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Johnson Road Bridge

   


Johnson Road Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: May 6, 2013
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Key Facts

Facility Carried / Feature Intersected
Johnson Road Over Grand River
Location
Rural: Ashtabula County, Ohio
Structure Type
Metal 7 Panel Pin-Connected Pratt Through Truss, Fixed and Approach Spans: Metal Stringer (Multi-Beam), Fixed
Construction Date and Builder / Engineer
1905 By Builder/Contractor: King Bridge Company of Cleveland, Ohio

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
128 Feet (39 Meters)
Structure Length
165 Feet (50.3 Meters)
Roadway Width
15 Feet (4.6 Meters)
Spans
1 Main Span(s) and 1 Approach Span(s)
NBI Number
432962

Historic Significance Rating (HSR)

Bridge Documentation

This Bridge No Longer Exists!

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

This bridge is a traditional example of a bridge built by the King Bridge Company. It has the distinctive teardrop and star design in the portal bracing knees, which was a unique detail that the company put on some of its through truss bridges. The bridge retains riveted hub guard type railing that is unusual since it has v-lacing instead of lattice on it. The bridge appears to retain good historic integrity, although a replaced hip vertical was noted.

HistoricBridges.org thinks that the findings of the Historic Bridge Inventory should be reconsidered, in light of how many King Bridge Company bridges have been demolished nationwide. This was a prominent Ohio bridge company and surviving examples of this significant firm deserve to be noted. Further, the ornamental knee braces, a distinctive detail of King bridges, are not to be found on bridges by any other company.

Information and Findings From Ohio's Historic Bridge Inventory

Setting/Context

The bridge carries a 2 lane road over a stream in a sparsely developed, rural setting.

Physical Description

The 2-span, 165'-long bridge is composed of a 128'-long pin-connected Pratt thru truss and a steel stringer approach span. The truss is traditionally composed of built-up compression members and eye bar or rod tension members. It has lattice portal bracing.

Integrity

Substruts added in the end panels as part of rehab prior to 1980s.

Summary of Significance

The 1905 pin-connected Pratt thru truss bridge is a later example of its type/design with no distinguishing features or details. It has some alterations in the end panels with the addition of substruts. Earlier, more complete, and distinguished examples better represent the significance of the bridge type/design. 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.

Bridge Considered Historic By Survey: No

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Photos and Videos: Johnson Road Bridge

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CarCam: Westbound Crossing
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