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Earthquake Induced Longitudinal Vibration in Earth Dams.
Abdel-Ghaffar, A. M.
National Science Foundation, Washington, DC. Engineering and Applied Science., December 1980, 135 p.
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Two-dimensional analytical elastic models were developed for evaluating natural frequencies and modes of vibration of a wide class of earth dams in a direction parallel to the dam axis. The nonhomogeneity of the dam materials was considered as well as both shear and normal (axial) deviations. Dynamic properties of three real earth dams in Southern California estimated from their earthquake records and the dynamic test results of one dam, are compared with those from the suggested models. It was found that the models in which both the shear modulus and the modulus of elasticity of the dam material vary along the depth provide the most appropriate representations for predicting the dynamic characteristics. The theoretical results from some of the models compared favorably with the experimental and earthquake data. An analysis of real earthquake performance of an earth dam, in the longitudinal direction, yielded data on the shear moduli, damping factors, and nonlinear constitutive relations for the dam materials; Ramberg-Osgood nonlinear stress-strain curves were then fitted to these data. As a result of the study, a qualitative picture is presented of the distribution of dynamic strains and stresses within an earth dam during an earthquake.
Stress strain diagrams; Earthquake engineering; Random vibration; Shear modulus; Resonant frequency; Earth dams; Modulus of elasticity; Earthquakes; Dynamic structural analysis