Earthquake input mechanisms for dam foundation interaction

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The seismic design of concrete dam-foundation-reservoir systems, must be able to ensure the survivability of these structures to extreme magnitude earthquakes. the need to represent non homogeneous geometrical and material foundation properties, and to predict damages which are generally due to non-linear effects implies that the the relative performances of various coordinates reduction techniques to solve the resulting time domain dynamic equilibrium equations have also been investigated. parametric studies have been conducted from numerical experiments by applying the proposed earthquake input mechanisms to simplified finite element models of gravity dam-foundation systems. the principal parameters retained in the analyses were the ratio of the modulus of elasticity between the foundation rock and the concrete dam and the damping ratio of the foundation. it has been found that the use of model a is not acceptable, producing significant artificial amplifications. model c, which is theoretically the most accurate model, and model d produced results which were almost identical for the complete range of selected parameters. model b although not as accurate as models c and d can be used for practical analyses if a proper modelling of the energy dissipation characteristics of the foundation is provided in the mathematical model. coordinate reduction techniques