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In architecture a girder is a main beam; a straight, horizontal beam to span an opening or carry weight, such as the ends of floor beams, etc. and hence, a framed or built-up member discharging the same office, technically called a compound girder.
Wooden girders were sometimes cut in two longitudinally and an iron plate inserted between the pieces, and the whole bolted together. This species of girder was called a sandwich-girder.
During the great engineering period of the Victorians, for bridges cast-iron girders were sometimes cast in lengths of 40 feet and upwards, but when the span to be crossed was much greater than 40 feet, recourse was had to wrought-iron, or to trussed, lattice, or box girders, and cast-iron was little used by the start of the 20th century.
A trussed-girder is a wooden girder strengthened with iron.
A lattice-girder is a girder consisting of two horizontal beams united by diagonal crossing bars, somewhat resembling wooden lattice-work.
A box-girder is a kind of girder resembling a large box, such as those employed in tubular bridges. There are also bowstring-girders, which are varieties of the lattice-girder, and consist of an arched beam, a horizontal tie resisting tension and holding together the ends of the arched rib, a series of vertical suspending bars by which the platform is hung from the arched rib, and a series of diagonal braces between the suspending bars.
The term girder is also applied in architecture to a small circular band around a column - like the steel band around an old wooden barrel (which is also called a girder).
Research Girder
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