Earthquake Response Reduction Analysis Of High-rise Reinforced Concrete Structures With Isolated Systems On The Top

The researches in the paper belong to natural science fund of Shanxi province(20051053), which concern high-rise reinforced concrete structures with upper floor vibration isolation systems in the passive seismic isolation and reduction fields. Main research utilizes the top part of construction as the quality one of TMD, also the flexible laminated bearings and dampers are inserted between a floor and the columns of top part of construction that support it. And the mass above isolation layer and isolation layer jointly make up TMD shock absorption system together which is to control seismic response.In this paper, the status of studies and applications of isolation bearing and high-rise building isolation technique is analyzed. It state the design thought of high-rise building interlayer seismic isolation structure, That is to say, earthquake isolation devices are settled on the top part of the foundation, and the tall building was separated into two parts by isolation floor. Dynamic interaction of upper and bottom structures and isolation devices were used to reduce seismic response. Its principle was stated through analysis and computing of two freedom degree system that is a concentrated mass model, in addition, the multi-degree of freedom system model based on lumped mass mode was analyzed, which test the conclusion of two-degree ahead. In conclusion, the main influence factors of high-rise building structure with isolated floor were found out. Those were gravitational load ratio and period ratio of upper and bottom structure, and damping ratio of isolation floor. The analysis indicated the feasible gravitational load ratio is R_g=0.01～0.35 and the feasible period ratio is R_T=0.9～1.1. When gravitational load ratio equals to smaller value, period ratio adopts smaller value, too.Based on the above-mentioned relevant conclusions, the paper have carried on qualitative analysis to some high-rise reinforced concrete structures with top story isolated systems, and contrast of two situations: one is the computational results of high-rise building with isolation floor system I were compared with the results of ordinary frame-shear structure I ,the other is the computational results of high-rise building with isolation floor system II were compared with the results of ordinary frame-shear structure II .in analysis, proper component FEM model and isolated element were adopted, through analysis of a high-rise structure with isolator or without by the way of software ANSYS. The researches indicated: it is effective that interaction of upper and bottom structures were used to reduce earthquake response of bottom structure. isolation action of upper isolation floor as TMD effect were exerted adequately to restrain from transferring earthquake effect, which is caused by earthquake. As under the effect of El-Centro earthquake wave, the layer-shear shock absorption ratio of top isolator system I can reach to 9.69% upward, maximum can reach to 45.5%, and the layer-shear shock ratio of top isolation system II only reach to 18.7%, the layer-displacement and displacement maximum shock absorption ratio of top isolator system I can separately reach to 46.2%, 44.2%, and top isolator system II can only reach to 19.5%,14.7%.from the analysis of the conclusion above, the shock absorption effect of top isolator system I is obvious highly. Of course , top isolator system II have certain effect. In sum, top isolator system have certain effect. And the merits of it consist in no need of extra mass and extra space, moreover, this scheme realized easily in actual project, and the cost can lower.Based on the former study, this paper analyzed the methods and the steps of top story isolation design, discussed the ways and the content of optimum design, and the requests of properties test of isolation component.