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Granite Street Bridge

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1902, American Bridge Company of New York. Granite St. at U.S. 2, City of Montpelier

The Granite Street Bridge was built at a time of significant change in the bridge industry. Its two-hundred-foot span is carried by a Baltimore through truss, a variant of the Pratt truss with subdivided panels widely used by the Baltimore and Ohio Railroad after 1871. Its riveted steel frame uses four different forms for its diagonal members, each precisely dimensioned for its location within the structure. Crested builder's plates and an outrigger pedestrian sidewalk, with rosettes, fluted end posts, orb finials, and interlacing on its rails, decorate the construction. It is a rare survivor of a time when bridge construction in Vermont was solely the domain of towns that negotiated their particular needs with regional bridge companies.

Circumstances soon encouraged greater standardization. First, the industry consolidated. Granite Street's builder, the American Bridge Company, was formed when J. P. Morgan merged twenty-four independent bridge contracting firms in 1900. Next, the state became involved in bridge standards, offering engineering assistance (1912) and then funding (1915). Finally, the Vermont flood of 1927 destroyed some 1,200 bridges in twenty-four hours. For efficiency's sake, their reconstruction necessitated standardization to a degree previously unknown in America. As Vermont built more than 1,600 bridges in the three years after the flood, the state became a national laboratory for standardized design. With the collaboration of engineers on loan from the American Bridge Company, the state established models based on standard widths and maximized the use of rolled I-beams produced by American Bridge's parent company, U.S. Steel. Spans under 100 feet were to be Warren pony trusses, 100 to 160 feet to be Pratt through trusses, and over 160 feet were designated to be Parker trusses.

With many bridges in a compact area, Montpelier is a good place to consider the impact of the state's rebuilding program on Vermont's metal truss bridges. Only the Granite Street bridge and a railroad bridge over the Winooski survived the flood. The city's other bridges all required replacement. The 69-foot Langdon Street and 78-foot School Street crossings, both 1928, over the North Branch are Warren polygonal pony trusses by the American Bridge Company. The 166-foot Taylor Street Bridge (1929) over the Winooski is a Parker through truss by the Berlin Construction Company of Connecticut. All display a stockiness and uniform membering that leave Granite Street looking graceful, if also archaic, in comparison.

Writing Credits

Author: 
Glenn M. Andres and Curtis B. Johnson
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Citation

Glenn M. Andres and Curtis B. Johnson, "Granite Street Bridge", [Montpelier, Vermont], SAH Archipedia, eds. Gabrielle Esperdy and Karen Kingsley, Charlottesville: UVaP, 2012—, http://sah-archipedia.org/buildings/VT-01-WA35.

Print Source

Cover: Buildings of Vermont

Buildings of Vermont, Glenn M. Andres and Curtis B. Johnson. Charlottesville: University of Virginia Press, 2013, 310-310.

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