地震载荷下的混凝土重力坝断裂原因分析外文翻译.docx

毕业设计（论文）外文翻译 题 目 榆林王圪堵水库枢纽 布置及重力坝设计 专 业 水利水电工程 班 级 学 生 指导教师 地震载荷下的混凝土重力坝断裂原因分析 ABBAS MANSOURI;MIR AHMAD LASHTEH NESHAEI;REZA AGHAJANY 1伊斯兰阿扎德大学，土木工程，伊朗德黑兰 2桂兰大学，土木工程，拉什特，土木工程伊朗 3伊斯兰阿扎德大学，土木工程，德黑兰（北支），伊朗 摘要：在本文中，对混凝土重力坝的地震裂缝采用有限元（2D）的行为理论进行了研究。巴占特模型（它是非线性的断裂力学标准作为衡量的增长和弥散裂缝）被选中来开发裂缝的剖面图。混凝土的应力-应变曲线作为简化的两线，欧拉-拉格朗日公式被选用于大坝和水库系统。根据1967年的地震记录，用上述模型对Koyna混凝土重力坝进行了研究。结果证实了第一个裂缝的图像有增长和扩张而第二个并没有受到它的影响。比较的结果显示了与其他研究者一致的结论。关键词：地震断裂；弥散裂缝；非线性断裂力学；混凝土重力坝。 在过去的十年里，有关在地震时混凝土大坝安全的的大坝抗震性能已受到广泛的研究。Chopra 等人(1972),通过使用线性弹性分析研究大坝的抗震性能的裂纹路径。分析显示,在损坏或有风险的地方会影响结构的稳定性。Pal(1976)是第一个利用非线性分析研究Koyna大坝的研究人员。在本研究中,假设没有水库的影响,在刚性地基上,用弥散裂纹模型对Koyna 大坝裂纹扩张和强度标准裂纹增长进行了分析。结果表明,裂纹的增长对材料性质以及元素大小是非常敏感的。图1(a)显示了这种分析造成的大坝裂纹区。Skrikerud（1986）采用离散裂缝裂纹扩展和裂纹增长的标准，通过Koyna大坝的个案研究了混凝土坝。在他们的研究中，裂纹在每一步的成长,长裂纹尖端的元素最终被认为是有效的。他把他们的模型试验结果归结于裂纹分析在与大坝开裂的膨胀系数不匹配、和水库相互作用并且缺乏大坝特性参数的实际值等原因。通过分析留在图1（b）中的裂纹就可以证实。El-Aidi和Hall（1989）研究了弥散裂缝的裂纹扩展和增长模型和强度准则。他们的研究认为裂纹轮廓线的出现证明了水库-坝和地基-大坝的相互作用。大坝裂缝如图1（c）所示。Fenves和Vargas-Loli还用断裂力学裂纹增长和弥散裂缝模型裂纹扩展（ Uang and Bertero,1990）的标准研究了松平大坝。不计由地基带来的结果，他们应用不同系数的塔夫脱的地震记录；对松平坝在有没有水库影响的两种情况下进行分析，本课题研究了大坝动水压力与裂纹分布对大坝的抗震性能的影响，此研究结果示于图1（d）。 在该文章中，对混凝土重力坝地震条件下非线性断裂行为的研究有以下部分： 第一，提交弥散裂纹模型与动态荷载作用下混凝土的性能和断裂的堤坝研究； 第二，对Koyna混凝土重力坝从非线性分析方面进行了抗震性能的评估。 采用有限元方法分析坝-库水相互作用和无水库作用的结果。从而可以得出结论，上游和下游都出现通过大坝上部的的预裂缝,这是符合观察原型特征的结论。比较分析表明，水库的作用不能忽视。 (d) Vargas-loli (c) El-Aidi (b) Skrikerud (a) Pal (h) 实验模型 (g) 实物模型 (f) Bhattacharjee (e) Calayir and and Leger Karaton 图1：关于重力坝开裂的过去调查资料。 欧拉-拉格朗日制定的动态相互作用的坝-水库系统和边界条件：使用不同的方法，为大坝和水库建模，而欧拉-拉格朗日模型是使用的一个标准。在这个研究中，大坝和水库建模系统的欧拉-拉格朗日关系被进行了调查研究。 在图 2 中，给出了大坝和水库的边界条件。 根据有限元理论方程，调整的大坝如下公式： 在这个公式中：质量矩阵，阻尼矩阵，结构刚度矩阵，相对节点的位移矢量，单位矩阵， 在方程（2）中：流体压力， 2. 远程边界条件 3.相交边界条件 4.底部边界条件 在这几个方程中：大坝加速度；地面加速度；垂直向量；流体密度。在水库中产生的加速度与大坝的数量加速度有关。其中：流体密度，坝体密度；声速。 考虑到边界条件和流体方程，水库关系矩阵的构成如下： 图（2）：大坝和水库系统公式中：流体质量矩阵；阻尼矩阵；流体刚度矩阵；流体压力向量；单位矩阵；锚加速度向量。 根据应力或应变张量，破裂方向被定义为潜在的导数。潜在损失可以是应力的一个函数或应变 （Kolari，2007年），在弥散裂缝模型中，潜在损失是应力的函数，这意味着该裂纹发生时应力达到极限的水平。另外，垂直于最大值的水平裂缝，被视为主应力的拉伸，因此在压应力状态下，没有损坏记录。随着压力的增加，非弹性变形的持久作用导致混凝土变软。在任何时候，混凝土初始边坡的最大抗压强度是平行于加载边坡的。当卸载方向变化时，混凝土（应力-应变）的反应具体是其弹性拉伸应力达到最大，然后发生开裂现象，最终结果导致混凝土的破坏。在该状态下（帮助减少弹性硬度），可以建立起一个裂纹展开的模型。如果再次被施加压缩应力，拉伸应力返回到零，该裂纹将被完全关闭。图3显示了混凝土在压缩和拉伸应力下的变化情况。 图3：混凝土单向应力变化（ABAQUS理论手册，2009）. 根据线弹性断裂力学的标准，裂缝的发展增长过程只发生在最大的裂缝部位，弹性元件的其余部分仍然呈线性变化，此方法适用于损坏面积相对较小的普通结构中。但是，非线性断裂力学模型更适合在巨大的建筑物中使用，如混凝土大坝，它的受损面积是比较大的，这种方法是在能量关系的基础上建立的，并且在断裂力学领域中提出了基于Hillerborg (1978) 和Bazant (1983) 的两种理论。根据1976年Hillerborg提出的模型，损坏的区域被认为是假想裂缝在真正裂缝的高峰期产生的。在 1983 年，Bazant表明裂纹的增长和扩张过程发生在条形破裂带上，在本研究中，Bazant弥散裂缝模型被用于研究Koyna坝。 总结: 在这个研究中，通过采用非线性断裂力学准则和弥散裂缝模型的发展概况，调查了大坝和水库在地震作用下裂缝的相互作用。结果，通过分析在有没有水库的条件下大坝的变化情况，得出以下结论： 1.通过与其他研究人员的结果对比，它显示出这项研究和其他人的引用是比较一致的：如(Guanglun等，2000年），（Calayir 和 Karaton，2005年），（Cai 等，2008年)，(Hal，1988年），（Saini 和 Krishna， 1974年）。因此，混凝土重力坝的抗震性能在非线性断裂力学准则和弥散裂缝模型的实验中得到了科学的证实。考虑大坝和水库之间的相互作用分析Koyna大坝，得到三个薄弱环节：大坝坝踵处，变化的边坡和大坝上部（在其中有大部分裂纹）的一些地区。在分析Koyna大坝而忽略水库的影响时所产生的结果后，表明在坝踵裂缝部位，斜率发生了变化。 从分析的结果可以看出，在受损的区域中，大坝和水库之间的相互作用的情况下大坝破坏程度预期的效果大于大坝单独作用的效果。 2.动态分析中使用的的弥散裂缝（延伸裂纹和裂纹扩展的材料的非线性断裂力学标准）的确是更新的物质性能，特别是裂缝能量和材料的性能。 3.如混凝土重力坝，它提供了大范围面积的断裂能根据各种文献，并考虑到，准确的测试也是正确定义材料性能时必要的条件。非线性断裂力学的理论定义的破坏面积和弥散裂缝模型定义的发展裂缝，可以视为一个适当的标准，并为我们提供了结构的实际行为。 参考文献 混凝土本构模型的非线性地震反应分析的重力水坝状态的艺术.加拿大土木工程学报,蔡.Q和罗伯特.J.M和范伦斯堡B.W.J.有限元的混凝土重力坝裂缝建模.南非土木工程学会杂志，2008年. 克莱尔.Y和卡若彤.M.地震裂缝分析混凝土重力坝，坝-水库的相互作用.电脑与结构，2005.查克拉巴蒂.乔普拉埃尔-艾迪.B和霍尔.J.非线性地震响应的混凝土重力坝第2部分,1989年. 光轮.W, 派库.O.A，楚汉相.Z，少民.W.基于非线性断裂力学的混凝土重力坝地震断裂分析.工程断裂力学分析，2000年. Fracture analysis of concrete gravity dam under earthquake induced loadsABBAS MANSOURI;MIR AHMAD LASHTEH NESHAEI;REZA AGHAJANY1 Civil Engineering, Islamic Azad University (South Branch of Tehran)Tehran, Iran2 Civil Engineering, University of Guilan, Rasht, Iran3 Civil Engineering, Islamic Azad University, (North Branch of Tehran), Tehran, IranABSTRACT: In this paper, seismic fracture behavior of the concrete gravity dam using finite element (2D) theory has been studied. Bazant model which is non-linear fracture mechanics criteria as a measure of growth and smeared crack was chosen to develop profiles of the crack. Behavior of stress - strain curves of concrete as a simplified two-line, dam and reservoir system using the formulation of the Euler-Lagrange was chosen. According to the above models, Koyna concrete gravity dam were investigated by the 1967 earthquake record. The results provide profiles of growth and expansion first with the effects of reservoir and second without it. Comparison of the obtained results shows good agreement with the works of the other researchers.Keywords: Seismic fracture; Smeared crack; Non-linear fracture mechanics; Concrete gravity dam. The seismic behavior of concrete dams has been the subject of extensive research during the past decade concerning dam safety during earthquakes. Chopra et al (1972), studies seismic behavior of dams crack path by using linear elastic analysis. The analysis shows, places that are in damage or and risk of the concerning stability of structure. Pal (1976) was the first researcher who examined Koyna dam by using non-linear analysis. In this research, assuming no effect of reservoir, being rigid foundation, smeared crack model use for crack expansion and strength criteria to crack growth, Koyna dam was analyzed and was shown that the results of material properties and element size are very sensitive. Figure 1(a) crack zone in the dam of which resulting from this analysis are shown. Skrikerud (1986) studied concrete dams through a case study on Koyna dam and by employing discrete crack for crack growth and strength criteria for crack expansion. In their study the growth of crack at each step of growth, the length of the crack tip element was considered that this is the final results were effective. He interpreted the results of their model, due to expansion mismatch with the cracking in their analysis of real crack in the dam, no match Foundation and reservoir interaction and lack of real values of characteristic parameters dam announced.Crack profiles from the analysis left in Figure 1(b) are presented. El-Aidi and Hall (1989) did a research on seismic fracture of Pine flat dam. Smeared crack model and strength criteria for crack expansion and growth were used. In their analysis is considering the reservoir dam and foundation dam interaction was crack profile presented. Figure 1(c), cracking in the dam will provide analysis. Fenves and Vargas-Loli also studied Pine flat dam by using fracture mechanics criteria for crack growth and smeared crack model to crack expand (Uang and Bertero,1990). They apply different coefficients of Taft earthquake record, regardless of the effect by foundation; Pine Flat dam in two cases with and without the effect of the reservoir was analyzed. In this study the effect of hydrodynamic pressure on the seismic behavior in the dam with the crack profiles presented. The results of this analysis were shown in Figure 1(d). Koy Koyna dam is one of a few concrete dams that have experienced a destructive earthquake. In this paper, study the nonlinear fracture behavior of concrete gravity dams under earthquake conditions. First, presented smeared crack model with the behavior of concrete under dynamic loads and fracture of dams. Secondly, Seismic behavior of concrete gravity dams was assessed with non-linear analysis to Koyna dam with regard dam reservoir interaction and without reservoir using finite element 2D method and presented results of analysis. From the results it is concluded that both the upstream and downstream faces of the dam are predicted to experience cracking through the upper part of the dam, which is consistent with the observed prototype behavior. Comparison analysis was done showed that the reservoir effect cannot be waived. (d) Vargas-loli (c) El-Aidi (b) Skrikerud (a) Pal (h) Experimental model (g) Real model (f) Bhattacharjee (e) Calayir and and Leger Karaton Figure 1: Past investigations into cracking profile in gravity dams. Euler - Lagrange Formulation for Dynamic Interaction of Dam - Reservoir Systems and Boundary Conditions: Different methods for dam and reservoir modeling are used. The Euler - Lagrange model is one criteria to used. In this research, the relations of Euler - Lagrange for dam and reservoir modeling system is investigated.In Figure 2, the dam and reservoir boundary condition is presented. According to the finite element theory equations governing the dam is as follows (Kucukarslan, 2003): In this equations,=Mass matrix,=Damping matrix,= Structural stiffness matrix,=Displacement vector of relative nodal,= Unit matrix,= Anchor acceleration vector.Equation governing the distribution of hydrodynamic pressure in the fluid environment is well known Helmholtz equation by two relations in which presented by the equation below: In Equation (2), the fluid pressures, the speed of sound in the fluid.Four boundary conditions are used to define the reservoir as follows.1. Free surface Boundary 2. Remote Boundary 3. Interaction Boundary 4. Bottom Boundary In this Equations,Dam Acceleration,Ground Acceleration,Vector perpendicular,Fluid density. Value of acceleration created in the reservoir, is related to the amount of dam acceleration.where:fluid density,Dam density,speed of sound. Considering the boundary conditions and fluid equations, the relationship matrix in the reservoir is formed as follows: Figure 2: dam and reservoir SystemsWhere:Fluid mass matrix,Damping matrix,Fluid stiffness matrix,Hydrodynamic pressure vector,Unit matrix,Anchor Acceleration vector. Rupture direction, is defined by potential derivative according to stress or strain tensor. Loss potential can be either a function of stress or strain (Kolari, 2007). In smeared crack model, loss potential is a function of stress. This means that crack happens when the stresses reach the level of submission. Also crack levels which are perpendicular to the maximum, are regarded as the tensile main stress. As a result in the state of compressive stress, no damage is recorded.As stress increases inelastic strains happen and concrete becomes soft. At any point, after the maximum compressive strength of concrete, initial slope is parallel to loading slope. When the unloading direction changes (strain - stress) the concrete response is to the maximum elastic tensile stress and then crack mechanism occurs. Than as a result concrete is damaged. In this state, with the help of reducing elastic hardness, a model can be made out of crack unfolding. If the compressive stress is applied again, by returning to zero, the cracks will be closed completely. Figure 3 shows the behavior of concrete when placed under compressive and tensile stress. Figure 3: Uniaxial behavior of plain concrete (Abaqus theory manual, 2009). According linear elastic fracture mechanics criteria, development process of crack and its growth occur only at the peak of crack and the rest of elastic element remains and behaves linearly. This method is applicable in ordinary structure in which damaged area is relatively small. But using nonlinear fracture mechanics model is more suitable in huge structures such as concrete dams where the damaged area is relatively big. This method is established on the base of energy relations. In the field of fracture mechanics two models have been presented based on Hillerborg (1978) and Bazant (1983) theories. According to the model presented by Hillerborg in 1976, damaged area is considered as imaginary crack at the peak of the real crack. In 1983; Bazant showed that growth and expansion process of crack occur on a stripe. In the present study, Bazant smeared crack model is used in studying Koyna dam. ConclusionIn this research interaction of dam and reservoir under earthquake was examined by employing nonlinear fracture mechanics criterion and smeared crack model of develop profiles of the crack. The results, through analysis in conditions of dam decomposition with reservoir and without it, the following conclusions were reached: 1.By comparing the results with other researchers it shows a fairly good agreement between this study and the others references: (Guanglun et al, 2000), (Calayir and Karaton, 2005), (Cai et al, 2008), (Hal, 1988), (Saini and Krishna, 1974), and therefore the philosophy of the nonlinear fracture mechanics criteria and smeared crack models at proper seismic behavior of concrete gravity dam seems to be confirmed. The obtained results of the analysis of Koyna dam considering interaction between dam and reservoir shows there are three vulnerable points: dam heels, changing areas of slope and some areas in upper part in which there are most of the crack elements. The results obtained in the analysis of Koyna dam regardless of reservoir effect on the dam, shows cracks in the heel areas of the dam, where the slope change. The results from analyses can be seen in damaged areas and the number of damaged elements in the case of interaction between dam and reservoir intended effect was bigger than effect of dam alone. Therefore it is important to attend thehydrodynamic pressure on concrete dam. 2.Dynamic analysis was used in the smeared crack to extend crack and the non-li