Frequency Domain Analysis of Submerged Tower-Dam Dynamic Interaction

Abstract

The dynamic response of a coupled gravity dam-reservoir water-intake tower-footing-rock foundation systems is investigated using frequency response functions of the concrete dam and the intake tower structures under horizontal and vertical ground motions. The effects of reservoir water level, reservoir bottom absorption, and presence of the dam on the tower response are studied for two tower and dam types: a squat tower adjacent to a low-height dam; a slender tower adjacent to a high dam. Using three-dimensional finite element method, it is shown that the presence of the low-height dam partially influences the response of the squat tower just for the full reservoir condition. But the high dam causes significant resonances in the response functions of the slender tower even for half reservoir. The reservoir bottom absorption strongly affects these resonances generated by the dam-water-tower interaction. It also drastically reduces the fundamental resonance amplitudes under vertical excitations. The degree of interaction between the dam and the tower is dependent on the flexibility of the foundation rock, the reservoir water level, the reservoir bottom absorption, and the slenderness ratio of the tower.