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Very Long and Very Safe Bridges

Episode One of a currently popular film series, “The Bridge” begins with a nighttime close up on the Øresund Bridge—a ‘body’ carefully placed over the line on the bridge marking the border between Denmark and Sweden.  This means that both the Danish and Swedish police will be involved; enter the Danish detective Martin Rohde played by Kim Bodnia and the Swedish detective Saga Noren played by Sofia Helin.

The different approaches of the two officers are highlighted immediately, Detective Noren commanding closure of the bridge to all traffic for at least two hours, Detective Rohde responding to the pleas of a woman accompanying her hospital-bound husband by waving through their ambulance.  Building communications between these two will be the challenge of the drama.  All of this is against the background of an outstanding engineering achievement – the steel and concrete structure from which the film’s name derives.

When ‘The Bridge’ film series launched in 2011, the ‘Øresundsbron’—the bridge company’s preferred Danish/Swedish composite name for the structure—had been in existence for 12 years, opening August 14, 1999, after four years of construction preceded by four years of planning and fund-raising.

The Øresund Bridge provides a fixed link crossing over the Øresund strait, a western channel into the Baltic Sea flowing between Malmo, Sweden on the east and Copenhagen, Denmark on the west.  At 16.4 km (10 mi) in total length, the structure is made up of three components.  Starting at the east (Swedish) side, the actual bridge component consists of a steel girder extending the full length supporting a four-lane roadway on top of a deck for two railway tracks.  At the center are three cable-stayed sections—the longest cable-stayed main span in the world (490 m) for both road and rail traffic.  On both approaches, concrete piers every 140 m support the girder.  

At approximately 12.4 km towards the western (Danish) side, the road and railways descend onto the artificial island of Peberholm (Pepper Islet)—the Danish chosen name complementing the natural island of Saltholm (Salt Islet) just to the north.  From here they enter a 4 km long, 20 m high, and 500 m wide immersed tunnel running beneath the Drogden Channel and emerging at the artificial peninsula at Kastrup, Denmark.  Peberholm is a designated nature reserve built from Swedish rock and the soil dredged up during the bridge and tunnel construction.

The Øresund Bridge connector tunnel is the longest immersed tube tunnel for both road and rail traffic in the world made from 20 prefabricated reinforced concrete segments, the largest in the world at 55,000 metric tons each, interconnected in a trench dug in the seabed.  Inside the tunnel are five side-by-side tubes: two for railway tracks, two for roads, and a small fifth tube for emergencies.

Great world cities are known for their iconic bridges.  In 2002 ‘Øresundsbron’ received the International Association for Bridge and Structural Engineering ‘Outstanding Structure Award’ recognizing” the most remarkable, innovative, creative, or otherwise stimulating structures completed within the last few years.”

In terms of traffic flow unimpeded by collisions, the bridge design seems to be achieving the intended safety goal.  These days, bridges like ‘Øresundsbron’ and Canada’s eight-mile-long Confederation Bridge between New Brunswick and Prince Edward Island, are safely providing vehicular connection countries and regions on a scale unequaled in the history of engineering marvels.

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