Research Of Mechanical Properties Of Rubber Bearings With Relative Rotation Between Upper And Lower Surfaces

In large span spatial structures,isolating technology is often used to set up rubber bearings between foundation and superstructure.In the design,the upper and lower surfaces of rubber bearings are guaranteed to be parallel to each other,so as to achieve the purpose of structural safety.While some built spatial structures,in the process of using rubber bearings,the surfaces of rubber bearings often have obvious relative rotation.It shows that the rubber bearings have to be taken a certain rotation angles at this time.It will directly affect the mechanical properties of rubber bearings and isolation effects,thus affecting the integrity and safety of buildings.In order to research rubber bearings rotation problems of large span spatial structures,the finite element simulation and experimental analysis of the mechanical properties of the rubber bearings with rotation angles are carried out in this paper.The main contents and conclusions of this paper are as follows:(1)Analysis the reasons for rubber bearings rotation.This paper analyzes and summarizes the engineering data of large span spatial structures with rubber bearings at home and abroad,to find out the cause of rubber bearings with rotation angles in the large span spatial structures,and determines the finite element models and the experiments plan.(2)Finite element simulation analysis.The ABAQUS finite element analysis software is used to establish the bearings model with rotation angles.The horizontal performances,stability performances,stress of steel plates and different parameters are analyzed.The results show that the three direction(X direction and Y direction and 45 degrees direction)horizontal displacement loadings,the horizontal stiffness decreases with the increases of rotation angles,and then increases with the increases of rotation angles(at small deformation range);in the engineering stress ranges,vertical pressures have little effect on the horizontal stiffness;compared without rotation angles,the rubber bearings with rotation angles will be “drums out” at laterally,it will affect the stability,When the direction of bearings rotation angle is in the same direction with the seismic horizontal force,the isolation effect is the worst;four different conditions(different model relations,different central pore diameters,different shear modulus and different rubber monolayer thickness)can be obtained: when the shear strains are small,the horizontal stiffness of rubber bearings with initial rotation angles are less than the horizontal stiffness of rubber bearings without initial rotation angles;when the shear strains are larger,the horizontal stiffness of rubber bearings with initial rotation angles are greater than the horizontal stiffness of rubber bearings without initial rotation angles.In the case of large deformation,the horizontal stiffness of rubber bearings without initial rotation angles is less than the horizontal stiffness of without initial rotation angles.(3)Experimental analysis.To verify the rationality of the finite element analysis results,the horizontal properties,hysteretic performances,stability and destructive performances of rubber bearings with rotation angles are used experiments to analysis.The results show that for no rotation angles rubber bearings,the horizontal stiffness increases with the increases of horizontal displacement,the damping ratios are also slightly increased;for rubber bearings with rotation angles,the horizontal stiffness decreases with the increases of rotation angles,the damping ratios increases with the increases of the rotation angles;in the aspect of stability,the bearings will “drum out” in the process of experiments,the larger the rotation angles,the “drum” phenomenon is more obvious;in order to make the bearings have a better isolation effects,it is suggested that the allowable rotation angle of bearing is 0.01 rad,the maximum horizontal shear strain should not exceed 200%,or the allowable angle can be larger,the corresponding horizontal shear strain is smaller,but the maximum rotation angle should not exceed 0.02 rad.(4)Comparison between experiments and finite element analysis.The results show that the results of the two methods are in good agreement,and the deviation of rubber bearings at horizontal properties and stability analysis are within the acceptable range.