If you were to build the longest suspension bridge in the world, what would be the biggest hurdles from an engineering perspective?
Looking closer at the East Bridge which forms part of the Great Belt Link in Denmark, one element looms larger than the rest: The strong winds swirling in from the Atlantic Ocean.
Sprogø, in the middle of Storebælt (Great Belt), connects the two bridges and the tunnel. As part of the construction work, the island was expanded and is now four times its original size.
Before we look closer at the challenging wind conditions, let's zoom in on the bigger purpose behind the Great Belt Link.
In the past millennium, people with family, friends, work or other interests at the other side of the Great Belt had to take a ferry or cross it by foot during the icy winters.
Ideas for a fixed link were first discussed in the 1850s, with a view to reducing travel times.
Finally, in 1986 a political agreement was reached and a new law was passed that gave the green light for the project to start.
“Time savings and ticket price savings for customers were the main drivers for the bridge,” explains Lars Fuhr, CTO and Technical Director at Sund & Bælt Holding A/S.
“Before the bridge, when we had the ferries, crossing the Storebaelt took an hour plus waiting time and meant planning ahead. Now, it takes 12 minutes,” Lars Fuhr says.
The Great Belt Link has made travelling around in Denmark much easier. For example, the number of available train seats have gone up from 11,000 to 40,000 per year.
The link across the Great Belt is 18 km long and connects the eastern and western parts of Denmark. It consists of two bridges and a tunnel, and with a main span of 1,624 metres, the East Bridge was designed to have the longest suspension span in the world.
Before the link's construction, it was argued whether such a large-scale infrastructure project was even technically and financially feasible. Not least due to the strong winds.
“We were entering completely new territory within bridge engineering. Nobody had succeeded in building a bridge with such a great span. A major issue was how to tame the wind inside the bridge's structure,” explains Allan Larsen, Chief Engineer at COWI.
Before the bridge, when we had the ferries, crossing the Great Belt took an hour, and meant planning ahead. Now, it takes 12 minutes.”
Chief Engineer Allan Larsen gives you the answer.
The tricky aerodynamics were far from the only technical challenge. Lars Hauge, Senior Vice President at COWI, had only just joined the company as a young engineer when the Great Belt Link project kicked off.
In June 1997, the first passenger train rolled through the tunnel under the Great Belt, and the bridge for car traffic opened the following year, in 1998.
The Great Belt connection is one of the world's largest bridge and tunnel constructions, and the connection has had a tremendous impact on the millions of Danes who use it.
“The link has increased growth and mobility. One example is that lorry traffic has more than doubled, ensuring flexible distribution. Companies within the industry have also benefitted greatly from knowledge gains in tunnel and bridge engineering by contributing to the construction. Today, several of them, including COWI, are industry leaders in bridge and tunnel design and construction,” says Lars Fuhr.
Lorry traffic has more than doubled ensuring flexible distribution.
COWI is responsible for maintenance of the Great Belt Bridge. Most of the inspection work is now handled by drones, whereas repairs are still in the hands of humans. Join the Rope Access Team at the top of the bridge, where they inspect it for cracks, hollows or corrosion in the concrete.
A/S Storebæltsforbindelsen (subsidiary to Sund & Bælt Holding A/S)
Regional Vice President
Bridge, Tunnel and Marine Structures, Denmark