Box girder bridges
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| Ancestor | Tubular bridge |
|---|---|
| Related | jetway, skyway |
| Descendant | segmental bridge |
| Carries | Pedestrians, automobiles, trucks, light rail, heavy rail |
| Span range | Medium |
| Material | Steel, reinforced concrete, prestressed concrete |
| Movable | Possible |
| Design effort | High |
| Falsework required | Yes, if cast-in-place reinforced or prestressed concrete is used, which is typical for freeway overpasses |
A box girder bridge is a bridge in which the main beams comprise girders in the shape of a hollow box. The box girder normally comprises either prestressed concrete, structural steel, or a composite of steel and reinforced concrete. The box is typically rectangular or trapezoidal in cross-section. Box girder bridges are commonly used for highway flyovers and for modern elevated structures of light rail transport. Although normally the box girder bridge is a form of beam bridge, box girders may also be used on cable-stayed bridges and other forms.
In 1919, Major Gifford Martel was appointed head of the Experimental Bridging Establishment at Christchurch, Hampshire, which researched the possibilities of using tanks for battlefield engineering purposes such as bridge-laying and mine-clearing. Here he continued trials on modified Mark V tanks. The bridging component involved an assault bridge, designed by Major Charles Inglis RE, the Canal Lock Bridge, which had sufficient length to span a canal lock. Major Martel mated the bridge with the tank and used hydraulic power generated by the tank's engine to manoeuvre the bridge into place. For mine clearance the tanks were equipped with 2-ton rollers.
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