【作者】 唐碧华；

【导师】 徐远杰；

【作者基本信息】 武汉大学 ， 工程力学， 2005， 硕士

【摘要】 随着市场经济的发展,能源需求的日益增加,水电事业正迅猛发展。我国即将建成一批巨型水电站,并向“高坝大库”形式发展,单机容量大,进水口坝段多为大孔口高坝,且多数水电站地处西南地区,结构抗震问题突出,因此对进水口的结构安全问题的讨论已经提高到了新的日程。 基于此,本文主要以龙滩水电站⑤机进水口坝段为例,采用了线性与非线性有限元方法,以ABAQUS为平台,完成了进水口结构三维静动力数值仿真分析。讨论了进水口结构的数值模拟方法,提出了一系列进水口结构的性能评价方法和增强结构安全的工程措施。 本文工作主要包括以下几个方面: 1、建立了进水口结构-基岩静力分析模型,完成了三维有限元分析,得到了典型静力工况下的结构位移和应力分布规律,分析总结了各重要部位产生拉压力的主要原因,并比较了各减小拉压力的工程措施和手段,且建议了适用于与龙滩进水口类似结构的具体措施。 2、提出以ξ=坝宽:引水洞洞径为描述进水口坝段体形的基本相对变量,得到了ξ与引水洞顶部拉应力峰值及其影响范围的关系曲线,可为其它同类工程设计和优化坝宽提供科学依据。 3、完成了结构-坝基复杂模型的非线性静力分析。结合非线性有限元分析成果,将重力坝与基岩之间抗剪断强度公式修正为适用于评定坝后坡结构安全储备的计算公式,得到了各工况下坝后坡的抗剪断强度系数,并评价了安全裕度。 4、建立了进水口坝段的动力分析模型,利用ABAQUS提供的用户子程序,成功地开发了4节点单自由度质量单元,较好地模拟了动水压力与大坝的相互作用,完成了进水口坝段的动力特性分析,得到了结构自振频率并总结了主振型规律;讨论了动水压力附加质量对结构自振特性的影响;并以后期坝体满库模型为例,讨论了复杂基岩对自振特性的影响,对坝体-基岩动力特性分析模型提出了合理建议。 5、完成了单独顺河向、竖向与两向同时激励的反应谱法分析和动力时程分析,得到了在各向地震激励下进水口结构的位移和应力响应,比较了两分析成果的异同,总结了地震工况下其控制应力及其部位,并提出了具体的抗震措施。 6、讨论了复杂地基的阻尼对高坝地震响应的影响,并建议了阻尼的合理取值。更多还原

【Abstract】 With the market economy developing in China, the demand for energy sources is gradually increasing and many hydropower projects are developing rapidly. Some huge hydropower stations with the characteristics of higher dam and larger reservoir will be built in reccent. The capability of generator unit and water turbine has become more and more greater. Those intakes are usually high dams with big holes. The problems of intake earthquake-resistance are arised because most of them are located southwest region, where the earthquake activites are stronger. Therefore, it is very significant to conduct the research on static-seismic simulaton and performance evaluation for structure of intake dam.Taking the NO. 5 intake of Longtan Hydropower station as an example, the intake dam was analyzed by using of 3-D linear and nonlinear FEM based on ABAQUS software. In thesis, some numerical methods for simulating intake dam were discussed, and a series of methods of performance evaluation and safety measures for intake were proposed.The major contents in the thesis are as follows:1 、 The model for 3-D static FEM analysis of the intake was presented, and the intake was fully analyzed by 3-D static FEM. Then the distribution of whole displacement, deformation and stresses of the intake were received. The primary reasons causing tension stress were summarized in important parts, and several measures minishing tension stress were analyzed and compared.2、 In order to scale the figure of the intake, a relative variable ζ that is the ratiobetween dam width and penstock diameter was brought forward. Then, a curve about the tension stress varying with ζ was obtained. The results provide scientific basis for otherengineering design and optimizing the width of dam.3、 The structure-foundation model was also analyzed by 3-D nonlinear FEM. Combining the result of FEM analysis, the shear strength formula between gravity dam and foundation was revised, then, a new shear strength formula was given for dam slope. The shear strength factors were received under every case in Longtan hydropower station, According to the results their safety margin was evaluated.4、 The model for 3-D dynamic FEM analysis was built. Making use of the user subroutine provided by ABAQUS, a user mass element with 4-nodes single freedom was developed successfully, and dam-reservior interaction was simulated preferably. Then, the dynamic characteristics of the intake dam were analyzed; natural vibration frequence andfundamental mode were obtained. The influence of hydrodynamic pressure and complex foundation upon dynamic characteristics was investigated. Finally, some reasonable suggestion for dynamic analysis was advised.5> The intake dam was analyzed by seismic response spectrum and dynamic time-history theory under three excitation inputs (horizontal, vertical and two orthogonal direction input), and the two results are compared. Then, the displacement and stress response were received, and control stresses and their position under earthquake case were summarized. Measures of earthquake-resistance were put forward.6^ The effect of damping on seismic response of high dam was discussed, and reasonable value of damping for seismic analysis was proposed.更多还原