【作者】 潘坚文；

【导师】 张楚汉；

【作者基本信息】 清华大学 ， 水利工程， 2010， 博士

【摘要】 高拱坝的动力反应与抗震安全分析受多种关键因素的影响,如考虑无限地基辐射阻尼、横缝开合、坝体混凝土损伤开裂引起的非线性行为等,需综合考虑这些因素,才能较真实地反映拱坝的动力反应。论文以此为目标,开展了系列研究工作,建立了考虑拱坝地基辐射阻尼、横缝张开与混凝土非线性断裂的耦合模型,并结合工程实际,对高拱坝的抗震损伤开裂行为进行了研究。本文的主要内容与创新点有:1.实现了弹簧―阻尼边界模型,并进行了精度验证。研究了不同坝高、基岩―混凝土弹模比(E_f/E_d)、地震条件下重力坝考虑辐射阻尼的抗震响应。一般地,辐射阻尼显著降低结构的动力反应,E_f/E_d越小,辐射阻尼效应越显著。2.提出无质量地基模拟地基辐射阻尼的等效模型,即界面阻尼等效模型和等效结构阻尼模型,并应用于重力坝和拱坝的抗震分析,结果表明,等效模型简单易用,可近似模拟混凝土坝考虑地基辐射阻尼的地震反应。3.在ABAQUS软件的虚结点扩展有限元(改进扩展有限元)静力功能基础上,实现了动力断裂分析功能,并应用于重力坝的强震多裂缝同时扩展研究。4.进行了两类混凝土断裂模型和不同本构关系的比较分析,建立了基于扩展有限元法的黏聚裂缝模型(XFEM-COH)、基于有限元弥散裂缝的塑性―损伤耦合模型(FEPD)和Drucker-Prager弹塑性模型(DP)间材料参数的转化关系和应力―应变关系等效原则。通过构件和重力坝的静、动力断裂分析表明,三种模型的结构总体反应接近,但DP模型的结构承载力偏高于其他两种模型。此外,三种模型对裂缝的描述存在重要区别,XFEM-COH的裂缝为连续的曲线状分离裂缝;FEPD的裂缝为条带锯齿状;DP的裂缝则呈现片状屈服区特征。5.建立了考虑拱坝地基辐射阻尼、横缝张开与混凝土非线性断裂的耦合模型,较真实地模拟了大岗山拱坝在设计地震条件下的损伤开裂过程。结果显示,大岗山拱坝下游面可能产生局部损伤开裂,横缝在地震中也将张开。据此,全面研究了辐射阻尼、横缝张开、混凝土断裂等因素对拱坝动力响应的影响。更多还原

【Abstract】 Dynamic response and seismic safety analysis of high arch dams are in?uencedby several key factors, such as earthquake input mechanism, radiation damping e?ectsdue to infinite foundation, contraction joint opening and closing during earthquakesand concrete damage cracking, etc. The major focus of this study is on development ofa nonlinear coupled model in which all the aforementioned physical e?ects are consid-ered. The nonlinear coupled model is used in realistically simulating the response ofhigh arch dams during extremely strong earthquakes. As an engineering application,the Dagangshan arch dam with 210m in height is analyzed for damage cracking processduring designed earthquakes. The main innovation and results in this study includes:1. A 2-D and 3-D viscous-spring boundary model and the corresponding earth-quake input method are implemented for seismic analysis of concrete dams consideringradiation damping. Numerical verification of accuracy is performed for the viscous-spring boundary model. In?uence of several features, including dam height, ratio ofelastic sti?ness of rock and concrete and di?erent earthquakes, on radiation e?ects inseismic response of gravity dams is studied. Generally, seismic response of gravitydams is significantly reduced when considering radiation damping. The smaller the ra-tio of elastic sti?ness of rock and concrete, the more significant reduction of responseof dams due to radiation e?ects.2. Equivalent models for considering radiation damping e?ects in massless foun-dation model are presented and used in seismic analysis of gravity and arch dams.The equivalent models are simple and have su?cient accuracy in seismic analysis ofconcrete dams.3. The phantom node extended finite element method (XFEM) (improved XFEM)based on static function of XFEM in the commercial finite element software ABAQUSis extended to dynamic analysis. The method can be used in analysis of multi-crackextension of gravity dams during strong earthquakes. 4. A comparison study of di?erent concrete fracture models is presented. Threefracture models are discussed herein, i.e. extended finite element method with cohesivecrack model (XFEM-COH), crack band finite element method with plastic-damage re-lations (FEPD) and finite element Drucker-Prager elasto-plastic model (DP). The cor-relation of material parameters and the equivalence principle of stress-strain relationsbetween the three fracture models are proposed. Several benchmark problems includ-ing mode I and mixed-mode static and dynamic fracture in concrete are analyzed usingthe three procedures. The results are compared with the corresponding experimentaldata demonstrating that the numerical results are accurate and comparable. Overload-ing capacity of gravity dams with longitudinal cracks and dynamic fracture of Koynagravity dam are analyzed using the three models. The three procedures give reason-able and comparable results. However, the crack patterns are of significant di?erencesfrom the di?erent fracture models. Smooth curvature discrete cracks are obtained inXFEM-COH model, while hackle band cracks appear in FEPD model and ?aky yieldzones emerge in DP model.5. A nonlinear coupled model for seismic analysis of high arch dams includingradiation damping e?ects, contraction joints opening and closing and concrete damagecracking is presented. The nonlinear coupled model is used for realistically simulatingthe response of Dagangshan arch dam during strong earthquakes. It is found thatdamage cracking appears in the upper portion of the dam. The cracks are localized inthe downstream face. Contraction joints are opening during earthquakes. In addition,the in?uence of the aforementioned factors on seismic response of arch dams is alsoinvestigated.更多还原