The six-lane A1 is one of the busiest motorways in Germany. Its Schwelmetal bridge needed to be replaced without disrupting the flow of traffic on and under the bridge. In a pilot project with DEGES, Arup shows how this complex design challenge can be met.

For the first time in Germany, we used BIM for the complete construction of a road bridge - including time and cost planning - setting new standards in construction efficiency. BIM was used not only for design, but also for construction supervision, cost control, sequencing and as-built documentation.

On busy routes such as the A1 motorway, traffic disruptions are particularly severe, as the closures hinder not only private but also freight traffic, resulting in significant economic damage. With our new planning approach, we were able to minimise traffic disruptions.

The demolition and construction process

With a length of 207 metres, the Schwelmetal Bridge spans a railway line, a federal road, a regional road and the River Schwelme. Built in 1969, the bridge's concrete girders and substructures no longer met today's stability requirements and had to be replaced. The work was carried out in several phases while traffic continued to flow on and under the bridge and was completed on schedule in the summer of 2024.

Our aim was to minimise disruption to road and rail traffic. We therefore developed a very detailed demolition and construction plan that took into account the very limited space under the bridge, where there was no room for a crane or for storing components and structural elements.

Our design enabled the girders of the new bridge to first serve as a large gantry: the steel structure of the new bridge was built before the old bridge segments were demolished and was erected above the existing bridge. The new steel girders were then placed on temporary support trestles and used to lower the dismantled bridge segments. Due to the lack of space, the bridge sections had to be lowered piece by piece and moved longitudinally to the demolition areas. A particular challenge was the design of the new bridge girders, which had to be designed for their dual function as demolition gantry and bridge girders.

Everything at a glance: 5D design with BIM

Due to the complexity of the project, we used 5D BIM for both the design and construction process, i.e. including time and cost planning. This was a first in Germany, where BIM is rarely used in bridge construction and only for individual design steps. 

By depicting all disciplines and special fields, the existing and new planning could be clearly represented in the BIM model. Additional information - e.g. on subsoil, groundwater level and deep foundations, obstructions, anchors, sewers and technical installations - also made it possible to identify potential clashes at an early stage.