| 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.
|
PDF Full Text Request