Seismic Analysis Of The Wavelet Decomposition’s Base-isolation Structure

In this paper, Seismic wave of Wenchuan is decomposed into non-overlapping and adjacent wavelet components through the use of the method of wavelet decomposition.The original wave and different wavelet components are input to the base isolated structure model and compare with non- isolated structural model,so that wecan get the influence of structural power by coming from riginal wave and different wavelet components.The main work and achievements are as follows:1. From the 5.12 Wenchuan earthquake database,we selecte Wenchuan Wolong seismic waves that is 19 km away from from the epicenter and Shaanxi marsh seismic waves that is 643 km away from from the epicenter.We use B-spline wavelets to decompose 8 times and get nine immediately adjacent and non-overlapping wavelet components.We use them to input time history analysis of seismic of base isolation system and not-isolated system.We draw acceleration diagram and Fourier spectrum diagram.2. This study shows that: no matter wolong wave and its different frequency band or grass wave and its different frequency band,whether or not the isolation structure with base isolated structure, the band which contains both the structure’s first mode frequency and original wave’s excellent frequency has excellent displacement response of the structure.Under the action of the band which contains structure’s first mode frequency, the displacement response of structure is also great.Under the action of the band which contains the original wave’ excellent frequency, the displacement response of structure is smaller, but it is higher than the displacementresponse of the structure under the action of other bands. Equivalent static force of structure is so.3. The high-frequency components that contribute to the structural displacement is very small, you can ignore the impact of high frequency components, the displaced contribution of low-frequency component is large,the isolated structural displacement of each floor is almost entirely contributed by the structure of the first vibration mode.The top displacement of the isolated structure is almost contributed by the base displacement.The isolated structure’s Layer deformation is greatly reduced compared to non-isolated structure. The each floor displacement of isolated structure under the long-period marsh wave is much larger than the displacement of isolated structures under the short-period Wolong waves, indicating long-period wave is more negative relatively isolated structure.4. In the action of Wolong wave and its wavelet components, the each floor’s equivalent static of isolated structure is far less than the equivalent static of non-isolated structure.But in the marsh wave,the each floor’s equivalent static of isolated structure is little difference than the equivalent static of non-isolated structure,indicating that isolated structure’s isolation effect is not so obvious in the marsh wave.Under the effect of the high frequency band,the each floor equivalent static of isolated structure under the long-period marsh wave is much smaller than the equivalent static of isolated structures under the short-period Wolong waves. Under the effect of high frequency component,the isolation structure’s equivalent static is far less than non-isolated structure.Isolation layer can be thought of a weak foundation,which has the effect of a low pass filter that filter some of the high frequency component of the seismic waves.5. Both in the action of a long period grass wave and in the action of a short period wolong wave, low modes play a leading role on the structure’s each floor ’s equivalent static. Isolated structure under the first and second order vibration mode has the largest proportion of the equivalent static, under the 3.13 Hz frequency band, the ratio of the first mode is greater than the proportion of the second mode, but in the above of 3.13 Hz frequency band, as a result of the action of inspired high ordervibration mode,which reduce the proportion of the first vibration mode.6. In the action of grass wave, wolong wave and corresponding different frequency band, isolation layer shear VA0 of isolation structure and the base shear VA1 of upper structure is roughly equal, isolation layer shear of building A is slightly greater than the base shear of the upper structure, but some frequency band will appear abnormal, between 6.25 and 12.5 Hz frequency band, VA0 is less than VA1, 3.13 ~ 6.25 Hz frequency band is also appear this kind of circumstance.