Uncertainty in the safety evaluation of dams: The floating factor of safety

The evaluation of structural safety should provide the flexibility to adjust the applied safety parameter to the uncertainties inherent in loads, strength and the mathematical model. The following concept tries to elaborate a relation between the traditional factor of safety and the degree of uncertainty. The outcome is that less uncertainty (more knowledge) warrants a lower factor of safety. Thus, it is not any more a constant, deterministic value: it floats with the level of data uncertainty. More knowledge involves less expenditures. The application of a floating factor of safety would respect this fact and reward those who are willing to curb uncertainty by additional investigations as lower factors of safety correspond to less expenditures without impairing structural safety.