For a pin connected Pratt through truss bridge,
this structure has a substantial span length. Its long length, which usually results in
higher trusses, combine with a narrow deck width to give the bridge a tall feeling. This bridge is composed of nine
panels yielding a total structure length of 142 feet. Although the builder
plaque obviously was stolen, the Penn Bridge Company is clearly associated with
this bridge. The Penn Bridge Company was a company that really took aesthetic
design of its bridges right down to the tiniest detail. Their bridges often
feature little medallion-like motifs on the portal bracing that feature various
figures or designs or say "PENN" on them. This bridge has those decorations, and in
addition, those motifs even appear on the railings!
Information and Findings From Ohio's Historic Bridge
The bridge carries a 1 lane road over a stream in a sparsely
developed, rural setting.
The 1 span, 142'-long, pin-connected Pratt thru truss bridge has
built-up compression members and eyebar tension members. It has lattice
portal bracing with decorative builders plaques atop the portals.
Summary of Significance
The 1893 truss bridge, which is among the early and
technologically significant surviving examples of its type/design in the
state, has been determined eligible as the result of advancing a
rehabilitation project (SHPO letter, 5/21/08).
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although eventually superseded in popularity by Warren trusses.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.
In 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.
The bridge is one of over 150 extant pin-connected truss bridges
dating from 1874 for pony trusses and 1876 for thru trusses. Twenty six
predate 1888 and represent the era of experimentation that evolved into
standardized designs by about 1888. This example has moderate
significance because the genre and the fabricator are so well
represented in Ohio.
Bridge Considered Historic By Survey: Yes
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