It's big, it's green and it's back! The Royal Engineers' General Support Bridge, a steroid-fed mobile structure, was on show at Civils 98 and it is returning to Birmingham next year for Civils 2000.
At 35m long, the GSB can carry a 70t tank. It is transported on three eight-axle trucks with a combined weight of 90t.
But the colossus takes only 45 minutes to erect. Crowds at Civils 98 were enthralled as a team of REs raced against the clock to assemble the bridge. This year's visitors will be able to see if the REs can beat their best time - demonstrations are being staged on each of Civils' four days.
The GSB is a modular structure designed by defence firm Vickers. Box section elements in 2m, 4m and 8m lengths, and a pair of 8m ramp elements, are carried on two of the trucks. These are positioned either side of the third vehicle, equipped with a telescopic carbon-fibre boom.
After the boom is extended across a river, deck elements are lifted from the adjacent trucks, suspended from the boom, and hauled along it to position. The deck elements are pinned together. When the span is completed the whole is lowered to support its own weight. The boom is finally retracted.
A team of 10 highly trained operators are needed to ensure the operation goes smoothly, an RE spokesman said.
A 50m model of the GSB is being developed at the moment, he added. To improve strength to weight ratios over longer spans post-tensioning cables are being added into the structure.
The 35m bridge has a design life of 15,000 tank crossings; there are a total of 30 units. GSBs were used in the early stages of helping Kosovo back to its feet following this year's conflict.