The Wavelet Compound And Application Of Time Frequency Non-Stationary Seismic Motion

Earthquake is a great danger of sudden natural disasters, and with this related aseismatic engineering research has been a hot research in the civil engineering. The analysis of time history is an important structure of a main seismic design method, its primary problem is the input of seismic motion. Because of the limitation of the existing record of the seismic motions and the complexity of the process to meet the actual request of the seismic motion record is almost impossible, thus the artificial seismic motion becomes one of the important sources in the earthquake response analysis to input the earthquake wave, and will be playing more and more vital role along with the computer simulation technology in the development of the seismic design. But, in the synthesis artificial seismic motion method, whether based random process theory nor response spectrum approximation theory, what more concern is the non-stationary, the phase change, the remarkable frequency and maximum amplitude of the earthquake fatigue, but the attention to the seismic motion time-frequency (frequency changes with time) characteristics is few, made the different between the artificial and the actual.In order to implement the non-stationary of synthesis seismic motion frequency, this article attempts to put the wavelet packet decompasition technique applies in the artificial seismic motion synthesis technology, in use the good time-frequency localization nature of the wavelet function, proposes one feasible artificial seismic motion synthetic method: through the wavelet package of decomposition technology, to put the initial seismic motion be decomposed step by step. According the engineering design needs, adjusts different frequency band's frequency component content, then uses the wavelet packet restructuring technology, reconstructs of the different band components , to obtain the time-frequency non- stationary seismic motion history. As this process may be divided by the time interval to carry on, it can realize the frequency non- stationary of the stochastic seismic motion, and also has made up the limitation of Fourier transformation. Finally, by the wavelet method approaching the seismic motion's goal response spectrum to obtains the artificial seismic motion history which satisfies the location needs.In order to confirm feasibility of this method, according to the response spectrum theory, unifying the seismic geologic condition of the Xiaowan hydroelectric dam site, the thesis calculates the location target response spectrum. Take the Tianjin wave as the initial seismic motion, use the above method to make the frequency adjustments, then approximate the procedure which has been adjusted to the location response spectrum of the Xiaowan area, this thesis obtains the artificial seismic motion history which met the project needed.