# A BIM-Enabled Workflow for the Rehabilitation of Heritage Steel Bridges
## 4 Case Study for the Savarsin Heritage Steel Bridge
### The Technical Report and Rehabilitation Decision  
The BIM workflow creates the structure for the information exchange. The technical component of the rehabilitation process for existing steel bridges involves several key steps that must be carefully analyzed and addressed by technical experts. As discussed in previous sections, the initial step requires the on-site assessment of the structure's technical condition, with several key factors to consider, such as identifying whether the bridge is made from wrought iron or mild steel. This distinction is especially important for older bridges, as mild steel became more common after 1900. The technical condition also includes the evaluation of structural damage, particularly to vertical members of the truss girders, which is often caused by insufficient clearance and vehicle impact. Furthermore, many heritage steel bridges in Romania suffer from insufficient maintenance due to historical ownership changes, which leads to significant corrosion and the absence of proper documentation about their construction and maintenance. For skewed or curved bridges, or continuous truss girders, advanced 3D space analyses enabled by modern computer-aided engineering (CAE) techniques are necessary to assess the current state of a structure as they can offer detailed information. Nevertheless, as older bridges are statically determined structures that are typically constructed perpendicular to their supports to ensure a uniform and direct load transfer, analytical methods can be employed as they offer sufficient accuracy. These old bridges are generally riveted, and the lack of knowledge regarding material quality presents additional challenges. To \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Field** & **Requirement** & **Format** & **Phase** \\ \hline \multirow{2}{*}{Structural element ID} & Unique identifier for each & \multirow{2}{*}{String (UUID)} & \multirow{2}{*}{Development} \\  & component (e.g., beams). & & \\ \hline \multirow{2}{*}{Material properties} & Steel composition and & \multirow{2}{*}{JSON,  XML} & \multirow{2}{*}{Development} \\  & corrosion resistance. & & \\ \hline \multirow{2}{*}{Geometric data} & Dimensions, curvature, & \multirow{2}{*}{IFC, e57} & \multirow{2}{*}{All phases} \\  & and alignment tolerances. & & \\ \hline \multirow{2}{*}{Heritage details} & Decorative features and & \multirow{2}{*}{PDF, linked IFC} & \multirow{2}{*}{
\begin{tabular}{l} Development, \\ handover \\ \end{tabular} } \\  & original designs. & & \\ \hline \multirow{2}{*}{Load capacity} & Maximum weight and & \multirow{2}{*}{Numeric (RN)} & \multirow{2}{*}{Implementation} \\  & stress tests results. & & \\ \hline \multirow{2}{*}{IoT sensor Data} & Vibration, stress, and & \multirow{2}{*}{JSON,  CVV} & \multirow{2}{*}{Implementation} \\  & temperature readings. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Sample data fields for the IDS. mitigate this, the Romanian Highway Administration (CNAIR) has developed a qualitative verification methodology, AND 522-2002 [62], to assess the condition of these structures, providing a categorization based on expert evaluation that informs decisions on repairs or replacement. However, this methodology is effective for newer bridges (less than 30 years old) and serves more as an informational tool for older steel structures, which require a more detailed assessment methodology, as outlined in Figure 2.  
Based on the AND 522-2002 [62] specifications, the technical condition of the structure is assessed in terms of a quality index given by Equation (1):  
\[I_{ST}=\sum_{i=1}^{i=5}C_{i}+\sum_{i=1}^{i=5}F_{i} \tag{1}\]  
where the quality index C is used as follows: C1 accounts for the main girder; C2 accounts for the deck elements; C3 accounts for the infrastructure and bearings; C4 accounts for the riverbed; and C5 accounts for the deck surface quality.