【作者】 陈明阳；

【导师】 陈健云；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2010， 硕士

【摘要】 使用损伤模型分析重力坝在地震中的破坏机理在近二十年有了突飞猛进的发展。研究表明混凝土是准脆性材料,在破坏过程中表现高度的非线性特性同时伴有塑性,基于应力等效与应变等效原理的损伤模型不能考虑其塑性发展,而基于能量等效原理的损伤演化本构不仅能够考虑混凝土中的塑性反应而且遵循能量守恒定律,因此本文采用这种塑性损伤耦合本构模型对西部某碾压混凝土高坝进行了地震分析,分析了地震中损伤因子的发展规律及截面应力的变化规律。混凝土材料发生断裂损伤的过程中,伴随着能量耗散,本文研究了损伤耗散的特点。并对大坝地震中的能量反应作了初步的研究,概括了地震输入能量、大坝弹性势能、动能、大坝阻尼耗散及损伤耗散的地震反应机理。目前使用断裂力学和损伤力学对大坝进行非线性动力响应分析成为热点,但研究如何使用这些结果对大坝进行整体安全评价还比较少,最主要的方法是采用危险截面上裂缝区的相对长度作为主要判断依据,再辅以裂缝的环境(如有水、无水等)进行加权求得最终的安全判定系数。这种方法仅考虑了大坝局部部位的裂缝危害,本文在此基础上,将损伤耗散能引入判定公式,用于考虑大坝的整体破坏情况,得到新的损伤评价指标。高烈度地震区高坝的抗震措施倍受关注,通过工程措施减小地震的危害是本文研究的重点。本文主要从优化材料分区和抗震配筋两方面研究了其抗震效果。通过对混凝土重力坝塑性损伤分析得知,不同的材料分区设置对重力坝顶部裂缝的形态影响很大,通过以大坝整体损伤评价指标为优化目标进行对比分析,得到了最有利的抗震材料分区设置。文章还介绍了钢筋混凝土有限元的作用原理,研究了结构中钢筋与混凝土相互作用的机理及大体积少筋混凝土的断裂能特点,使用ABAQUS开发了各向异性的钢筋混凝土有限元本构,并考虑了脆性材料的损伤局部化效应,考虑了非线性刚度阻尼效应,使用这种本构进行了动力分析。最后文章对大坝进行了抗震配筋效果分析,指出了规范中弹性力学配筋方法的不合理处,确立了依照危害程度进行配筋的原则,通过非线性对比分析选出最为合适的配筋设计。更多还原

【Abstract】 There has been a great improvement in seismic analysis of gravity dam by damage in the last 20 years. It was discovered that there is plastic strain during cracking, however concrete is brittle materials. As the plastic strain can’t been considered in stress-based damage model and strain-based damage model, the energy-based damage is adopted in this paper. It studies the seismic response of a high RCC gravity dam in China western by plastic-damage model. It reveals the evolution of damage index and stress in cross section.It studies the energy dissipation in the fracture process of concrete. Then the energy response of gravity dam in earthquake is presented. The hysteretic characters, energy dissipation ability, failure mechanism and characteristics are researched, it introduces the responses of input energy、damping energy、elastic energy、kinetic energy、plastic energy dissipation and damage energy dissipation. Though it is popular in seismic analysis by damage mechanics or fracture mechanics, there almost isn’t a common criterion for dam safe evaluation using these mechanics. Some people have explored a global dam damage index, which is main formed by the length of crack in the dam cross section and the modifying coefficient, the crack environment (such as upstream、downstream、underwater and so on) determines the value of modifying coefficient. But this global dam damage index just considers the local damage influence, in order to improve degree of accuracy a new global dam damage index is proposed, in this index the damage energy dissipation is considered, using this factor we can get the information of the damage area rate of the whole dam section.People have paid attention to the strengthen measures of high gravity dam for high intensity seismic, study of the measures is the main work in this paper. It proposes two measures:optimizing the material assigning design. It has been found that the different material assigning designs can lead very different dam cracking, so though comparing the global dam damage indices we get the optimum design. Then the paper introduces the theory of reinforced concrete finite element and the reaction between rebar and concrete in big volume rare-reinforcement concrete structure, the crack characteristic is very different from brittle plain concrete, so it also studies the fracture energy of reinforced concrete. In ABAQUS it develops a new constitutive model of reinforced concrete. in this constitutive model the local effect of crack is considered, once a crack processes the crack opening displacement takes place rapidly, but the strain of other undamaged zone will decreases, it leads to form just one crack in characteristic length. It studies the damping characteristic in the constitutive model, the nonlinear Rayleigh damp is adopted. Then it studies the seismic crack of dam using this constitutive model. At last it introduces the methods of calculating the reinforcement percentage, it states the disadvantage of the method in hydraulic concrete structure design code by linear finite element, explores a new method by nonlinear finite element according to the damage degree, and finds the appropriate reinforcement percentage.更多还原