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Oresund Crossing
Denmark to Sweden
associated engineer
Ove Arup & Partners
Setec Travaux Publics & Industriels
Gimsing & Madsen A/S
ISC Consulting Engineers A/S
Sir William Halcrow & Partners
Tunnel Engineering Consultants
Carl Bro
Symonds Travers Morgan
VBB Anlaggning AB
date  August 1995 - 1st July 2000
era  Modern  |  category  Bridge  |  reference  OO301316
The Oresund Crossing is one of the world’s most ambitious engineering endeavours, linking Denmark and Sweden over a busy shipping channel between Copenhagen and Malmo. The 16km road and rail structure consists of an immersed tube tunnel, a manmade island and a 7.8km bridge with a cable-stayed high section for navigation. Oresund is Europe’s longest bridge for road and heavy rail traffic.
In August 1991, the Danish and Swedish parliaments ratified an agreement (signed 23rd March 1991) to establish a fixed link across the strait of Oresund. The Oresund region covers 21,203 sq km of eastern Denmark and southern Sweden, including the Danish islands of Zealand, Lolland-Falster, Mon and Bornholm and the Swedish province of Skane. It has a population of 3.73 million people (January 2010) and generates around one quarter of Denmark and Sweden’s combined gross domestic product.
From west to east, the crossing passes through an immersed tube tunnel from the south east of Copenhagen to the artificial island of Peberholm, then over a series of double-deck bridge structures to the south west of Malmo. It carries road and rail — the E20 motorway with two lanes of traffic plus one emergency lane in each direction, and a twin-track standard gauge (1.435m, 4ft 8.5in) railway, where trains are capable of reaching speeds of up to 200kph (124mph).
The Danish and Swedish government agreement sets out the aim of constructing a scheme with due consideration for "what is ecologically motivated, technically possible and financially reasonable to prevent any detrimental effects on the environment".
Environmental considerations were particularly important because the Baltic Sea is the world’s largest body of brackish water. Its unique marine ecosystem depends upon on the water flow through the sound from the North Sea, carrying salts and dissolved oxygen. The crossing had to have no net impact on the marine environment. This was indeed achieved, providing a model for other mega-construction projects in mitigating environmental impacts.
The crossing’s commissioning authority is Øresundskonsortiet, a joint venture between A/S Øresund and Svensk-Danska Broförbindelsen SVEDAB AB, in which the Danish and Swedish governments each hold a 50 percent stake. Øresundskonsortiet was established in January 1992, through a partnership agreement. However, the project is not only a Scandinavian achievement but also an international collaboration of engineers from Denmark, Sweden, Britain, France, Germany, the Netherlands and the USA.
The design competition was won by the ASO Group, consisting of Ove Arup & Partners, Setec Travaux Publics & Industriels, Gimsing & Madsen A/S, ISC Consulting Engineers A/S and architect Georg Rotne. ASO took part in the early planning of the whole link and subsequently prepared the bridge design. The group also was responsible for quality auditing during construction.
The consultant for the tunnel, dredging and reclamation works design was Oresund Link Consultants, a consortium consisting of Ramboll, Scandiaconsult, Sir William Halcrow & Partners, Tunnel Engineering Consultants and architect Dissing + Weitling.
The overall project was divided into contract packages, each let to a group of contractors responsible for furthering the detailed design and selecting the construction techniques.
Dredging and artificial island construction was carried out by Oresund Marine Joint Venture: Per Aarsleff A/S, Ballast Nedam Dredging b.v. andGreat Lakes Dredge & Dock Company, with engineering consultant Carl Bro.
The tunnel was constructed by Oresund Tunnel Contractors: NCC AB, Dumez-GTM SA, John Laing Ltd, E. Pihl & Son and Boskalis Westminster, with consultant Symonds Travers Morgan.
All bridge works were constructed by Sundlink Contractors — Skanska AB, Hojgaard & Schultz A/S, Monberg & Thorsen A/S and Hochtief AG, with consulting engineers COWI A/S and VBB Anlaggning AB.
Official commencement followed the Danish Ministry of Transport’s approval of the general design, alignment and environmental conditions for the crossing on Danish territory. On 16th September 1993, ground was broken on the Danish landward approach works. In June 1994, the Swedish government approved construction of the link on Swedish territory.
Manmade island
In August 1995, dredging operations began in the sea bed of the strait — required for the navigation channels, placement of the tunnel tube and the bridge foundations. All the excavation arisings were used to create the artificial island of Peberholm and to reclaim land on the Kastrup peninsula.
Forming the land reclamation and the island consisted of constructing pebble bunds to enclose basins lined with geotextile membrane, into which the dredged material was tipped and compacted to minimise differential settlement. The basins were then backfilled with clay and the new land protected by rock revetments.
On Amager Island, north east of Copenhagen airport near Kastrup, an artificial headland covering 0.9 sq km was constructed to accommodate the west portal of the Oresund tunnel. It extends some 430m seaward of the original coastline. Peberholm, south of the natural island of Saltholm, acts as a transfer structure for traffic emerging from the tunnel and moving onto the bridge. The 4km long rhombus-shaped island is 20m high, an average of 500m wide and has an area of 1.3 sq km. It contains 1.6 million cu m of stone and 7.5 million cu m of sand and dredged material.
The east portal of the tunnel is at the west end of Peberholm. Exiting traffic crosses the island (road to the north and railway to the south) to the western bridge approach. Here the road runs over the bridge’s upper deck and the railway is carried on the lower deck.
With a portal to portal length of 4.05km, the tunnel is the longest of its type in the world, for road or rail. It runs from the Kastrup headland to Peberholm beneath the Drogden navigation channel, and consists of a 3.15km immersed tube with 270m entry tunnels at each end. Building it involved pouring almost 500,000 cu m of high-strength reinforced concrete in just 24 months. At peak, some 8,000 cu m of concrete per week was being placed.
The immersed tube section comprises 20 precast concrete tunnel units, manufactured in a purpose-built casting yard at Copenhagen's north harbour. Each unit is 175.5m long, weighs up to 55,000 tonnes, and consists of eight segments 38.8m wide and 8.6m high. Parallel production lines enabled two units to be constructed at a time.
The casting was done on dry land, with new segments cast against the previous ones as the units were slid gradually into a split level dry dock. Steel bulkheads were installed at the ends of the units to keep them watertight. As each unit was finished, a sliding gate closed the dock, water was let in and the unit was floated out to sea. On 8th August 1997, the first unit was towed to the pre-dredged tunnel trench and sunk into position using GPS navigation.
On 4th August 1998, one of the bulkheads failed while a unit was being placed. The flooded unit was lowered into the trench, several metres out of position. Repair and relocation took eight weeks.
Once all were in place, the units were connected into a single tube and the trench backfilled at the sides. A layer of stone ballast was placed over the top for protection, and lies some 10m below the water surface.
The south side of the tube carries two train tunnels, each with a single high-speed track. The north side has two road tunnels, each with two lanes and ceiling mounted ventilation fans. Within the wall between road tunnels are three voids, one above the other, for services, an escape route and cabling.
On 16th March 1999, the first official vehicle — a bus carrying the Danish transport minister and the Swedish minister for industry, employment and communications — was driven through the finished tunnel, from Copenhagen to Peberholm.
Oresund Bridge is some 7.8km long, almost 40m wide and is made up of three sections — the 3km western approach bridge, the high 1.1km bridge over the Flintrannan (Flinte) navigation channel and the 3.7km eastern approach bridge. As it crosses international shipping lanes and airspace, its design had to take into account potential ship impact and aircraft collision.
The high bridge, with a maximum clearance of 57m above water, is the crossing’s most eye-catching feature and marks the border between Denmark and Sweden. At 490m between pylons, it has the longest cable-stayed main span in the world for both road and rail traffic. The flanking spans are 160m and 141m on each side. Cable-staying was chosen because it gives greater deck rigidity than a suspension bridge and so is more suitable for the railway, which cannot accommodate as much deflection as a roadway can.
All bridge sections have a two-level deck superstructure. Steel girder trusses support the reinforced concrete upper decks, carrying the motorway. The lower deck carries the high speed railway, with the tracks in a reinforced concrete trough on the approach bridges and a steel deck on the high bridge. Double-acting jacks were used for positioning the lower deck bridge elements on their bearings, and for supporting the upper deck.
The approach bridge piers and all bridge caissons were prefabricated in dry docks at Malmo north harbour. The approach bridge decks were manufactured by Dragados in Cadiz, Spain, while the high bridge decks were made at Karlskrona shipyard, Sweden, and shipped to Malmo. The various components were transported from Malmo to the bridge site by the floating crane Svanen.
On 1st April 1997, the first of the two 35m x 37.2m prefabricated concrete caissons for the high bridge were towed to site from Malmo by two catamaran barges and sunk into a trench excavated in the sea bed. Each caisson is founded on hard limestone 14-17m below sea level, and incorporates the bases for two pylon legs.
The concrete pylons consist of pentagonal twin towers, rising to 203.5m above sea level and free standing above the deck. Their slender tapering design gives flexibility in the case of aircraft strike, reducing the impact on the foundations. Since the stability of very tall towers increases with taper, the final design required extensive numerical modelling to achieve the optimum balance between efficiency and aesthetic appeal.
They were slip-formed in situ with each 4m lift taking 7-10 days to cast around prefabricated reinforcement cages. The four pylon legs contain 3,200 tonnes of steel and 17,340 cu m of concrete, supplied from a floating batching plant moored next to the pylon cofferdam. Each leg is solid for the lower 17m and hollow higher up.
Cross beams connect the pylon legs beneath the deck, 44-45m above sea level. They were also cast in situ with prefabricated reinforcement cages. The first pylon leg reached full height on 18th January 1999. Rock protection was placed around the bases of the pylons and the neighbouring piers to protect against ship impact.
The superstructure of the 490m span was prefabricated in eight sections, joined in pairs and erected in four pieces. The sound is not too deep so the deck was supported on temporary piers during construction, similar to a propped cantilever.
The upper (road) deck is of post-tensioned concrete and the lower (rail) deck is a steel Warren truss. The concrete slab is cantilevered 4.1m on both sides of the steel truss, resulting in an even distribution of moments. Shear studs transfer longitudinal shear forces from the deck to the truss.
The stay cables were installed after the main and side span superstructure had been completed. The cables are arranged in a harp pattern, anchored to the superstructure truss at 20m intervals and to the pylons at 12m centres. The linear arrangement is echoed by the geometry of the girder truss, where every diagonal follows the angle of the cables (30 degrees).
In all, there are 80 pairs of cables, 10 on each side of the pylon legs. Their combined length is about 25km and the total weight 2,300 tonnes. They have a tensile strength of 2,000 tonnes and and each contains 68-73 strands of seven 5mm wires. The wires are galvanised, waxed and encased in plastic.
Hydraulic units at the expansion joints between the approach and side spans of the high bridge accommodate temperature variations and absorb and transfer forces from the cables to prevent bending of the pylons.
The approach bridges are carried over a total of 51 piers, spaced at 140m centres for 1.3km on either side of the high bridge and 120m on the outer sections of the approaches. The prefabricated reinforced concrete piers have a cellular internal structure, partly filled with sand for stability in case of ship impact. Below the sea bed, the pier caissons measure 29m x 20m overall and have 4 x 9 cells. Above the sea bed, the slightly tapering pier shafts are about 7m x 19m in section and contain 2 x 5 cells.
The double decks of the approaches are constructed in concrete, with the upper deck similar to that over the high bridge. The trough girders for the railway (lower) deck are 4.5m wide by 1.8m deep, with cross members at 20m centres. The girders are of high strength C60 concrete 370mm thick, with 80mm of cover to the reinforcing steel.
At the top of the piers, the edges of the deck truss are supported on pot bearings (rubber disks inside steel cylinders), allowing rotational movement. Longitudinal fixed bearings on certain piers limit the longitudinal movement resulting from temperature variations but are able to absorb the longitudinal forces that would be generated by ship collision or an earthquake.
On 14th August 1999, the final section of the bridge was lifted into position, closing the link between Denmark and Sweden. A monitoring system was set up for the bridge consisting of ultrasonic anemometers, accelerometers on the stay cables and gauging for data collection about wind velocity and direction, rainfall, atmospheric pressure, relative humidity and temperature.
The crossing opens
At the east end, on Swedish soil, the motorway is transferred from the upper bridge deck to ground level and its carriageways diverge, north and south, to the toll plaza. Tolls are collected over 11 lanes in each direction. The railway exits the lower bridge deck and runs overland between the roads and the toll plaza.
The railway between Copenhagen and Malmo was completed on 1st December 1999. The two countries use different electrification and signalling. The railway uses the Danish electrical supply (25kV, 50Hz) over the crossing and switches to the Swedish supply (15kV, 16.7Hz) at the east bridgehead. The line follows standard Danish signalling through the tunnel and changes over to the Swedish signalling system on Peberholm. More than 150 trains cross the bridge each day.
On 9-12th June 2000, special open days allowed members of the public to cross the bridge on foot or bicycle — hundreds of thousands of people did so.
On 1st July 2000, the Oresund Crossing was inaugurated several months ahead of schedule. At first, some 6,000 vehicles a day used it — around half of the predicted traffic volume — so toll charges were cut in October 2000. After five years of operation, in July 2005, crossing traffic had increased by 74 percent.
In late 2006, during a routine inspection, cracks and spalling were found at 50 separate locations on the east (Swedish) end of the bridge. The defects occurred in patches about 200-250mm long, 100-120mm wide and 15mm deep, in the lower inside corners of the twin concrete trough girders carrying the rail tracks. The troughs were designed to be installed 10mm apart but the gap did not exist on the east part of the bridge. Additionally, the bridge's east-west alignment means the south side is subject to solar heating, while the north side is in shade, causing differential movement.
Structural repairs were carried out in the first half of 2007. Remedial works included making 10mm slots between the trough girders using a circular saw.
Architect (design competition): Georg K.S. Rotne
Architect (tunnel): Dissing + Weitling
Contractor (manmade island and peninsula): Oresund Marine Joint Venture
Contractor (tunnel): Oresund Tunnel Contractors
Contractor (bridge): Sundlink Contractors
Hydraulic systems: Enerpac
Railway: Banverket Industridivisionen
Approach bridge decks: Dragados
High bridge decks: Karlskrona Shipyard
Research: ECPK
"The Øresund Bridge – Linking Scandinavia to the continent" by Nils Francke, Ingenia, Issue 6, pp.23-28, London, November 2000
"Displacements of Øresund bridge piers for ship impact" by Helge Gravesen and Morten Faurschou, Carl Bro, Glostrup, September 1998
"Ship Collision Analysis", eds Henrik Gluver and Dan Olsen, Proceedings of the international symposium on advances in ship collision analysis, Copenhagen, 10-13th May 1998

Oresund Crossing