This historic bridge was demolished and replaced in May 2009!
This bridge is an attractive pin-connected structure.
Although relatively traditional in design, the tall height of the trusses
give this bridge a distinctive appearance that allows it to stand out among
other truss bridges of the period. The southern portal bracing was damaged
by what appears to have been a clearance violation. The bottom portion of
said portal brace was replaced, as well as the bottom of the southernmost
sway bracing. The floor beams do not appear to be original.
Information and Findings From Ohio's Historic Bridge
The bridge carries a 2 lane road over a stream in a rural area of active farms.
The 1 span, 169'-long, pin-connected Pratt thru truss bridge has built-up compression members and eyebar tension members. There is a secondary set of upper laterals due to the extreme depth of the trusses.
Summary of Significance
The 1907 pin-connected Pratt thru truss bridge is later example of a common type/design and has no distinctive details or features. 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design of the last quarter of the 19th century and continued to be built into the 20th century, although eventually superseded in popularity by Warren trusses.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.
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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Maps and Links: Cromley Road Bridge
This historic bridge has been demolished. This map is shown for reference purposes only.