Archive for April, 2010

Originally published in the BDHS newsletter, January 2010

By Frank Hammock

It’s made of stringers, portal struts, top and bottom chords, top and bottom lateral bracing, sway bracing, portal and counter bracing, diagonals, inclined end and vertical posts, floor beams, and panels. Geometrically, it’s composed of a series of triangles joined together by pins and rivets that is either structurally built above or below the main traffic component called the deck. From its design, it is only subject to compression and tension forces, whereby bending forces have been eliminated. Thus, the various arrangements of its members make the final determination as to what type it will be categorized as—boasting such names as Parker, Howe, Camelback, Queen Post, Warren, Kellogg, Stearns, and Pratt. These are the basic descriptions of the Truss bridge that originated in the history of structural engineering from as early as 1820, to a more common use era of 1870 to 1930 during the railroad boom. (more…)

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