Europe closes in on the crossings
First publishedin World Highways
Earlier construction of the Queensferry Crossing (photo coutesy of Wacker Neuson)
Workers continue to push ahead with three prestige crossings in the UK while Norway considers using wood to build a major bridge
The Mersey Gateway bridge project off England’s west coast passed a milestone recently with the first joining of two of the deck sections. The key segments, as the sections are called, link the north approach viaduct to the north pylon deck span and are the first of four deck-joins scheduled for this summer. In total, there are five sections of bridge deck and approach roads that need to be joined.
Under construction is a six-lane cable-stayed structure with three towers that will span the Mersey River’s expansive mud flats between the towns of Runcorn and Widnes near Liverpool.
Including the approach viaducts on each side, the project will be 2.3km long with a river span of 1km. The main bridge deck will be reinforced concrete. The 80m-high central tower will be shorter than the two outer towers, where the north tower will be 110m high and the south tower will reach 125m.
Mersey Gateway - first bridge deck join completed
The deck is being built outwards from each of the three pylons at a rate of around 6m a week.
As well as being linked to each other, the north and south main bridge deck sections also need to be linked to the approach roads – the viaducts built over the saltmarsh and the canals – approaching the river.
“We have now linked the sections of deck together by bridging the gap between the two decks with four steel restraint struts that resemble giant bolts and a concrete pour,” said Hugh O’Connor, general manager of Merseylink, the consortium building the bridge.
“Once the concrete has set, the decks are further locked together with external post-tensioned tendons. This is a major step for the project and we remain on target to complete the final three joins this summer with the bridge expected to open to traffic this autumn.”
It took around two hours to pour 40m³ of concrete to fill the 2m gap between the north approach viaduct and north pylon deck span.
“We could complete the pour only once the form traveller was moved into position and the mould had set. The gap between sections was only two metres wide, but runs the entire 32 metres width of the bridge deck,” said O’Connor. “Around 18 hours after the pour, the concrete sets to full load-bearing strength.”
Merseylink Consortium was appointed by Halton Borough Council to a 30-year design, build, finance and operate contract. Equity partners are Macquarie Capital Group, BBGI, and FCC Construcción. The construction joint venture is made up of Kier Infrastructure and Overseas, Samsung C&T and FCC Construcción. Emovis will deliver and operate tolling through its merseyflow brand.
Progress in Sunderland
Meanwhile, across England, off the north-east coast, workers are preparing to install cable stays on the city of Sunderland’s new bridge. The New Wear Crossing is on track for opening in 2018, improving the links between the A19 and the city centre and Port of Sunderland.
Global structural engineering company VSL International, which specialises in the installation and tensioning of cable stays, will be installing the 28 stays over the summer. Each stay will be contained inside a white protective plastic tube that is installed first, followed by cable strands.
Each tube will contain between 45 and 85 strands about the diameter of an UK penny coin and have the capacity to lift 7tonnes. A tube containing the maximum 85 wire strands will have the capacity to lift 595tonnes.
Liebherr cranes working on Queensferry Crossing piers
Before the cables can be installed, however, 674 concrete deck panels must be joined, or stitched, together. Workers are now pouring concrete into the joins between the panels, connecting them to the steel deck frame that supports them. Once the stitching on the south side of the deck is complete, the cable installation can begin. Work is also continuing to assemble the remaining 40m of bridge deck on the north side of the river, which is due to be complete later this summer. Once finished, it will bring the deck to its final span of 330m, explained Stephen McCaffrey, project director for FVB, a joint venture of Farrans Construction and Victor Buyck Steel Construction which started work on the bridge in May 2015.
Farrans Construction operates as a building and civil engineering contractor across the UK and Ireland. Victor Buyck is based in Belgium and is one of Europe's major structural steelwork contractors, specialising in steel bridges. FVB JV is being supported by a design team led by Buro Happold Engineering and Roughan & O'Donovan, and independent checker Ramboll.
Norway's proposed 1.7km wooden bridge across Lake Mjosa
Norway could be home to the world’s longest wooden bridge if the government gives the go-ahead for a span across Lake Mjosa.
In a new report, researchers conclude that it is possible, both technically and economically, to build a 1.7km wooden bridge between the towns of Biri and Moelv. Importantly, the report notes that there would be little construction cost difference between a wooden and concrete structure.
Estimates for a wooden bridge are around €420 million while a concrete structure would come in about €410 million, according to Trond Arne Stensby, project manager at the Norwegian Public Roads Administration - Statens vegvesen.
The 468m-deep Lake Mjøsa is one of the deepest in Europe and the fourth-deepest lake in Norway. It stretches for 117km and is about 15km at its widest. The lake is 123m above sea level and lies about 100km north of the capital Oslo.
One bridge already crosses the lake, the Mjøsa Bridge that was opened 1985 and is part of the main north-south highway in Norway, the E6. The concrete box girder bridge has spans of around 69m and rests on piles in water up to 40m deep. The bridge has two lanes of traffic and separate pedestrian and cycling lanes.
Previous studies have considered a four-lane link on Highway E6 between the cities of Hamar and Lillehammer – site of the 1994 Winter Olympics. Timber construction alternatives include a truss structure with two underlying trusses composite with a concrete bridge deck. Typical cable stay span width is 69m.
Sunderland's New Wear Crossing is prepared for cable installation
Walking the Queensferry
Back in the UK, the Scottish government recently announced that the Queensferry Crossing will open to traffic on August 30. The bridge will then briefly close to traffic on September 2 and 3 to allow the public to take part in what the government is calling a once-in-a-lifetime chance to walk over the new structure.
But the number of walkers will be limited to 50,000, for which spaces are up for grabs through a ballot – the Queensferry Crossing Experience.
The new €1.53 billion bridge is the centrepiece of a major upgrade to the important transport corridor across the Firth of Forth near the Scottish capital Edinburgh. The 2.7km structure will be the longest three-tower, cable-stayed bridge in the world and also by far the largest to feature cables which cross mid-span to provide extra strength and stiffness, allowing the towers and the deck to be more slender and elegant.
In total, the overall Forth Replacement Crossing scheme - of which the new bridge is part - is 22km long, including major motorway upgrades to the north and south of the bridge and also the first ever use in Scotland of variable mandatory speed limits to smooth traffic congestion via an Intelligent Transport System. This also controls dedicated bus lanes within the motorway hard shoulders – another first in Scotland.
The existing 2.5km Forth Road Bridge was one of the longest suspension bridges in the world when it opened in 1964 to connect Edinburgh, at Queensferry, to Fife, at North Queensferry. Opening the new Queensferry Crossing will allow the Forth Road Bridge to be used as a public transport corridor for buses and taxis and possibly trams.
Transport Scotland is the client for the Queensferry Crossing project while Jacobs Arup is client advisor. The contractor is Forth Crossing Bridge Contractor, a German, Spanish, UK and US joint venture comprising Hochtief, Dragados, Morrison Construction and American Bridge International. The designer is a partnership between Ramboll, Grontmij, Leonhardt and Andra und Partners.