Box Girder
A box or tubular girder is a girder that forms an enclosed tube with multiple walls, rather than an I or H-beam. Originally constructed of riveted wrought iron, they are now found in rolled or welded steel, aluminium extrusions or pre-stressed concrete.
Compared to an I-beam, the advantage of a box girder is that it better resists torsion. Having multiple vertical webs, it can also carry more load than an I beam of equal height (although it will use more material than a taller I beam of equivalent capacity).
The distinction in naming between a box girder and a tubular girder is imprecise. Generally the term box girder is used, especially if it is rectangular in section. Where the girder carries its "content" inside the box, such as the Britannia Bridge, it is termed a tubular girder. Tubular girder is also used if the girder is round or oval in cross-section, such as the Royal Albert Bridge.
Where a large box girder contains more than two walls, i.e. with multiple boxes, it is referred to as a cellular girder.
Read more about Box Girder: Development of The Box Girder, Box Girders in Bridges, Safety Concerns Over Box Girder Bridges
Famous quotes containing the word box:
“Nobody has ever before asked the nuclear family to live all by itself in a box the way we do. With no relatives, no support, we’ve put it in an impossible situation.”
—Margaret Mead (1901–1978)