The credibility measure of probabilistic approaches in life-cycle assessment of complex systems: a discussion.

The life-cycle assessment of complex systems over time suffers of uncertainty and its probabilistic modeling is required. Two kinds of uncertainties reside in a probabilistic model: epistemic and aleatory. Both of these uncertainties can be reduced but cannot be eliminated. In this chapter the effect of the epistemic uncertainty on the service life prediction of a steel truss subjected to deterioration will be investigated. For this purpose, an opportune credibility indicator will be introduced. This indicator will be able to compare two models and decide which one is the most reliable. The results prove that the credibility index is able to recognize, in qualitative and quantitative terms, the most reliable modeling. Using the case study proposed it is shown how the influence of the epistemic uncertainty can have a relevant influence on the lifetime prediction and, consequently, on the possible maintenance strategies and their related costs.