News
December 14, 2011
NEW case study Far Moor Bridge
Far Moor Bridge is a unique timber bridleway bridge, a combination of stress-laminated arches and screw-laminated deck, which crosses the River Ribble in remote moorland near Ribblehead in the Yorkshire Dales. It is designed for horses, cyclists and walkers who take the new Pennine Bridleway trail. Funded by Natural England and with the support of Sport England, the bridleway enters the Yorkshire Dales National Park at Long Preston and weaves through the Dales to Kirkby Stephen.
A new section of bridleway, together with the new bridge over the Ribble, has been created near Selside, only a few miles from the famous Ribblehead railway viaduct. Here the commissioning authority saw an opportunity to build a comparably iconic structure which would also be environmentally sustainable and low budget.
The idea of using stress-laminated timber techniques to construct rural bridges was developed by Dr Geoff Freedman, who, before his retirement from the Forestry Commission in 2011, ran a specialist design and construction service for rural bridges within the Commission (a service which continues today as Geoff Freedman Rural Bridges).
The spans, flood characteristics and topography meant that the bridge deck would have to be supported by three arches. The central span of 24 metres over the river is taken by the central arch; two side arches, spanning 10.8 and 16.8 metres, were additionally needed to maintain the integrity of the flood plain.
The main construction material is Scottish larch treated with the wood preservative Tanalith E, with oak on the outer section of the arches to withstand and spread the stress loading of 150kN. All timber laminates, posts and rails were pre-cut, drilled and pressure-treated before being delivered to site. On site, a clear coat of wax waterproofing was applied to the soffits of the arches to encourage shedding of windblown rain and to protect cuts around posts. The screw-laminated deck is finished with an epoxy resin and bauxite non-slip surface on bitumen macadam, applied in-situ to provide waterproofing and a cushion for horses' hooves. The balustrade posts are substantial enough to take lateral load from horses; they also connect the deck with the arches below, additionally stiffening the deck.
A previous tender, of similar size but of a different design, had indicated a price of around £500,000. Far Moor Bridge cost £130,000 - about £1,000 per square metre of deck.
To view the case study in full click here
Recent Stories:
News stories are listed in order of relevance.
