Changes In Mechanical Properties Of Vibration-isolated Rubber Bearings At Low Temperatures And Their Influence On Seismic Response Of Vibration-isolated Structures

Because of its reliable performance in earthquakes,the isolation structure has developed into a mature means of shock-absorbing disaster prevention,and the isolation system using rubber shock-absorbing support has been widely used.With the vigorous promotion of seismic isolation technology,the application environment of rubber support isolation system is becoming more and more complex,and the influence of changes in the temperature of different applications on the technical performance of the isolation device and the seismic response of the isolation structure has gradually become an unavoidable problem.However,at present,when china is designing the isolation structure,the parameters of the performance of the rubber isolation support in different temperature environments are generally used as solid values,and the adaptability of the rubber isolation support and insulation structure to the temperature is not reflected in the seismic design specification,which makes the rationality of the design results uncertain.Coupled with the minimum temperature stipulated in the rubber isolation support temperature correlation test only reached-20℃,but the winter temperature in northern China is cold,the average temperature in the northern part of Heilongjiang in January is-28℃,it is clear that the minimum test temperature given does not adapt to these cold areas for the temperature correlation test of the support.In order to further study the change of the support dynamics in low temperature environment and the influence on the dynamic characteristics of the isolation structure,it provides a useful reference for the seismic design of the high cold and high intensity areas.This article conducts the following research work:(1)The vertical compression test and horizontal shear test were carried out on natural rubber vibration isolation bearings and lead rubber vibration isolation bearings at-40℃,-30℃,-20℃,-10℃ and 23℃,and systematic exploration the influence of low temperature changes on the mechanical properties of the bearing and the changing laws of mechanical properties parameters are discussed.The test shows that the vertical compression stiffness of the two types of bearings in the vertical compression test gradually increase with the decrease in temperature;the horizontal equivalent stiffness of the natural rubber isolation bearing in the horizontal shear test is approximately exponential with the decrease in temperature as the function increases,its equivalent damping ratio remains basically unchanged as the temperature decreases.The equivalent damping ratio,post-yield stiffness,yield shear force and equivalent horizontal stiffness of the lead rubber vibration-isolated bearing all increase nonlinearly with the decrease of temperature.With the decrease of temperature,the shape of the hysteresis curve of the two supports gradually becomes fuller,the area gradually increases,and there is a tendency of upward warping.Finally,according to the test results,the function of the mechanical parameters of the support(vertical stiffness,horizontal equivalent stiffness and stiffness after yielding)with temperature is fitted.(2)The shear properties of vulcanized rubber at the same low temperature were tested.The results show that the shear modulus of rubber increases with the decrease of temperature.Then,combined with the relevant research on the performance changes of steel and lead core at low temperature,the reasons for the mechanical parameters changes of the isolation bearing caused by the mechanical properties changes of the main components of the bearing at low temperature are discussed.(3)In order to study the laws of the changes in the mechanical properties of the rubber isolation bearings due to low temperature and the dynamic characteristics of the isolation structure,the analysis model of the base isolation structure is established,and the test results obtained through the pseudo-static test of the isolation bearings at low temperatures are used.According to temperature,it is divided into 5 working conditions for time history analysis.Systematically explored the shock absorption coefficient of the seismic isolation structure,the hysteresis curve of the support under the fortified earthquake and the rare earthquake,the maximum displacement of each support of the isolation structure under the rare earthquake,and the change of the maximum displacement angle between the structure layers at each low temperature.law.The analysis results show that the damping coefficient of the base-isolated structure gradually increases with the decrease of temperature.When the temperature is lower than-10℃,the structure will not be able to reach the isolation target of 1 degree drop;earthquake isolation is rare The maximum displacement of each support of the structure decreases as the temperature decreases,and the maximum interstory displacement angle of the seismic isolation structure increases as the temperature decreases,but the maximum interstory displacement angle of the structure as a whole is within the allowable range of the specification Inside.