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Bridges special: Steeling the show

A series of major steel bridges will help complete the M74 extension in Glasgow in time for the 2014 Commonwealth Games. Martin Cooper reports.

Just south of Glasgow city centre across the River Clyde, in an area once known for its heavy industry, a new 8km stretch of the M74 is being constructed.

The highway will provide a major economic boost by completing the city’s missing inner city motorway link and will breathe new life into a deprived area.

Known as the M74 Completion, the new six-lane motorway begins at the Fullarton Road Junction in the east of Glasgow where the M74 currently terminates. It continues west to link up with the M8 motorway west of the Kingston Bridge.

The aim is to bring new jobs to the region as well as help regenerate Glasgow and the suburbs of Rutherglen and Cambuslang.

The project − funded by government agency Transport Scotland with Glasgow City Council, South Lanarkshire Council and Renfrewshire Council − is part of the Scottish government’s massive transport infrastructure investment programme.

The aim is to bring new jobs to the region as well as help regenerate Glasgow and the suburbs of Rutherglen and Cambuslang. The M74 also plays a key role in the transport plan for the Commonwealth Games to be held in Glasgow in 2014.

The works contract was awarded to the Interlink M74 joint venture in early March 2008 for a fixed price of just under £445M.

The main challenges

One of the project’s main challenges is the number of roads and railways the route must cross. Because of this, the project includes 14 bridges − including crossings of the West Coast Main Line and the River Clyde, plus numerous underpasses and deep embankments.

“We are erecting bridges over some of Scotland’s busiest roads and, in the case of the West Coast Main Line (WCML), one of the UK’s busiest railway lines,” explains steelwork contractor Cleveland Bridge project manager Stephen Osborne.

“Our aim is not just to build and erect these bridges but to cause as little disruption to these vital transport links as possible.”

Working on behalf of Interlink, Cleveland Bridge is building the four main bridges for the project. There is the 232m M8 eastbound link bridge, the 750m Port Eglinton Viaduct, the 186m Rutherglen Station Bridge and the 90m Auchenshuggle Bridge across the River Clyde.

The first of the major bridges to be erected was the M8 eastbound link bridge which went up last month. This steel composite structure will connect the M8’s eastbound carriageways to the M74, while a shorter Westbound Link bridge − to be completed later this year and constructed with precast concrete − will connect to the outer Westbound carriageway of the M8.

Steelwork sections

Steelwork for the bridges is being prefabricated at Cleveland Bridge’s Darlington facility. In the case of the M8 eastbound link bridge, steel was delivered in 20 sections, ranging in size between 16m and 34m long, and weighing between 40t and 70t.

Once on site these fabricated sections were welded together, at two assembly yards either side of the M8, to form eight large girders weighing up to 200t each and measuring 70m in length. These main girders were then lifted, two each night, during four partial and full carriageway closures of the M8.

Lifting these huge steel girders into place required months of planning one of the UK’s largest mobile cranes − a 1,200t capacity Gottwald AK-680. The crane itself needed 30 trucks to deliver it to site.

The Gottwald crane initially erected the two girders which span the existing Paisley slip road. “Although this crane has a very substantial lifting capacity, the assembly area available was limited so that self-propelled modular trailers were used to move the assembled sections to within pick up radius of the crane,” explains Osborne.

An important milestone

When the first two lifts had been completed, the entire crane, fully assembled with its 95m long jib, was moved by the same self propelled trailers to a second position on the same side of the motorway to lift the next two girders. The crane was then fully dismantled and moved to the other side of the motorway to lift the final four girders over the M8 westbound carriageway during two nighttime closures.

“We were delighted to reach this important milestone on the project,” says Interlink project director David Welsh. “The works are already visible and these beams, which will be seen by thousands of motorists each day, emphasise the progress being made on this job.”

Work is now progressing towards the next bridge challenge which involves the largest steel bridge structure on the route, the Port Eglinton Viaduct.

“These beams, which will be seen by thousands of motorists, emphasise the progress being made on this job.”

David Welsh, Interlink

This 750m bridge incorporates 14,500t of steel and spans the WCML, Metro tunnels near West Street Station, the Paisley, City & Union rail lines, and Eglinton Street − one of the busiest roads into Glasgow city centre.

The large box girders for this structure have been prefabricated are currently being brought to site in sections and then welded together in two separate assembly yards. One of the yards is for the section of the bridge which will span the Paisley Line, City & Union Line and the SPT Underground tunnels and the other is for the larger box girders which will span the WCML.

Steel erection for the Rutherglen and Auchenshuggle bridges is due to start early next year. The whole M74 extension project is scheduled for completion in 2011.

Fact file

  • Client: Transport Scotland, Glasgow City Council, South Lanarkshire Council, Renfrewshire Council
  • Main contractor: Interlink M74 JV, a joint venture comprising Balfour Beatty, Morgan Est, Morrison Construction, Sir Robert McAlpine
  • Structural engineer: Jacobs/Atkins JV
  • Steelwork contractor: Cleveland Bridge
  • Steel tonnage: 19,000t
  • Project value: £445M

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