Analysis Of Influence Of Long Period Ground Motion On Core Structure Of Super-high-rise Frame With Sudden Change In Stiffness

With the rapid development of urban super high-rise building structure,in the pursuit of architectural art at the same time,irregular high-level structure has been widespread,Due to the characteristics of the long-period auto-oscillation for the super-high-rise structure,under the action of long-period ground motion,the floor with sudden stiffness change is easier lead to weak layer,which can cause huge damage to the super-high-rise structure if there will be a resonance reaction.Some previous disasters already proved,such as the 2008 Wenchuan earthquake and the 2011 earthquake in Japan,the impact of the super-high-rise structure under long-term ground motion is greater than that in ordinary earthquakes.However,due to the fact that China’s previous seismic code does not take long periods earthquake effects into account.Then many cases can not guarantee aseismic safety of the stiffness of the mutation super high-rise structure.Therefore,this essay are based on the analysis of long-period ground motion and ordinary ground motion,the main problems are analyzed from the aspects of ground motion spectrum characteristics and stiffness response super-high-level structure dynamic response as followed:1.Based on the factors such as seismic fortification standard,site condition and the period corresponding to the first vibration mode of the building,some long-period earthquakes recorded in the 1999 Taiwan-based Richter magnitude 7.6 earthquake are selected.Through Fourier spectrum,Magnification coefficient β spectrum,displacement response spectrum comparison,analysis spectrum differences between selected long-period ground motion and ordinary ground motion.2.This essay will discuss a super-A-level high-level high-rise frame structure Xiamen Baojia Center Tower project for the background,the building structure height of 168.4m,with 10th floor,19 layer,and 28 layer are uesed as refuge layer.Which is typically with vertical stiffness mutation,at the same time,according to the seismic code,it belongs to super high-rise building.The structure of the structure is analyzed by Satwe and SAP2000.The rationality of the structure and displacement ratio,cycle ratio,shear weight ratio,weight ratio,floor shear bearing capacity ratio should be able to meet the requirements of the specification were also verified by this two different software.3.In this essay,the layer displacement,the interlayer displacement angle,the floor shear and the overturning moment of the super-high-rise frame-core tube structurethe in three different intensity,which were the seven-degree zone(0.15g)and the 8-degree zone(0.3g)and the 9-degree zone respectively,they were analyzed by using mode decomposition response spectrum method and the oscillation time history analysis method with software SAP2000.In order to further explain problems,action of these three different intensity under earthquake had been carried out in this essay with elastic-plastic time-history analysis method,the influence of the weak layer and its upper and lower stress and deformation was analyzed emphatically.4.The design of the high-rise structure of the seismic design,the designer generally based on Seismic design specification and high-rise building codes,then only select the first few types of vibration mode,did not consider impact of high-end vibration to super high-rise structure.In order to study the influence of high-order modes on the super-high-rise structure,the seismic response of the super-high-rise structure under different modes is calculated by using the structural dynamic time-history analysis method.The results show that the influence of high-order modes on the internal force of the super-high-rise frame-tube structure is larger than that of the displacement,and the influence degree of the high-order mode is related to the dynamic characteristics of the structure and the spectral characteristics of the ground motion.