Study On The Basic Problems Of Site Seismic Response Based On Equivalent Linearization Method

A large number of seismic damage investigations,strong ground motion observation data and theoretical results show that the site conditions have a significant effect on the amplitude characteristics and spectral characteristics of ground motion,which directly affect the degree of earthquake damage.Therefore,determining a reasonable and reliable site seismic parameters according to the site conditions and site response analysis is the key technical issues for seismic zoning,site seismic safety evaluation and seismic analysis of engineering structures.The seismic response analysis of site involves the problems of input ground motion of underlying rock,soil dynamic model and soil seismic response calculation method,which are interrelated.Due to the fact that the ground motion parameters are affected by complex factors,these problems can invoke large uncertainty of the resulting seismic fortification parameters.In view of the above problems,this paper studied the basic problems of the application of seismic response analysis in engineering practice based on the traditional theory of ground motion synthesis and site seismic response analysis.The method of ground motion synthesis and site seismic response calculation are put forward,and the degree of influence of the uncertainty of the input ground motion on the ground motion parameters is analyzed.The works are as follows:1.By probing into the traditional ground motion synthesis method based on trigonometric series superposition method,the paper proposed a method of ground motion synthesis for fitting “densified” target response spectrum,the number of whose controlling points coincides with the number of frequency points for Fourier transform.The method also considers the baseline drift problem of synthetic ground motion.Two baseline correction methods are proposed,one being superimposing pulse function in time domain and the other adjusting the Fourier amplitude in frequency domain.2.Based on the wave theory,a one-dimensional equivalent linear calculation program of site response was developed.And the applicability of the program is verified by the actual site data and array observation records.3.Based on the method of ground motion synthesis and seismic response calculation,this paper studied the problem of inversion analysis based on the equivalent linearization method.Also,the method of determining the reasonable input ground motion for the major infrastructures,such as nuclear power plant,which should take into account the effect of soil-structure dynamic interaction,was proposed.4.This paper analyzed the influence of the randomness of the input ground motion on the calculated ground motion parameters under different site conditions and different input ground motion intensity.And it was revealed that the number of input ground motion used in the current seismic safety assessment cannot ensure reliable evaluation of site-specific ground motion parameters,which might present large disperse due to the limited number of input ground motion.The paper is engaged in the theoretical study of ground motion synthesis method and site seismic response analysis method.And besides,the application of the methods in the field of earthquake engineering is also considered.In the aspect of application,there are some problems in the ground motion inverse for determining the input ground motion of significant structure and in the influence of the randomness of input ground motion.The paper put forward reasonable suggestions for the related issues.