Design certification with information-gap uncertainty

Abstract

This paper presents a concept for formulating structural design-codes which is based on information-gap models of uncertainty rather than on probabilistic concepts. Info-gap models quantify uncertainty as the size of the gap between what is known and what could be known. Info-gap models of uncertainty are particularly useful when data on the uncertainties are quite limited. In the proposed procedure a design is certified if the robustness to failure from uncertain fluctuations exceeds a code-specified threshold. Design is thus based on immunity to uncertainty rather than on probability of survival. The key conclusion is that design-certification can exploit data about uncertainties without introducing probabilistic models. This is important when information is scarce, since verification of probabilistic models can then be difficult. Second, when partial probabilistic information is available, it can be incorporated in a hybrid info-gap/probabilistic analysis. Third, the proposed design certification incorporates recognition of the dual nature of uncertainty: that it may be pernicious but may also entail propitious possibilities. Examples are presented which illustrate the design procedure. The incorporation of partial probabilistic information is also demonstrated. The antagonism between the pernicious and propitious potentials of ambient uncertainty is illustrated.