The Equivalent Dynamic Characteristics Study Of Three Dimensional Dam In The Frame Structure

Nowadays most of the hydraulic engineering projects in China are located in the southwest districts. On the other hand, earthquakes often happen in the southwest of China, thus threatening to the construction and operation of these hydraulic engineering projects. So it is meaningful to study the dynamic characteristics of the dam.The usual way to investigate the dynamic characteristics of the dam is called the ratio of similitude theory. This theory aims to conduct dynamic model tests using the model structure which is proportionally reduced in the physical dimension. The results of the model test multiply the ratio of similitude will make the anticipated prototype results. But when the dynamic test results' nonlinearity is remarkable, it is quite complicated to use the ratio of similitude theory.This article uses the Koyna Dam as the prototype, and modal analysis to get the natural frequency and the vibration mode. Calculate the frequency and vibration mode of the reduced scale model according to three model scales. This will be helpful to study the size effect made on the dynamic characteristics.In order to reduce the size effect, this paper presents the frame structure model to change the structural type and the materials to reduce the natural frequency. In the equivalent modal structure, the distribution of the mass and stiffness will be improved by the adjustment of the pillars section and the steel plate thickness. The reasonable structure will make the natural frequency and vibration mode closer to the dam. Another way to test the degree of dynamic approximation between the model and the prototype is using the external excitation. This paper has studies the response of the two structures under the sine wave and EL centro wave respectively. Based on the computed results, the frame structure has the similar dynamic characteristics with the prototype.According to the equivalence theory, this paper suggests the frame structure, which has the similar dynamic characteristics with the dam. Compared with the common similarity rate of model method, this new way will reduce the complicated calculation process. In a word, the conclusions in this paper are useful in the model tests of the dynamic characteristics.