Building fragility curves of sliding failure of concrete gravity dams integrating natural and epistemic uncertainties

Abstract

In the majority of engineering problems, two kinds of uncertainty are generally considered: natural uncertainty, resulting from the inherent variability in natural processes, and epistemic uncertainty, linked to lack of knowledge. When performing a quantitative risk analysis, considering both types of uncertainty separately before integrating them when performing risk calculations, allows a better understanding on how both types of uncertainty influence risk results.The main purpose of this paper is presenting a consistent procedure to perform fragility analysis for dams in order to identify and track natural and epistemic uncertainty separately. This procedure is particularized for the sliding failure mode of concrete gravity dams, due to its importance. The resulting fragility curves provides a valuable input to quantitative risk models in order to compare the effect of risk reduction and uncertainty reduction investments.The proposed procedure combines the concepts of the Electrical Power Research Institute (EPRI) guidelines to develop fragility curves for the nuclear industry with existing reliability techniques for computing fragility curves in the context of concrete dams engineering. The procedure has been applied to a dam to illustrate how it can be used in a real case in such a manner that fragility curves are obtained integrating natural and epistemic uncertainties without losing track of their separate contribution to risk results.