Study On Time-frequency Characteristics Of Effective Energy Of Earthquake Based On Displacement Evaluation And Application In Wave Selection

At present,dynamic time history analysis is often used in structural analysis,and the rational selection of ground motion records is the primary problem of time history analysis,which is related to the reliability of the analysis results.In the selection method of ground motion record,normal acceleration response spectrum is used to reflect the amplitude and spectrum characteristics of ground motion,while the time and non stationary characteristics of ground motion can not be fully described.This is an important factor affecting the uncertainty of the structural seismic response analysis.In this paper,the effective energy of ground motion,which considers the time and non stationary characteristics of ground motion,is put forward by time frequency analysis.The effective energy of ground motion based on the displacement evaluation is the effective energy of ground motion based on the displacement evaluation.In this paper,based on the problem of determining the time frequency range of effective energy of ground motion based on displacement evaluation,and the initial use of effective energy to evaluate the selection results of ground motion records,the time frequency characteristics of effective energy of ground motion based on displacement evaluation are studied.Based on the single degree of freedom system and the multi degree of freedom system,the time-frequency characteristic of the effective energy of ground motion based on the displacement evaluation is studied by using the wavelet packet transform as the time frequency analysis method.A simplified calculation model of the time length and the frequency domain width of the time frequency range of the effective energy of the ground motion is established by a large number of statistical analysis.The ground motion is proposed.The method of determining the time and frequency range of effective energy is put forward,and the effective energy intensity index of ground motion is put forward combined with the determination method.Based on the actual engineering structure model,the reliability of the time frequency range determination method of the effective energy of ground motion is verified,and the results of the ground motion record selection are preliminarily evaluated on the basis of the effective energy intensity index of the ground motion.The main conclusions of the research work are as follows:(1)It is found that the larger the structure damping ratio is,the smaller the effective energy duration is.The effective energy duration increases with the increase of V/A value.Model parameter alpha and V/A have little influence on the effective energy frequency domain width.With the increase of ductility,the effective energy duration is smaller,but the effective energy frequency width is close.With the increase of the basic period,the effective energy duration increases and the frequency width decreases.(2)Based on the study of effective energy time-frequency characteristics,a simplified calculation model and effective energy time and frequency range determination method for effective energy duration and frequency domain width are proposed.In the proposed model,the effective energy duration increases with the basic period and then enters the platform stage.The frequency domain width is logarithmic with the basic frequency.(3)The effective energy intensity index of ground motion proposed by the time frequency range determination method of effective energy,which is directly proportional to the maximum displacement of the structural ground motion,can directly reflect the effect of ground motion on the displacement response of the structure,and can be applied to the preliminary evaluation of the selected Seismological records.The research of this subject can take full account of the non stationary and time holding characteristics of ground motion.It is of great significance to solve the problem of the selection of ground motion input in the process of the elastoplastic time history analysis of the building structure,as well as the seismic design of the building structure and the analysis of the demand for the probability of the earthquake.