Powell Bridge

Information and Findings From Ohio's Historic Bridge Inventory

Setting/Context

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

Physical Description

The 1 span, 40'-long, 3-panel, pin-connected Pratt pony truss bridge is traditionally composed of built-up compression members and eye bar tension members. The upper chords are toe-out channels with cover plate and battens. The cover plate of the end posts has been replaced by welding, also with loss of the builder's plaque shown in ODOT inventory photos (ca. 1981). The verticals are toe-out channels with battens. The lower chord eyebars are heavier in the interior panel. The lower chord eyebars have welded repairs in the end panels. The floorbeams are suspended from the lower-chord pins by U-shaped hangers. The stringer, deck, and railings are modern (ca. 1985). The rubble stone abutments have concrete caps.

Integrity

Replaced stringers, deck, and railings (ca. 1985). Also welded repairs to upper chords and lower chords. New bridge seats. There was a builder's plaque, but it is gone (see attachment d). The plaque gave the builder's name but no date.

Summary of Significance

The ca. 1895 pin-connected Pratt pony truss bridge has no distinguishing features or details, and it has been irreversibly altered by welding of the end posts and lower chords. More complete and distinguished examples better represent the technological significance of the type/design and the work of this builder.

The Toledo Bridge Company was established as the Smith Bridge Company in 1870 by Robert W. Smith. Smith had begun building his patented wood-truss bridges in Tipp City in the late 1860s. He relocated to Toledo in 1870, establishing a bridge works, that continued to fabricate the wood trusses, but eventually transitioned into metal-truss fabrication. The company sold bridges throughout the Midwest and was very prolific, sometimes licensing its patented design to other builders. In 1890 Smith sold to new owners who changed the name to the Toledo Bridge Company. Toledo Bridge Company was merged into the American Bridge Company monopoly in 1901. The inventory includes at least 14 bridges built by the Smith Bridge Company (11 covered bridges; 3 pinned Pratt truss) (May 2009).

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design of the last quarter of the 19th century and continued to be built into the 20th century, although eventually superseded in popularity by Warren trusses.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.

Justification

Not Currently Available.

Bridge Considered Historic By Survey: No