Study Of The Simulation Technology Of Ground Motion For Soft Soil Site Based On Statistical Characteristic

Simulation technology of ground motion plays a very important role in the work of seismic safety evaluation,structural dynamic time history analysis and aseismic design.Currently,the simulation technology of ground motion at soft soil site usually can be obtained in two steps.Firstly,confirm bedrock ground motion via attenuation relationship and then obtain the ground motion via computational model for site seismic response.However,attenuation relationship is usually confirmed through the statistic of surface ground motions,while seismic response of soft soil site is complex and model for site seismic response also has larger uncertainty.This paper carries out statistical analysis to the engineering characteristic parameters of ground motions at soft soil site based on the data of recorded ground motions,and conducts proper discussion and improvement of the application of simulation model of ground motions by Sanaz Rezaeian in the simulation of ground motion at soft soil site,and conducts ground motions simulation via parameter regression results and makes the validation.The main work and conclusions of this paper are as follows:(1)Ground motions recorded on soft soil site and bedrock site nearby have been collected.The confirmation of engineering characteristic parameters for quantitative description of ground motions from three aspects of traditional characteristics,intensity envelope and frequency non-stationarity;and study of the regression relationship between parameters and moment magnitude and fault distance.The comparative analysis to the regression results of the engineering characteristic parameters of ground motions recorded on soft soil and bedrock site.(2)The discretized simulation formula of ground motions by Sanaz Rezaeian is the theoretical basis.The advantages of simulation model of ground motions by Sanaz Rezaeian are discussed.According to the comparison of power spectrum model,the impulse response function(IRF)for the absolute acceleration response is selected as the model IRF.(3)The discussion of recognition of model frequency parameter via instantaneous predominant frequency obtained by HHT method.It's found that the natural logarithm of instantaneous predominant frequency is approximate to normal distribution through the statistic in stochastic simulation process when parameters of model IRF are fixed.There's approximate linear correlation between its standard deviation and damping ratio of IRF.Linear fitting is carried out to instantaneous predominant frequency of ground motions after taking natural logarithm to recognize model parameters which control the predominant frequency,and the fitting residual standard deviation is used to recognize the damping ratio of model.(4)Statistical regression is made to model parameters recognized from ground motions recorded on soft soil site,and simulation of ground motion is further made via parameter regression results.Comparisons with two real ground motions and NGA model by Boore and Atkinson(2008)are respectively conducted and the simulation results are validated.