Statistical Analysis of Landslide Risk Assessment Parameters for Bridges and Viaducts Under New Italian Guidelines

In July 2022, following the tragic collapse of the Morandi Bridge in Genoa, Italy, the Italian Ministry of Infrastructure and Transport approved new Guidelines for the Classification and Management of Risk, Safety Assessment, and Monitoring of Existing Bridges (GLs). These guidelines aim to systematically evaluate and classify the safety of bridges and viaducts, providing a reliable tool to estimate a Class of Attention (CoA) for each structure, thereby identifying those requiring special precautions and maintenance. The GLs employ a multi-level approach across four risk areas: structural, seismic, hydraulic, and landslide.Each risk area is evaluated based on hazard/susceptibility, vulnerability, and exposure. For landslide risk, susceptibility is determined by parameters such as the state of activity, unstable volume, and characteristic speed of the landslide, along with secondary parameters like assessment reliability and existing mitigation measures. Vulnerability includes factors like average span, construction material, static scheme, type of foundationand structure-landslide interaction. Finally, exposure considers average daily traffic, maximum span length, and the strategic importance of the infrastructure. Given the methodical and standardized nature of the new regulation and the limited experience with it,this paperpresents a statistical study based on generating around 10,000 synthetic cases of landslide-bridge interactionsto evaluate their impact on Landslide-CoA outcomes. The study identifies trends, potential imbalances, and the sensitivity of parameters in landslide risk assessment. The study focuses also on specific case scenarios, comparing results for structures interacting with large, slow-moving landslides with those for structures potentially affected by rockfall phenomena characterized by smaller volumes but much higher impact velocities, examiningtheir different effects onLandslide-CoA levels. Findings suggest potential improvements to the calculation methods andpotential enhancements of the new guidelines, contributing to safer and more reliable infrastructure management.