This bridge is one of Hunterdon County's unusually large population of multi-span pony truss bridges. Multi-span pony trusses are uncommon in other parts of the country, where single span pony trusses are usually the only type of pony truss commonly found, with most multi-span truss bridges being through trusses. Of the multi-span pony truss bridges, this structure is without a doubt the most significant. Featuring Phoenix columns for the top chord and the end post, this bridge is significant as a bridge displaying that unique and historically important form of structural beam. Interestingly, this bridge does not use Phoenix columns for the vertical members, instead more typical built-up beams with v-lacing are present. Markings on these beams indicate that they too were fabricated by Phoenix. Phoenix manufactured standard rolled and built-up beams in addition to their patented columns.
Information and Findings From New Jersey's Historic Bridge Inventory
Discussion of Bridge
Summary: The 2-span pin-connected Pratt pony truss bridge built in 1885 uses patented Phoenix columns for the end posts and top chord. The cast footing bearings on ashlar abutments and pier appear unaltered. The outriggers are part of the original design. The bridge is in a nearly complete state of preservation with no apparent welded repairs or alterations. One of the better preserved Phoenix column pony truss spans in the state, it is the only known multi-span example.
BIBLIOGRAPHY: Hunterdon County
Engineer's Office, Bridge card F 65.
PHYSICAL DESCRIPTION: The two-span, cast- and wrought-iron pin-connected Pratt pony truss bridge survives in a remarkably complete state of preservation. The trusses and floor beams are original and unaltered. Each five panel truss consists of Phoenix column section top chords and inclined end posts. All of the truss verticals are built up from a pair of angles with lacing rather than Phoenix sections. The pins at both the top and bottom of the verticals pass through the gusset plates. Because the verticals are not Phoenix sections, the cast connecting pieces at the intermediate chord panel points are not needed. At these locations, the pins pass through the walls of the Phoenix section. Castings are present at the top chord/end post connections and the bottom chord/end post connection, or feet. The expansion bearing feet sit on nested rollers, a standard period detail. The bottom chord consists of round-headed eyebars. The principal diagonals consist of needle-headed eyebars. The counters are rods which thread into devises at both ends which pass around the pins. The floor beams are built up from a web plate with four riveted flange angles. The two top flange angles extend out to form part of the knee brace at each vertical. The floor beams hang from the bottom chord pins on U suspenders. All bridge components are stamped with the order number. The spans bear on stone abutments and a mid-stream pier.
HISTORICAL AND TECHNOLOGICAL SIGNIFICANCE: The well-preserved 2-span 1885 pony truss bridge is historically and technologically significant as an example of the a Dean & Westbrook built Phoenix-section bridge (criterion C). The use of the Phoenix section without all of the castings at the nodes (panel points), as in this truss design, represents a transitional stage where the Phoenix truss system was being simplified to be competitive with "standard" pin connected trusses of built-up members. The bridge is one of four Phoenix-section pony truss spans in the state. The patented Phoenix column, developed in 1864 by David Reeves of the Phoenix Iron Company at Phoenixville, Pennsylvania, "was a great factor causing the substitution of wrought iron for cast iron in compression members of pin-connected bridges," according to noted engineer and author J.A.L. Waddell. It enjoyed tremendous popularity in the 1870s and 1880s, and was one of the most important details in the general acceptance of metal truss bridge technology in those decades. In the earliest days, Phoenix-section bridges were designed by, marketed by, and erected by the Clarke, Reeves Company, a separate company with some of the same owners as the Phoenix Iron Company. They primarily built railroad bridges. In 1884 Clarke, Reeves & Company was reorganized as the Phoenix Bridge Company, and in 1885 it entered into an agreement with Dean & Westbrook of New York City for the marketing and erection of highway bridges with Phoenix-section compression members. The agreement was in effect until 1895. After that date few metal truss bridges with Phoenix sections were built. Dean & Westbrook built at least 70 bridges with Phoenix sections in New Jersey, and about 10 survive. The bridge is the only documented 2-span Phoenix column span in the state. It enjoys integrity of design and setting.
Boundary Description & Justification: The bridge is evaluated as individually distinguished. The boundary is limited to the substructure and superstructure.
Discussion of Surrounding Area
The bridge carries one lane of rural Hamden Road (River Road) over the South Branch of the Raritan River. It is located on a sharp curve of an unimproved, lightly traveled road that parallels the river. The surrounding area has scattered 19th-century farm houses. The bridge enjoys integrity of setting.
Bridge Considered Historic By Survey: Yes
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