Multi-dimensional And Multi-point Seismic Waves Simulation Based On Site Characteristics And Seismic Response Analysis Of The Bridge Structures

Correct earthquake input is a key factor to ensure the accuracy of structural seismic response,especially for large span structures with large plane dimension such as bridges,oil pipelines and offshore platforms.It is clearly not accurate if the seismic analysis is based on consistent earthquake excitation because the size of large span structure can not be ignored compared with the wavelength of seismic wave and the ground motions of fulcrums are different.The limited number,randomness and uncertainty of seismic wave have limited the application of multi-point direct dynamic analysis in practical engineering.Only by considering the different seismic excitations of fulcrums can the accuracy of the seismic response of the large span structure be ensured.Therefore,it is an important aspect in this paper to study the multi-point ground motion with characteristic parameters.In order to simulate the multi-dimensional properties,spatiality and nonstationarity of actual ground motion more accurately,following aspects are studied in this thesis;(1)The characteristic parameters of the acceleration time history of the ground motion are discussed and the statistical models and corresponding regression parameters of time domain characteristic parameters and frequency domain characteristic parameters of ground motion are summarized.(2)The process of fitting power spectrum and fitting design response spectrum synthesizing spatial multi-point non-stationary ground motion time history is studied.First,the design response spectrum is transformed into equivalent power spectrum(target power spectrum).Then the power spectral density function matrix is extended from one dimension to three dimensions to consider the multidimensional nature of seismic waves.Then the envelope function model is added with the consideration of the non-stationarity and the non-stationary vibration time course is synthesized by inverse Fourier transform.Finally,the amplitude of the synthesized earthquake time history is corrected by the frequency domain method to obtain the time course curve of the ground motion with enough accuracy.(3)Multi-dimensional and multi-point spatial non-stationary earthquake time course is synthesized based on phase difference spectrum.Firstly,the relationship between the phase spectrum and the non-stationarity of the ground motion is studied and The random phase distribution of[0,2?]generated by the computer can not make the ground motion time non-stationarity.Then the phase difference spectrum and frequency distribution is introduced and the impact on the nonstationarity of ground motion is studied.Finally,the tectonic phase difference spectrum model is used to synthesize the multi-dimensional and multi-point spatial non-stationary vibration time course.(4)The response of the bridge structre under the PEER seismic data selection and the artificial synthetic two ground motion is studied,the accuracy of artificial ground motion is verified.Finally,the multi-dimensional and multi-point non-stationary ground motion is used to calculate the seismic response of the Oujiang Bridge to calculate the local field effect.