Timber bridges are not only beautiful to look at but provide long life at an economic cost. Indeed, the ‘whole-life’ costs of timber bridges, coupled with the environmental advantages of using a renewable resource like timber, make them very competitive with other alternatives.
Timber, as a natural material complements any landscape, whether blending naturally into the countryside or providing a contemporary striking design alongside modern architecture in our towns and cities.
Timber bridges can take man forms and commonly provide spans up to about 70 m. They can be used as simple footbridges or designed to take vehicular traffic. Some common forms and typical spans are shown below:
Beams: single or multiple span; typical spans from 3 to 24 m
Girders: single or multiple span: typical spans from 9 to 45 m
Arches: typical spans from 12 to 70 m
Cable-stayed, suspension or tension ribbons: typical spans up to 70 m
Lift and swing bridges: typical spans up to 24 m
The long term durability of timber bridges is achieved through a combination of good conceptual and detailing design coupled with the optimum choice of materials – such as very durable hardwoods or in-depth preservative treatment and protection of the finished structure with properly maintained surface finishing treatments. There are many examples of timber bridges that have lasted for decades and even centuries.
The 'Horse Bridge' at Marsh Lock, Henley on Thames
Modern engineering techniques and materials are opening up new opportunities for designers. Longer span bridges can now be fabricated using Glued Laminated Timber or other forms of wood-based structural composites like Laminated Veneer Lumber and stressed laminated bridge decks. Modern jointing techniques now include adhesive bonded rods and fibre reinforced polymers which can replace the more traditional metal components such as nails, screws, bolts and connectors, and prefabricated devices such as hangers, brackets and straps.
With sustainability now a priority, timber bridges are already increasingly common but there is scope for more. For example some 1,000 new footbridges are needed to bring all UK footpaths and bridleways into good order – using timber this can be achieved economically and in an environmentally friendly manner.
