Study On Input Seism Based On Interaction Of Upper And Lower Parts In Layered Soil-Field

For a long time, the rigid ground assumption has been used for earthquake response analysis in the seismic design in which only superstructure is considered in the model and the free field surface input of ground motion is adopted. However, as for the case of tall building with colossal vol. and vastness mass built on non-bedrock, the effect of interaction of upper and lower parts will be not allowed neglect, the structural input seism would be highly different from free field ground motion, so the input seism of seismic response analysis on tall building needs further and detailed examination.Centered on the problem above, this paper aims at integral method, which means the analysis of seismic response on soil-foundation-superstructure integral model, adopted at large for the moment, indicates the irrationality of the free field surface input of ground motion is adopted on this model, bring forward the input seism on this model is supposed to adopt seism acceleration time-history of the depth that correspond with the depth of using foundation. The research of the problem above makes the input seism of seismic response analysis on tall building to accord with fact better, and reduces the calculation error which is begotten by the unreasonable input seism.Below are the conclusions:1. The math model, which is linearity superpose of cosine function with uniformity district, is adopted to compose earthquake wave what is required, this method not only meets three elements of earthquake, but also corresponds to methods of response table in moderncriterion, so it is provided with practicability, this paper creates calculation procedure according to correlative theory, and makes manmade earthquake wave for Laxiwa Hydroelectric Power Station.2. It is feasible that earthquake acceleration time-history of interior stratum is obtained by Inversion of earthquake ground motion acceleration Time-History based on the theory that transient seismic response on soil deposits with linear hysteretic damping, this paper creates calculation procedure according to correlative theory. As demonstrated by numerical examples that using computer program SHAKE91 and finite element model, this approach can significantly improve the simulation of earthquake acceleration time-history of interior stratum.3. In contrast with earthquake ground motion acceleration Time-History, the amplitude of earthquake acceleration time-history of interior stratum plays down, and frequency speciality changes in a certain extent, this phenomenon indicates that soil deposits has magnifying and filtration effect on incidence wave.4. It is different obviously between the earthquake ground motion acceleration Time-History and the earthquake acceleration time-history of interior stratum.