PEDESTRIAN & CYCLIST BRIDGE, TAMAR VALLEY WORLD HERITAGE SITE
In October 2005 we won a limited competition involving a new bridge for the then proposed new World Heritage Site. On the competition shortlist were also Clash Associates and Wilkinson Eyre Architects. In 2006 UNESCO declared the Tamar Valley Mining District a World Heritage Site and it was also the year of 200 anniversary of the birth of Isambard Kingdom Brunel, designer of the Royal Albert Bridge on Tamar at Saltash. The new bridge was to cross the Tamar Valley and link the town of Gunnislake with the mining heritage areas. It is a unique structure, a stress ribbon with a Y-shaped plan, linking three abutments at different ground levels, with three spans of 45 m, 47 m and 37 m. The Y-shaped plan form of the bridge followed from an analysis of desire lines on the east side of the river, with two different paths and levels to be connected to the bridge, and was based on practical and logical consideration of the problem of flooding. The Y-shaped plan provides excellent resistance to lateral loads during an extreme flood, with upstream branch of the Y acting in tension to resist the flood loads and prevent high transverse bending effects in the bridge deck. A special saddle shaped element, the main visual attractor of the otherwise very low key bridge, forms a link that joins together the main span and the two arms of the Y over an inclined prop. Its flowing shape provided a gradually changing stiffness and thus “softened” a structural hard spot and reduced peak stresses in the deck.
- Bridge Engineer :
- Flint & Neill Partnership
