rubber isolation bearings will be affected by the initial rotation,and the isolation effect of structural isolation system will also be affected.In this paper,in order to study the influence of the initial rotation produced by the rubber isolation bearing on the long-span steel grid isolation structure,the construction of large-span steel grid structure is selected as the research case.The finite element simulation is carried out by using the large-scale general finite element software SAP2000.Combined with the mechanical performance test of rubber isolation bearings,the influence of rubber isolation bearings with different initial rotation sizes on the isolation effect of steel grid structure is analyzed,and it is hoped that it can provide reference for the isolation design of steel grid structure in the future.The main research contents and conclusions are as follows:(1)The application and development of long-span steel grid building structure and Isolation bearings in this structure are introduced.(2)The rubber isolation bearings with different rotation are experimentally analyzed.The analysis results shown that the vertical stiffness of natural rubber isolation bearing is hardly affected by the bearing rotation angle,the horizontal stiffness of natural rubber isolation bearing is greatly affected by the bearing rotation angle.The horizontal stiffness of the bearing increases with the increase of the bearing angle.When the bearing angle reaches0.015 rad,the horizontal stiffness of the bearing decreases by 15.9%.(3)The construction of large-span steel grid structure is selected as the research case,and the finite element model of long-span steel grid structure is established by using the large-scale general finite element software SAP2000,which structural model is analyzed by time history.The axial deformation of steel grid members,the degradation of horizontal stiffness and size effect of natural rubber isolation bearing,and the influence of external temperature difference on bearing angle are analyzed.The analysis revealed that the initial rotation angle of the rubber bearing increased with the increased of the axial deformation of the rod,when the members reach the ultimate strain,the maximum rotation angle of the support reaches 0.01304 rad,which is 228.5% higher than that of the support with zero axial deformation of the members;The initial rotation angle of rubber bearing increases with the degradation of the horizontal stiffness of the bearing.When the stiffness of the bearing degrades by 25%,the initial rotation angle of the bearing increases by 131.1%;the initial rotation angle of rubber bearing decreases with the increase of bearing size.When the bearing in the structure is LNR1000,the rotation angle of bearing decreases by 47.6%;the initial rotation of rubber bearing increases with the increase of temperature difference.Compared with the structure with temperature change of 0℃,the initial rotation with temperature change of 60℃increases to 0.00749 rad,i.e.an increase of 80.7%.(4)After studying the influence of various factors on the initial rotation of the rubber bearing,the grid structure with isolation bearings at different corners is analyzed by seismic time history.The analysis results shown that The initial rotation of the support will have a great impact on the isolation performance of the space truss structure.The node displacement and node acceleration of the space truss structure and the horizontal displacement of the rubber support will increase with the increase of the rotation angle of the support.When the bearing angle is 0.015 rad,the vertical displacement of the grid structure node reaches-357.6mm,which exceeds the specification limit.The horizontal displacement of the rubber bearing on the XZ plane in the grid isolation system exceeds the specification limit(220mm).The use of the bearing fails,which is not conducive to the isolation of the grid structure.