Newbattle Abbey Bridge
Special Award: Best Use Of British Timber 2010
Building Owner: Newbattle Abbey College
Architect: Forestry Civil Engineering
Structural Engineer: Forestry Civil Engineering
Main Contractor: JKF
Joinery Company: Forestry Commission
Wood Species: Larch
Newbattle Abbey College and Forestry Commission Scotland (FCS) entered into a Concordat agreement for Newbattle Abbey’s Policies and Landscape setting to benefit the college and local communities through personal and cultural development, and improved health and wellbeing of visitors, local people, staff and students by giving them access to safe and diverse woodland, that is rich in biodiversity and history.
The bridge link between the parkland and woodland is an essential part of the access from the college. The existing bridge, known as the ‘Grotto Bridge’ was installed as a Bailey bridge in the 1940’s by the Army when they occupied the estate and site. The bridge was inspected by Forestry Commission Civil Engineers in 2006 and again in 2008. Dr Geoff Freedman, Head of Design, Forestry Civil Engineering (FCE) in his report of March 2008 stated that:
“The cost of removing the decking, dismantling and repainting, along with the abutment repairs were very close to a full replacement cost”.
This project will promote health and well being for local residents and visitors to the college by providing excellent all year round access to Lord Ancrum’s ancient woodland and the beautiful grounds of the college. The bridge and footpaths will be accessible for both old and young alike.
Planning insisted that the replacement bridge was on the existing abutments which would have to be partially rebuilt. This set the span as 14m which was well within a new type of timber construction that had been developing over recent years. It was therefore decided to pursue a vertically laminated timber arch design for maximum sustainability and low cost while displaying innovation and the ultimate in aesthetic blending. This bridge is set against an ancient woodland and the corroded Bailey Bridge, which had been there for over 60 years, gave the impression of a decaying shipyard instead of taking the opportunity of inspiring students.
The college was essentially the client and FCS acted as partner and fund manager. FCE were the consultants who designed the bridge and supervised the construction. JKF were the contractors who won a competitive tender and fortunately were well known to FCE as conscientious and reliable contractor. They have built many bridges for FCE and now have a reputation for taking care of detail and are willing to take on the construction of our new innovative designs. Waste Recyling Environmental Limited (WREN) were the funders. They require a rigorous approach to providing funds to ensure the public money is spent wisely. This project was very worthy so we only had to complete the applications correctly and follow all of their requirements for sustainability and to ensure public use of the bridge and thus benefit.
The vertically laminated structure was a glued and screwed timber arch supporting a flat deck designed for rural crowd loading or light vehicles. The design was based on the research work done by the designer as part of a PhD study on stress laminated arch bridges. This form of construction allows 100 to 1 span to depth ratio which is efficient in material terms. This is possible because timber is good in bending and compression. The timber was air dried, pressure treated Scottish Larch to give maximum durability and sustainability.
The new bridge has provided access and inspiration. The latter will hopefully lead to the Local Authority adopting similar sustainable designs for other projects and the students to view timber as a primary structural material capable of competing with steel and concrete.