The Bailey bridge is a portable pre-fabricated truss bridge, designed for use by military engineering units to bridge up to 60 m (200 ft) gaps. It requires no special tools or heavy equipment for construction, the bridge elements are small enough to be carried in trucks, and the bridge is strong enough to carry tanks.
A bailey bridge is a prefabricated bridge used by combat engineers, which can be rapidly constructed on the battlefield. The system was devised by British engineer Sir Donald Bailey during World War 2, and consists of a basic diamond braced unit of welded steel, 3×1•5 m/10×5 ft square, which can be easily manipulated by a squad of six men and joined together to make complex bridging structures.
A large part of what made Bailey bridges as successful and unique as they were is the modular design, and the fact that it could be assembled with minimal aid from heavy equipment. Most, if not all, previous designs for military bridges required cranes to lift up the preassembled bridge and lower it into place. Finally, the modular design allowed engineers to build each bridge to be as long and as strong as needed, doubling or tripling up on the supportive side panels, or on the roadbed sections.
Each unit constructed in this fashion creates a single 10 ft (3 m) long section of bridge, with a 12 ft (4 m) wide roadbed.
For added strength several panels (and transoms) can be bolted on either side of the bridge, up to three. With three panels across and two high, the Bailey Bridge can support tanks over a 200 ft (60 m) span.
An astonishing feature of the Bailey bridge is its ability to be "launched" from one side of a gap. In this system the frontmost portion of the bridge is angled up with wedges into a launching nose and most of the bridge is left without the roadbed and ribands. The bridge is placed on rollers and simply pushed across the gap, using manpower or a truck or tracked vehicle, at which point the roller is removed (with the help of jacks) and the ribands and roadbed installed, along with any additional panels and transoms that might be needed.
The Bailey bridge was originally developed by the military to construct quickly across rivers in wartime. There's a lake to the right of the bridge and a hydroelectric dam to the left.
They are a bit noisy when you drive over them but they are very stable. There isn't much traffic here as it's almost at the end of a valley. Cars, trucks and even tanks can easily pass through them.
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