The Dynamical Responses Of Base-Isolated System With Soft Soil Base Under Earthquake Situation

This dissertation firstly summarized present research work of structural control and base-isolation, and the necessity of considering soil-structure interaction for base-isolated structures is emphasized. The soil models that usually used in this kind of research work and the results are briefly introduced. Then, the steps of finite element dynamic analyses and the mathematical methods of resolving the equations are also particularly introduced.Through setting up the finite element models and performing the calculations, the basic frequency and the seismic isolation performance of lead-rubber bearing base-isolated structure considering soft soil-structure interaction under earthquake excitations are analyzed. There are four kinds of models being selected for the analyses, which include ordinary structure without soil-structure interaction (OS), base-isolated structure without soil-structure interaction (BIS), base-isolated structure considering soil-structure interaction (BIS-SSI), ordinary structure considering soil-structure interaction (OS-SSI). Each kind of model considered the variety of the stiffness of soil base or base-isolated layer. The input earthquake excitations are El Centro wave and Shanghai artificial wave.From the analysis results, one can get the conclusions as follows: (1) The soft soil's affection to the basic frequency of BIS-SSI is much less than the ordinary structure. (2) The isolation performance of BIS-SSI with soft soil base is not much better than OS-SSI under earthquake condition;the mid and low compressibility soil base have less effect on BIS-SSI and the seismic isolation performance is remarkable. (3) Under earthquake, the sway movement of lead-rubber bearing base-isolated structure with soft soil base is more obvious.