Analytical and numerical modeling of hydrodynamic distress of rigid and flexible concrete dams

Abstract eng:
It is widely accepted that the dynamic response of any retaining system is not yet clearly understood, mainly due to the dynamic interaction between the system and the retained material. Especially, the cases when the retained material is liquid (e.g., water behind dams) is of much greater interest and complexity for engineers, as during a seismic excitation significant hydrodynamic pressures may be developed. The dynamic response of various types of dams that retain a semi-infinite water deposit has been examined in the past analytically, numerically and experimentally. Most frequently, seismic design of dams (either rigid or flexible) is based on the method described in the pioneer work of Westergaard, which undoubtedly is a simplified approximation of the real conditions of the problem. In particular, when a concrete dam is founded on soft soil, the dynamic interaction between the dam the reservoir and the soil becomes much more complex, and cannot be realistically simulated by such simplified methods. In the present study, the dynamic interaction between a concrete dam, the retained water and the underlying soft soil is investigated. Initially, the dynamic pressure distributions are calculated in the case of resonance, whereas the resultant water thrust and moment at the dam base are evaluated as functions of the imposed steady-state frequency. Subsequently, the water is replaced by a pair of springs to simulate the transitional and rotational response of the reservoir. The stiffness constants of these springs are estimated by approximate empirical formulas that have been developed using the numerical results. Finally, the distress contours in the dam body are presented for various cases of the reservoir depth and the underlying soil layer stiffness. The results justify the necessity for a more elaborate consideration of the aforementioned dynamic interaction complex phenomena and their impact on the seismic design of concrete dams.

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