Curved steel tubes feature in two striking new footbridges in southern England. Both comprise twin parabolic tubular arches with shallow decks suspended beneath by rod hangers, but there the similarity ends.
On the £410,000, 41m span bridge linking two of SmithKline Beecham's sites in Harlow, Essex, designer Amec Design & Management canted the arches inwards until they almost touch in the middle. By contrast, the arches on the 30m span Renaissance Bridge across the Great Ouse at Bedford spring from a single point on each bridge and cant outward.
So distinctive is the effect produced that the £400,000 crossing is now becoming known as the 'Butterfly Bridge'. Designer was Chris Wilkinson Architects with engineer Jan Bobrowski, client was Bedford Borough Council and Littlehampton Welding was the main contractor.
Steelwork contractor for the Harlow bridge was SH Structures, and the tubes for both bridges were bent by the Angle Ring Company.
Angle Ring's ability to bend tubes up to 915mm diameter, and rectangular hollow sections up to 650mm square, to simple circular curves, to elliptic or parabolic curves, or to co-ordinates offers bridge designers new design flexibility, the company claims.