Hamp Road Bridge

Information and Findings From New Jersey's Historic Bridge Inventory

 Summary

The 4-panel pin-connected half hip Pratt pony truss bridge is supported on random ashlar abutments with wingwalls. The diagonals are joined to the chords and through bearing assembly with cast iron connectors, a detail found on another WIBC span in the county (10XXL95). This span is well preserved, and it is one of the most distinctive and complete examples of the over 20 Pratt half hip pony trusses in the county. Its state of preservation and construction details make it significant.

Physical Description

The four-panel, pin-connected, half-hip Pratt pony truss bridge is supported on random ashlar abutments with wingwalls. The top chord and inclined end posts are riveted box members composed of shallow channels, toe out, with cover plates and widely spaced battens. Vertical members are back-to-back angles joined by lattice. The bottom chord and diagonals are stamped roundheaded eyebars. Pin connections are through gusset plates riveted to the vertical ends. An unusual feature is the cast iron bearing shoes with rollers at both the expansion bearing plate and the fixed end. Cast iron connectors are also used for the node connecting the inclined end posts and top chord. The diagonals pass through the node and are secured by bolts. The original lattice railings remain. Alterations are not intrusive and include the addition of outriggers, small welded reinforcing plates at panel points, duplicate diagonals welded to the outside of the top chords in the end panels, and small repairs. A new deck has been added. The bottom chord appears to be sprung.

Historical and Technological Significance

Although the fabricator and date of construction are not documented, the ca. 1895 pin-connected Pratt pony truss bridge appears to be very like the "Low Truss, Half Slope End Posts" bridge described in the 1885 Wrought Iron Bridge Company Illustrated Pamphlet. The castings used at the bearings and the node between the end posts and top chord are unusual construction details that distinguish the span as technologically significant (criterion C). The span, one of over 20 Pratt half hip pony truss bridges in Hunterdon County, is a valuable example of both an important local bridge type and idiosyncratic details. It is attributed to The Wrought Iron Bridge Company based on those details. The Wrought Iron Bridge Company of Canton, Ohio was founded in 1864 by David Hammond, and it was incorporated in 1871. It operated as such until 1899, when it was absorbed by the American Bridge Company (Darnell, 48.) By the use of illustrated catalogues and through the efforts of traveling bridge agents, distant fabricators were able to successfully compete with local contractors for the county award of bridge contracts. WIBC was one of the most successful late-19th century bridge companies, and their bridges are not uncommon in the state. This example is distinguished by its relatively good state of preservation, integrity of setting, and distinctive details. The modifications do not preclude the span from functioning as originally designed, and they do not outweigh the significance of the seldom-seen details.

Boundary Description and Justification

The bridge is located on an unimproved road in a rural area that was not evaluated for historic district potential. There are no above-ground resources adjacent to the bridge, which is individually distinguished. The boundary is thus limited to the substructure and superstructure of the span itself.

Sources

Darnell, Victor C. A Directory of American Bridge-Building Companies, 1840-1900. Washington D.C.: Society for Industrial Archeology, 1984.

Bridge Considered Historic By Survey: Yes