Probabilistic seismic demand model and optimal intensity measure for concrete dams

•Safety of a concrete dam is assessed for the first time in the context of PBEE.•Over seventy intensity measure parameters are mathematically identified and evaluated.•Optimal intensity measure is determined for a gravity dam.•Fragility curves are determined for a gravity dam based on cloud analysis. This paper addresses the probabilistic seismic demand model (PSDM) which is the relationship between the intensity measure (IM) (such as spectral acceleration) and the engineering demand parameter (EDP) (such as displacement and crack ratio – ratio of crack length to total crack path). It expresses the probability that a system experiences a certain level of demand for a given IM level. Formulation is for a concrete gravity dam. First, IMs are categorized and the criteria for the selection of an optimal one presented. Then, cloud analysis is performed where the structure is subjected to a large set of un-scaled ground motions and the maximum responses are extracted for each one and plotted as a cloud of results. This methodology is applied to Pine Flat gravity dam. Model is first presented followed by results and conclusions. When the results of the cloud analysis are aggregated, then one can plot the seismic fragility curve which is the probability of EDP exceedance in terms of the IM parameter.