Inclined Plane Bridge

The Inclined Plane Bridge is a 237-foot (72 m), Pennsylvania through truss bridge that spans Stonycreek River in Johnstown, Cambria County, in the U.S. state of Pennsylvania. It connects the city to the lower station of the Johnstown Inclined Plane. The bridge was listed on the National Register of Historic Places in 1988 and was documented by the Historic American Engineering Record (HAER) in 1997.

Inclined Plane Bridge
Coordinates40°19′33″N 78°55′33″W
CarriesSR 3022 spur
CrossesStonycreek River
LocaleCambria, Pennsylvania, United States
Other name(s)Bridge in Johnstown City
Maintained byPennDOT
NBI #113022001000000[1]
Characteristics
Total length72.2 m (237 ft)[1]
Width5.7 m (19 ft)[1]
Load limit5 short tons (4.5 t)
History
Constructed bySparks and Evans
BuiltJune 1, 1891
MPSHighway Bridges Owned by the Commonwealth of Pennsylvania, Department of Transportation TR
NRHP reference No.88000805[2]
Added to NRHPJune 22, 1988
Inclined Plane Bridge
Location of the Inclined Plane Bridge in Pennsylvania

History

On May 31, 1889, the South Fork Dam on the Little Conemaugh River, upstream of Johnstown, collapsed.[3] The resulting deluge devastated the city, killing over 2,000 people. As the city rebuilt, the Cambria Iron Company started work on a residential development atop Yoder Hill, overlooking the city.[3] To provide easy transportation across the steep slope for the residents of the new community of Westmont, as well as to function as an escape route for future floods, the company opted to construct the Johnstown Inclined Plane, a funicular. A bridge had to be built to connect Johnstown to the lower station of the incline, on the opposite side of Stonycreek River as the city.[3]

Work started on the bridge on June 11, 1890, with excavation of the bridge's abutments finished a week later.[4] By March 20, 1891, only the approach to the bridge remained to be completed. The bridge, officially, was opened on June 1, 1891, at the same time as the incline. On March 17, 1936, nearly 4,000 people crowded on the approach, the bridge, and numerous boats to escape to higher ground via the incline as Stoneycreek and Conemaugh Rivers overflowed their banks.[5] The floodwaters continued downstream and eventually reached Pittsburgh.

The Works Progress Administration appropriated $17,812 in October 1936 to repair the bridge's approach and replace stringers, handrails and the road deck.[6] The Pennsylvania Department of Highways, the predecessor to the Pennsylvania Department of Transportation (PennDOT), acquired the bridge in 1964.[6] It was listed on the National Register of Historic Places on June 22, 1988.[2] On September 1, 2000, PennDOT undertook a $2.3 million renovation of the bridge and the access road leading to it.[7] Work was suspended from April to September 2001, to allow operation of the incline. The renovations were completed on December 14, 2001, after PennDOT finished repairs to the bridge deck.[7]

Design

The Inclined Plane Bridge was made from wrought iron and steel riveted together to form a Pennsylvania truss.[8][9] The Pennsylvania, or Petit, truss is "essentially a Pratt truss" with the outermost horizontal girders being "polygonal" and having "subdivided panels" to "stiffen the truss under heavy loads."[9] At 237 feet (72 m) long, the Inclined Plane Bridge is relatively short for a Pennsylvania truss; bridges of this sort are generally 250 to 600 feet (76 to 183 m) long.[1][9]

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See also

References
  1. Federal Highway Administration (2010). "State: PA, Place Name: Johnstown, County: Cambria, NBI Structure Number: 113022001000000". National Bridge Inventory. Nationalbridges.com (Alexander Svirsky). Retrieved June 21, 2011. Note: this is a formatted scrape of the 2010 official website, which can be found here for Pennsylvania: "PA10.txt". Federal Highway Administration. 2010. Retrieved June 21, 2011.
  2. "NPS Focus". National Register of Historic Places. National Park Service. Retrieved January 8, 2011.
  3. Gruen 1997, p. 2.
  4. Gruen 1997, p. 6.
  5. Gruen 1997, pp. 8–9.
  6. Gruen 1997, p. 9.
  7. Springirth 2006, p. 118.
  8. Davis 1982, p. 4.
  9. Gruen 1997, p. 7.

Sources
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