Identifier: americanrailwayi00cool (find matches)
Title: The American railway; its construction, development, management, and appliances
Year: 1889 (1880s)
Authors: Cooley, Thomas McIntyre, 1824-1898 Clarke, Thomas Curtis, 1827-1901
Subjects: Railroads Railroads
Publisher: New York : C. Scribner's sons
Contributing Library: University of California Libraries
Digitizing Sponsor: Internet Archive

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The New Portage Viaduct. by wrought-iron columns, two pairs of columns forming a skeletontower 20 feet wide and 50 feet long on the top. There are six ofthese towers, one of which has a total height from the masonry tothe rail of 203 feet 8 inches. There are over 1,300,000 pounds ofiron in this structure. The fundamental idea of a bridge is a simple beam of wood.If metal is substituted it is still a beam with all superfluous partscut away. This results in what is called an I beam. Whengreater loads have to be carried, the I beam is enlarged andbuilt up of metal plates riveted together and thus becomes a plategirder. These are used for all short railway spans. For greaterspans the truss must be employed. Before referring, however, to examples of truss bridges, a de-scription should be given of the Britannia Bridge, built by Robert 8o FEATS OF RAILWAY ENGINEERING.
Text Appearing After Image:
enai Straits, Noah Wales. Stephenson in 1850, over the Menai Straits. This g-reat con-struction carries two Hnes of rails and is buih of two square tubes,side by side, each being continuous, 1,511 feet long, supported ateach extremity and at three intermediate points, and having twospans of 460 feet each and two spans of 230 feet each. The tow-ers which support this structure are of very massive masonry, andrise considerably above the top of the tubes. These tubes areeach 27 feet high and 14 feet 8 inches wide ; they are built up ofplate iron, the top and bottom being cellular in construction, andthe sides of a single thickness of iron. The tubes for the longspans were built on shore and floated to the side of the bridge andthen lifted by hydraulic presses to their final position. The rapidcurrent, and other considerations, made the erection of false worksfor these spans impracticable. The beautiful suspension bridge,built by Telford in 1820, over the Menai Straits, is only a mileaway

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