The role of uncertainties in Aeolian risk assessment

The design of slender structures subject to wind actions must take into account many sources of uncertainty in the environmental parameters that describe the wind field at the site, in the structural mechanical properties, and in the parameters that influence the interaction phenomena. For the sake of simplicity, three types of uncertainty can be distinguished: (i) aleatory uncertainty, related to the natural variability of the parameters and their unpredictability; (ii) epistemic uncertainty, related both to the lack of information and to the errors of experimental measures; (iii) model uncertainty, related to the choice of the models of wind actions, structural dynamic response and interaction phenomena. In this paper, the relevance of the different sources of uncertainty is discussed and illustrated with reference to an example case. In detail, the effects on the risk assessment of a long span suspension bridge induced by the uncertainty of the model of the aeroelastic forces are investigated. The study is aimed at the development of a procedure for Performance-Based Wind Engineering.