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All Hands On Deck
The annual tradition of festive upgrade work on Britain's railways is well established, while most of the country is enjoying mince pies or New Year parties, engineers and workers across the rail industry are out improving the network.
However, this year's Christmas work included something a little bit different when a huge 1,000t bridge deck was manoeuvred into place in Reading as part of Network Rail's £850m project to upgrade the railway around the town by 2016.
The new deck is a key part of the plans to double the station's passenger capacity by 2030. The station revamp will increase capacity to cope, by remodelling the existing track layout and building five new platforms.
The new 40m long, 17m wide bridge deck widens the throat at the station's western entrance, providing space for seven tracks to help serve the new platforms.
The new deck is one of the largest orthotropic steel bridge decks in the UK. Just 650mm deep, it replaces four existing single span bridges, as well as creating space for future rail alignment improvements.
Two of these bridges were removed in September 2010, as they carried disused freight lines, while two bridges carrying relief lines were lifted out on 30 December ahead of the installation of the new deck.
Contractor BAM Nuttall's project manager Mark Hepburn says that a steel deck was chosen because it could be designed to be slim enough to clear the road below while maintaining the vertical alignment of the railway.
With a necessary highway clearance of 4.75m, he said: 'To maintain a highway we weren't left with much space.'
The bridge is made up of 14 steel sections fabricated by Bolton steel company Watson Steel, having been designed by BAM's design consultant Gifford. Each section was delivered to site in Reading, wherethe entire deck was constructed on top of six precast concrete cill beams.
Hepburn explains that each section was bolted together, with the ends of the joint also welded. A cast insitu concrete trimmer beam was attached to the till beams.
The bridge deck sits on a total of 44 bearings, which is more than a conventional rail bridge due to the structure's width need to transfer live loads from seven tracks from the bridge deck to the abutments without the use of supporting girders.
Deck construction was completed at an assembly site close to the bridge's final location on 23 November, and temporarily connected the cill beams and the deck so it could move as one. Preparatory work including waterproofing and the laying of ballast for the reinstalled railway lines was completed before the bridge was moved into position.
The deck was moved into place along the cutting that forms Caversham Road to the west of the station by a 72-axle multi-wheel transport vehicle.
Each of the wheels on the transporter could move independently, allowing it to navigate the tight confines of the construction site.
The move started at 8pm on 30 December, lasting until around 1am on 2 January. Moving the deck was one of the main project challenges, as it had to be manoeuvred with just 250mm to spare as the transporter moved it past the corner of an office building on its loom journey along Caversham Road. Part of the fascia of the office building at the town's former Royal Mail depot had to be removed to make way for the move from assembly site to the bridge's permanent location to provide an extra 1m clearance.
The final part of the operation involved lowering the bridge onto abutments, which had supported the original bridge decks. These had been strengthened and extended to support the new structure, onto which the two relief lines were then put in place by Network Rail once the move had been completed. The railway was handed back on 4 January as planned.
The scale of the effort put into the project was vast. More than 250 engineers worked around the clock on the project, which will be followed by more improvement works at and around the station.
'The work we've completed this Christmas is the launch pad for a huge programme of improvements for Reading's railway,' says Network Rail project director Bill Henry. 'Over the coming years we'll build a bigger, better station and make substantial changes to the track layout to improve journeys on the entire western route, from London to Penzance and Swansea.
'Our people have put in 16,000 hours over the past 10 days to deliver this work on time, and some two years of planning have gone into keeping disruption to the railway and road network to a minimum.'
Hepburn himself said that the move 'all went to plan, and was a well executed bit of possession work'.
The bridge lift was part of work that completes the first stage of the project to upgrade the railway at Reading.
Also over the festive period, signalling for the area was transferred to a new signalling centre at Didcot. It was this, rather than the bridge work, that meant that no trains could run through Reading between 27 and 30 December.
 There are two rail over road bridges approaching Reading station, Caversham Road to the west of the station, where the Great Western mainline heads towards Bristol and Cardiff, and Vastern Road to the east, heading to London.
Increasing the capacity of these bridges is key to the station upgrade, and work on the Vastern Road railway bridge will be, completed this year.
The existing railway bridge is being widened on both sides to create room for track to serve the new platforms, and Hepburn says this work is more technically challenging than the work at Caversham Road.
The bridge extension has to match the existing structure, a concrete bridge deck on top of steel portals, to meet planning requirements.
This makes the tolerances for the structure even tighter than Caversham to maintain the road clearance, as this bridge deck is naturally deeper.
Also, there is the challenge of making the new parts of the structure act under loading in the same way as the old one.
Work has had to be undertaken to measure how the current structure behaves when loaded. The work will add a total of eight bridge portals to the structure and 16m to the width and will be completed by the end of April.
Network Rail will demolish the signal box at Reading this year, which is now disused following the transfer of signalling to Didcot, to make way for new platforms and a new entrance to the north of the existing station.
Also this year, station modernisation work will start. The project also includes a new viaduct to the west of the Caversham Road to boost capacity, which should be finished in 2015.
Changes to the track layout to serve the new platforms will not be completed until 2016. |
Article courtesy of New Civil Engineer - january 2011
Further Info
Peter Bishop - Head of Public Relations & Corporate Communication
BAM Nuttall Limited
St James House, Knoll Road, Camberley,
Surrey GU15 3XW
Tel: 01276 63484
Fax:01276 66060
peter.bishop@bamnuttall.co.uk
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