Study On The Sensitivity Of Seismic Response Of Seismically Isolated Structures Based On The Randomness Of Rubber Bearing Performance

At present,rubber seismic isolation bearings are more and more widely used in structural engineering.The mechanical properties of the bearing play an important role in the seismic isolation effect of the structure,and the randomness of the mechanical properties of the bearing will affect its normal operation,thus making the seismic response of the structure more complicated.However,the random effects of the mechanical properties of rubber seismic isolation bearings are rarely considered in the current seismic isolation design,so it is necessary to conduct an in-depth study.In this paper,the probability distributions of the vertical and horizontal mechanical properties of sample bearings are analyzed with rubber seismic isolation bearings,and the effect of the randomness of the bearing performance parameters on the seismic performance of the foundation seismic isolation structure is investigated to determine the sensitivity of the seismic response of the structure to different mechanical parameters of the bearings.The main work of this paper includes:(1)Vertical and horizontal performance tests were conducted on three different types of rubber isolation bearings,LRB-600,LRB-800 and LNR-800,and the hysteresis curves and mechanical performance parameters of 90 sample bearings were obtained.The results of the basic performance tests of the rubber isolation bearings revealed that the mechanical properties of LRB-800 bearings were significantly higher than those of LRB-600 bearings and LNR-800 bearings.The test results of different mechanical parameters of the bearings were statistically analyzed,and their statistical parameters and frequency distribution graphs were obtained.The results show that the coefficients of variation of different mechanical parameters of the three sample bearings are small and the data distribution is relatively concentrated.(2)Statistical methods were applied to analyze the dispersion of different mechanical parameters of the rubber vibration isolation bearings,and to quantify the probability distribution characteristics of different mechanical parameters of the bearings by the kurtosis and skewness of the mechanical properties results of the bearings.The goodness-of-fit test was used to examine the fitting effects of the normal distribution model,the extreme value type I distribution model and the log-normal distribution model,respectively.The results show that the probability distribution of the vertical stiffness of the rubber isolation bearing is optimal using the lognormal distribution model,and the probability distribution of the horizontal equivalent stiffness,post-yield stiffness and yield force is optimal using the normal distribution model.(3)Considering the random influence of the mechanical properties of the bearing,the finite element model of the foundation seismic isolation structure was established by ETABS software,seven seismic waves were selected for two-way ground vibration time analysis,and the interstory displacement angle of the above structure,the horizontal damping coefficient and the maximum horizontal displacement of the bearing were taken as the seismic response indexes of the structure to evaluate the sensitivity of the seismic response of the structure to the mechanical parameters of the bearing.The results show that the seismic response of the structure is the most sensitive to the yielding force of the lead-core rubber isolated bearing,the second most sensitive to the post-yielding stiffness of the bearing,and the weakest sensitive to the horizontal equivalent stiffness of the bearing.