Box girder

Girder Gird"er, n. [From {Gird} to encircle.] [1913 Webster] 1. One who, or that which, girds. [1913 Webster]

2. (Arch. & Engin.) A main beam; a stright, horizontal beam to span an opening or carry weight, such as ends of floor beams, etc.; hence, a framed or built-up member discharging the same office, technically called a compound girder. See Illusts. of {Frame}, and {Doubleframed floor}, under {Double}. [1913 Webster]

{Bowstring girder}, {Box girder}, etc. See under {Bowstring}, {Box}, etc.

{Girder bridge}. See under {Bridge}.

{Lattice girder}, a girder consisting of longitudinal bars united by diagonal crossing bars.

{Half-lattice girder}, a girder consisting of horizontal upper and lower bars connected by a series of diagonal bars sloping alternately in opposite directions so as to divide the space between the bars into a series of triangles. --Knight.

{Sandwich girder}, a girder consisting of two parallel wooden beams, between which is an iron plate, the whole clamped together by iron bolts. [1913 Webster]