深厚场地大型桥梁桩基础随机地震反应及可靠性分析
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摘要
以苏通长江大桥主墩特大型群桩基础为研究背景,考虑地震动的不确定性,将地震激励作为平稳随机过程,采用随机地震反应分析方法,对深厚场地上群桩基础受上部桥墩荷载下的地震反应进行研究。土体动力非线性性能采用等效线性化方法考虑。由于桥墩惯性作用以及软土土层对桩身位移的约束作用,地震激励下桩身位移呈三角形分布。土体位移与土体和基础间距离有关,桥墩-桩-土相互作用对基础两侧1.5倍基础宽度的土体位移有较大影响。桩体内力反应结果表明,桩顶及桩身上部剪力及弯矩均较大,边桩剪力显著大于中间桩剪力。此外,基于强度破坏准则,对以桩身屈服剪力作为控制指标的群桩基础动力可靠性进行了分析。
The giant pile group foundation of the Su-Tong Bridge located on the Yangtze River is selected to be the subject investigated.The seismic excitation is regarded as stationary stochastic process considering the uncertainties of real seismogram.A stochastic seismic response method,in which the complex response technique is employed,is applied to study the dynamic responses of this pile group foundation with a large pier cap.The dynamic nonlinearity of soils is considered through the equivalent linearity method.During a seismic motion,the displacements along depths of pile shaft appear triangle because of inertia force of pier and weak restraint of soft soil.The displacement of soil is related to the distance between soil and pile foundation.The effects of pier-pile-soil interaction on displacement response of the soil surrounding the pile foundation are significant.The effected range is about 1.5 times width of pile foundation.The internal force responses of piles indicate that the bending moments and shear forces of pile head and upper portion of pile shaft are larger relatively.The shear force of outer piles is marked larger than that of center piles.In addition,based on the principle of intensity damage,the dynamic reliabilities of the pile foundation are analyzed under four different yield shear force levels.
The giant pile group foundation of the Su-Tong Bridge located on the Yangtze River is selected to be the subject investigated.The seismic excitation is regarded as stationary stochastic process considering the uncertainties of real seismogram.A stochastic seismic response method,in which the complex response technique is employed,is applied to study the dynamic responses of this pile group foundation with a large pier cap.The dynamic nonlinearity of soils is considered through the equivalent linearity method.During a seismic motion,the displacements along depths of pile shaft appear triangle because of inertia force of pier and weak restraint of soft soil.The displacement of soil is related to the distance between soil and pile foundation.The effects of pier-pile-soil interaction on displacement response of the soil surrounding the pile foundation are significant.The effected range is about 1.5 times width of pile foundation.The internal force responses of piles indicate that the bending moments and shear forces of pile head and upper portion of pile shaft are larger relatively.The shear force of outer piles is marked larger than that of center piles.In addition,based on the principle of intensity damage,the dynamic reliabilities of the pile foundation are analyzed under four different yield shear force levels.
引文
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[2]Brown D,Shie C.Modification of P-Y Curves to accountfor group effects on laterally Loaded Piles[A].Pro-ceedings of Geotechnical Engineering Congress,ASCE[C].[s.l.]:[s.n.].1991.479-490.
[3]Chai Y H,Song S T.Assessment of seismic performanceof extended pile-shafts[J].Earthquake Engineering andStructural Dynamics,2003,32(12):1 937-1 954.
[4]刘汉龙,陆兆溱,钱家欢.土石坝非线性随机反应及动力可靠性分析[J].河海大学学报,1996,24(3):105-109.LIU Han-long,LU Zhao-zhen,QIAN Jia-hua.Permanentdeformation of foundation and embankment dam due tostochastic seismic excitation[J].Journal of HohaiUniversity,1996,24(3):105-109.
[5]刘汉龙.随机地震作用下地基及土石坝永久变形分析[J].岩土工程学报,1996,18(3):19-27.LIU Han-long.Earthquake-induced permanent defor-mation of earth-rock dam[J].Journal of GeotechnicalEngineering,1996,18(3):19-27.
[6]俞载道,曹国敖.随机振动理论及其应用[M].上海:同济大学出版社,1988.
[7]Vanmarcke E H.Properties of spectral moments withapplications to random vibration[J].Journal ofEngineering Mechanics,ASCE,1972,98(EM2):72-88.
[8]Kiureghian A D.Structural response to stationaryexcitation[J].Journal of Engineering Mechanics,ASCE,1980,106(EM6):875-884.
[9]陈国兴,谢君斐,张克绪.土坝地震性能二维随机分析方法[J].地震工程与工程振动,1994,14(3):81-90.CHEN Guo-xing,XIE Jun-fei,ZHANG Ke-xu.A methodof 2-D random response analysis of earth dam earthquakeperformance[J].Earthquake Engineering and Eng-ineering Vibration,1994,14(3):81-90.
[10]杨伟林,陈国兴,王志华,等.特大型桥墩-桩-土体系地震反应的二维和三维数值模拟分析[J].地震工程与工程振动,2004,26(5):172-183.YANG Wei-lin,CHEN Guo-xing,WANG Zhi-hua,et al.2D and 3D seismic response analyses of supergiant bridgepier-group pile-soil interaction system on deepoverburden layers[J].Earthquake Engineering andEngineering Vibration,2004,26(5):172-183.
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