## 3 Proposal of Bridge Maintenance Prioritization Model
### Criteria for Evaluating Scores Based on Priority Index (PI) Weights  
Through the detailed safety inspection reports of the Korea Expressway Corporation, the structural characteristics and safety status of bridges can be comprehensively assessed. These reports provide a thorough analysis of six structural categories: superstructure, sub \begin{table}
\begin{tabular}{c c} \hline
**AADT (Cars/Day)** & **Score** \\ \hline AADT \textless{} 20,000 & 0.03 \\ \hline
20,000 \(\leq\) AADT \textless{} 40,000 & 0.07 \\ \hline
40,000 \(\leq\) AADT \textless{} 60,000 & 0.13 \\ \hline
60,000 \(\leq\) AADT \textless{} 80,000 & 0.19 \\ \hline
80,000 \(\leq\) AADT \textless{} 100,000 & 0.26 \\ \hline
100,000 \(\leq\) AADT & 0.32 \\ \hline
**Secondary Damage** & **Score** \\ \hline River: Impact on environment, water quality, flood risk & 0.2 \\ \hline Road: Traffic disruption, access to businesses/residences & 0.3 \\ \hline Bridge: Structural damage, cost of repair/replacement & 0.5 \\ \hline \end{tabular}
\end{table} 
Table 4: Scores by criticality factor. \begin{table}
\begin{tabular}{c c c} \hline
**Safety Grade** & **Content** & **Score** \\ \hline \multirow{4}{*}{Facility classification} & Type 3 & 0.23 \\ \cline{2-3}  & Type 2 & 0.32 \\ \cline{2-3}  & Type 1 & 0.45 \\ \hline \multirow{4}{*}{Number of lanes} & Lanes \textless{} 2 & 0.03 \\ \cline{2-3}  & 2 \(\leq\) Lanes \textless{} 4 & 0.07 \\ \cline{2-3}  & 4 \(\leq\) Lanes \textless{} 6 & 0.13 \\ \cline{2-3}  & 6 \(\leq\) Lanes \textless{} 8 & 0.19 \\ \cline{2-3}  & 8 \(\leq\) Lanes \textless{} 10 & 0.26 \\ \cline{2-3}  & 10 \(\leq\) Lanes & 0.32 \\ \hline \end{tabular}
\end{table} 
Table 5: Scores by comparison factor. structure, bearings, and other components, including deck slabs, girders, piers, abutments, and expansion joints. This detailed assessment helps in determining the safety rating of the bridge. However, since the safety of a bridge varies based on the condition and characteristics of each of its parts, applying a precise safety rating to each superstructure type offers a more reliable approach. By individually identifying and managing the structural vulnerabilities of a bridge, specific safety issues can be detected and addressed early on. Therefore, assigning detailed safety ratings to each structural component enhances the overall safety of the bridge and improves maintenance efficiency by optimizing resource allocation. The Priority Index (PI) score is calculated using the weights for damage types (Dn), member types (Mn), performance types (Pn), and grade types (Gn), as shown in Equation (4). \[\text{Priority Index}=\text{Dn}\times\text{Mn}\times\text{Pn}\times\text{Gn} \tag{4}\]  
It is assumed that the damage-type weight is uniformly set at 1.0, because the member type condition rating is influenced by various potential defects. The weights for member types are detailed in Tables 6 and 7, while the performance-type weights are shown in Table 8, and the grade-type weights are provided in Table 9. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Facility** & \multicolumn{2}{c}{**Girder-Detached Bridge**} \\ \hline \multirow{2}{*}{Superstructure} & Deck & 0.15 \\  & girder & 0.25 \\ \hline \multirow{2}{*}{Substructure} & Abutment & 0.13 \\  & pier & 0.13 \\ \hline \multirow{2}{*}{Bearing support} & Bearing support & 0.15 \\ \hline \multirow{2}{*}{Other} & Expansion joint & 0.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: General bridge (girder detachable bridge) weights. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Facility** & \multicolumn{2}{c}{**Integral Bridge**} \\ \hline \multirow{2}{*}{Superstructure} & Deck & 0.15 \\  & girder & 0.25 \\ \hline \multirow{2}{*}{Substructure} & Abutment & 0.13 \\  & pier & 0.13 \\ \hline \multirow{2}{*}{Bearing support} & Bearing support & 0.15 \\  & girder & 0.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: General bridge (integral bridge) weights.