Experimental Study On The Dynamics Mechanical Properities About The Laminated Rubber Specimens

Earthquakes are sudden and destructive,a large number of buildings are destroyed and collapsed,which is the direct cause of disasters.In recent years,with the increasing progress and improvement of earthquake prevention and disaster reduction technology,Seismic isolation,which as a new type of earthquake prevention measure,has been gradually applied to a large number of Engineering practices.At present,the most mature isolation system is the laminated rubber bearing isolation system.The mechanical properties of rubber are greatly affected by the strain rate,the difference between dynamic and static mechanical properties is obvious.Therefore,it is necessary to study the effect of strain rate on mechanical properties of laminated rubber specimens with response laminated rubber isolation bearings.Shearing performance is one of the most important mechanical properties of laminated rubber bearings,including shear strain dependence,loading frequency dependence and temperature dependence.In order to study this property,compression-shear tests are often used.For the purpose of this study,the laminated rubber specimens and the loading devices used to meet the test requirements are designed and developed.In this paper,the frequency dependence and shear strain dependence of shear stiffness and energy dissipation performance of laminated rubber specimens are mainly studied from experimental aspects.In order to realize the scheduled loading speed,which satisfy both the preset load amplitude(shear strain)and the preset loading frequency,compression-shear tests were carried out on the small specimens meeting the requirements of the national codes,and the working conditions of different loading frequencies and amplitudes were combined.Which mainly studies the the variation of the horizontal equivalent stiffness and the equivalent damping ratio of rubber materials with the loading speed.The compression-shear test of laminated rubber specimens was simulated by ABAQUS finite element software,which is studied by the static test and the pseudo-static testing.The test is divided into three parts:the first part is the compression-shear test with the upper frequency limit of 1.5Hz under 100%shear strain;the second part is the compression-shear test with the upper frequency limit of 1.2Hz under 150%shear strain;the third part is the compression-shear test with the frequency of 0.2Hz under 250%,300%and 400%large shear strain.The stiffness values obtained from the first two parts of the tests ranged from 400 MPa to 500 MPa,and the equivalent damping ratio of the specimens ranged from 4%to 5%.By analyzing the test data,it can be seen that for the frequency dependence of shear performance,the horizontal equivalent stiffness of rubber material increases with the increase of loading frequency,and the equivalent damping ratio is not affected by loading frequency;For shear strain dependence of shear properties,the equivalent stiffness of rubber material decreases with the increase of loading amplitude,and the equivalent damping ratio increases with the increase of loading amplitude.The large shear deformation test of laminated rubber specimens was also carried out.The specimens were not destroyed after three large shear deformation,which indicates that the rubber materials used in this paper can withstand 400%or greater shear deformation.The regularity of test phenomena and results is obvious,which indicates that the design of the test is correct and reasonable,and reflects the shear properties of rubber materials used in the test accurately.The simulation of static test and quasi-static test at 0.2Hz are carried out respectively with the shear strain about 50%,100%and 150%.The results show that the horizontal equivalent stiffness values of the rubber materials studied in this paper are similar to those obtained in the simulation of quasi-static loading,which indicates that there is little difference between the two loading modes for rubber materials,and that quasi-static loading can not completely replace dynamic loading.It is necessary to apply dynamic loading method to reflect the dynamic shear properties of rubber materials.It is necessary to strengthen and perfect the research on dynamic loading test and Simulation of rubber materials.