地基土模型对土–结构相互作用体系地震响应影响的初步分析
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摘要
在目前常用的土–结构动力相互作用分析方法中,通常将地基土简化为弹性半空间模型,通过弹簧–阻尼器单元考虑土体对结构的影响,而弹簧–阻尼器单元的计算参数则通过阻抗函数确定。但实际工程中地基土并不是弹性半空间模型,将地基土简化为弹性半空间模型将会给土–结构相互作用体系地震响应带来多大的误差,针对该问题,本文主要考虑3种地基土模型:理想弹性半空间模型、置于刚性地基表面的分层地基土模型和置于弹性半空间上的分层地基土模型。先从不同地基土模型阻抗函数经验公式表达式入手,定性分析不同公式对地基土阻抗函数的影响;然后基于2个具体的算例,分析不同地基土模型对土–结构动力相互作用体系自振频率、加速度响应及其反应谱等的影响。计算分析表明:虽然由不同经验公式得到的静阻抗值有一定差异,但在综合考虑刚度系数后,动阻抗值相差并不大。因而,不同地基土模型对体系频率特性和地震响应的影响并不大。研究成果可为土–结构动力相互作用体系初步抗震设计提供参考。
The soil is usually simplified as an elastic half space model and its influence is replaced by springs and dashpot elements,which is the most common method for soil-structure interaction(SSI) problem. The computation parameters of spring and dashpot elements are determined by soil impedance functions. But this is not the case in practical engineering because soil is not always a half space. Focusing on this problem,the aim of the paper is to study the influence of different soil modes on seismic response of soil-structure interaction system. Three kinds of soil models are considered,which are elastic half space model,stratum-over-rigid model and stratum-overhalf-space model. The influence of different models on impedance functions are analyzed qualitatively firstly based on the formulas. Then the natural frequency,structure acceleration response and response spectra of structure acceleration are computed and analyzed by two specific cases. It is showed from the calculation results that the static stiffness impedance values from three models have some differences,but the dynamic stiffness impedance values are almost the same,and hence the influence of different soil models on system natural frequency and seismic response are not significant. The research results can provide references to the preliminary seismic design of soil-structure dynamic interaction system.
The soil is usually simplified as an elastic half space model and its influence is replaced by springs and dashpot elements,which is the most common method for soil-structure interaction(SSI) problem. The computation parameters of spring and dashpot elements are determined by soil impedance functions. But this is not the case in practical engineering because soil is not always a half space. Focusing on this problem,the aim of the paper is to study the influence of different soil modes on seismic response of soil-structure interaction system. Three kinds of soil models are considered,which are elastic half space model,stratum-over-rigid model and stratum-overhalf-space model. The influence of different models on impedance functions are analyzed qualitatively firstly based on the formulas. Then the natural frequency,structure acceleration response and response spectra of structure acceleration are computed and analyzed by two specific cases. It is showed from the calculation results that the static stiffness impedance values from three models have some differences,but the dynamic stiffness impedance values are almost the same,and hence the influence of different soil models on system natural frequency and seismic response are not significant. The research results can provide references to the preliminary seismic design of soil-structure dynamic interaction system.
引文
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[9]GAZETAS G.Analysis of machine foundation vibration:state of art[J].Soil Dynamics and Earthquake Engineering,1983,2(1):2–42.
[2]RICHART F.E,HALL J R,WOODS R.D.Vibrations of soils and foundations[M].Englewood cliffs,New Jersey:Prentice Hall Inc.,1970:194–215.
[3]VELETSOS A.S,VERBIC B.Vibration of viscoelastic foundations[J].International Journal of Earthquake Engineering and Structure Dynamics,1973,2(1):87–102.
[4]VELETSOS A.S,VERBIC B.Basic response functions for elastic foundations[J].Journal of Engineering Mechanics Division,ASCE,1974,100(2):189–202.
[5]ARTUR P,KAUSEL E.Approximate formulas for dynamic stiffness of rigid foundations[J].Soil Dynamics and Earthquake Engineering,1988,7(4):213–227.
[6]LUCO J E.Impedance functions for a rigid foundation on a layered medium[J].Nuclear Engineering and Design,1975,31(2):204–217.
[7]DOBRY R,GAZETAS G.Dynamic response of arbitrary shaped foundations[J].Journal of Geotechnical Engineering,1986,112(2):109–135.
[8]GAZETAS G.Formulas and charts for impedances of surface and embedded foundations[J].Journal of Geotechnical Engineering,1991,117(9):1 363–1 381.
[9]GAZETAS G.Analysis of machine foundation vibration:state of art[J].Soil Dynamics and Earthquake Engineering,1983,2(1):2–42.
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