Experimental And Numerical Study Of Spring-asphalt Three-dimensional Isolation Buildings

With the frequent occurrence of earthquake disasters and the development of construction technology in recent years,the isolation structure has been widely used in practical engineering.However,the traditional isolation bearings can only carry out horizontal isolation,but more and more seismic records show that the level of vertical seismic action has been underestimated.At the same time,recent studies show that the impact of vertical seismic action on the structure cannot be ignored.Therefore,lots of researchers all over the world are committed to the development and research of threedimensional isolation bearing which can isolate horizontal and vertical seismic action simultaneously.However,at present because of the high cost and complex constructions of the three-dimensional isolation bearing,it is difficult to use it in ordinary houses,especially in rural areas.In this paper a low-cost three-dimensional isolation device is proposed.Furthermore,theoretical,and experimental research are conducted.In the spring asphalt three-dimensional isolation bearing,the spring is the core load-bearing component to bear the weight of the upper structure and the horizontal,vertical earthquake actions.Therefore,how to select the spring parameters determines the safety and isolation effect of the isolated structures.The selection method of spring parameters and the design procedure of spring-asphalt three-dimensional isolation structure are proposed in this paper according to the stiffness formula of spring and the theory of structural dynamics.The results show that the ratio of height to diameter of spring is an important design index to control the stability and isolation effect of spring.The larger the ratio of height to diameter is,the smaller the horizontal and vertical stiffness of spring is.When the height diameter ratio is less than 2.6,the spring will not lose stability.However,to ensure better isolation effect in the design process,the height diameter ratio of spring is often greater than 2.6.At this time,the spring stability should be checked,that is,the spring deformation should be less than the instability critical displacement.The displacement of the superstructure is supposed to be relatively large during the earthquake due to the small stiffness of the isolation bearing.Therefore,it is necessary to add damping material to the isolation bearing to reduce the displacement response of the superstructure.The asphalt plays an important role in preventing the spring from erosion and providing additional damping in the isolation device.In this paper,cyclic simple shear apparatus was used to carry out reciprocating shear test of asphalt specimens,and the correlation between asphalt damping characteristics between Heavy Calcium Carbonate(HCC)mass ratio,cycle times,loading frequency,loading displacement and temperature was studied.The results show that the damping characteristics of asphalt are independent of the number of cycles,positively correlated with the loading frequency,and negatively correlated with the loading displacement,temperature,and the content of HCC.To verify the seismic capacity and isolation effect of spring asphalt isolation structure,the multi-dimensional shaking table test of spring asphalt three-dimensional isolation model was conducted.In this test,the role of asphalt ointment in the isolation bearing was studied by setting a control group.During the test,different intensity levels of horizontal,vertical,and multi-dimensional ground motions were loaded to study the influence of vertical ground motions and rocking ground motions on the seismic response of isolated structure.The test results show that the horizontal isolation effect of the isolation model is obvious in all test conditions,and all vertical accelerations have amplification effect in non-asphalt test.After adding the asphalt,the vertical acceleration decrease coefficient of Wolong wave is about 50%,while the vertical acceleration of Pacoima wave still has amplification effect;asphalt can significantly increase the damping ratio of the isolated structure,and can effectively reduce the displacement response of the superstructure;Based on the shaking table test data,the role of asphalt in the isolation structure was studied in this paper,the influence of vertical ground motions and rocking ground motion component on the isolation structure is researched.Furthermore,the influence of each damping solution method and its parameters on the damping ratio results was studied.The results show that asphalt can provide sufficient damping and reduce the displacements of superstructure by about 50%.The component of rocking ground motion can increase the acceleration and displacement response of superstructure;Both vertical and rocking ground motions could increase the seismic response of the isolation model.Vertical ground motions affect the seismic response of the structure by changing the horizontal stiffness of the structure.The rocking ground motion can change the earthquake forces of the structure and affect the seismic response of the structure.In order to further study the dynamic characteristics of the spring asphalt threedimensional isolation structure,the finite element model of the test model was established by using the finite element software ANSYS,and the modal analysis and dynamic time history analysis were carried out to verify the rationality of the finite element model.The results show that the finite element model can well simulate the horizontal response of the isolation model,and the single degree of freedom model can well simulate the vertical response of the isolation model.