On the seismic performance evaluation of dam-foundation-reservoir system for the effect of frequency content and foundation flexibility

The present paper investigates the effect of earthquake frequency content and foundation flexibility on the performance of the Koyna dam-foundation-reservoir system. Ground motions that match the conditional mean spectrum (CMS) are adopted for the seismic analysis. The concrete damaged plasticity model is used to represent the dam's nonlinear behavior; however, the foundation is assumed to be linear elastic. To study the foundation flexibility effect on the seismic performance of the dam, three different cases which comprise different elastic modulus of the foundation are considered. The damage indices, based on the crack length and dissipation energy, are evaluated for the performance assessment of the dam-foundation-reservoir system. The ground motion parameters such as predominant period, mean period, and effective ground period are chosen in order to explore the earthquake frequency content effect on the performance of dam-foundation-reservoir system. Results indicate that foundation flexibility has a significant effect on the dam. Further, the frequency content has a substantial impact on the dam's seismic response compared to the intensity and duration of ground motion. It can be concluded that the mean period is a good indicator of the earthquake frequency content and has a strong correlation with the damage parameters. • The effect of earthquake frequency content and foundation flexibility on the performance of a large gravity dam was studied. • Ground motions are selected based on the Conditional Mean Spectrum approach. • Ground motion parameters such as predominant period, mean period, and effective ground period were explored. • Foundation flexibility has a significant effect on the dam response. • The mean period is a good indicator of the earthquake frequency content.