Energy-Based Passive Control Parameters Optimization Of Segmented Isolation System For High-Rise Building

In recent years, more and more high-rise buildings are moving toward irregular shapeand functional integration. Usually, it is necessary to set one or more transfer stories forarchitectural layout, which has become the development trend of modern high-rise buildings.However, structural engineers have been perplexed by how to design high-rise buildingswith transfer story, especially those with multi-level complex transferring or high-positiontransferring, because the discontinuity in stiffness, internal force and its transferring path willcause quite complex force and deformation in the components of neighboring stories aboveand below the transfer story, which is extremely unfavorable to earthquake resistance. It isdifficult to ensure the safety of these buildings using traditional systems and methods alone,due to the strong randomness of earthquake ground motion. Even if the building survives inthe earthquake, it usually suffers serious damages during earthquake, resulting in enormouseconomic loss and casualties, and exceptionally difficult and costly seismic rehabilitation.Therefore, it is a feasible way to conceive new earthquake-resistant structural systems ordesign concepts.Enlightened by the excellent seismic performance of the above ancient buildings, thispaper proposes the so called segmented isolation system to improve the poor seismicperformance of complex high-rise building with transfer story. The seismic isolation layers,composed of lead-rubber bearings and displacement-dependent dampers, are arrangedbetween the adjacent stories where structural system or structural configuration changes, andbase isolation is set at the same time.In this study, random vibration theory a·nd the principle of energy balance are adopted toestablish the method of energy-based parameters optimization. Subsequently, the optimalcontrol parameters are obtained by analyzed the parameters in 18 conditions. At the same time,energy analysis shows the change rules of the ratio of the isolation layer hysteretic energy andthe total seismic input energy which are showing as follows.Firstly, the mass ratios of the intermediate isolation layer and the base isolation layer aredifferent from the position of the intermediate isolation layer. Since the increase of the mass ratio, the displacement variance maximum of the base isolation layer decreased. While, thedisplacement variance maximum of the intermediate isolation layer is always approximate tothe ruled displacement limit of isolation layer. Moreover, the hysteretic energy of theintermediate isolation layer is larger than that of the base isolation layer.Secondly, there is a optimal frequency ratio that associated with the maximum ratio ofthe isolation layer hysteretic energy and the total seismic input energy, and the optimalfrequency decreased with the increase of the isolation layer mass ratio and the damping ratio,and increased with the increase of the isolation layer post-yield stiffness ratio.Thirdly, the mass ratio depends on the layout of the intermediate isolation layer. Whenthe intermediate isolation layer is close to the middle department of the structure, the ratio ofthe isolation layer hysteretic energy and the total seismic input energy is the largest.Fourthly, when the mass ratio is very small, the structure reduces the seismic response bytransferring the frequency ratio. With the increases of the mass ratio, the structure reduces theseismic response by transferring the frequency ratio and extending its natural vibration period.When the mass ratio increases to a certain value, the structure reduces the seismic response byextending its natural vibration period completely. It is clearly that, the mass ratio is animportant parameter to the design of the segmented structure.Moreover, when the mass ratio, frequency ratio and the post-yield stiffness ratio are ascertain, the ratio of the isolation layer hysteretic energy and the total seismic input energyincreased decreased with the increase of the damping ratio. Analogously, when the mass ratio,frequency ratio and the damping ratio are certain, the ratio decreased with the increase of thepost-yield stiffness ratio.Finally, the result worthy to be pointed out is that the larger the mass ratio and the softerthe site foundation, the larger the total seismic input energy. In the design of segmentedstructure, the site type should be choosen carefully.