桥梁群桩基础非线性静力计算模型及拟静力试验研究
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摘要
线弹性地基反力法(m法)仅适用于正常使用时桥梁桩基础变位较小的情况,但在强震作用下基础的变位较大。为了研究桩基础在地基土及桩身进入非线性状态下的水平承载能力及变形特性,通过群桩基础缩尺比例模型,采用拟静力试验研究桩基础的破坏机制、承载能力、变形性能以及滞回特性。提出水平荷载作用下群桩基础的非线性静力计算模型,在该模型中采用分布PMM塑性铰模拟变轴力作用下桩身的弹塑性,采用美国API规范给出的p-y曲线、t-z曲线以及q-z曲线模拟地基土的非线性(其中,p为桩侧土水平抗力,y为水平位移,t为桩周土竖向摩阻力,q为桩端土竖向抗力,z为桩土竖向相对位移)。研究结果表明:(1)本文提出的分析模型与模型试验结果吻合较好;(2)可采用Clough退化双线性模型模拟桩基础的滞回特性;(3)桩身受力薄弱部位在桩顶以下0~4倍桩径范围内。研究结果可为应用能力谱法评价桩基础的抗震性能提供参考。
Horizontal bearing characteristics of bridge pile foundations can be analyzed by using linear elastic subgrade reaction method(m-method) when displacement of pile foundation is generally smaller.However,displacement of pile foundations is often larger under the effect of strong earthquakes.In order to understand the horizontal bearing capacity and deformation characteristics of pile foundations considering nonlinear behaviors of pile shaft and subsoil,a model of pile foundations is constructed.Failure mechanism,bearing capacity,deformation characteristics and hysteresis characteristics of pile foundations are studied by using pseudo-static test.A nonlinear static calculation model of pile group foundations is put forward under horizontal load.The elastoplasticity of pile shafts in variable axial loads is simulated by distributed PMM plastic hinge;and nonlinearity of subsoil is simulated by the curves of p-y,t-z and q-z,respectively,which have been given in the code of American API;where p is horizontal soil resistance at lateral of pile shaft;y is horizontal displacement;t is vertical frictional resistance around piles shaft;q is vertical bearing resistance at pile tip;z is vertical relative displacement of interface between pile and soil.The results show that:(1) The numerical results are in good agreement with those obtained from experiments.(2) Hysteretic characteristics of pile foundations can be simulated using Clough degradation bilinear model.(3) Weak positions of pile shaft are 0–4 times around the radius of pile below pile top.The results can provide references for evaluating seismic performance of bridge pile foundation using capacity spectrum method.
Horizontal bearing characteristics of bridge pile foundations can be analyzed by using linear elastic subgrade reaction method(m-method) when displacement of pile foundation is generally smaller.However,displacement of pile foundations is often larger under the effect of strong earthquakes.In order to understand the horizontal bearing capacity and deformation characteristics of pile foundations considering nonlinear behaviors of pile shaft and subsoil,a model of pile foundations is constructed.Failure mechanism,bearing capacity,deformation characteristics and hysteresis characteristics of pile foundations are studied by using pseudo-static test.A nonlinear static calculation model of pile group foundations is put forward under horizontal load.The elastoplasticity of pile shafts in variable axial loads is simulated by distributed PMM plastic hinge;and nonlinearity of subsoil is simulated by the curves of p-y,t-z and q-z,respectively,which have been given in the code of American API;where p is horizontal soil resistance at lateral of pile shaft;y is horizontal displacement;t is vertical frictional resistance around piles shaft;q is vertical bearing resistance at pile tip;z is vertical relative displacement of interface between pile and soil.The results show that:(1) The numerical results are in good agreement with those obtained from experiments.(2) Hysteretic characteristics of pile foundations can be simulated using Clough degradation bilinear model.(3) Weak positions of pile shaft are 0–4 times around the radius of pile below pile top.The results can provide references for evaluating seismic performance of bridge pile foundation using capacity spectrum method.
引文
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[4]American Association of State Highway and Transportation Officials.AASHTO LRFD Bridge design specifications[S].Washington,D.C.,USA:AASHTO,2009.
[5]叶爱君,鲁传安.基于Pushover分析的群桩基础抗震性能分析方法[J].土木工程学报,2010,43(2):88–94.(YEAijun,LU Chuan an.A seismic performance analysis approach based on Pushover analysis for group pile foundations[J].China Civil Engineering Journal,2010,43(2):88–94.(in Chinese))
[6]CHAI Y H.Flexural strength and ductility of extended pile-shafts.I:Analytical model[J].Journal of Structural Engineering,2002,128(5):586–594.
[7]CHIOU J S,YANG H H,CHEN C H.Use of plastic hinge model in nonlinear pushover analysis of a pile[J].Journal of Geotechnical and Geoenviromental Engineering,2009,135(9):1 341–1 346.
[8]陈仁朋,顾明,孔令刚.水平循环荷载下高桩基础受力性状模型试验研究[J].岩土工程学报,2012,34(11):1 990–1 996.(CHEN Renpeng,GU Ming,KONG Linggang.Large-scale model tests on high-rise platform pile groups under cyclic lateral loads[J].Chinese Journal of Geotechnical Engineering,2012,34(11):1 990–1 996.(in Chinese))
[9]袁志林,段梦兰,陈祥余,等.水平荷载下导管架平台桩基础的非线性有限元分析[J].岩土力学,2012,33(8):2 551–2 560.(YUAN Zhilin,DUAN Menglan,CHEN Xiangyu,et al.Nonlinear finite element analysis of jacket platform pile foundations under lateral loads[J].Rock and Soil Mechanics,2012,33(8):2 551–2 560.(in Chinese))
[10]汪优,刘建华,王星华,等.软土地层桥梁群桩基础桩土共同作用性状的非线性有限元分析[J].岩土力学,2012,33(3):945–951.(WANG You,LIU Jianhua,WANG Xinghua,et al.Nonlinear finite element analysis of pile-soil interaction of bridge pile group foundation in soft soil stratum[J].Rock and Soil Mechanics,2012,33(3):945–951.(in Chinese))
[11]朱敏.结构阻尼体系地震反应分析方法的研究[博士学位论文][D].哈尔滨:中国地震局工程力学研究所,2002.(ZHU Min.Seismic response analysis method of structural damping system[Ph.D.Thesis][D].Harbin:Institute of Engineering Mechanics,China Earthquakes Administration,2002.(in Chinese))
[12]中华人民共和国行业标准编写组.JTJ 254—98港口工程桩基础设计规范[S].北京:人民交通出版社,1998.(The Professional Standards Compilation Group of People s Republic of China.JTJ254—98 Code for pile foundation of harbour engineering[S].Beijing:China Communications Press,1998.(in Chinese))
[13]American Society of Civil Engineers.Prestandard and commentary for the seismic rehabilitation of buildings[S].Washington,D.C.:Federal Emergency Management Agency,2000.
[2]陈兴冲,朱晞.允许提离的弹塑性Winkler地基上桥墩的地震反应[J].工程力学,1999,16(5):101–107.(CHEN Xingchong,ZHU Xi.Seismic response of bridge piers on elasto-plastic Winkler foundation allowed to uplift[J].Engineering Mechanics,1999,16(5):101–107.(in Chinese))
[3]日本の鉄道総合技術研究所.鉄道構造物などの設計基準及び解説V耐震設計[S].東京:丸善株式会社出版事業部,1999.(Japan Railway Technical Research Institute.Seismic design standards and explanations for railway structures[S].Tokyo:Maruzen Co.,Publishing Division,1999.(in Chinese))
[4]American Association of State Highway and Transportation Officials.AASHTO LRFD Bridge design specifications[S].Washington,D.C.,USA:AASHTO,2009.
[5]叶爱君,鲁传安.基于Pushover分析的群桩基础抗震性能分析方法[J].土木工程学报,2010,43(2):88–94.(YEAijun,LU Chuan an.A seismic performance analysis approach based on Pushover analysis for group pile foundations[J].China Civil Engineering Journal,2010,43(2):88–94.(in Chinese))
[6]CHAI Y H.Flexural strength and ductility of extended pile-shafts.I:Analytical model[J].Journal of Structural Engineering,2002,128(5):586–594.
[7]CHIOU J S,YANG H H,CHEN C H.Use of plastic hinge model in nonlinear pushover analysis of a pile[J].Journal of Geotechnical and Geoenviromental Engineering,2009,135(9):1 341–1 346.
[8]陈仁朋,顾明,孔令刚.水平循环荷载下高桩基础受力性状模型试验研究[J].岩土工程学报,2012,34(11):1 990–1 996.(CHEN Renpeng,GU Ming,KONG Linggang.Large-scale model tests on high-rise platform pile groups under cyclic lateral loads[J].Chinese Journal of Geotechnical Engineering,2012,34(11):1 990–1 996.(in Chinese))
[9]袁志林,段梦兰,陈祥余,等.水平荷载下导管架平台桩基础的非线性有限元分析[J].岩土力学,2012,33(8):2 551–2 560.(YUAN Zhilin,DUAN Menglan,CHEN Xiangyu,et al.Nonlinear finite element analysis of jacket platform pile foundations under lateral loads[J].Rock and Soil Mechanics,2012,33(8):2 551–2 560.(in Chinese))
[10]汪优,刘建华,王星华,等.软土地层桥梁群桩基础桩土共同作用性状的非线性有限元分析[J].岩土力学,2012,33(3):945–951.(WANG You,LIU Jianhua,WANG Xinghua,et al.Nonlinear finite element analysis of pile-soil interaction of bridge pile group foundation in soft soil stratum[J].Rock and Soil Mechanics,2012,33(3):945–951.(in Chinese))
[11]朱敏.结构阻尼体系地震反应分析方法的研究[博士学位论文][D].哈尔滨:中国地震局工程力学研究所,2002.(ZHU Min.Seismic response analysis method of structural damping system[Ph.D.Thesis][D].Harbin:Institute of Engineering Mechanics,China Earthquakes Administration,2002.(in Chinese))
[12]中华人民共和国行业标准编写组.JTJ 254—98港口工程桩基础设计规范[S].北京:人民交通出版社,1998.(The Professional Standards Compilation Group of People s Republic of China.JTJ254—98 Code for pile foundation of harbour engineering[S].Beijing:China Communications Press,1998.(in Chinese))
[13]American Society of Civil Engineers.Prestandard and commentary for the seismic rehabilitation of buildings[S].Washington,D.C.:Federal Emergency Management Agency,2000.
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