Influence Of Basement On Seismic Response Of Superstructure

Based on the theory about three-dimensional time-domain viscoelastic artificial boundary and seismic wave inversion,this paper uses finite element software(ANSYS)to establish a three-dimensional analysis model of high-rise building structures.The effects of soil type,basement stiffness,and basement depth on the seismic response of the superstructure are analyzed by considering the soil-structure interaction.The analysis shows that the ratio of the dynamic characteristics of the soil body to the basement is the main factor affecting the seismic response of the superstructure.Based on the theory about equal-rigidity shear-type rod unit period,the period ratio of the soil body to the basement is derived.The main conclusions are as follows:(1)Taking the basement roof as the embedded end of the calculation model,the seismic response of the superstructure is greater than the calculation model considering the soil-basement structure interaction.In engineering design,when the periodic ratio of soil to basement ζ≥1.0and shear stiffness ratioye≥1.0,the basement roof can be regarded as the embedded end of the superstructure.(2)With the increase of the lateral displacement stiffness of the basement(the increase of the period ratio ζ or the increase of the shear stiffness ratio γe),the seismic response of the superstructure tends to decrease.And compared with the model where the basement roof is embedded,which can reduce about 3%～ 10%.In engineering design,the lateral stiffness of the basement can be appropriately increased to reduce the seismic response of the superstructure.(3)The horizontal distance between the basement shear wall and the superstructure has little effect on the seismic response of the superstructure.The influence of the horizontal distance between the basement shear wall and the superstructure can be ignored in the engineering design,and all the shear walls in different positions are included in the basement overall lateral stiffness.(4)The analysis shows that the seismic response of the large-chassis multi-tower structure is slightly larger than that of a single tower,but it is still smaller than the structural analysis model using the basement roof as the embedded end.In engineering design,under the condition of meeting the overall lateral stiffness of the basement,the basement roof is regarded as the embedded end of the superstructure,and each tower is analyzed separately to achieve the purpose of simplifying structural analysis and design.(5)The increase of the buried depth of the basement is helpful to reduce the seismic response of the superstructure,but the reduction is not obvious,and this beneficial effect may not be considered in the engineering design.