Nonlinear Earthquake Response of Concrete Gravity Dams.

Abstract : A mathematical model is proposed for the mechanical properties -- constitutive relation and strength -- of concrete subject to dynamic cyclic reversible stresses and strains that may occur in gravity dams subjected to earthquake ground motion. The model describes properties of concrete under a two-dimensional state of stress. The effects of strain rate -- the time rate of change of strain -- on the mechanical properties are incorporated in the model. Experimental results available in the literature form the basis for the proposed model. A method is developed for nonlinear analysis of response of concrete gravity dams to earthquake ground motion wherein mechanical properties of concrete are defined by the mathematical model mentioned above. Earthquake analyses reveal that cracking of concrete is confined to areas near the upstream and downstream faces of dams -- especially in the upper parts and in some cases also near the heel. The estimated cracking is very sensitive to the assumed tensile strength.