Denmark and Sweden share many things, including a claim to being the true home of Tycho Brahe, the 16th century astronomer who made what were at the time—before Galileo’s invention of the telescope—the most precise measurements ever of the motions of the planets and the positions of more than 700 stars. His observations laid the groundwork for Johannes Kepler’s early 17th century theories about the workings of the solar system.
Brahe, along with characters from Swedish and Danish mythology, was a central figure in the ceremony to mark the opening of the Øresund Fixed Link on July 1, 2000. The ceremony included music, song, dance and theater performances.
Other, more modern, figures present at the opening of the 10-mile bridge and tunnel complex between Sweden and Denmark across the Øresund sound included Queen Margrethe II of Denmark and King Carl XVI Gustaf of Sweden and the prime ministers of the two countries, Gösta Persson of Sweden and Poul Nyrup Rasmussen of Denmark.
The Øresund Bridge is the strongest cable-stayed bridge in the world, built to carry the combined weight of a motorway and a dual-track railway. The tunnel is the world’s largest immersed tunnel in terms of volume, with four parallel tunnel tubes. The total budget for the project was $2 billion.
The European Union gave the Øresund Fixed Link high priority as the backbone of a future major, prosperous European center for trade, science, industry and culture with 3.5 million inhabitants.
The Engineers’ Society of Western Pennsylvania, in association with Bayer Corp., gave the bridge the Gustav Lindenthal Medal, presented at the International Bridge Conference in Pittsburgh on June 4. The Lindenthal Medal is given for a single, recent outstanding achievement in bridge engineering. The project must exhibit one or more aspects of significant improvement or advancement in bridge technology through technical or material innovation, achievement of high aesthetic merit, harmony with the environment or successful community participation in planning and design.
Since the opening, the Link has established itself as an important element of the social and economic life of the region around Øresund.
"The Øresund region is developing into a Medicon Valley," Henrik Christensen told Roads & Bridges by e-mail, borrowing a theme from the Silicon Valley of California. Christensen was the design manager of the project. The design group consisted of up to 25 designers from the ASO Group, Copenhagen, the main consultant on the cable-stayed bridge.
"Many medical companies gain from the synergy effects," added Christensen, "which is a result of the already very dense amount of companies in the branch plus the great number of universities on both sides of the Link."
For example, he said, the U.S. company Biogen has chosen the region as the site of its first production facility abroad.
In its first year of operation, the Øresund Link carried 13 million travelers: 8 million on the roadway and 5 million on the railway. The numbers account for half of all the travelers to cross the sound between Sweden and Denmark. There were 2.9 million vehicles that crossed the roadway and 5 million trains.
Travelers across the bridge include those looking for leisure activities (their favorite is eating out), but they also include students commuting to colleges and universities on the other side of the sound and people looking for work. The most frequent users of the BroBizz bridge pass are in the 25-29 age group.
The Øresund Job Centre reported a 50% increase in the number of job applications this spring at its office in Malmö at the Swedish end of the bridge. These applications represented Swedes looking for work in Denmark. There also was about a 40% increase in applications from Danes looking for work in Sweden.
Across the sea without ships
From east to west, the Øresund Fixed Link begins at Malmö, Sweden, with a 2.32-mile eastern approach bridge, a 0.68-mile cable-stayed bridge over the Flinterenden navigation channel and a 1.87-mile western approach bridge to an artificial island. The roadway and railway cross the 2.51-mile artificial island above ground, then dip underground. The immersed tunnel stretches 2.51 miles under the Drogden channel and emerges on an artificial peninsula near Copenhagen, Denmark.
About 10 big ships per day pass through the Flinterenden navigation channel, which has a draft of less than 28 ft. The Drogden channel, with a deeper draft, carries more shipping. Encyclopædia Britannica calls the Øresund strait one of the busiest sea lanes in the world. It is 70 miles long and varies between 3 and 9 miles wide, with three islands—Amager, Ven and Saltholm—influencing the flow of water and shipping.
Ven (formerly Hven) island was the location of Tycho Brahe’s observatory, which he established in 1576. Denmark’s King Frederick II gave Brahe the title to the island to keep him from relocating to Germany. Brahe named the observatory Uraniborg after Urania, the Muse of astronomy in Greek mythology.
Saltholm island is located just north of the artificial island constructed as part of the Fixed Link.
The Link is owned by Øresundskonsortiet, which is made up of A/S Øresundsforbindelsen and Svensk-Danska Broforbindelsen SVEDAB AB, which are owned by the Danish and Swedish nations. Øresundskonsortiet was responsible for the design and construction of the Fixed Link and holds the concession to operate it and collect tolls.
The cable-stayed bridge is the largest of its kind in the world, according to the Øresundskonsortiet, carrying both passenger trains, freight trains and motorway traffic. Christensen noted the traffic load as the most challenging factor for the bridge designers.
"The bridge should accommodate a freight train on one track and a passenger train on the other track at the same time," commented Christensen. "This load is by far a world record seen in relation to the length of the main span."
The bridge superstructure is a composite steel-concrete structure with truss girders. The four-lane roadway rides on the upper deck, while the two-track railway rides on the lower deck. The main span stretches 1,617 ft across the navigation channel, with a clearance of 188 ft above sea level.
Each of the two pylons consists of two cast-in-situ concrete towers extending to a height of 673 ft above sea level. Side-span piers consist of single, prefabricated concrete box-section shafts, with bearings at the top to support the bridge girder. The side-span piers are provided with a tie-down arrangement to resist uplift forces from the superstructure.
Foundations for the pylons and side-span piers are prefabricated concrete caissons sunk into the Copenhagen limestone 46 to 56 ft below sea level. The pylons are surrounded by submerged protection islands, according to Christensen, not to protect the pylons from ships that might collide with them but to protect the ships.
"The pylons are able to withstand a ship collision," said Christensen. "The two times three piers closest to the pylons are also surrounded by similar protection islands, but here it is for protecting the piers and not the ships, as these piers cannot withstand a collision."
All the bridge piers are protected from scour by stones. The combination of a maximum current velocity of 5.67 mph, a maximum wave height of 8.25 ft and a water depth of only 33 ft makes scour protection necessary.
On the approach bridges, the double-deck superstructure is supported by precast concrete single-shaft piers with precast concrete caisson foundations sunk into the Copenhagen limestone up to 49.5 ft below sea level.
"The placing of the girders, pier shafts and caissons was a special challenge," said Christensen, "since it was necessary to prefabricate these large elements to be able to stick to the timetable."
A floating crane, named Svanen, with a lifting capacity of 9,600 tons, was shipped from Canada to work on the Fixed Link. Svanen carried the prefabricated bridge sections out to the site and placed them in position.
Christensen said the method of erecting the main span girders also was unusual: "It is only possible where the temporary towers are not placed in an existing navigation channel or where the temporary towers are protected by use of, for example, guard ships."
The first 462-ft section of the superstructure was supported on one of the big pylons and on a temporary pillar. The next section was supported at one end by the first section at the pylon and on the other end by a permanent pier. Several of the stay cables were then attached.
Next, a pair of 396-ft spans and a second temporary pier were added, more cables were strung, and the first temporary pier was dismantled. These sections extended the structure to the middle of the main span on one end and to the second permanent pier on the other. With that done, and the same process for the other pylon, the builders could join the two halves of the main span in the middle and remove the second temporary pier.
Environmental harmony
One of the main requirements of the Swedish and Danish governments was that the Fixed Link should not alter the flow of water through Øresund between the Kattegat Strait to the northwest and the Baltic Sea to the south.
"The tendency in the industrial societies is towards less impact on the environment," said Christensen. "Between two Scandinavian countries which both are proud of being the cleanest industrial country in the world, the public and therefore the politicians do not allow for any impact from such a big bridge."
To manage the water flow, including the flow of salt and dissolved oxygen, and protect the region’s water quality, flora, fish, birds and mammals, the designers made accurate calculations of the effects of the bridge and artificial island. The Link was designed to limit water blockage to 0.5%. Dredging of the sea floor, including the Flinterenden navigation channel, compensated for the small remaining blockage caused by the new structures. Compensation dredging amounted to 1.8 million cubic meters.
The Swedish and Danish authorities also carefully monitored spillage of sediment during construction. Eelgrass, an aquatic plant that grows in the area, is particularly sensitive to changes in light conditions, and the consortium made careful surveillance of eelgrass growth as an early indicator of the condition of the marine environment.
Taking a toll
The consortium expects to pay for the Link by 2027 by collecting tolls from travelers. All motorists pay a toll to cross the Link. The toll station, which is at the Swedish end, has 11 lanes in each direction. Two lanes are reserved for automatic toll payment: one for private cars, with a speed limit of 50 km/h, and one for trucks, with a lower speed limit.
Motorists can pay the toll by cash or by credit or debit card. There also is the option of paying automatically by way of an electronic pass affixed to the windshield. The BroBizz electronic transponder will automatically register the vehicle and collect the toll as the vehicle passes through the toll station. As of July 1, 2001, travelers can register for a BroBizz transponder—and receive immediate confirmation—at the Link’s website (www.oeresundsbron.com).
Also as of July 1, trucks and coaches can sign up for an iTicket, an eight-digit code that the driver must present at the toll station. To be assigned a code, the hauling company must sign a contract with the Øresundskonsortiet in advance.
The Link Control Centre, located near the toll station, is in operation 24 hours a day. It gathers information on the technical condition of the Link, such as ventilation, drainage and lighting in the tunnel, as well as traffic flow. There are traffic detectors, variable message signs, remote-controlled barriers, traffic lights and closed-circuit television cameras stationed along the Link. There also are emergency telephones at regular intervals.
Christensen said there have been no traffic incidents where emergency vehicles were not able to get past the traffic to the incident. There was only one accident that caused serious injury.
In Tycho Brahe’s time, Sweden and Denmark fought over control of the Øresund region and its commercial benefits, including exacting tolls from ships passing through the sound. Today, they build links between their two countries and share the commercial benefits.
