Study On Seismic Behavior Of The Box Foundation-high Rise Structure

As the land used for buildings of major cities is decreasing,the buildings can only develop to the underground and air to increase space.Therefore,the high-rise buildings with box foundation are more and more favored by people.With the emergence of box foundation-high rise structure,the earthquake disaster prevention is becoming more and more prominent.However,the study on seismic performance of high-rise buildings in our country started late,although the current code for seismic design of buildings(GB50011-2010)gives some explanation to the structural design under dynamic interaction of soil-foundation-superstructure,there is still a great lag in the theory of seismic design due to the complexity of dynamic interaction.In particular,the study of domestic scholars are more concentrated in the pile foundation than common box foundation in project.Therefore,it is necessary for us to strengthen the research on the seismic performance of the box foundation-high rise structure.The dynamic time history analysis of building model was carried out by using the finite element analysis software ANSYS with some building as the engineering background,and the seismic performance of the box foundation-high rise structure was researched in this paper.First,the appropriate material constitutive model and seismic response analysis method were selected,and the soil,box foundation and superstructure were modeled reasonably,whose validity and accuracy were verified by comparison between the results of static analysis in the gravity field with the real measurement data in project.Next,the time history analysis of the structure on rigid foundation and the soil-foundation-structure dynamic interaction system was carried out by inputting EL-centro wave,Kobe wave and Shanghai artificial wave,and the displacement and internal force response of the box foundation in interaction system under different earthquake excitation and different working conditions,the contact pressure between the foundation and the soil,and the influence of the core tube were analyzed.Last,the differences of natural vibration characteristics,displacement response,acceleration response and internal force response between two models were further discussed quantitatively.The main conclusions are as follows:(1)the displacement time history curve of the corresponding measuring points on both sides of the box foundation is basically consistent,which means that the vibration of each part of the box foundation in the seismic process is overall orderly,and this is the basic reason for the excellent seismic performance of the box foundation.(2)the stiffness difference of each direction of the box foundation caused by the irregular shape was balanced by core tube structure,which improved the seismic performance of box foundation.(3)the phenomenon of separation and reclosing between box foundation and soil in vibration indicates that the foundation is constantly swinging in the process of vibration,which explains the reason for the tilt and the overturning of the high-rise buildings during the earthquake and confirms the importance of the foundation of anti overturning ability.(4)The effect of shock absorption of the dynamic interaction of soil-foundation is mainly reflected in the high-rise building,and the seismic design of high-rise buildings under the assumption of rigid foundation tend to be conservative overall and unsafe partially while it is more in line with the actual situation considering the foundation-box foundation-structure dynamic interaction.The rationality of practical engineering design scheme is verified,and the important theoretical basis for the subsequent seismic optimization design of the background project is provided by the research results of this paper.At the same time,it has a certain significance for the improvement and development of the seismic design of high-rise building.