This attractive bridge is a rare example of a
pin-connected truss bridge that remains in use for vehicular traffic in
genuinely good condition, but also with excellent historic integrity. Each
span is composed of eight panels. Original lattice railings remain on the
bridge behind modern railings. Vertical members feature v-lacing, with
lattice on the sway and portal bracing. The sway bracing is nearly identical
to the portal bracing. The bridge may have not been considered historic by Ohio's Historic Bridge Inventory, but it is HistoricBridges.org's opinion that this bridge still has heritage value and a large amount of aesthetic quality as
well. As such, the bridge is worthy of preservation. Many of the other better examples that the inventory refers to are being demolished. Good for this bridge, but sad for Ohio, this bridge will become much more rare and significant in the
context of Ohio's dropping truss bridge population.
Information and Findings From Ohio's Historic Bridge
The bridge carries a 2 lane road over a stream in a sparsely developed, rural setting.
The 2-span, 255'-long, pin-connected Pratt thru truss bridge is traditionally composed of built-up compression members and eyebar tension members. It has lattice portals and railings. It is supported on concrete
abutments and pier.
Summary of Significance
The 1910 pin-connected truss bridge is a technologically undistinguished, later example of its type/design with no unusual or significant details/features. Earlier and more distinguished examples in the state
better represent the significance of the type/design. The not eligible recommendation of the prior inventory remains appropriate.
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century and continued to be built into the 20th century, although eventually superseded in popularity by Warren trusses.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.
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.
Bridge Considered Historic By Survey: No
Photo Galleries and Videos: Scioto Darby Road Bridge
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Maps and Links: Scioto Darby Road Bridge
This historic bridge has been demolished. This map is shown for reference purposes only.