Beneath the surface of the light rail bridges

When Greater Copenhagen Light Rail is completed, it will stretch from Lyngby in the north to Ishøj in the south. The passengers will be able to board at 29 stations, six of which link the light rail to the S-train network. Aarsleff, Artelia and the Spanish company IDOM are responsible for the construction work on two of the sectors, which cover a length of 18 km out of 28 km in total.

This major infrastructure project has many technical facets, and our bridge expertise is one of them. In Brøndby the light rail will cross the Holbæk Motorway. This will require two new bridges for the light rail – one in each direction. In conjunction with this, a bridge for cyclists and pedestrians will also be built. The two light rail bridges will of course have the greatest load-bearing capacity, but all three bridges will be characterised by a slimline appearance.

The actual bridges are made of steel and manufactured in a workshop, while the substructure consists of concrete columns in the central reservation of the Holbæk Motorway and concrete abutments at the ends of the bridges. In all three cases, the bridge will arrive in two finished sections, which will be lifted into place and constructed on site.

Rhino, Grasshopper and Tekla
Our bridge department has made good use of their digital tools on this project. Especially in regards to the BIM models of the three steel bridges. The level of detail is extremely high, so the contractor can manufacture the bridges directly from the model with few adjustments.

The bridges have been engineered using a parametric design. This means the models are based on parametric input, where geometric changes can simply be made by changing the geometric input. The model and drawings are then automatically updated with the modified input parameter. The geometry is built up in Rhino/Grasshopper, and is then exported to Tekla. The same method is used for the concrete components, and here we have even gone one step further. The reinforcements in the concrete columns and abutments have also been modelled in 3D. This provides better reinforcement drawings and anticipates a number of problems that could easily arise on the construction site.

There is another collateral strategic benefit regarding the nordic market. In Denmark, the contractor produces cutting and bending lists for the reinforcements. However, in Norway and Sweden, this is the responsibility of the engineer. Since our 3D models allow automation of this process, we are able to develop an established practice that will be of value to the other Nordic countries.

Greater Copenhagen Light Rail is expected to open to passengers by 2025, and in addition to the bridge design, Artelia is contributing expertise in roads, traffic planning, geotechnical engineering, drainage, installations, the environment and rail engineering.