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Planning the world's longest floating bridge over Bjørnafjord, Norway

Photo: COWI

​​Bjørnafjord is too wide for conventional types of bridges

​When the Norwegian Public Roads Administration opts for a floating bridge or a tubular bridge over Bjørnafjord, it will be around 5 km long and the longest of its type in the world.

​COWI is heading one of the three working groups planning the floating bridge solutions to cross the five km wide Bjørnafjord. The team comprises COWI, Aas-Jakobsen and Johs Holt, with Global Maritime, L2 Arkitekter, NGI, Teknisk Data and Skanska as sub-contractors.

“The combination of depths of up to 550 m and a total length of around 5 km make conventional types of bridge impossible. Floating bridges and submerged tubular bridges are the only options when you want to build a road link across such a wide fjord,” says the project manager, Erik Sundet.

The bridge is to carry a four-lane motorway and is part of the megaproject to establish a ferry-free coastal highway between Kristiansand and Trondheim (E39).

Two floating bridge concepts

The working group is examining two different floating bridge concepts.
“There are two main alternatives. One is a straight bridge over the fjord at the crossing point with a seaway under an elevated span in the middle. The other is a curved bridge which can be raised like the handle of a bucket, also with a high point in the middle of the fjord,” Sundet explains to the Norwegian weekly magazine TU.no.

The first solution will be anchored on each side to the bottom of the fjord to provide lateral stability, while the second will only be anchored at the ends.

Cooperation without borders

COWI will carry out a number of technical analyses which demand top-level expertise in marine operations, hydrodynamics, wind dynamics, civil engineering, risk analysis and collision response to impacts from ships.

“The assignment is technically very challenging. To tackle the project, we have established an international team with experts from Denmark, the USA and Canada as well as Norwegian engineers. We also have several external partners in the project group,” says Per Arnesen, VP Bridge Design.

The Norwegian Public Roads Administration has engaged three professors at the Norwegian University of Science and Technology (NTNU) who are involved in the work. The project has also set up an international expert group. This comprises four professors from the University of California at Berkeley, the Technical University of Denmark (DTU), ETH Zürich and Imperial College London.

The world’s largest bridge engineer

In 2014, COWI was ranked as the world’s largest bridge engineer. The selection was made by the renowned ENR Yearly Sourcebooks list, which ranks more than 250 international companies in the BAE industry in a number of categories each year. The ranking is based on global revenues.

COWI’s bridge division has been steadily climbing up the list, from third place in 2011 to second in 2012 and first in 2014.

LAST UPDATED: 22.02.2017