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River Road Bridge

   


River Road Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: November 8, 2015
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Key Facts

Facility Carried / Feature Intersected
River Road Over Railroad (New Jersey Transit, Raritan Valley Line)
Location
Branchburg: Somerset County, New Jersey
Structure Type
Metal Deck Girder, Fixed and Approach Spans: Wood Stringer (Multi-Beam), Fixed
Construction Date and Builder / Engineer
1886 By Builder/Contractor: Unknown

Technical Facts

Rehabilitation Date
1949
Main Span Length
47 Feet (14.3 Meters)
Structure Length
81 Feet (24.7 Meters)
Roadway Width
13.8 Feet (4.2 Meters)
Spans
1 Main Span(s) and 2 Approach Span(s)
NBI Number
1861159

Historic Significance Rating (HSR)

Bridge Documentation

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

This is a rare and unusual case where a bridge is historic not because of its superstructure, but on the merits of its substructure only. The superstructure of this bridge dates to 1949 and for the purposes of discussion and evaluation by HistoricBridges.org is being ignored, as it lacks any historic significance. The substructure of this bridge however is extremely rare and incredible in design. It is compose of cast iron bents which in turn rest on stone foundations. The use of cast iron as a major structural element in United States bridges is a category that typically marks the rarest of historic bridges, and the oldest of metal bridges. Apparantly dating to 1886, these cast iron bents are actually relatively late examples of major cast iron structural elements in a bridge, since by this time wrought iron was more common instead. However, cast iron from any date remains among the rarest things to find in any bridge. Even more unusual is in this case, the cast iron was used for the substructure. As rare as cast iron superstructures are, cast iron substructures are even moreso. Another remarkable aspect of these cast iron bents is the fact that the four bents each appear to have been cast as a single element, rather than smaller castings that would be fitted together, which is what was more common. To cast items as large as these bents as a single casting is a rare and amazing demonstration of the skill of 19th century foundries in America.

Today, while the bents may be safe for use, they have not been maintained and have rusted severely causing section loss and scaling. This has had a devastating effect as it has irreversibly damaged the beautiful architectural elements of many portions of the bents. It is truly tragic to see such a rare structure allowed to slowly deteriorate in this manner. What remains of these bents should immediately be cleaned, repaired, and painted to ensure that the architectural elements that do remain are not further damaged.

Information and Findings From New Jersey's Historic Bridge Inventory

 Summary

The bridge has been rated not eligible by the NJT Historic Bridge Survey due to the undistinguished nature of the timber stringer superstructure which was built in 1949 when the vertical clearance was raised. What is of technological merit are two pairs of well-detailed cast iron bents composed of hexagonal columns and cross bracing. They appear to be monolithic castings. Although the bridge itself is insignificant, the bents are exceptionally unusual and significant structural elements.

Physical Description

The single-lane 81'-long bridge is three span resting on stone abutments and impressive monolithic cast-iron column bents on ashlar plinths. The center span of the superstructure, placed in 1949 has rolled steel I beam fascia stringers and interior wood stringers. Two rolled section floor beams are hung from the fascia stringers. The shorter end spans are exclusively wood stringers. The superstructure has been raised from its original elevation and the stone abutments and pier bases have concrete caps. The bridge has a timber deck, timber curbing, and wood railings. The handsome cast-iron column bents consist of two sets of paired columns with lateral and diagonal cross bracing. The columns are octagonal in cross section and are tapered and finished with pedestals and capitals. The lateral and diagonal bracing are x-shaped in cross section, except for the top and bottom laterals which are t-shaped. The bents appear to be monolithic, one-piece castings. The number "10" is cast in the eastern piers, and the number "12" is cast in the western piers.

Historical and Technological Significance

Although the bridge has been altered by the 1949 rebuilding of the superstructure, the two castiron columns bents are exceptionally significant examples of a very rare type of bridge structural element. According to Central Railroad of New Jersey records, the overpass bridge was initially constructed in 1886, and the superstructure was raised in 1949 with the original bents remaining. The railroad right-of-way was originally developed in 1848 by the Somerville and Easton Railroad and later taken over by the Central Railroad of New Jersey. The cast-iron bents appear to be monolithic castings, and they are highly crafted. No other bents of this type have been identified to date. Much of the early success and eventual general acceptance of metal bridges and related structural elements is directly attributable to the skill of foundry men. These bents stand as a record of their knowledge and ability. Cast iron came into increasing use as a structural element in the early-19th century but was replaced with other materials such as wrought-iron, steel, and concrete by the end of the century. The NJT Bridge Survey incorrectly identified the piers as "Phoenix Columns," which were always segmental, riveted, wrought-iron structural elements patented and manufactured by the Phoenix Bridge Company of Phoenixville, Pennsylvania. In the 1880s the Phoenix Bridge Company produced many other types of wrought-iron, cast-iron and steel structural elements. The NJT Bridge Survey recommends a status of not eligible for the bridge; because of the rarity of the cast-iron bents, A. G. Lichtenstein recommends a status of eligible.

Boundary Description and Justification

The boundary is limited to the bents. The other portions of the bridge are not significant.

Sources

DeLeuw, Cather, and Company. New Jersey Transit Historic Bridge Survey, 1991. New Jersey Department of Transportation. Bridge Plans, 1949.

Bridge Considered Historic By Survey: Yes

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