Study On Evolution Of Non-stationary Seismic Ground Motion Estimation And Modeling Of Power Spectrum

In this paper,the evolutionary power spectrum and the time-varying power spectrum estimation formula of non-stationary process are derived by using the generalized harmonic wavelets,and the non-stationarity response of Bouc-Wen system is analyzed on the basis of this formula,By estimating the evolutionary power spectrum of the realistic ground motion,the parameter model of the engineering ground motion power spectrum is proposed,and the parameters are identified.Specific contents include:Firstly,based on the basic theory of evolutionary power spectrum and wavelet transform,according to the general method of wavelet estimation and evolutionary power spectrum proposed by Spanos and Fallia,the formula for estimating the power spectrum and time-varying spectrum of non-stationary process is obtained by using the generalized harmonic wavelet,and the power spectrum and time-varying spectrum of the realistic ground motion record measured by Taiwan's SMART-1 station sequence is estimated.The time course of ground motion is simulated by spectral performance method,The results show that The characteristics of the acceleration time of artificial ground motion are similar to the original recording.After that,the response of the Bouc-Wen system under nonstationary harmonic excitation is calculated,and the evolutionary power spectrum of the response is obtained by using the proposed method for estimating the power spectrum of non stationary processes by generalized harmonic wavelet.The results show that the nonstationary characteristics of harmonic excitation have influence on the nonlinear response of the structure.When the period of harmonic excitation is close to the natural vibration period after the system enters the nonlinear phase,the reaction and failure of the system will be further increased,Resulting in secondary resonance phenomenon.Finally,a parametric model of evolutionary power spectrum is proposed,which consists of frequency domain energy distribution function and a series of normalized time-dependent envelop functions for different frequencies.The frequency domain energy distribution function model considers the influence of the seismic source and the local site on the spectrum of the seismic ground motion,the normalized time-dependent envelop function takes the form of piecewise smooth function.Based on the proposed evolutiona power spectrum model,the realistic ground motion record measured by Taiwan's SMART-1 station sequence is Modeled and parameter identified.The modeling results show that the engineering ground motion power spectrum model can reflect the nonstationary characteristics of the realistic ground motion and can be used to simulate the artificial seismic ground motion time histories.The research of this paper provides a theoretical basis for the estimation and modeling of evolutionary power spectrum for non-stationary ground motion,and also provides the basis and technical means for seismic response analysis and seismic design of civil engineering structures.