BRIDGES AND
TUNNELS OF
ALLEGHENY COUNTY,
PENNSYLVANIA
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HAER
Smithfield Street Bridge, Pittsburgh, PA
01 Cover Page
02 Foreword
03 Ferries
05 Monongahela
Bridge and
Fire
12 Masonry
17 Removal
of Old and
Erection of
New Bridge
18 Flooring
19 Ornamental
Towers and
Painting
22 Alterations
23 Footnotes
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Smithfield Street Bridge, Pittsburgh, PA Historic American Engineering Record PA-2 page 9
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Suspension Bridge Demise In 1859 an agreement was made with the Pittsburgh and Birmingham Railway Company, a horse car line then being constructed from Pittsburgh to the South Side across the river, to permit the line to cross the bridge at the price of fifteen dollars per car each month. In 1865 the structure was lit by gas and the foot toll was reduced to one cent per person. (21) In 1861, a wooden truss bridge was built a little further upstream at South Tenth Street; (22) Roebling's span was now not the only one crossing the river and in later years it was increasingly referred to as the Smithfield Street Bridge. The structure during its years of service was often sorely tried -- sometimes when it was crowded with people viewing a steamboat race and sudden rushes would be made from one side of the bridge to the other. (23) Such conditions afforded a real test of the designer's foresight in providing various features that assured enduring stability. The bridge continued in service for thirty-five years, carrying the heaviest kind of street traffic, horse cars, steam rollers, eight-horse teams pulling heavy trucks loaded with iron and machinery. The multiple span arrangement though quite satisfactory for an aqueduct with its loading constant or uniform in all spans is under a disadvantage in a suspension bridge carrying variable loading. Despite the system of inclined stays which Roebling had installed, a loaded span sometimes deflected as much as two feet with a corresponding smaller rise of the adjoining spans. Not only the designer but the profession profited by this experience. (24) Due to the enormous volume of traffic on Roebling's bridge, it began to show signs of strain and the Board of Managers of the Bridge Company decided to look into the possibility of providing a new structure. On February 1, 1871, bids were presented to the Board, but soon afterward the City of Pittsburgh tried to secure the franchise. This brought out a stockholder's meeting on May 27, 1872, contesting the city's right to such action. (25) This difficulty retarded the new improvement and the Panic of 1873 with its resultant difficulties prevented anything being done, but in the summer of 1880 the Board finally decided to demolish the Roebling bridge and construct a new one. (26) The Board of Directors of the Bridge Company called to their aid a local engineer, Charles Davis (1837-1907) who submitted a design for another suspension bridge. Davis was one of those American engineers who seem to have learned their profession "in the field", so to speak, particularly in railway surveying. He had been consulting engineer for Pittsburgh's Point (suspension) Bridge (1875-77) and in 1881 was elected Engineer of Allegheny County, a position he held until his death. (27)
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Introduction Last modified on
30-Sep-99
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