Dynamical Analysis Of Cushioning Effect Of Isolation Project For Structures With Changing Vertical Stiffness

The technology of installing shock-isolation devices between a building's basic top and its upper structure so as to realize the shock-isolation effect, is called basic isolation. With further research and applications of basic isolation in engineering practice, interlayer seismic isolation which is to put shock-isolation devices between stories so as to have the result of shock insolation is developed. Depending on locations of seismic isolation devices in a building, interlayer seismic isolation is classified into mid-story seismic isolation and top-story seismic isolation. The research emphasis of this dissertation is on the response of isolation structure to an earthquake when the isolation bearings are located under the top floor, isolation and cushioning effect.This paper is going to elaborate on the characteristics and choices of isolation bearings, form finite element computational modelling of top sotry isolation, and deduce structural power balance equation. A 22-floor building with 4 under chassis is introduced as an example, where the upper shear wall has large changing vertical stiffness. With the use of ANSYS, elastic and elastoplastical time-history response analyses are conducted on traditonal aseismic structure and top story isolation structure. And according to the result of time-history analysis, respective story's relative displacement and acceleration can be worked out.A comparison is made between response of general aseismic structure and that of top story seismic isolation. Research shows that, through specific reseach design of story isolation, top story isolation structure has far more obvious and desirable effect than that of aseismic structure.