成层液化土中单桩-土-结构系统的水平振动分析
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摘要
根据地震场地液化特征,将土层分为上部液化土层与下部非液化土层,并基于桩-土相互作用的Winkler模型,将桩等效为Rayleigh梁.建立了考虑上部结构的质量、转动惯量、桩身转动惯量和轴力效应的单桩-土-结构系统的控制方程和边界条件,在频率域给出了问题的解析封闭解.通过与相关实验结果的比较,验证模型和解析解的合理性和有效性,分析几何、物理参数等对单桩-土-结构系统位移放大因子、动力放大因子的影响.研究结果表明:桩身轴力使系统的基频更加趋向地震的主频;土壤的液化使得上部结构动力响应更加剧烈,随着土体液化程度的发展,桩的临界载荷将减小,最终导致桩发生失稳破坏.
According to the characteristics of liquefiable soil in earthquake,we divide the liquefiable soil layer into a top liquefied layer and a bottom non-liquefied layer.Based on the Winkler model for the pile-soil interaction and treating the pile as a Rayleigh beam,the governing equations and the corresponding boundary conditions for interaction of the single pile-soil-superstructure are established.This is done by taking into account the mass and inertia moment of the superstructure,and the inertia moment and the axial force of the pile.A closed-form solution is obtained in the frequency domain,of which results are in agreement with experiments.Influences of the geometrical and physical parameters on the displacement amplification factor and the dynamic amplification factor are investigated.It is shown that the axial force drives the first natural frequency of the system to approach the dominant frequency of earthquake.Soil liquefaction increases the system's dynamic response,and the critical load of the pile decreases with the degree of soil liquefaction,leading to unstable failure of the pile.
According to the characteristics of liquefiable soil in earthquake,we divide the liquefiable soil layer into a top liquefied layer and a bottom non-liquefied layer.Based on the Winkler model for the pile-soil interaction and treating the pile as a Rayleigh beam,the governing equations and the corresponding boundary conditions for interaction of the single pile-soil-superstructure are established.This is done by taking into account the mass and inertia moment of the superstructure,and the inertia moment and the axial force of the pile.A closed-form solution is obtained in the frequency domain,of which results are in agreement with experiments.Influences of the geometrical and physical parameters on the displacement amplification factor and the dynamic amplification factor are investigated.It is shown that the axial force drives the first natural frequency of the system to approach the dominant frequency of earthquake.Soil liquefaction increases the system's dynamic response,and the critical load of the pile decreases with the degree of soil liquefaction,leading to unstable failure of the pile.
引文
[1]BHATTACHARYA S,MADABHUSHI S P G.A critical review of methods for pile design in seismically liquefiable soils[J].Bulletin of Earthquake Engineering,2008,6(3):407-446.
[2]Japanese Road Association.Specification for highwaybridges,partⅤ:seismic design[M].17th ed.Washington:AASHTO,2002.
[3]ABDOUN T H,DOBRY R.Evaluation of pile foundation response to lateral spreading[J].Soil Dynamics and Earthquake Engineering,2002,22:1051-1058.
[4]BHATTACHARYA S,MADABHUSHI S P G,BOLTON M D.An alternative mechanism of pile failure in liquefiable deposits during earthquakes[J].Geotechnique,2004,54(3):203-213.
[5]李雨润,袁晓铭,梁艳,等.桩-液化土相互作用p-y关系分析[J].地震工程与工程振动,2008,28(3):165-171.
[6]汪明武,TOBITA T,IAI S.倾斜液化场地桩基地震响应离心机试验研究[J].岩石力学与工程学报,2009,28(10):2012-2017.
[7]李培振,程磊,吕西林,等.可液化土-高层结构地震相互作用振动台试验[J].同济大学学报:自然科学版,2010,38(4):467-474.
[8]MYLONAKIS G,GAZETAS G.Lateral vibration and internal forces of grouped piles in layered soils[J].Journal of Geotechnical and Geoenviromnental Engineering,1999,125(1):16-25.
[9]American Petro Institute.Recommended practice for planning designing and constructing fixed offshore platforms[M].Washington:API,2003.
[10]BHATTACHARYA S,ADHIKARI S.Vibrational characteristics of a piled structure in liquefied soil during earthquakes:experimental investigation(partⅠ)and analytical modelling(partⅡ)[R].Oxford:Oxford University,2007.
[11]HAN S M,BENAROYA H,WEIK T.Dynamics of transversely vibrating beams using four engineering theories[J].Journal of Sound and Vibration,1999,225(5):935-988.
[12]CUBRINOVSKI M,ISHIHARA K.Simplified method for analysis undergoing lateral spreading in liquefied soils[J].Soils and Foundations,2004,44(5):119-133.
[13]CHOPRA A K.Dynamics of structures:theory and applications to earthquake engineering[M].Prentice-Hall:Englewood Cliffs,2001.
[14]TOKIMATSU K,ASAKA Y.Effects of liquefaction-induced ground displacements on pile performance in the 1995Hyogoken-Nambu earthquake[J].Special Issue of Soils and Foundations,1998,38(2):163-177.
[2]Japanese Road Association.Specification for highwaybridges,partⅤ:seismic design[M].17th ed.Washington:AASHTO,2002.
[3]ABDOUN T H,DOBRY R.Evaluation of pile foundation response to lateral spreading[J].Soil Dynamics and Earthquake Engineering,2002,22:1051-1058.
[4]BHATTACHARYA S,MADABHUSHI S P G,BOLTON M D.An alternative mechanism of pile failure in liquefiable deposits during earthquakes[J].Geotechnique,2004,54(3):203-213.
[5]李雨润,袁晓铭,梁艳,等.桩-液化土相互作用p-y关系分析[J].地震工程与工程振动,2008,28(3):165-171.
[6]汪明武,TOBITA T,IAI S.倾斜液化场地桩基地震响应离心机试验研究[J].岩石力学与工程学报,2009,28(10):2012-2017.
[7]李培振,程磊,吕西林,等.可液化土-高层结构地震相互作用振动台试验[J].同济大学学报:自然科学版,2010,38(4):467-474.
[8]MYLONAKIS G,GAZETAS G.Lateral vibration and internal forces of grouped piles in layered soils[J].Journal of Geotechnical and Geoenviromnental Engineering,1999,125(1):16-25.
[9]American Petro Institute.Recommended practice for planning designing and constructing fixed offshore platforms[M].Washington:API,2003.
[10]BHATTACHARYA S,ADHIKARI S.Vibrational characteristics of a piled structure in liquefied soil during earthquakes:experimental investigation(partⅠ)and analytical modelling(partⅡ)[R].Oxford:Oxford University,2007.
[11]HAN S M,BENAROYA H,WEIK T.Dynamics of transversely vibrating beams using four engineering theories[J].Journal of Sound and Vibration,1999,225(5):935-988.
[12]CUBRINOVSKI M,ISHIHARA K.Simplified method for analysis undergoing lateral spreading in liquefied soils[J].Soils and Foundations,2004,44(5):119-133.
[13]CHOPRA A K.Dynamics of structures:theory and applications to earthquake engineering[M].Prentice-Hall:Englewood Cliffs,2001.
[14]TOKIMATSU K,ASAKA Y.Effects of liquefaction-induced ground displacements on pile performance in the 1995Hyogoken-Nambu earthquake[J].Special Issue of Soils and Foundations,1998,38(2):163-177.
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