PSI - Issue 62

Manuel D’Angelo et al. / Procedia Structural Integrity 62 (2024) 9–15 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Table 1. Average number of G5 defects and percentage of bridge in critical condition for each structural scheme Structural Scheme n° G5 / bridge Critical Condition Arch 0.75 15% Maillart/Tied-Arch 3.00 0% Box Girder 8.50 0% Culvert 0.00 0% Simply Supported Slab 0.48 0% Moment Resisting Slab 1.17 9% Simply Supported Beams 4.41 15% Continuous Beams 7.08 25% Half-Joint Beams 9.67 33% Cable-Stayed or Suspended 8.00 0%

5. Risk analysis As previously mentioned, the procedure proposed by the Guidelines defines the so-called Overall Warning Class, as a result from the combination of the Warning Class of four risks. The Warning Class stands for a risk indicator, and indicates the subsequent actions for the resilience of the infrastructural networks. Figure 6 shows the Warning Class for the four risks and the Overall Warning Class. Note that when assessing the structural-foundational and the seismic risks, the analysis encompasses the entire set of 207 bridges. In contrast, when evaluating landslide and hydraulic risks, the data only reflects the distribution for bridges where hydrogeological risk is present - 33 bridges for landslide risk and 187 for hydraulic risk. In fact, landslide risk applies for bridges in hilly and mountain areas, whilst hydraulic risk is related for bridge over rivers, that flows also especially in valley areas. The five levels of the hydrogeological risks are not homogenously populated: for the landslide risk, the central levels are predominant, while the externals (low and high) are almost absent. For the hydraulic risk, there is a net predominancy of the medium-high level (more than half of the sample in this risk level). From one side, the Guidelines consider the hydraulic risk of great impact, in concordance with the statistics of bridge collapse in Italy and worldwide ( D’Angelo 2022, Wardhana 2003). On the other side, with such high number of bridges in the same level of risk, there is a less capacity of prioritizing the bridge with high criticality. For what concerns the structural-foundational risk, the five levels of risk are more uniformly distributed, with lower frequency for the medium-high class. Finally, for the seismic risk, the distribution appears with a normally distributed shape. The four risk consider aspects and features related to the hazard of that particular risk and the vulnerability of the bridge towards this hazard. However, it is also function of the exposure (which depends from traffic levels, resilience network, and other parameters) which tends to assume low values at the local level. In fact, almost the totality of bridges shows low and medium-low exposure (75% and 15%, respectively). As a result, within a single municipality, the risk prioritization depends mainly on hazard and vulnerability. Finally, the Overall Warning Class shows a stronger correlation with the structural-foundation WC, as a result of logical fluxes defined in the Guidelines. Thus, the following action for the bridge owner are defined for each bridge, according to the indications provided by the Guidelines.