Study On The Response Spectrum Characteristics Of The Earthquake In Yongsheng,Yunnan

Response spectrums from seismic records in different regions are very different.At present,the study on the acceleration response spectrum of high intensity seismic region in Yunnan province is less.Defining earthquake effect of engineering structures is according to the national unified response spectrum specification.The acceleration spectrum is suitable for inertial force sensitive ground structure.Underground structures or pipeline engineering are insensitive to inertia forces.However,speed and displacement have the most impact on them.Therefore,their velocity and displacement spectrum should be studied.This study focuses on acceleration spectrum,velocity spectrum and displacement spectrum according to the actual 6-level seismic records in Yongsheng,Lijiang,Yunnan Province in October 27,2001,mainly including the following aspects:(1)The response spectrum characteristics of engineering structures with damping ratios of 2%,5%,10%and 15%are discussed and the variation characteristics and the changing tendency of the response spectrum under different damping ratios are studied.(2)The article studies on the standard spectrums of 100 typical seismic records of earthquake records in Yongsheng.The research objects include the relative displacement spectrum,relative velocity response spectrum and the absolute acceleration response spectrum.According to the characteristics of the actual spectrum curve,it can be divided into four segments for fitting so that the fitted spectral function which can reflect the actual spectrum is obtained.The study has some difficulty in the determination of inflection points.In this paper,the inflection points of 100 actual response spectra are extracted,which are divided into groups,by least squares method,intercept slope average method and Weibull distribution parameter estimation method,to determine the coordinates of the inflection points and connect inflection points for fitting spectrum function.Finally,fitting spectrum function and the actual spectrum function are compared and analyzed,which is obtained by three different methods.(3)At the same time,the non-stationary characteristics of the 100 actual ground motion frequencies are studied.The crossing-zero rates model and the cumulative crossing-zero rates model are established.The relationship between the crossing-zero rates model parameters and the characteristic period of response spectrum is studied.The characteristics of non-stationary frequency are also analyzed.