# A Methodological Framework for Bridge Surveillance
## 3 Preliminary Results and Considerations  
The CUGRI has been involved in Surveillance activities since 2020, during which a large amount of data were collected for both ordinary inspections and the LG20 requirements.  
The adopted methodology for the ordinary inspections leads to evaluating the bridge priority index. Such an index considers a degradation score, assigned to each type of defect in the range 10 (the defect will not evolve into another defect) to 70 (immediate interventions), the defect extension (punctual DP-widespread DD), and the evolution rate (slow EL-fast ER). The bridge priority indices (low priority A-high priority E) are evaluated as in the following matrix (Table 2).  
In particular, the CUGRI methodology for ordinary inspections takes into account the degradation score defined in the guideline adopted by ASPI (Italian highway main management corporation) in 2015 [33] and a qualified assessment of the local and overall safety conditions. The priority indices matrix has been instead elaborated by CUGRI taking into account the available historical inspection data.  
The results (Figure 10) of 2022 ordinary inspections highlight that most of the MG3 bridges (62%) are characterized by a degradation score between 43 and 50, while 4% of the bridges result in high priority (E) and 22% in medium-high and medium (D-C). The obtained priority indices seem to describe quite well the real safety conditions checked by an overall expert judgement in the case of the A3 highway. Moreover, the latter indices are consistent with detailed structural checks performed by independent organisms for the worst cases.  
Figure 11 describes the Structural and Foundational CdA and a preliminary forecast of the Overall CdA in terms of the percentage of MG3 bridges in the case of the LG20 rules. The results highlight that 73% of bridges are characterized by a medium-to-high CdA, while 99% of the bridges present an overall CdA from medium to high, with a peak of 45% of high overall CdA. The approach to assess Level 2 will be complemented in 2023 by interdisciplinary contributions such as geological, geomorphological, and geotechnical knowledge.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**SCORE**} \\ \cline{2-7}
**EXTENT** & \multicolumn{2}{c}{**40–43**} & \multicolumn{2}{c}{**50**} & \multicolumn{2}{c}{**60**} \\ \cline{2-7}  & **EL** & **ER** & **EL** & **ER** & **EL** & **ER** \\ \hline DP & A & B & C & D & D & E \\ \hline DD & B & C & D & E & E & E \\ \hline \hline \end{tabular}
\end{table}
Table 2: Priority indices matrix, according to CUGRI methodology.  
Figure 9: Bridge single element ID code.  
A large amount of data related to the ordinary inspection are currently available, while the LG20 approach is only at the beginning. Considering that the managing body needs to assure a homogeneous maintenance policy with finite economic and time resources also in this transient period, it is relevant to have the possibility to supply the absence of the LG20 data with ordinary inspections. Moreover, with regard to the LG20 experimental period, it is relevant to assess the effectiveness of the single steps considered in the LG20.  
The comparison between the results obtained by the ordinary inspection and the LG20 ones highlights similar values in terms of degradation score and structural and foundational CdA, in a range from medium-to-high classes. However, the overall CdA seems to be too penalizing due to the relevance of local hazards in the evaluation of the process using the class and logical operator approach. Thus, the LG20 approach, unlike ordinary inspections, facilitates a more detailed defect identification of the single structural components.