Moving troops into battle-torn Kosovo last year saw the Royal Engineers' General Support Bridge - a muscular mobile structure - in action under emergency conditions for the first time. Units were used to relay US heavy armour across otherwise impassable rivers. One of the bridges is still serving civilians and peace keepers there.
The GSB has a 35m span and can carry a 70t tank. The deck is broken into segments, transported on three eight-axle trucks with a combined weight of 90t. This is testosterone-enhanced mobile plant.
RE Lieutenant Colonel Bob Shuler describes the GSB as 'relatively complex to build.' A team of 10 highly trained operators is needed to ensure assembly goes smoothly. But the colossus takes less than 45 minutes to erect.
The modular structure has been designed and supplied 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 three trucks. These are positioned either side of the third vehicle, equipped with a telescopic carbon fibreboom.
After the boom is extended across a river, deck elements are lifted from the adjacent trucks, suspended from the boom, and hauled along it into position. The deck elements are pinned together and once the span is complete the whole structureis lowered to support its own weight. The boom is finally retracted.
The bridge has a design life of 15,000 tank crossings; there are a total of 30 units.
Shuler reports that two new versions of the GSB are being tested - a 50m single span structure and a double span bridge. Vickers is improving the strength to weight ratio in the 50m model by adding post-tensioning cables.
The double span version will be supported mid-length on a pier launched, like the individual deck elements, along the beam. A pontoon is being developed for deployment where suitablefootings for the pier cannot be found.
In addition to the 35m span GSB a shorter span tank bridge was deployed in Kosovo, says Shuler. Using a specially equipped tank hull, two GSB ramp elements can be positioned on top of existing but damaged bridge structures.
Shuler points out that using engineered abutments for support and the relatively shortspan of the tank bridge makes erection cheaper and faster than for the GSB.