Mill 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 sparsely developed, rural setting. Fields and woods are to all quadrants.

Physical Description

The 1 span, 137'-long, pin-connected double-intersection Pratt (Whipple) truss bridge is supported on stone abutments with wingwalls. The bridge is composed of upper chord of toe-out channels with cover plate and battens; built-up verticals of I-beams with cover plates; and diagonals and lower chords of eyebars. The arched lattice portals are composed of bars, pipes, and bolts similar to how this fabricator built-up the arches in its patented bowstring trusses. The built-up fishbelly floorbeams are suspended from the lower-chord pins by U-shaped hangers. Original railings have been removed and replaced with beam guide rails.

Integrity

Floor replaced in 1979. Railings replaced. The bridge was rehabilitated in 1996-97.

Summary of Significance

The 1881 truss bridge is a technologically significant example of the double-intersection Pratt thru truss by a prominent Ohio fabricator, the Massillon Bridge Co. (Criterion C). The 1996-97 rehabilitation maintained the integrity of design. Double-intersection Pratt trusses, also known as Whipple or Murphy-Whipple trusses, were among the most successful of long-span thru truss designs (up to 300' long) of the 1860s to 1890s for both railroad and vehicular crossings. Surviving examples are uncommon nationally and considered technologically significant; Ohio with at least 14 identified examples dating from 1881 to 1898 (Phase 1A survey, 2008) has a very high number in comparison to most other states. The truss design is characterized by diagonals that extend over two panels. In 1847, Squire Whipple, one of America's foremost bridge engineers, developed the design figuring that the double-intersection configuration increased the depth of panel without altering the optimal angle of the diagonals, thus allowing for increased span length. His design was further refined in 1859 by John W. Murphy, the talented chief engineer of Pennsylvania's Lehigh Valley RR, who substituted wrought-iron pins for cast-iron connecting pieces, thus developing the connection detail that would prove to be advanced construction practice for this and other truss designs for the next several decades. Ohio's surviving examples, which mostly date to the 1880s, were not cutting edge for their time, but they show how the form had evolved into the preferred long-span thru truss design of the period. Most have documented associations with prominent Ohio-based fabricators.

Justification

There are 13 examples of the bridge type important to the development and maturation of the pin-connected thru truss bridge. They date from 1881 and concentrate in the 1880s. Even though there are more than 12 extant examples in Ohio, each built in the 1880s has high significance based on overall scarcity (everywhere but in Ohio) of the design. This is a major and technologically significant bridge type. The bridge has high significance.

Bridge Considered Historic By Survey: Yes