Structural and seismic risk classification of bridges according to the italian guidelines: a critical perspective from the jointed experience of Fabre and ANAS

Bridge risk assessment is recognized as a fundamental part of the process for guaranteeing the structural and seismic reliability of transport networks. To achieve this goal, a variety of strategies are being used around the world, and in 2020, specific guidelines were issued in Italy that provide a homogeneous, standardized multi-level and multi-hazard approach to risk classification and monitoring to be applied to existing bridges by all road managers. The first step of the approach is the preliminary screening of bridge assets based on essential typological and geometric data and periodic inspections. This allows for the continuous and upto-date monitoring of infrastructure works, filtering out situations that require special attention and prioritizing investigations and actions at the next level. Although the effort required is lower than that required for more advanced assessment procedures, it remains considerable, as demonstrated by the field experience gained through the collaboration between FABREand Anas S.p.A. (Autonomous National Agency of Highways) and reported in this study. Based on the data systematically collected in the field and organized in a specific database, the study presents a statistical characterization of an inventory of 746 existing bridges, including descriptive statistics for the key classification parameters of the Italian Guidelines. Through this large sample, one of the largest among similar studies, the research first presents an in-depth analysis and characterization of the most common bridge typologies in Italy. In the next part of the research, statistical methods were applied to critically analyze the possible calibration of the structural-foundational and seismic risk classification, as the actual boundary conditions of some parameters involved in the classification logic of the Italian Guidelines vary. In particular, the parameters: Average Daily Traffic; Average Daily Truck Traffic; presence of Road alternatives; and Strategic importance of the bridge have been taken into account, evaluating a series ofmultiple independent scenarios on which the impact on the structural and seismic risk classification within the stock was analyzed. The results highlighted how boundary conditions could affect the risk classification and confirmed the role of other parameters (e.g., Defectiveness class) in the risk classification. Thanks to the breadth, richness of data, and representativeness of the available sample of bridges, the statistical analysis and sensitivity assessment presented can be considered a useful basis for calibrating future improvements in the Italian Guidelines calculation process.