John A. Roebling's Allegheny Aqueduct and Smithfield Street Bridge: Nineteenth-century innovation in multi-span suspension bridges
Author(s): |
Stephen G. Buonopane
Dario A. Gasparini |
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Medium: | conference paper |
Language(s): | English |
Conference: | 6th International Congress on Construction History (6ICCH 2018), July 9-13, 2018, Brussels, Belgium |
Published in: | Building Knowledge, Constructing Histories [2 vols.] |
Page(s): | 399-407 |
Year: | 2018 |
Abstract: | John A. Roebling's first two suspension bridges—the 1845 Allegheny Aqueduct (7 spans of 160 ft) and the 1846 Smithfield Street Bridge (8 spans of 188 ft)—in Pittsburgh, Pennsylvania were multi-span bridges constructed on the stone piers of earlier wooden covered bridges. A critical design condition for multi-span bridges was the ability to accommodate unequal gravity loads on adjacent spans. The effects of unequal loads depend on the type of cable saddles, the design of the deck or trunk, transfer of load between cables and trunk during construction and pretensioning of diagonal stays. Comprehensive historical assessment of these bridges is achieved through examination of archival writings and calculations; original bridge specifications; contemporary published accounts of construction and performance; and modern structural analyses. Roebling was deeply familiar with existing design knowledge, yet developed two different innovative solutions that created the foundation for the daring and success of his later bridges. |