The architect was appointed by the London Borough of Newham to plan a high-level link between two school buildings that stand 67 m apart and are separated by a busy main road. The architect鈥檚 first design in stainless steel and glass was rejected as too expensive, and, last autumn, the practice was sent back to the drawing-board with a budget of 拢500 000. The result, which was designed with structural engineer Techniker, was a cheaper but more dynamic and sculptural design. 鈥淲e knew that the only cheap enclosure was a fabric structure,鈥� explains Mike Russum, partner in Birds Portchmouth Russum. 鈥淪o we supported the fabric around steel hoops like a covered-wagon. We also wanted double curvatures on the fabric to keep it taut. Then we thought, what happens if we make the hoops asymmetrical and alternate them? So the structure became like a range of snowy peaks.鈥�
Every element in the design has been carefully examined to reduce costs, and at the same time, exploited for its sculptural value. The steel hoops supporting the fabric roof were alternated to give the 鈥渟nowy peaks鈥� effect, but also split into two smaller sections so they would fit into a galvanising bath. The split sections also allowed the designer to fit a round light fitting between the two adjoining end flanges.
The other basic elements are a floor, a handrail on either side and a supporting structure. The structure is provided by a pair of steel universal beams running along either side of the bridge and spanning between columns of folded steel plate. The beams were specified at 900 mm deep, the largest standard size available, and the handrails in tubular steel were simply planted on the top. A steel deck spans between the lower chords of the beams. The supporting columns are designed out of simple steel plate, yet tapered and curved at the top to add stiffness.
The sculptural design culminates in a spectacular set piece at the midpoint of the bridge over the road. Both sides of the bridge extend at right angles from the existing school buildings and kink slightly to meet at the midpoint. Here, the two intersecting geometries have been teased out to provide a viewing balcony on either side with fitted seats and oriel windows.
Russum acknowledges that the fabric enclosure could be ripped by a determined vandal with a sharp knife. But he points out that the school has no record of vandalism, and that the fabric is kept well out of reach and, in the worst event, could be replaced in modules between steel hoops.
However, he thinks the pupils will be won over by the attractiveness of the bridge. 鈥淚t literally and symbolically unites the school,鈥� he says.
Credits
Client Education Department, London Borough of Newham Architect Birds Portchmouth Russum Structural Engineer Techniker Cost Consultant Gardiner & Theobald Main Contractor C Spencer, Chepstow
