【作者】 李永波；

【导师】 张鸿儒；

【作者基本信息】 北京交通大学 ， 岩土工程， 2013， 博士

【摘要】 摘要：桩基桥梁结构是寒区线性交通工程的重要组成部分,其在强地震作用下的抗灾害性能对线路的安全运营具有重要影响。然而一些按照现行抗震规范设计的桥梁结构在近些年历次强地震中仍出现了大量破坏现象,表明了桥梁抗震设计理论及方法还需进一步的研究和发展。目前,在对寒区长大桥梁结构抗震性能进行研究分析时,通常需要综合考虑局部地形效应、桩-土动力相互作用、地震动多点激励以及地表土层冻融变化的影响。由于冻土物理、力学性质的复杂敏感性,使得对冻土环境中桩基动力特性进行深入研究成为分析寒区长大桥梁工程地震响应规律、评估其安全性能中不可或缺的内容。本文在国家自然科学基金重大灾变研究计划《强地震作用下冻土区长大桥梁桩-土-结构动力耦合效应研究》支持下,在前人研究的基础上主要完成了以下工作：1.开展了冻结粉质黏土的直剪试验及静、动三轴压缩试验,研究了该类冻土的摩擦角、粘聚力、动强度、动弹性模量以及阻尼比等物理量随负温及冻前含水量的变化关系,为相关计算参数的选择提供依据。2.研制了冻土-桩动力相互作用模型试验系统,介绍了动力加载系统性能参数的确定及其各组件的设计、模型试验箱的设计及制冷效果分析、加载工作架的设计等。验证试验结果表明该模型试验系统能提供适当的冻土环境,结构牢固,可较好地模拟分析冻土-桩相互作用的动力性能,为该领域及其他一些冻土问题的研究提供了良好的试验平台。3.基于自制模型试验系统,对-5℃、-3℃及表层融化冻土中模型桩基进行了水平向循环动力加载试验,研究了均匀冻结及上层融化冻土中模型桩基桩头的位移-荷载关系、桩基水平动刚度变化及桩身弯矩分布情况,并提出了层状冻土中考虑桩-土分离效应及摩擦效应的动力BNWF分析模型。4.建立了考虑桩、土材料非线性及二者接触效应的多年冻土地基中桩-墩结构动力耦合二维计算模型,研究了地层条件变化时,不同频谱特性地震动以SV波形式垂直入射下桥墩的动力响应情况。5.基于黏-弹性大工边界条件的外源地震动等效荷载输入方法,实现了瞬态平面SV波以不同角度入射时地震波动问题的数值模拟。并对寒区一典型河谷场地在地震动作用下的空间动力响应进行了计算分析,指出了考虑局部地形效应、地震波入射角度、地表融土厚度及地震动频谱特性的必要性,为该场址桥梁结构的地震响应分析提供了输入地震动。6.建立了寒区多跨简支梁桥和刚构桥的非线性地震响应分析模型,研究了局部地形效应、桩-土动力相互作用、地震波入射角度以及地表融土厚度对桥梁结构动力响应的影响。计算结果表明局部地形效应和桩-土动力相互作用对桥梁地震响应影响显著。更多还原

【Abstract】 ABSTRACT:Bridge with pile foundations is an important component of linear traffic engineering, whose anti-seismic performance of has great influence on the safety operation of railway under strong earthquake. However, the earthquake damages of bridge structures designed by current seismic codes in bridge were very serious under some recent earthquakes. This phenomenon indicates that the seismic design theory and method of bridge used in present still need further research and development. At present, local topography effect, dynamic pile-soil interaction, multi-support excitation and frozen and thawed surface soil effect are need to consider when analysis the anti-seismic performance of grand bridge in cold area. Considering the physical and mechanical properties sensitivity of frozen soil, the further study on dynamic characters of pile in frozen soils becomes an indispensable content in analysis the seismic response of grand bridge engineering in cold region.In support of National Natural Science Foundation of China (90715013), the main studies in this dissertation are listed as follows:1. Direct shear test and static tri-axial and dynamic tri-axial compression tests of frozen sility soil were present, and the relationships of friction angle, cohesion, dynamic strength, dynamic elastic modulus, damping ratio and other physical quantities with temperature and moisture were studied. The test results can provid physical mechanics parameters of frozen sility caly for numerical calculations.2. A set of model experimental system for dynamic frozen soil-pile interaction was developed in this dissertation. Determination of performance parameters of dynamic loading system, design of model test chamber, analysis of refrigeration effect, design of loading frame and connection with experimental chamber were also introduced. The results of verification test show that the test system can supply frozen soil environment for experiments, can simulate and analyze the dynamic behaviors of frozen soil-pile preferably. Moreover, this system can be used in other researches on frozen soils.3. Based on the self-made model experimental system, experiments about dynamic property of model pile foundation under lateral dynamic loads in-5℃,-3℃and partially thawed permafrost were conducted. The displacement-force relationship of pile head, dynamic stiffness of pile foundation in horizontal direction and bending moment distribution of pile body in different permafrosts mentioned above were studied. At last, a dynamic BNWF model of dynamic frozen soil-pile interaction including separation effect and friction effect of pile and soil was proposed in this dissertation.4. A calculation model of dynamic pile-pier interaction system in permafrost considering the pile and soil material nonlinearities and contact effect between them was built, and the dynamic response of pier in different permafrost site under two earthquakes is studied.5. Based on the equivalent load method for earthquake input of the viscous-spring artificial boundary theory, numerical simulation of external source wave problem for obliquely incident transient plane SV wave was realized in ANSYS software. Seismic responses analysis of a typical valley site in cold region were carried out by method mentioned above. The results show that considering local topography effect, seismic incident angles, surface thaw soil thickness and seismic spectrum characteristics is very necessary.6. Nonlinear seismic response analysis models of a multi-span simply supported bridge and a rigid frame bridge were built, and effects of local topography effect, pile-soil dynamic interaction, seismic wave incident angle and the surface thawed soil thickness on the dynamic response of bridge structures were studied in this dissertation. The results show that the effects of topography and pile-soil dynamic interaction on seismic response of bridges have important influence than thawed soil thickness.更多还原