SEISMIC RESPONSE OF CONCRETE GRAVITY DAM INCLUDING DAM -RESERVOIR-FOUNDATION INTERACTION

Abstract

The response of dam subjected to seismic loading is the combined effect of the interaction of the three systems namely dam, reservoir and foundation. A single dam monolith is considered and is assumed to respond as a two-dimensional system under plane stress conditions. The two-dimensional assumption is also extended to model the compressible reservoir water body impounded upstream of the dam. The foundation is also assumed two dimensional system under plane strain condition. Energy dissipation in the foundation and in reservoir through radiation in the infinite upstream direction has been approximately accounted by using infinite elements. The absorption at the bottom of the reservoir has been taken into account. Koyna dam has been taken for the study. Ground accelerations recorded during Koyna earthquake (1967) have been taken for the study in time domain. Finite element software ABAQUS (version 6.5) has been used throughout. The importance of interaction has been established in frequency domain as well as time history studies. The linear response of the dam to horizontal or vertical harmonic ground motion is presented for a range of the important system parameters characterising the foundation medium and impounded water with the excitation frequency varied over a relevant range. The earthquake response of the dam in time domain is investigated with emphasis on the nonlinear behavior associated with tensile concrete cracking and water cavitation. Concrete damaged plasticity model has been used for simulating the tensile damage in the dam body.