Event tree analysis and time-integrated reliability design approach for quantifying rockfall risk reduction

The quantification of risk in terms of loss of lives represents the essential parameter to manage rockfall risk in urbanized areas. Rockfall barriers are among the most adopted structural mitigation measures. Despite their wide use, the partial safety factors design approach is not able to guarantee a specific failure probability and, consequently, to assess the precise risk reduction. To tackle all these issues, a quantitative risk assessment method for infrastructures and a time-integrated reliability design approach for rockfall barriers developed by the Authors are combined in a unique framework to quantify risk reduction. The former computes the risk as annual probability of having at least one fatality; the latter allows defining an annual failure probability for a given product in a given site. Merging these methods, the evaluation of risk reduction in case of barrier installation or the definition of the required performances, are defined. An example of application is provided.