Drawing-free bridge project in Norway

Sweco’s BIM experts from Finland, Norway, Denmark and Poland will handle the modelling of a unique concrete bridge across the Randselva river in Norway. The parametric 3D model will be used as the only official documentation for the international infrastructure project.

Randselva Bru is a box girder bridge designed by the Portuguese Armando Rito Engenharia engineering company. It is 634 metres in length with a main span of nearly 200 metres. The designs were in the form of 2D images, although all large infrastructure projects in Norway are modelled without paper drawings.

“Norwegian authorities require information models for all bridges, and Norway is the most advanced among the Nordic countries in terms of paper-free projects,” says Antti Jussila, department manager for bridge exports at Sweco. “Sweco’s role in the project was to model the designs, manage the drawing-free process and engineer the road structures surrounding the bridge.”

The information model as the only document at the worksite

The construction method of the bridge that contains many complex geometric forms was unusual. The balanced cantilever method involves building the bridge in the shape of the letter T. First a large support pier is constructed in the middle, after which bridge construction begins in two directions. This means that the information model needs to be organised with care.

“The model was designed to ensure that every member of the project team stays informed of the status of all model elements and knows what information can be used for ordering supplies, for example,” says Rasmus Sainmaa, BIM specialist and developer of parametric modelling at Sweco.

In the cloud, the information model and its details are available to all parties, and the model alone is used as the basis for communication at design and worksite meetings. The model also served as the only official piece of documentation at the worksite.

“The contractor had access to a moveable container containing a BIM kiosk and computer,” Sainmaa explains. The model allows the various surfaces to be transferred directly into machine automation systems and the excavations to be dimensioned and positioned accurately. The structures are also dimensioned in-site by means of the coordinate and measurement information in the model. “This helps to avoid challenging work phases. For example, coordinate points in paper drawings do not need to be typed into a measuring device.”

Pioneering in design technologies

The bridge project utilises a method of parametric modelling, which provides numerous concrete benefits.

“Even though we received the initial data at the last minute, the parametric method enabled us to model many details beforehand,” Sainmaa says. In traditional modelling, the time allotted would have been too short and the information model would not have been completed in time. “Now the basic details had already been modelled and we only needed to update the model with the final calculations.”

The massive project would be very difficult to manage without an accurate information model. “The bridge currently contains more than 200 unique tendons and 200,000 reinforcements. It would be impossible to process all the information manually.”

A team of experts put together from international networks

Sweco’s specialists pooled their resources in Norway, Finland, Denmark and Poland. The group has a vast pool of first-rate expertise all over the world.

“The bridge project is an excellent example of multitier networking and the value of contacts,” Jussila says. “We are used to doing things together and networking across national borders. By joining forces, we can secure large-scale projects and provide the customer with the optimal end result.”

In Finland, only some pilots and part projects have been completed without drawings so far. However, we have plenty of experience in these types of implementations. “We have already completed multiple drawing-free bridge projects in Norway, so we know the process well and can support the customer through the entire project,” Jussila emphasises.