Study On Seismic Performance For Story Isolation Structures And Analysis Of The Sensitivity For Isolation Bearings

The story isolation structure is a new type of seismic structure evolving from the application of base isolation technologies in engineering practices. It makes the story isolation to be established between some pillar and floor to control the earthquake reaction on the structure. The story isolation may also regard as the result which base-isolation layer transfers to the upper part of the structure, according to the characteristic of structure, in general, isolation layer is set in the part where the structure's vertical stiffness is sudden changed. It can be set on the top of the first layer, middle layer, conversion layer of the structure, and so on. The present research work is at the initial stage, and also does not have system's theory and the experimental study achievement.For the structure with a large podium and the multi-tower high-rise structure with a large podium, the base structure is one or several podiums, but the above is several multi-layered or the high-level domestic buildings. Because the base area is big, base isolation needs to use the massive rubber support, making the construction cost increased, therefore the isolation layer is not suit to be established in the foundation, if adopting the story isolation technology, installing isolation layer between multi-tower and a large podium, simultaneously improve the stress condition of the large podium structure and the earthquake resistance performance of the above structure, reducing the construction cost greatly.Firstly the multi-tower structure with large podium where the stiffness of the structure is changed sharply. This will cause the destruction under the earthquake function, Applying story isolation to this kind of big podium and vertical anomalous structure, installing isolation layer in the rigidity sudden change place. Using the finite element software Etabs, which will carry on the time history analysis for the structure of one-way and two-way seismic response, compare the changes between isolation structure and non-shock insulation structure in the shearing force, the cycle, the aspect and so on, judging the damping effect of the story isolation. Secondly evaluating the key point of the story isolation structure is the substructure, analyses alone to the substructure must exert the influence from superstructure to the substructure in the substructure, then the vertical anomalous structure's substructure is regarded as the non-shock insulation structure to carry on the Pushover analysis, the result indicated after the isolation layer is established, the substructure still had the very good seismic performance。Confirms once more, under near fault pulse-like ground motions, the story isolation structure have the very good absorption of shock effect, but the max horizontal displacement distortion fill-out which compared to the conventional earthquake wave, therefore the protective measures should be completed.Finally carry on the optimized analysis to design parameter of the story isolation structure in two design methods:(1) taking the support level shear stiffness as the optimization design variable, then mading a series of time-history analyses to the story isolation structure. the result indicated that the level shear stiffness was smaller, the shock insulation effect was better; (2) respectively when the isolation layer is with damping and without damping, carry on a series of time-history analyses on story isolation structure of differential preyield stiffness, for the optimization design of the story isolation structure, which provides an effective way and a useful reference.