Mechanical Properties Research And Application Of Bridge Rubber Bearings Based On Viscoelasticity

In this paper,the hyperelastic,viscoelastic and viscoelastic constitutive models of chloroprene rubber used for bridge bearings were studied.The heat flux characteristics,pre-strain effect and Payne of the materials were analyzed to establish the viscoelastic constitutive modulus,which were employed for the analysis of the static and dynamic viscoelastic properties of the bearing.The laws,which may provide theoretical guideline for practical design for bridges,were found by varying the factors as creep,energy consumption and others.The main research work and results are summarized as follows.1.Uniaxial tensile,compression and creep tests were carried out on rubber from the static point of view,and the constitutive model was studied by theoretical analysis of the test data.Firstly,the results of uniaxial tension and uniaxial compression tests were used to compare the fitting results of several hyperelastic models and select the appropriate hyperelastic model.Secondly,the creep test is carried out on the principle of stress acceleration to obtain the creep curve for a long time,and the relaxation modulus and relaxation time parameters are obtained by the finite element software.Finally,by combining the hyperelastic model and viscoelastic model,the finite element analysis of compression creep and relaxation is carried out,and the feasibility of the constitutive model is verified by comparing with the experimental data.2.From the perspective of dynamic viscoelasticity of rubber,temperature scanning and frequency scanning DMA tests were conducted on rubber materials to study the viscoelasticity constitutive model of rubber.The experimental results show that the storage modulus and loss modulus at different temperatures can be translated along the frequency axis to form a smooth curve,which explains the simplicity of the heat flux of the material,and gives the corresponding displacement factor by WLF equation.A linear viscoelastic constitutive model is obtained by using generalized Maxwell model to fit the main curves of storage modulus and loss modulus.The obtained constitutive model is substituted into the finite element model,as shown in the figure below.The model is modeled and analyzed for the compressed frequency scanning,and the calculated results are close to the experimental results,indicating the practicability of the model.3.The pre-strain effect of rubber was studied.Firstly,the relationship of storage modulus and loss modulus with prestrain was obtained by frequency scanning test of rubber material under different prestrain effects.Secondly,based on the finite deformation theory,a constitutive model containing the pre-strain effect is proposed.The constitutive model is used to fit the storage modulus and loss modulus to obtain the corresponding constitutive model parameters.Finally,the parameters of the dynamic compression specimens with different prestrain are analyzed,and the calculated results differ little from the test results,which proves that the constitutive model can reflect the prestrain effect well.4.The Payne effect of rubber was studied.Based on the relationship between hysteresis curve area and loss modulus,the loss modulus of rubber under different dynamic strain amplitude-and the test data of loss modulus are in good agreement.The similar empirical formula is used to predict the storage modulus,and the prediction results are also of high accuracy.It can be seen that the empirical formula presented is simple and has certain accuracy in predicting the dynamic modulus(storage modulus and loss modulus)under different strain amplitudes.5.Analyze the static viscoelastic mechanics of rubber bearings.The static viscoelastic properties are mainly reflected in creep.This paper studies the influence of various parameters on creep from three angles: stress,time and bearing geometry(layer thickness and diameter).The expressions of compressive elastic modulus containing these four parameters are established,which can be used in the design and calculation of bearings.6.Dynamic viscoelastic analysis of rubber bearings.The dynamic viscoelastic properties of compression and shear are studied respectively.Considering the three influencing factors of frequency,pre-strain(pre-pressure)and displacement amplitude respectively,the equivalent stiffness and equivalent damping ratio under each influencing factor are obtained,and the parametric regression of equivalent stiffness and equivalent damping ratio is carried out to obtain the fitting equation of each parameter.7.Combining the static and dynamic analysis results of the bearings and the expressions of each parameter above,the rubber bearings used in a 5×30m T beam are designed and selected as an example.