The Adjustable Factor of Safety: A reliability-based approach to assess the factor of safety for concrete dams

Factors of safety are applied to accommodate uncertainties in the assumptions for load, resistance, and model parameters. The sources of uncertainty are physical variability inherent in nature, statistical uncertainty of input data, and limited knowledge. This paper analyses the effect on safety when curbing uncertainty. It argues that deterministic factors of safety are unsatisfactory. Linking them to the level of knowledge produces a more adequate assessment of structural safety. The proposed approach is based on reliability-based codes used in common civil structures. The authors hope to initiate discussion on the usefulness of the Adjustable Factor of Safety (AFS).