Seismic Performance Of Multi-Tower Buildings With Mechanical Floor

With the progress of science and technology and the continuous improvement ofproductivity level, architectural design develops from a single function to multifunctionand multipurpose, comprehensive direction, hence, a series of complicated high-risestructures appears. Multi-Tower Buildings is one of complicated high-rise structures,Due to the change of the function of the upper and bottom part of the structure system,the bottom is always set for commercial use，upper with two or more than two towers asthe main structure. Between the base and the towers, it has to place a mechanical floorto transfer the function. Mechanical floor hight is usually below2.2m, in order tocontrol the building area. Below the mechanical floor, it is for the public use, so thefloor hight can reach5.0m or more. To the opposite, the upper towers’ floor hightmostly focus in3.0m.To that reason, the lateral resisting stiffness ratio has difficulties toachieve uniform change, which leads to structure interal force mutations. It hasimportant engineering practical significance that how to deal with the lateral stiffnessmutations.Multi-tower building has complicated structure form, the lateral stiffness mutationis hard to meet the code requirement and has a great influence on the building safety.The natural period of vibration has the characteristics of close and high frequency,which brings about the obvious high frequency vibration. Therefore, we need chooseenough vibration modes and proper vibration mode combination method whileanalyzing. In this paper, firstly, the author elaborates multi-tower buildings’ researchstatus and the existing problems and analyses the necessity of solving this problem. Then, the solution is raised--delivering the load from the upper floor to the mechanicalfloor by a support structure. Thirdly, combining to the case, the author builds theoriginal model and the support one in SAP2000and does response spectrum analysisand elastic dynamic analysis. The two models were compared on stress and deformation,demonstrating that the support structure plays an important role in improving the wholebuilding’s performance.Using PERFORM-3D software of finite element analysis, the joist structuremodel is taking the elastic-plastic time-history analysis under expected rare earthquakeof8degree. Studying the seismic performance and the component damage of this kindof structure, the author suggests that the elastic-plastic time-history analysis should bedone to find out the seismic weak floors, which are different in the elastic dynamicanalysis and the elastic-plastic time-history analysis. So we should pay more attention tothis while designing.This paper demonstrates the feasibility of the joist structure, systematicallystudies the dynamic characteristics of the multi-tower building with mechanical floorstructure system under horizontal earthquake action, proving that the joist structureproduces a positive role to the whole building. It provides advices to this kind ofstructures’design.