Inflatable dams are flexible, cylindrical structures anchored to a foundation. They are used for various purposes, e.g., diverting water for irrigation or groundwater recharging, impounding water for recreational purposes, and raising the height of existing dams or spillways. Early inflatable dams were anchored along two of their generators, but recently-constructed dams are anchored along a single line. They also have a fin near the top which is useful in overflow conditions. The vibrations of such dams in the presence of external water are considered in this paper.

The dam is modeled as an elastic shell inflated with air and resting on a rigid foundation. First the equilibrium shape of the inflated dam is determined. Next, the dam is clamped with this cross-sectional shape at its two ends, and then water is applied on the anchored side with a height less than the “dry” equilibrium height. The new equilibrium configuration is obtained and small vibrations of the dam about this equilibrium shape are analyzed. The water is assumed to be inviscid and incompressible, and potential theory is used. The infinite-frequency limit is assumed on the free surface. A boundary element technique is utilized to determine the behavior of the water, and the finite element method is applied to model the structure using ABAQUS with a shell element (ABAQUS, 1994). Three-dimensional vibration frequencies and mode shapes are computed. The effect of the internal pressure of the dam is investigated, and the results are compared to those for the dam in the absence of external water.

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