Science Projects And Inventions

A Clun Castle steam engine crossing the Royal Albert Bridge, built by 1. K. Brunei in the 1850s in England.

The viaduct above the Upper Genesee Falls at Portageville, New York, exemplifies the truss bridge.

The concept of a bridge built from trusses— frameworks of straight parts connected to form a pattern of triangles—was first described by the Italian father of Western architecture, Andrew Palladio, in 1570. However, trussed frames had already been in use by the ancient Egyptians and Greeks, and simple timber trusses are believed to have been used in bridge construction in Europe by the time Palladio was writing.

However, the heyday of the truss bridge came in the early nineteenth century in the United States. The impetus came from the development of rail transport and the need to convey heavy rail vehicles safely across spans of varying length. Trussed frameworks offer an adaptable solution, rather like a toy construction set on a grand scale. The nineteenth- century explosion in truss designs was kick-started by Ithiel Town (1784-1844), who filed a patent for his wooden lattice truss bridge in 1821. Town was a renowned New England architect, whose design allowed unskilled workers to construct bridges quickly without the need to transport huge sections.

Truss bridges were often covered by a roof, and two bridges made to Town's design survive to this day in Connecticut, his home state. Part of the design's success can be attributed to Town's skill at marketing, and his control of the patent made him a rich man.

From the 1870s until the 1930s, iron replaced wood in truss bridge construction, and steel replaced iron thereafter. Many different designs, like the Pratt, Warren, and Howe trusses, were developed. The world's longest truss bridge, at 2.3 miles (3.7 km), connects Kansai International Airport to Osaka in Japan. But steel trusses are less suitable for long spans, for which the suspension bridge has now become the usual choice.