Dry Creek Private Bridge

Information and Findings From Ohio's Historic Bridge Inventory

Setting/Context

The bridge carries a 1 lane private drive over a stream in a wooded setting. The lane provides access to an active farm.

Physical Description

The 1 span, 63'-long, 5-panel, pin-connected Pratt pony truss bridge is supported on concrete abutments. It is composed of built-up upper chords of toe-out channels with coverplate and battens; end posts of toe-out channels with lacing and battens; verticals of toe-out channels with lacing; and diagonals and lower chords of eyebars. The floorbeams are suspended from the lower-chord pins by U-shaped hangers. The floorbeams carry timber stringers and plank deck. The members appear to be wrought iron based on visual inspection.

Integrity

Surface corrosion.

Summary of Significance

"The pin-connected Pratt pony truss is a complete, representative example of its type/design that is for the most part conventionally composed. It is dated ca. 1890 based on style of the end posts (no cover plates) and the material, which appears to be wrought iron not steel. It is among the earlier, complete surviving examples of its type/design and is technologically significant (Criterion C). 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design of the last quarter of the 19th century and continued to be built into the 20th century, although eventually superseded in popularity by Warren trusses.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: Yes