Omega Road Bridge

Information and Findings From Ohio's Historic Bridge Inventory

Setting/Context

The bridge carries a 1 lane road over a stream in a rural area of active farms.

Physical Description

The 1 span, 84'-long, rivet-connected Warren pony truss bridge has polygonal upper chord ,verticals, and built-up members. The upper chord is composed of toe-out channels with cover plate and lacing. The verticals, diagonals, and lower chords are angles with battens. The built-up floorbeams are connected above the lower-chord panel points. The bridge is supported on concrete abutments.

Integrity

The bridge has some bolted repairs at the polygonal upper chord gusset plates

Summary of Significance

Although complete except for some bolted repairs, the Warren with verticals pony truss bridge placed in 1910 by the county is not historically or technologically significant. It is a later example of a standardized design that was used throughout the state. The fabricator is not documented. Extant riveted pony truss bridges in Ohio date to 1897 (25XXXX1), and it is the early examples that represent the transfer of technology from pinned to riveted field connections.

Warren trusses are the most common design found in Ohio and the nation. The Ohio Phase 1A survey (2008) has identified more than 500 examples dating from 1897 to 1961, accounting for well over half of the approximately 800 pre-1961 metal trusses. The Warren design was particularly well suited to rigid (riveted, and later welded connections), but not as well suited to pin connections; this helps to explain its popularity in the 20th century rather than the 19th century, although it is based on a British patent issued to engineers James Warren and Willoughby Monzani in 1848. In the U.S., the popularity of the Warren truss coincided with improvements in pneumatic field riveting equipment starting about 1900. The Warren, which is based on a series of equilateral triangles, is identified by its simplicity of design, ease of construction with equal-sized members, and ability of some diagonals to act in both tensions and compression. Warren trusses are often stiffened by the addition of verticals; they can also have polygonal (sloped) upper chords to achieve greatest depth at midspan.

Warren trusses were a standard design of the Ohio State Highway Department in the 1910s and 1920s, but they achieved their greatest popularity with county engineers, who purchased the bridges from Ohio fabricators such as the Champion Bridge Co. and the Mt. Vernon Bridge Co. Fewer than 12 surviving rivet-connected Warren trusses date prior to 1910, and they represent the period when the rivet-connected design solidified its position as the most popular prefabricated county truss design.

A noteworthy change in the technological development of Warren trusses was the transition from riveted to welded connections that began in the mid to late 1930s. The development was based on improvements in arc-welding equipment and the propagation of welding techniques as a substitute for riveting in many fields of construction, such as steel-hull ships and steel-frame buildings. While most of Ohio's remaining truss fabricators went out of business in the depression of the 1930s, Ohio Bridge Corporation (OBC) of Cambridge grew its business on the development of a standard weld-connected Warren pony truss with polygonal upper chords in the years immediately following WWII. OBC remains in operation and many Ohio counties continue to find the weld-connected Warren trusses to be a desirable economical alternative to other bridge types. More than 360 of the 500 Warren trusses in the study are weld-connected and most are attributable to OBC from the late 1940s to 1960. It is the early examples of weld-connected Warren trusses dating from the mid 1930s to mid 1940s that are the technologically significant examples.

Bridge Considered Historic By Survey: No