桩土界面力学行为对桩基动力特性的影响
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摘要
结合构建的饱和土结构性动力本构模型以及通用有限元程序,以城市高架桥梁建设中常采用的单柱墩基础为原型,建立了摩擦桩-土-结构体系、端承桩-土-结构体系的有限元-无限元计算模型。分完全粘结、滑移无开裂、开裂无滑移、开裂滑移四种情况考察了桩土界面力学行为对两种系统动力反应特性的影响,得出如下结论:无论是端承桩还是摩擦桩,界面力学行为对桩截面的剪应力和桩身水平位移分布形态影响均不大。四种情况中,完全粘结时,摩擦桩在近地表处桩截面剪应力值最大,开裂滑移时最小,而端承桩则刚好相反。水平位移分布均可分为线性增大和加速非线性增大两个阶段,以近地表处为分界点,且均以开裂滑移时最大,完全粘结时最小。界面力学行为极大地改变了端承桩桩身加速度时程的分布形态,但对摩擦桩则几乎没有改变;对于不同界面力学行为,两种桩型在近地表处均出现加速度峰值,完全粘结时值最大,开裂滑移时最小。相比摩擦桩而言,界面力学行为对端承桩的影响要大的多,研究分析时应引起足够的重视。
Conbining dynamic constitutive model of saturated soil with general finite element program,the finite-infinite element models of end bearing and friction pile foundations were established.Four situations of interface between pile and soil including absolutely jointed,slippage,crack,both slippage and crack were considered to study the interface's effect on pile foundation's dynamic characteristics.The results are as follows: no matter end bearing pile or friction ones,the interface's mechanical behavior has a little influence on the distributions of pile section's shear stress and pile's horizontal displacement.In these four situations,frictional pile section's shear stress arrives at the maximum when interface is absolutely jointed,and arrives at the minimum ones when interface is both slippage and crack.But the end bearing pile is just opposite to it.Horizontal displacement could be devided into two phases of linear increase and accelerated non-linear increase and the earth's surface is the dividing point.The interface's behavior greatly changes the distribution of end bearing pile's acceleration time-history curve,but has no effect on the friction ones.To different interfaces,both of two types pile's maximum acceleration are located at the earth's surface.On the whole,the interface's behavior has much more influence on end bearing pile than that on friction ones,which should be emphasized in the studies from now on.
Conbining dynamic constitutive model of saturated soil with general finite element program,the finite-infinite element models of end bearing and friction pile foundations were established.Four situations of interface between pile and soil including absolutely jointed,slippage,crack,both slippage and crack were considered to study the interface's effect on pile foundation's dynamic characteristics.The results are as follows: no matter end bearing pile or friction ones,the interface's mechanical behavior has a little influence on the distributions of pile section's shear stress and pile's horizontal displacement.In these four situations,frictional pile section's shear stress arrives at the maximum when interface is absolutely jointed,and arrives at the minimum ones when interface is both slippage and crack.But the end bearing pile is just opposite to it.Horizontal displacement could be devided into two phases of linear increase and accelerated non-linear increase and the earth's surface is the dividing point.The interface's behavior greatly changes the distribution of end bearing pile's acceleration time-history curve,but has no effect on the friction ones.To different interfaces,both of two types pile's maximum acceleration are located at the earth's surface.On the whole,the interface's behavior has much more influence on end bearing pile than that on friction ones,which should be emphasized in the studies from now on.
引文
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[4]Tara Crystal Hutchinson.Characterization and evaluation of the seismic performance of pile-supported bridge structures[D].California:The Uni-versity of California,2001.
[5]Hibbitt,Karlsson,Sorensen.Inc.ABAQUS/Standard User’s Manual;ABAQUS/CAE User’s Manual;ABAQUS Keywords Manual;ABAQUS QUS Theory Manual[D].American:HKS Company,2002.
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[7]庄茁,张帆,岑松.ABAQUS非线性有限元分析与实例[M].北京:科学出版社,2005.Zhang Zhuo,Zhang Fan,Cen Song.ABAQUS non-linear finite element analysis and examples[M].Bei Jing:Science Press,2005.
[8]胡伟.饱和黄土动力本构模型及其在桩-土-结构体系地震动力相互作用中的应用[D].西安:西安建筑科技大学,2008.Hu Wei.Saturated Loess’Dynamic Model and It’s Application to the dynamic interaction of pile-soil-structure system under earthquake[D].Xi’an:Xi’an University of Architecture and Technology,2008.
[9]朱向荣,王金昌.ABAQUS软件中部分土模型简介及其应用[J].岩土力学,2004,25(Supp.2):144-148.Zhu Xiangrong,Wang Jinchang.Introduction to partly soil models in ABAQUS software and their application to the geotechnical engineering[J].Rock and Soil Mechanics,2004,25(Supp.2):144-148.
[10]徐远杰,王观琪,李健,唐碧华.在ABAQUS中开发实现Duncan-Chang模型[J].岩土力学,2004,25(7):1032-1036.Xu Yuanjie,Wang Guanqi,Li Jian,Tang Bihua.Development and implementation of Duncan-Chang constitutive model in ABAQUS[J].Rock and Soil Mechanics,2004,25(7):1032-1036.
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