This bridge is a traditional pin-connected pony truss with
excellent historic integrity. The bridge is seated on concrete abutments
which look newer than this bridge suggesting this bridge was relocated from
someplace else to this location, or at the very least that the abutments
were replaced at some point. Further evidence of relocation is holes on the
floorbeam and small riveted place on the floorbeam, part of which was cut
off, evidence of a past use that differed from its current use. These also
suggest that the bridge may have once had a sidewalk which was removed, or
alternatively, some brackets to hold a pipe. The pipe currently running
under the bridge deck is mounted in a different part of the bridge.
Information and Findings From Ohio's Historic Bridge
The bridge carries a 1 lane private road over a stream in a sparsely developed, rural setting at the Berry Boy Scout Camp.
The 1 span, pin-connected Pratt pony truss bridge is traditionally composed of built-up compression members and eyebar or rod tension members. It has lattice railings.
Summary of Significance
The ca. 1900 pin-connected Pratt pony truss bridge is short span and has no distinctive details or features. The builder and year built are not documented by available records. It was probably relocated here.
Pratt trusses were undoubtedly the most popular truss design of the last quarter of the 19th century and continued to be built into the 20th century, although eventually superseded in popularity by Warren trusses. The design,
which initially was a combination of wood compression and iron tension members, was patented in 1844 by Thomas & Caleb Pratt. Ohio has three covered bridges that use this combination configuration, but they are all modern
reconstructions based on the Pratt patent. The great advantage of the Pratt over other designs was the relative ease of calculating the distribution of stresses. More significantly, it translated well into an all-metal design in
lengths of less than 200'. Significant surviving examples of all-metal Pratt trusses mostly date to the last quarter of the 19th century, and they are found with thru, pony, and the less common bedstead configuration. Prior to about
1890, a variety of panel point connections were in widespread use (including bolts, cast-iron pieces, and pins), but engineering opinion was coalescing around pins as the most efficient and constructible. Many of the connection
details were proprietary and associated with individual builders or companies, and thus earlier examples are generally taken to be technologically significant in showing the evolution of the design. Later post-1890 Pratt trusses
show a progression toward less variation in their details such that by 1900 the design was quite formulaic with few significant differences between the designs of various builders. This marked the end of the pin-connected Pratt's
technological evolution and, in fact, it was soon waning and eclipsed in the highway bridge market by more rigid, rivet-connected truss designs, particularly the Warren but also riveted Pratts. The transition to riveted connections,
which happened even earlier with railroads than highways, was in no small part due to concerns about stress reversals at the pins under heavier loads and improvements in pneumatic field riveting equipment in the early 1900s. In
Ohio, Pratt truss highway bridges, whether pinned or riveted, were almost always built under the auspices of counties and local units of government; the Pratt was not a standard design of the state highway department.
Ohio, there are 185 Pratt trusses dating from ca. 1874 to 1945 with at least 60 dating prior to 1900 (Phase 1A, 2008). The technologically significant unaltered examples of pin-connected Pratt trusses for the most part date prior to
1900 and have documented or attributed builders and dates of construction and/or significant connection or member details. Later post-1900 examples are less technologically significant. Significant unaltered examples of
riveted-connected Pratt trusses date from ca. 1900 to 1915.
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