Modeling and analysis of uncertainties for risk-informed decisions in infrastructures engineering

Engineers deal with uncertainties in all their activities, and must often make decisions under conditions of uncertainty and risk. Infrastructures engineering is no exception-design codes are developed to ensure a desired level of safety and performance, or to ensure a specified operational life with a prescribed level of reliability; the required decisions must often be formulated without complete information and thus contain uncertainties. In considering uncertainties, it is important to recognize two broad types; namely, the aleatory type which is associated with natural randomness and the epistemic type which is associated with imperfect knowledge. Proposed here is a framework for the proper modeling and treatment of each type of uncertainty in the formulation of risk-informed engineering decisions. The concepts are illustrated with applications to bridges and offshore marine structures.