Trusses (structural elements)

In engineering, structural members such as beams, bars, or rods, usually fabricated from straight pieces of metal or timber, that form a series of triangles lying in a single plane; based on the principle that a triangle cannot be easily distorted by stress. Trusses were probably first used in primitive lake dwellings during the early Bronze Age, about 2500 BCE. The first trusses were built of timber. The Greeks used trusses extensively in roofing; trusses were used for various construction purposes in the European Middle Ages. A major impetus to truss design came in the development of covered bridges in the United States in the early 19th century. Cast iron and wrought iron were succeeded by steel for railroad truss bridges. Trusses are also used extensively in machinery, such as cranes.