Tail effects of uncertainty modeling in QRA

The paper discusses the general feeling of uneasiness engineers and scientists experience when they assume probability models for basic uncertainties governing a risk or reliability analysis. Specifically, the aspect of tail behaviour is addressed. It is well known that quantitative risk estimation is critically dependent on the tail behavior. The present paper focuses an tail heaviness and the effect of tail heaviness of basic uncertainties on the overall risk or failure probability. This is of interest to a model-based risk analysis as well as a structural reliability analysis. Two examples are included to illustrate some of the concepts introduced.