Evolution law of overall damage of concrete gravity dam under near-fault ground motion

Abstract Strong earthquake cases of concrete gravity dams show that the foundation damage has an important influence on the seismic response and damage characteristics of the dam body. Compared with non-pulse ground motions, pulse-like near-fault ground motions have a wider response spectrum sensitive zone, which will cause more modes of the structure to respond, resulting in more serious damage to the structure. In order to study the real dynamic damage characteristics of concrete gravity dams under the action of near-fault ground motions, this paper takes Koyna gravity dam as the object and establishes a multi-coupling simulation model that can reasonably reflect the dynamic damage evolution process of dam concrete and foundation rock mass. A total of 12 near-fault ground motion records with three types of rupture directivity pulse, fling-step pulse and non-pulse are selected, deep research on the overall damage evolution law of concrete gravity dams. Considering the additional influence of different earthquake mechanisms, different site types and other factors on the study, the selected ground motion records are from the same seismic events (Chi-Chi), the same direction but different stations. The results show that the foundation of the concretes gravity dam often get damaged before the dam body under the action of strong earthquakes. Compared with the near-fault non-pulse ground motion, the structural damage of the gravity dam under the action of the near-fault directivity pulse ground motion is significantly increased, and causes greater damage and displacement response to the dam body. The near-fault fling-step pulse ground motion has the least impact on the dynamic response of the gravity dam structure.