【作者】 傅光耀；

【导师】 刘健新；

【作者基本信息】 长安大学 ， 道路与铁道工程， 2007， 博士

【摘要】 探索地裂缝对桥梁结构地震反应的影响,是工程抗震防灾减灾研究和桥梁结构抗震设计提出的新课题。黄土地裂场地是一种特殊的工程场地,目前国内外关于黄土地裂场地桥梁结构地震反应研究尚处于空白。本文针对这一崭新课题,以西安地区黄土地裂场地为研究工作背景,采用跨学科、跨专业的研究手段,进行了比较基础性的试探研究,并且初步取得了一些具有创新性的成果。本文旨在初步探索一般混凝土公路梁桥,在黄土地裂场地上考虑近震、远震等条件下的地震反应,与普通场地条件下地震反应的差异。为此,本文主要完成的关键性工作有。(1)黄土动三轴试验与黄土动力本构关系计算模型的确定。本文研究探讨了土的各种本构关系的理论模型,并且通过完成大量黄土土样在不同围压下的动三轴试验,获得了黄土的动力实验关系曲线。本文认为粘弹性Hardin双曲线模型适合于描述黄土,在一定的应变范围内可以简化为直线关系。(2)黄土场地土层勘探、动力特性实验与有限元土体模型。详细搜集研究了我国黄土地层分布资料,完成了实际场址土层勘探以及动特性(剪切波速等)实验。在此基础上建立了土体的二维层状有限元模型,它能够适合于一般黄土场地的有限元动力计算。(3)地裂缝竖向分布勘探测试实验和地裂缝的模拟建模方法。实验方法定量地勘探测试了西安地裂缝的竖向分布状况:同时,研究和尝试了有限元的各种高级建模技术,将“生死单元”与“参数弱化”技术相结合,寻求到了地裂缝模拟建模的一条新途经。(4)研究了一般黄土场地的地震反应。采用“大质量法”从模型底部边界施加地震激励,研究了一般黄土场地的地震时程反应。本文借用几条频谱特性不同的典型地震记录,分别以0.1g、0.2g和0.4g最大加速度幅值水平,对两种尺寸的场地模型,模拟了场地在大、中、小震,和近震远震条件下的地震反应。(5)研究了黄土地裂场地的地震反应。在有限元土体模型中,利用本文的方法近似模拟构造了地裂缝缺陷,建立了黄土地裂场地的计算模型。以地裂缝的深度为研究参数,借用几条频谱特性不同的地震记录波作为激励波,进行了一系列的动力时程计算。研究结果揭示:黄土地裂场地的地震反应,与地裂缝深度、激励波的频谱等因素之间的关系丰富。(6)实际桥梁结构的地震反应研究。参照混凝土桥梁的标准设计,构造了两个混凝土梁桥的结构模型;分别对比计算了直接由桥墩底部、经由一般黄土场地,和经由黄土地裂场地,输入水平地震激励时,结构顺桥方向的时程反应。实际桥梁结构的地震反应研究表明,黄土地裂场地条件对桥梁结构的地震反应有多方面的影响。(7)开发编写了基于EMD的数据处理程序。基于EMD(Empirical Mode Decomposition,经验模态分解)原理,在MATLAB环境中,开发编写了能够剔除结构地震反应“位移漂移”成份的算法程序,成功地完成了结果数据的后处理。本文的创新之处在于:(1)国内首次提出该课题的研究。采用跨学科、跨专业的研究手段,在线弹性范围内,比较系统的完成了试探性研究,并且取得了初步的成果。研究结果发现,黄土地裂场地对于输入的地震激励波存在显著的修正作用。(2)从土体模型和土的本构关系的建立,到选择地震激励输入方式、确定动力计算方法、编制APDL计算程序、以及结果数据的后处理,摸索到了一套完整的跨学科、多方法的研究方法和各种先进算法的集合应用方式。(3)将经验模态分解法与输入地震激励的“大质量”法相结合,找到了能够有效消除地震反应“位移漂移”成份的一种新途经。另外,作者还使用了国际上科学论文通用排版软件LaTex,完成了本文的撰写和排版。更多还原

【Abstract】 Exploring the affects of grounds fissures to bridge structure earthquake responses is a difficult problem in reduce earthquake disaster research and engineering resistance designs field.Loess fissure ground is a species engineering sites,at present the research of the bridge structure earthquake responses in this loess sites is still the blank in domestic research.In view of this brand-new topic,this thesis on the basis of loess sites conditions with ground fissures of Xi’an areas,adopt intercross research methods to relate to multiple professional fields,have completed initial exploratory research,and have got some achievement.This thesis goal is to explore the difference of earthquake response for highway beam bridges structures,on the condition of loess ground fissures site considering near-seism, tele-seism and from under other conditions.The main contents as follows:(1) Tri-axis dynamic test and loess dynamical constitutive relation model confirmthis thesis discuss all kinds of constitutive relation models of clay soils,and obtain many test curves of loess clay soils samples by Tri-axis dynamic test.Hardin hyperbolic curve model is fit for description of loess clay and it can also be simplified to linear.(2) Loess soil layers prospect,dynamic characteristics test and building loess FEM modelsExploration soil layers distribution on a loess engineering site.And test the shear velocity of layers.Further more,building up the 2D layer FEM models,which can be used for loess sites for earthquake response analysis.(3) Prospect of vertical distribution of ground fissures in loess site and building models method of simulating loess fissuresTest vertical distribution of loess ground fissures in Xi’an by experiment method,after discussion the advantage and disadvantage in different advanced model building technique. Combining "live and death element" with "reduction parameter",have found a new way to simulate loess fissures in soil FEM model.(4) Completing the earthquake response analysis of loess clay site without fissuresInput the seismic waves excitations on the bottom of model by "Large mass method", complete time-stepping response analysis of loess site without fissures.Using several typical earthquake waves records with differential spectrum character,calculate earthquake response with different accelerated velocity levels on 0.1g,0.2g and 0.4g,to simulating the different condition of violent seism,minor seism,near seism and tele-seism.(5) Completing the earthquake response analysis of loess site with fissuresBuilding up the FEM soil models with fissures by the former skill.Using depth of fissures as variable,completing a series of time-stepping response analysis under different excitations with several typical earthquake waves records.The result indicate that there are complex relations in depth of fissures and excite spectrum.(6) Earthquake response analysis about reality bridges structuresAccording to standard design of concrete bridges structure,construct two models of reality beam bridge structure;completing a series of earthquake response analysis in bridge longitudinal direction,respectively input earthquake excitement on bottom of the bridge piers, through losses site,as well as through ground fissures.Through analysis reality bridges structures,the result indicate that the condition of loess fissures can affect the bridge earthquake responses in many respect.(7) Compile the program of data processing on basis of EMD principleOn basis of EMD(Empirical Mode Decomposition,EMD) principle,compile the program that can remove "drift component in displacement response",successfully complete data post treatment.The originality ideal and method of this thesis are:(1) In domestic,first put forward research the subject of bridge structure earthquake response in loess ground fissure site.Adopted multi-learning-fields and subjects intercross research methods,in linear elastic range,have completed initial exploratory research,and have got some research achievement.The research results indicate that loess ground fissure site has remarkable amendment response to earthquake drive waves.(2) From establishment loess site soil models and loess stress-strain constitutive relation to selection the input way manner of earthquake excitation waved,confirmation the dynamical calculate method,compile program of APDL,and post data processing,tried to find out a set of complete technical route for research work and the advanced technology integrated method.(3) Combine the EMD method with Large-Mass-Method of the input earthquake exciting, found one new way to effectively eliminate "the displacement drift" in the earthquake time-stepping methods.更多还原