Performance indexes for seismic analyses of earth dams

The seismic performance of dams must be checked against expected ground motions verifying the possible occurrence of a serviceability or of an ultimate limit state. In this framework it is generally recognised that the earthquake-induced settlement of the dam crest can be assumed as a reliable index of performance since it is representative of the overall seismic response of the dam and is suitable for the evaluation of the level of damage induced by earthquake loading. Accordingly, threshold values of the crest settlement can be introduced to check the occurrence of a given limit state. A large set of data related to 90 case histories of damages produced by seismic events to dams and pertinent facilities was collected and is presented in the paper. The dataset isre-examined to define proper threshold values of the crest settlement to be used as possible reference indexes in performance-based seismic analyses of dams.