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Sonora Road Bridge

TR-445 Bridge

Sonora Road Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: May 7, 2006

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Key Facts

Facility Carried / Feature Intersected
Sonora Road (TR-445) Over Twin Creek
Location
Rural: Preble County, Ohio: United States
Construction Date and Builder / Engineer
1902 By Builder/Contractor: Indiana Bridge Company of Muncie, Indiana

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
87 Feet (26.5 Meters)
Structure Length
93 Feet (28.3 Meters)
Roadway Width
15.7 Feet (4.79 Meters)
Spans
1 Main Span(s)
NBI Number
6837255

Historic Significance Rating (HSR)
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Bridge Documentation

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

Built in 1902, this is a classic six panel pin connected Pratt through truss. Two rows of channel form the original or old guardrails that remain on the bridge. There is v-lacing under the built-up top chord and on the built-up vertical members. Some idiot must have driven across the bridge with too tall a load and they knocked out the bottom section of the a-frame portal bracing. Unsurprisingly, the county posted a clearance sign above the bridge. It is unknown if the sign was posted before, or if the county only did it only after the damage had been done. The only other significant alteration noted with this bridge is the addition of an extra rolled i-beam under the floor beams. The deck of the bridge is wooden with an asphalt wearing surface. The bridge sits on stone abutments.

As of 2012, there have been rumors going around that Preble County may rehabilitate this bridge. HistoricBridges.org sincerely hopes that these rumors are true, since far too many of the county's historic truss bridges have been demolished since HistoricBridges.org documented the county in 2006.

Information and Findings From Ohio's Historic Bridge Inventory

Setting/Context

The bridge carries a 2 lane road over a stream in a rural area of active farms.

Physical Description

The 1 span, 93'-long, pin-connected Pratt thru truss bridge is conventionally composed of built-up compression members and eyebar tension members.

Summary of Significance

The 1902 pin-connected Pratt thru truss bridge is later example of a common type/design and has no distinctive details or features. The builder is not documented by available county records. 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

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Photo Galleries and Videos: Sonora Road Bridge

 
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Maps and Links: Sonora Road Bridge

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