Study On Equivalent Linearization Method Of Isolation Layer Under Moderate Earthquake

In the " Standard for seismic Isolation design of building " implemented in 2021,the calculation method of equivalent stiffness and equivalent damping ratio of isolation layer is proposed.However,the calculation method is complex and the accuracy is low,so it is not widely used in China.At present,domestic and foreign scholars have studied and put forward the equivalent stiffness and equivalent damping ratio formula according to the actual situation,but whether the formula can be applied to the isolated structure in China remains to be discussed.Based on this,in view of the accuracy of the acceleration response spectrum of the current equivalent linearization method with the " Standard for seismic Isolation design of building ",this paper uses the complex mode decomposition response spectrum method and the time history analysis method to analyze the isolation structure with different initial periods,yield displacement,ductility coefficient and post-yield stiffness ratio,and discusses the accuracy of the equivalent linearization method through the displacement and shear force accuracy coefficient.The main contents and conclusions of the study are as follows:(1)Under the fortification intensity,the nonlinear seismic response analysis of the isolated structure is carried out by using natural wave and artificial wave.The results show that the time history results under the action of natural wave and artificial wave are discrete.Compared with natural wave,enough artificial wave can effectively reduce the discreteness of time history results.When using three artificial waves for time history analysis,the discreteness of analysis results can be controlled within 30%.When more artificial waves are used,such as 100,the discreteness of the time history analysis results can be reduced to less than 3%.However,the method brings a large computational cost to the computer.(2)The R-H method combined with the bottom shear method is used to calculate the seismic response of the two-degree-of-freedom isolation model,and compared with the time history results of 100 artificial waves.The results show that the error between the seismic response calculated by the R-H method combined with the bottom shear method and the time history results is as high as 27.22%.The equivalent stiffness and equivalent damping ratio formula combined with the equivalent linearization method of the acceleration response spectrum of the " Standard for seismic Isolation design of building " is difficult to provide accurate guidance for the design of isolated structures.(3)The displacement and shear response of the two-degree-of-freedom isolation model with different initial period,yield displacement,ductility coefficient and post-yield stiffness ratio are estimated by using the equivalent linearization method of 14 equivalent periods and equivalent damping ratio formulas combined with the "Standard for seismic Isolation design of building " acceleration response spectrum method,and compared with the average time history results of 100 artificial waves.The accuracy of the equivalent linearization method is analyzed by the displacement and shear accuracy coefficients.1)The accuracy of the equivalent linearization method is affected by the model parameters.Considering the characteristics of the isolated structure,the YWZ method and the Ou method combined with the acceleration response spectrum of the " Standard for seismic Isolation design of building " can obtain the seismic response of the isolated structure with higher accuracy,which is more suitable for the isolated structure with high ductility.The remaining 12 equivalent linearization methods are based on the research of reinforced concrete structures and cannot reflect the characteristics of isolated structures.2)Under the condition of high initial period,14 equivalent linearization methods have achieved high accuracy.