Model Simplification For Seismic Calculation Of Aqueduct Structure

Aqueduct is an important hydraulic structure, will be widely applied and play an important role in South-to-North water diversion project in China. Their seismic issues not only have academic significance, but also have engineering significance and social significance. Based on these, seismic analysis was carried out on aqueduct and a simplified calculation method was proposed.First, Westergard added mass method, Housner spring - mass model and Birbraer added mass method were introduced which are widely used in the seismic analysis of the aqueduct . Taking an aqueduct for example, three kinds of fluid - structure interaction theories were used to calculate its dynamic characteristics and seismic response, and were compared with each other.Next, dynamic response of free field was carried in detail by using of vibration method. Equivalent linearization principle was employed to deal with the nonlinear characteristics of the soil. The seismic response analysis of free field was carried with the introduction of viscous artificial boundary theory, and reasonable value of the free field area was discussed. The dynamic response will be stable and the deviation was not more than 5% when the length of free field is 100 times longer then the thickness of layered soil, the deviation was not more than 0.5% when the length of free field is 1000 times longer then the thickness of layered soil.Then, based on Housner fluid-structure coupling model and Penzien pier-soil interaction model, a simplified model of an aqueduct was developed with fluid-structure coupling and pier-soil interaction. The detailed derivation and calculation parameter was given.Finally, analysis on dynamic characteristics and horizontal seismic response of an aqueduct was carried with the pile - soil simplified model and rigid foundation model which ignored pile - soil interaction. The results show that water and piles -soil are both able to extend the natural cycle of aqueduct. For the displacement response, the water in aqueduct can reduce the displacement of tank and increase the displacement of pier in the same foundation. When aqueduct with or without water at the same time, the displacement of pier will be reduced and the displacement of the tank may be increased or reduced if considering the pile-soil interaction. For the internal force of aqueduct, the internal force of aqueduct with water will be increased, which is nothing to the foundation; the internal force of aqueduct is smaller with pile - simplified model. That is, the water and piles-soil will be useful for reducing the seismic response of aqueduct. The results were in good agreement with experimental data of pseudo-dynamic test.