Probabilistic evaluation of DAM base sliding

Concrete gravity dams represent a relevant part of the 500 large dams existing in Italy. Most of them were built following obsolete seismic design criteria, so they need to be verified with modern seismic analyses according to the new Italian Code on Dams (2014). Many of the parameters utilized in this evaluation are affected by large uncertainties. In the paper we present a procedure based on Monte Carlo simulation which evaluates the probability of exceedance of the sliding equilibrium of the dam obtained via static or response spectrum analysis in case of seismic action, as well as the probability of exceedance of different sliding displacements via nonlinear dynamic analyses. The application to four seismic sites (of different seismic hazard) and to three dams with different heights is presented.