Because of the curve of the bridge an early structural decision was made to use a closed box girder to carry the resulting torsion, or twisting.

The relatively short spans (up to just over 30m) meant that we wanted to make the girder carry the loads on its own, without additional help from, say, cable-stays or arches. In any event such structural forms as these were not considered appropriate for the landscape.

The need to minimise the length of the approaches meant that we tried to limit the depth of the box girder below the deck level (a 100mm extra depth on the deck means a 2m longer ramp at 1:20). The box was therefore stiffened by the upstand on the outside of the curve, the upstand being necessary anyway as part of the requirement for an equestrian bridge.

The box girder is formed using sheet weathering steel plate and is stiffened internally using smaller plates at right angles locally where the stresses are highest. This is an efficient use of steel, optimising weight and cost. Cross diaphragms are at 1.8m centres. These help support the deck plates and stop it distorting as it twists.

The steel piers are also boxes fabricated from plate but with the necessary stiffeners on the outside. On a painted steel bridge this would be a lot of additional surface area to paint but this is not an issue with weathering steel.