Hollow Brook Road Bridge
at this point in time all the diagonals have been replaced
Photo taken by Andrew Pearce in August 2012
BH Photo #238068
"The skewed 2-panel pin-connected Fink-like truss bridge bears on random stone abutments with wingwalls. There are minor welded
alterations and repairs, but the unusual trusses perform like a Bollman with a floor beam hung from the diagonals. Undocumented as to
original date and fabricator, the bridge dates stylistically to ca. 1880 and is the sole known example of its type in the county. It is
technologically significant based on the design of the trusses.
Physical Description: The 33'-long, one-span, pin-connected pony truss bridge is a variation of the Bollman truss in which the chief
characteristic is that the floor beam(s) are supported by a pair of diagonals which span from end of span to end of span, accomplished in
this 2-panel bridge by pairs of loop forged eye bars. Bars in one panel are fitted with a turnbuckle for adjustments. The top chord, end
posts, and one vertical appear to be original, although repaired several times. The trusses consist of vertical end posts which are a pair of channels with a full-height cover plate on the approach roadway face and a top and bottom batten plate on the span face. The top chord is made up of a pair of channels with a top cover plate and bottom batten plates. It extended beyond the end post by about 8" and is finished with a decorative cast cover. The top chord is a compression strut that holds the supporting columns (end posts) from falling in to the middle. There are no bottom chord elements. The vertical is a pair of channels with top and bottom battens. The one on the upstream side is a modern replacement. The vertical is a "dummy" member which serves only to halve the unsupported length of the top chord. The rolled I-section floor beam is supported on an inverted U-hanger which passes over the pin connecting the diagonals. The end posts are set on plates on the ashlar abutments. The steel grid deck was placed in 1962.
Historical and Technological Significance: Although undocumented as to date of construction and fabricator, the span is a rare example of
a Fink or Bollman truss type where the floor beams are supported by a pair of diagonals that span from end of span to end of span.
Originally designed for the combination of wood and iron, the Bollman truss was developed in 1850, and while it increased the possible
length of bridges of its day, it passed from favor by 1880 because it is not a rigid truss. Dated stylistically to ca. 1880, the bridge
represents the most basic expression of the Fink or Bollman truss form (it is not developed enough to indicate which diagonal pattern it
would have been had it been more than two panels long), and it is historically and technologically significant as a rare and fairly complete survivor of the pre-Civil War bridge technology."
- Pony truss bridge over a branch of Lamington River on Hollow Brook Road
- Tewksbury, Hunterdon County, New Jersey
- Open to traffic
- Built 1880
- Kingpost pony truss
"a variation of the Bollman truss"; "a rare example of
a Fink or Bollman truss type"; maybe so. But at their core, both those rare trusses are based on king posts, and that's all that this little bridge is. A single inverted king post. I think the bridge documentation person may have been having a bit of fun with us, guessing rightly that 20 years would pass before anyone checked up on his description with a camera and a tiny bit of truss knowledge.
Sure, at some point a "whipple-ized" multiple King or Queen Post truss can grow to be called a Fink or a Bollman. But I think it would require at least 3 verticals, if not 4 or more, to differentiate amongst them.
Length of largest span: 32.2 ft.
Total length: 33.1 ft.
Deck width: 16.4 ft.
Posted to the National Register of Historic Places on December 12, 2002
- Approximate latitude, longitude
- +40.71719, -74.73611 (decimal degrees)
40°43'02" N, 74°44'10" W (degrees°minutes'seconds")
- Approximate UTM coordinates
- 18/522288/4507397 (zone/easting/northing)
- Quadrangle map:
- Average daily traffic (as of 2015)
- Inventory numbers
- NJ 100T022 (New Jersey bridge number)
NRHP 02001510 (National Register of Historic Places reference number)
BH 25263 (Bridgehunter.com ID)
- Inspection report (as of July 2015)
- Overall condition: Fair
Superstructure condition rating: Good (7 out of 9)
Substructure condition rating: Fair (5 out of 9)
Deck condition rating: Very Good (8 out of 9)
Sufficiency rating: 73.6 (out of 100)
View more at BridgeReports.com
- May 30, 2017: Updated by Christopher Finigan: Added category "Pin-connected"
- August 26, 2012: Updated by Andrew Pearce: added data and pictures