Simulation Analysis Of Ultimate Performance Of Natural Rubber Isolation Bearing

The serious damage caused by the earthquake promotes the continuous development of earthquake engineering.The seismic reduction and isolation technology can greatly reduce the loss caused by the earthquake.The state also continues to promote the wide application of seismic reduction and isolation technology in the field of building structures.As one of the most mature isolation bearings,natural rubber isolation bearing has the characteristics of reliability,effectiveness and economy.However,due to the complex action mechanism between rubber layer and steel plate layer under earthquake,and the internal stress and strain are also difficult to measure,there are few research results of natural rubber isolation bearing in the limit state dominated by inertial force,and more research focuses on compression shear test,This can not reflect the actual working performance of natural rubber isolation bearing under earthquake.In this paper,the shear performance of natural rubber under compressive stress is studied through experiments,and the process of reaching the limit state of natural rubber isolation bearing under earthquake is simulated and analyzed based on ABAQUS software.The main research contents and conclusions of this paper are as follows:(1)Through uniaxial tensile test and simple shear test,the basic mechanical properties of natural rubber are obtained,and the constitutive equation of natural rubber is fitted by ABAQUS finite element software,and the advantages of the Ogden model in the study of large deformation are compared.(2)Based on the improvement of simple shear test,a novel compression shear test method is proposed.The results show that with the increase of the compressive stress of the rubber plate,the "hysteretic circle" of the rubber plate gradually increases,and the energy dissipation capacity of the rubber plate increases.At the same time,the maximum shear value and shear modulus of the rubber plate gradually increase,and the ultimate shear strength of the rubber plate is improved,but the ultimate deformation capacity decreases;With the increase of shear strain,the influence of compressive stress on rubber plate decreases gradually,and the shear modulus decreases gradually.The fracture of the rubber layer occurs near the steel plate layer.(3)Based on ABAQUS software,the finite element model of natural rubber isolation bearing is established,and the mechanical parameters of natural rubber obtained from the test are input into the model.The feasibility of the finite element model is verified by simulating the compression shear test and comparing with the test results of NRB250 compression shear test previously completed by the research group.(4)The superstructure is regarded as a rigid body and replaced by mass points.The ultimate performance of NRB250 under earthquake is studied by changing the added mass of the superstructure,the peak acceleration of seismic wave and the boundary conditions brought by the overall structure.The results show that without considering the influence of the overall structure on the isolation bearing,changing the additional mass has less influence on the relative displacement of the bearing and greater influence on the response acceleration.The acceleration determines the horizontal displacement of the isolation bearing,and then determines whether the overturning phenomenon occurs or not.The added mass of the superstructure and the acceleration will affect whether the bearing is damaged due to inertial force.Among them,the middle hole of the bearing is the most prone to damage.The stress of the middle and lower layers of the bearing is larger than that of the upper layer,and the maximum stress and maximum response acceleration of the isolation bearing occur at the same time.When the acceleration of NRB is large,the relative displacement will increase rapidly,so limit or other energy dissipation devices must be used.Compared with considering the action of superstructure,the response acceleration and relative displacement of the two are basically the same,and the maximum equivalent stress is quite different.