# A BIM-Enabled Workflow for the Rehabilitation of Heritage Steel Bridges
## 2 Current State of the Art
### Traditional Heritage Steel Bridge Rehabilitation Process
Regarding material, it must be mentioned that a wealth of experimental test results on heritage steel bridge materials has been accumulated over the years, resulting in a highly reliable and statistically robust database. This extensive body of data provides detailed insights into the properties of steels used in various periods, making it a valuable resource for assessing material performance. Given the database extent, performing new experimental tests on materials for existing bridges rarely changes the statistical understanding of their properties. Due to this, bibliographic research has become a reliable and common approach for material assessment, particularly for bridges whose construction period is well documented. By referencing historical data and leveraging the wealth of experimental results available, the materials' behaviour can be accurately predicted, thus removing the need for additional testing. As a result, experimental tests are typically reserved for cases where unusual conditions, damage, or a lack of historical documentation warrant additional investigation. Once enough data have been collected, an exhaustive assessment is conducted. This includes the assessment of a bridge's load-carrying capacity, the analysis of its stress history, the identification of areas most susceptible to failure and, finally, the estimation of its remaining fatigue life. A CAD model of the bridge is usually developed, providing detailed insights into bridge behaviour under various conditions. To ensure accuracy, the digital model is developed to account for geometric data mapped on site and specific material properties, and is generally calibrated against on-site tests. The results of such assessments are used to guide the next steps. If the structure is deemed safe, or it requires minimal intervention, it can remain operational under specific restrictions, supplemented by ongoing monitoring to ensure safety. For bridges requiring more significant attention,  
Figure 2: Technical process for rehabilitation of heritage steel bridges. repair or strengthening strategies can be implemented to restore their full, or at least partial, functionality. For cases where the structure is severely damaged or the rehabilitation costs are prohibitive, the focus may shift toward planning and executing deconstruction and/or replacement. Alternatively, the bridge can be considered for repurposing, e.g., the conversion of a railway bridge for automotive use, the conversion of an automotive bridge for pedestrian or cyclist traffic, or other adaptive reuse scenarios that align with the community's needs. Throughout the entire process, a technical report is developed, documenting findings, analyses, and recommendations that are to serve as a critical references for stakeholders. In most cases, information exchange is conducted using traditional paper-based methods (or digitalized paper, i.e., a pdf), and the technical documentation typically includes only the information mandated by law. While the focus remains on the technical aspects of rehabilitation, this workflow underscores the importance of comprehensive assessment and strategic decision-making in tackling the unique challenges associated with ageing steel bridges effectively.