Study On The Influence Of Intensity Envelope On The Synthetic Ground Motion

Earthquake is a nature disastrous phenomenon which causes casualty and catastrophic losses to human society and economy. To test the seismic response of structures in seismic design, especially the key structures, ground motion on the same site category has to be input to the structures. Then the resistant capacity of structure can be evaluated with respect to a level earthquake. However, there are a few seismic recordings actually, most of which are recorded in small earthquakes or in far field. Also these recordings can not be predicted precisely and repeated, thus synthetic ground motion can be used. The synthetic ground motion has to fit the response spectrum but the reliability of the synthetic accelerogram is scarcely assessed. In this thesis, it is demonstrated that the parameters of intensity envelopes can determine the shape and amplitude of the synthetic accelerogram. Therefore, study on the influence of intensity envelope on the synthetic ground motion is apparently necessary and significant.In this thesis, firstly introduction of synthetic ground motion technology and development as well as ground motion basics are presented, and then the theory and method of synthetic ground motion are illustrated herein. Using trigonometric series, the computer program for synthesizing ground motion accounting for phase has been coded, which modifies the iterative formula of adjusting amplitude and presents the background for synthesizing ground motion. Secondly, the concepts of intensity envelope and the effects of intensity envelope on the trigonometric series spectrum and response spectrum have been discussed in the thesis. Eventually, random number series and time series with initial phase the same as Elcentro ground recording are chosen respectively to obtain the effects of intensity parameters on spectral synthesizing and accelerogram by changing the parameters (e.g. t1, t2 and c ) and site category.In this thesis, the effects of intensity parameters on synthetic ground motion have been investigated, which provides the theoretical background for synthetic ground motion and presents referring suggestions for future research.