Effects of Near-Fault Ground Motions on the Seismic Response of Concrete Gravity Dams

摘要

This paper investigates the effects of near-fault ground motions on the base slipping response of concrete gravity dams. The numerical modeling of the dam-reservoir-foundation system includes the consideration of the nonlinear material behavior of the dam concrete and the foundation rock, the contact interaction between the dam, the reservoir, and the foundation, the unbounded features of the reservoir and foundation domains, and the spatial variation of seismic surface motions. The developed numerical model is then applied to the Koyna Dam, which is subjected to a range of spatially varying near-fault ground motions generated using actual earthquake records. The investigation reveals that spatially non-uniform seismic excitations cause a severer damage behavior of the dam than uniform ones. Specifically, the base slipping response of the dam is found to increase as the apparent propagation velocity decreases. It is also shown that the peak ground acceleration of the near-fault motion is an important parameter that influences the slipping response. Generally, higher peak ground accelerations tend to produce larger permanent slipping displacements.