# A BIM-Enabled Workflow for the Rehabilitation of Heritage Steel Bridges
## 1 Introduction
Aligned with this, the rehabilitation of heritage steel bridges has become a cornerstone of sustainable development and cultural preservation. Furthermore, refurbishing these structures aligns with the principles of sustainability by reducing the need for new materials and construction, limiting CO\({}_{2}\) emissions while retaining historical and aesthetic value. To address the pressing challenges of ageing structures and enable better decision-making, while also accounting for multidimensional complexity, advanced technologies are being increasingly integrated into infrastructure management. Among these, Building Information Modelling (BIM) has emerged as a revolutionary digital process, transforming the way we approach design, construction, and rehabilitation. It facilitates the definition of information requirements and the creation, management, and exchange of detailed digital representations of the physical and functional characteristics of assets throughout their lifecycles. By enhancing efficiency in project development and implementation and by fostering collaboration, BIM offers a robust solution for streamlining the information flow during the rehabilitation of heritage steel bridges, supporting cultural heritage preservation and sustainable development. Despite its success in the building sector, the adoption of BIM in transportation infrastructure has been slower and less uniform [5]. Authorities, industry, and academia alike are increasingly focusing on the implementation of BIM in non-building civil infrastructure, including bridges, tunnels, and railways. However, much of this effort lacks a structured framework tailored specifically to the unique challenges and requirements of transportation systems. Currently, there is a notable gap in the development of BIM workflows for the rehabilitation of ageing transportation infrastructure, especially steel bridges, which form a critical subset of these systems. Addressing this gap requires an understanding of both the initial costs, i.e., operational and maintenance costs, together with the substantial long-term benefits of implementing a BIM workflow. While the upfront investment in BIM may appear significant during initial project phases (i.e., current estimations brings BIM use within projects to the level of design costs), research consistently shows that the long-term benefits far surpass these costs, often leading to savings ranging from 1.5% to 15% [6], with a 5% to 9% [7] cost reduction seen during the construction phase alone due to reduced change orders and rework. Additionally, BIM workflows enable the incorporation of lifecycle cost (LCC) considerations into the design phase, adding significant value. This approach enables a thorough analysis of costs throughout the asset's lifecycle, spanning from planning, design, material selection, construction, operation, and maintenance to eventual decommissioning. LCC integration within the BIM workflow supports informed decision-making, optimizing outcomes in terms of both cost and performance. For instance, prioritizing durable, corrosion-resistant materials might increase upfront expenses but drastically reduces maintenance needs and repair costs over time. Additionally, designing with ease of access for inspections, enabled by 3D modelling and providing special consideration for soft collisions, simplifies routine maintenance, cutting labour and equipment expenses. Figure 1 (an adaptation of the LCC concept [8]) illustrates two contrasting approaches to project cost management over the lifecycle of an asset. The graph on the left represents the scenario where sharp cost increases occur due to unplanned rehabilitation interventions and repairs, while the graph on the right demonstrates a smoother, more predictable distribution of costs stemming from a planned and proactive lifecycle asset management. The unexpected spikes in costs shown on the left will likely result from reactive maintenance strategies, where issues are addressed only after they arise.