Year-long viaduct deck operation gets underway
Pioneering composite structure reaches critical stage at Buckinghamshire bridge.
A THIRD of a mile of bridge deck will be gradually moved into position for Wendover Dean viaduct in Buckinghamshire during the course of this year.
Instead of using solid prestressed concrete, the 492-yard viaduct will consist of ‘double composite’spans.
In this method, two steel beams are sandwiched between two layers of reinforced concrete, creating a hollow, lightweight yet strong structure which is designed to maximise the combined strength from both materials.
HS2 Ltd says it is the first major railway bridge in the UK to be built using this kind of composite approach. By adopting this rather than a more traditional method, the carbon footprint of the structure is estimated to have been more than halved. Once construction is complete, the field boundaries and hedgerows will be recreated to provide uninterrupted access for farmers and local residents.
Three stages
The viaduct deck will be assembled in three stages, using sections ranging from 90-180m (98-197 yards) in length.
In what HS2 Ltd has described as a “critical” and “delicate” stage of construction, each section of the deck will be pushed out from its north abutment and the next attached behind it.
This process means that the weight of the deck will gradually increase during the year, from an initial 590 tonnes to 3,700.
This is the longest deck slide on the HS2 project to date, and a winch will be used to move the deck forward onto the viaduct’s nine piers, which are up to 14 metres (46 feet) high. As this part of the railway is on a slight gradient, the finishing point is 1.8 metres higher than the start.