A probabilistic method for the seismic assessment of existing concrete gravity dams

This work presents a probabilistic seismic assessment method able to manage the physical complexity of the dam– foundation–reservoir system and the uncertainties regarding structural data and external actions. The seismic response of the structure is estimated from a reduced number of dynamic time-history analyses, performed employing a finite element discretisation of dam body, reservoir water and foundation rock mass. The system fragility curves are then obtained via a standard Monte Carlo simulation procedure. The methodology has been applied to the case of Kasho Dam, a concrete gravity dam located in Japan, which experienced in 2000 the Western Tottori earthquake with no damage at dam body. The assessment has been carried out with respect to an operational limit state, for which several ‘critical’ failure mechanisms have been identified and numerically evaluated, both in terms of demand definition and capacity evaluation.