The Inclined Plane Bridge is a ,

Pennsylvania through truss A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, usually forming triangular units. The connected elements (typically straight) may be stressed from tension (mechanics), tensi ...

bridge that spans

Stonycreek River The Stonycreek River (also referred to as Stony Creek) is a tributary of the Conemaugh River, approximately 45 mi (72 km) long, in southwestern Pennsylvania in the United States. Course It rises in the mountains of eastern Somerset ...

in Johnstown,

Cambria County Cambria County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 133,472. Its county seat is Ebensburg. The county was created on March 26, 1804, from parts of Bedford, Huntingdon, and Somerset Cou ...

, in the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sove ...

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

. It connects the city to the lower station of the

Johnstown Inclined Plane The Johnstown Inclined Plane is a funicular in Johnstown, Cambria County, in the U.S. state of Pennsylvania. The incline and its two stations connect the city of Johnstown, situated in a valley at the confluence of the Stonycreek and the Li ...

. The bridge was listed on the

National Register of Historic Places The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance or "great artistic v ...

in 1988 and was documented by the

Historic American Engineering Record Heritage Documentation Programs (HDP) is a division of the U.S. National Park Service (NPS) responsible for administering the Historic American Buildings Survey (HABS), Historic American Engineering Record (HAER), and Historic American Landscapes ...

(HAER) in 1997.

History

On May 31, 1889, the

South Fork Dam The South Fork Dam was an earthenwork dam forming Lake Conemaugh (formerly Western Reservoir, also known as the Old Reservoir and Three Mile Dam, a misnomer), an artificial body of water near South Fork, Pennsylvania, United States. On May 31, 1 ...

on the

Little Conemaugh River The Little Conemaugh River is a tributary of the Conemaugh River, approximately 30 mi (48 km) long, in western Pennsylvania in the United States. The main branch rises in eastern Cambria County, along the western slope of the Appalachi ...

, upstream of Johnstown, collapsed. 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. 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

, a funicular. A bridge had to be built to connect Johnstown to the lower station of the incline, on the opposite side of

as the city. Work started on the bridge on June 11, 1890, with excavation of the bridge's

abutment An abutment is the substructure at the ends of a bridge span or dam supporting its superstructure. Single-span bridges have abutments at each end which provide vertical and lateral support for the span, as well as acting as retaining walls ...

s finished a week later. 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. The floodwaters continued downstream and eventually reached Pittsburgh. The

Works Progress Administration The Works Progress Administration (WPA; renamed in 1939 as the Work Projects Administration) was an American New Deal agency that employed millions of jobseekers (mostly men who were not formally educated) to carry out public works projects, i ...

appropriated $17,812 in October 1936 to repair the bridge's approach and replace stringers, handrails and the road deck. The Pennsylvania Department of Highways, the predecessor to the

Pennsylvania Department of Transportation The Pennsylvania Department of Transportation (PennDOT) oversees transportation issues in the Commonwealth of Pennsylvania. The administrator of PennDOT is the Pennsylvania Secretary of Transportation, currently Yassmin Gramian. Presently, Pe ...

(PennDOT), acquired the bridge in 1964. It was listed on the

on June 22, 1988. On September 1, 2000, PennDOT undertook a $2.3 million renovation of the bridge and the access road leading to it. 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.

Design

The Inclined Plane Bridge was made from

wrought iron Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag Inclusion (mineral), inclusions (up to 2% by weight), which give it a ...

and steel riveted together to form a Pennsylvania

truss A truss is an assembly of ''members'' such as beams, connected by ''nodes'', that creates a rigid structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assembl ...

. The Pennsylvania, or Petit, truss is "essentially a

Pratt truss A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, usually forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or ...

" with the outermost horizontal girders being "

polygonal In geometry, a polygon () is a plane figure that is described by a finite number of straight line segments connected to form a closed ''polygonal chain'' (or ''polygonal circuit''). The bounded plane region, the bounding circuit, or the two to ...

" and having "subdivided panels" to "stiffen the truss under heavy loads." At long, the Inclined Plane Bridge is relatively short for a Pennsylvania truss; bridges of this sort are generally long.

References

Sources

* * *

External links

* {{NRHP bridges Bridges completed in 1891 Road bridges on the National Register of Historic Places in Pennsylvania Buildings and structures in Johnstown, Pennsylvania Bridges in Cambria County, Pennsylvania Pennsylvania truss bridges in the United States Wrought iron bridges in the United States Historic American Engineering Record in Pennsylvania 1891 establishments in Pennsylvania National Register of Historic Places in Cambria County, Pennsylvania Steel bridges in the United States

History

Design

See also

References

Sources

External links