Study On Time-frequency Spectrum Input And Structural Reliability Of Yunnan Yongsheng Earthquake

Seismic signal is a non-stationary stochastic process,which has strong non-stationary characteristics in time domain and frequency domain.Therefore,non-stationary ground motion will cause great damage to the structure.Traditional seismic signal analysis methods can not obtain the distribution of signal characteristics in time domain and frequency domain respectively.Because the distribution of signal characteristics in time domain and frequency domain can be obtained simultaneously by wavelet transform theory when analyzing non-stationary random processes,this paper chooses harmonic wavelet to study the time-frequency power spectrum of actual ground motion.By studying the time-frequency power spectrum of ground motions,the time-domain analysis or frequency-domain analysis of ground motion has been extended to the time-frequency domain for fine analysis,deepens the understanding of time-frequency characteristics of non-stationary ground motions,and provides theoretical basis for structural random seismic response analysis.In this paper,the relationship between power spectral density function and instantaneous power is established from the perspective of energy,and the estimation relationship between power spectrum and harmonic wavelet coefficients is obtained.A time-frequency power spectrum estimation model is established based on harmonic wavelet theory.The actual seismic signal energy is analyzed,and the correctness of the model is verified in time domain and frequency domain respectively.By studying the time-frequency characteristics of Yongsheng seismic record in Yunnan,the energy distribution of seismic record in time domain and frequency domain is obtained.The random dynamic response of the structure under Yongsheng earthquake is obtained by random vibration analysis of the building structure,The time-frequency power spectrum model based on harmonic wavelet is used to estimate the time-frequency power spectrum of the dynamic response of the structure,and the first-order failure criterion based on the assumption of mapxob process is used to study the dynamic reliability of structures.The results show that the structural reliability is the highest in the initial stage of earthquake,and the reliability in the peak acceleration section decreases sharply,and the reliability in the acceleration attenuation section tends to be stable.