Norway is in the lead of model use in road construction
When the new highway between Løten and Elverum in south-eastern Norway is finished in the fall of 2020, it is built for the second time. The first time it was built as a virtual model, as a digital twin.
The road stretch is at times heavily trafficked by ski tourists and cabin owners on their way to or from the resort village of Trysil, and by transport trucks on their way between Oslo and Trondheim. The new route will have 16 km of four lanes and 9 km of two lanes with mid-barrier. With speed limits between 90 and 110 km/h it will not only reduce the travel time, but also connect the inland towns of Elverum and Hamar closer together.
The Public Roads Administration has a PPP contract with the builder Hedmarksvegen AS. The contractor Skanska is responsible for the actual construction. The two companies are responsible for all project financing and construction, as well as the operation and maintenance for 20 years. The contract form is well suited for the new way of working with models.
“Actually, there has existed good presentation models since the 1990s, but it has not always been possible to base the construction on them,” says Merete Tøndel. She is EMEA Sales Manager at Trimble, an American company that in 2015 acquired Oslo-based Vianova Systems AS, pioneers in BIM for infrastructure.
BIM for infrastructure is different and a bit more complicated than BIM for buildings when it comes to adapting to the terrain.
“The terrain, and not least the rock surface, is exposed during the project, so the model design must be adapted accordingly,” Tøndel explains.
Trimble offers the industry a central collaboration platform, Quadri, where you have a central object model, ensuring that you will always have a common updated database. You know exactly where in the world a curbstone, lamp post or drain basin can be placed. With control across all disciplines, and with digital insight from both the contractor and consultant, you get an optimized and constructible model in Quadri.
Norway is in the lead
The Public Roads Administration is a driving force in the use of constructible BIM models in Norway. Already in 2012, the administration published a design model manual for road projects, Handbook V770. By demanding model deliveries, the Norwegian Public Roads Administration has experienced significant cost reductions in the form of fewer errors and fewer change orders. This also includes fewer conflicts, because all parties understand a model and hence have a better overall picture of the project.
Trimble has assisted the Norwegian Public Roads Administration in studying what kind of cost effects the use of Handbook V770 had in a few concrete road projects completed in 2015 and 2016. In some drawing-based projects, the number of change orders can be many hundreds – a very costly number that everyone wants to reduce of course.
The analysis looked at how much effect the change orders had in relation to the contract sum of the road project.
“The result of the analysis showed that there was a significant decrease in change order costs where the project used a methodology using models and the use of Handbook V770,” explains Tøndel. “You got fewer errors at the construction site and lower construction costs.”
Industry goes for BIM Level 3
The road projects that so far have been built according to Handbook V770 are based on what is defined as BIM Level 2, using 3D models and project-based collaboration. However, the industry is now well on its way towards BIM Level 3, were you have a common central database model which is always up-to-date.
“We see there are cost savings at Level 2, but we know for a fact there is even more to be gained at Level 3,” says Tøndel.
“Local authorities in the UK, Germany, France, Poland, Italy and others are all now setting standards for using models for infrastructure projects. From 2021-2025 these nations will demand BIM Level 3, requiring a common central model database and objects with properties, such as Quadri,” Tøndel says enthusiastically.
We build what we design
At the work barracks at Ånestad, where Highway 25 from Hamar meets Highway 3 between Kolomoen and Elverum, we meet Katrin Johannesdottir at Skanska. The contractor is busy building the road that the consultants have modelled digitally. That is, the design is not necessarily finished yet, because the BIM methodology is allowing the construction to start before the design is actually ready.
“This is the biggest advantage, I believe. We have very clever people with 30-50 years of construction experience. When they contribute to the design, we get incredibly good solutions. When we combine the theoretical knowledge of the designers with the practical contractor knowledge in the modeling, we get better and more constructible models, and also better roads,” says Johannesdottir. She is no doubt passionate about this way of working.
One example of how this works in practice is that the contractor can make frost protection suggestions to the road body design. Designers are drilled to optimize the road construction in relation to the ground conditions, but the contractor can come up with his practical knowledge and his overview of available quality earth masses, optimizing the structure, because this is more cost-effective and provides a stronger road.
“In this way we don´t have to do a lot of refined work, and the consultant does not have to fine-tune things on centimeters,” explains Johannesdottir.
When the contractor has access to the model in progress, one can also make sure that the contractor gets exactly what is needed from the designer, ensuring also that the designer does not spend time on things the contractor does not need.
Improving constructability is about two things, Johannesdottir explains:
“The person doing the modeling must know how it´s being done on the building site – ensuring that the design is practically possible to build. But it is also about getting the design model out to the field without anyone actually transferring the data manually.”
“We have had a lot of success with this in this project. We have used the Quadri platform to gather all discipline models in the project from Novapoint, CAD and Tekla and given the foremen and production managers full insight into what is happening in the design process at all times,” says Jóhannesdóttir.
It is valuable to spend a lot of time on the modeling, because it is much cheaper to build a digital model first, than to start the construction prematurely.
“Here at the construction site we have excavators of both 70 and 90 tons, so obviously it is very expensive to have these very large machines in operation. The fact that we now don´t have to return with the excavators later and dig again, is of course cost-saving. Both "rework" and construction halts are expensive, so we avoid this to a greater extent now,” she says.
Both Tøndel and Johannesdottir emphasize that the simultaneous design and construction means that the time it takes from the design starts until the road is finished, is reduced. This also means that the contractor can plan better. This has evidently been very important for the project progress in the forests between Løten and Elverum, where winter can be both snowy and very cold. The contractor is dependent on good planning of what can be done in the winter and what needs to be done in the summer.
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