RMD Kwikform’s engineering team has designed its largest ever light-weight single span temporary access pedestrian bridge, in support of Interserve Project Services’ £1.5m restoration project to refurbish the historic 39 tonne, 19th century Southease bridge for the Environment Agency
The Grade II listed Southease bridge, near Brighton, crosses the River Ouse between Lewes and Newhaven, providing an important link for local residents to Southease train station and ramblers using the popular South Downs Way track.
Having identified the need to refurbish the bridge as part of a restoration project to preserve the rich heritage of the Ouse, the Environment Agency awarded the contract to lift out, repair and reinstate the 18th century historical bridge to Interserve Project Services.
As part of the project delivery, Interserve Project Services had to provide a temporary bridge crossing for pedestrians who depend on the bridge, whilst the original bridge was lifted out in sections and refurbished over a number of months.
In order to achieve this, a temporary pedestrian bridge had to be constructed and lifted into place. Due to the location, restricted site space and crane access issues, Interserve Project Services were faced with the challenge to create a strong, lightweight yet rigid temporary bridge structure that could span 47m. It was at this stage they contacted RMD Kwikform whose engineers at its Aldridge headquarters worked with the project team to design the overall solution complete with landing piers.
Commenting on the project Interserve Projects Service’s Noel Baker said “This project was by no means an easy task. The location of the bridge was a major issue as it was situated down a narrow lane. In addition, all equipment had to cross a rail line, with no other potential route available, as the site is surrounded by protected meadows of special scientific interest, with limited site access and storage. This meant we had a major dilemma of getting a crane big enough for the job into the site.
“Following remedial widening works to the lane, we were able to get a 500 tonne crane into place which was capable of lifting the cast iron bridge. Thanks to its swing design we were able to lift the bridge out in two sections, one 12 tonne and the other 27 tonne, reducing the crane weight significantly. However in order to install the temporary bridge we needed to make sure the structure designed by RMD Kwikform was both ridged enough to span the 47m gap and light enough to be craned into place.”
The pedestrian temporary access bridge was erected onsite by a team of Interserve Project Service site operatives, who also prepared the concrete base and temporary piers on each side of the river that would support the bridge. The complete structure was then lift tested before it was moved into place. Once the testing was complete, the task of lifting the new bridge into place on top of the piers took less than15 minutes from lift to first fix.
Commenting on the bridge, John Porter, RMD Kwikform sales representative said: “The bridge itself is the longest single span temporary bridge we have ever designed in the UK. In order to meet the, strength, rigidity and weight requirements of the structure we designed it using our R700 steel girders for strength, that were then laced top and bottom with steel supports for rigidity. Lightweight aluminium beams were also used on the base to hold the decking in place.
“For the landing piers, we designed a special landing plate mounted onto a steel section girder with supports that were fixed to a concrete base. The strength of this landing pier was designed to bear both the load of the bridge and the passengers crossing it.”
As an important part of the local and regional history, saving the bridge was an important challenge for the Environment agency as Ian Nunn, East Sussex Team Leader commented: “With this project we are protecting the rich heritage of the Ouse while ensuring the full and safe use for the local community in the future.
“This is an extremely interesting and challenging project and we look forward to re-opening the bridge for use by the community and visitors in the coming months.”
The bridge project is due to be completed in November 2010 when the pedestrian bridge will be removed and the refurbished Southease bridge will be lifted back into place and reinstated.