This is a tiny half-hip Pratt pony truss. It features pinned connections. Original lattice railings remain on the bridge. There is lattice on the vertical members. There is v-lacing under the top chord / end post. The bridge has certainly had a hard life, and several crude repairs were made to the bridge, which mainly consisted of welding small pieces of plate steel to various parts on the bridge. Still the bridge was not beyond rehabilitation and did not deserve to be demolished. With these small bridges, rehabilitation should not be too costly. These small bridges are easy to lift off of their abutments and have restored in a shop setting, which reduces cost and increases quality of the rehabilitation.
Information and Findings From Ohio's Historic Bridge Inventory
The bridge carries a 1 lane road over a stream in a rural area of active farms.
The 1 span, 35'-long, pin-connected Pratt pony truss bridge has a concrete jack arch deck.
Summary of Significance
The 1911 pin-connected Pratt pony truss is a late
example of its type/design with no distinguishing features. 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century, although eventually superseded in popularity by Warren trusses.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.
Bridge Considered Historic By Survey: No
This historic bridge has been demolished. This map is shown for reference purposes only.
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