7 Mile Road 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 of active agriculture. There are fields to the bridge's east. To the west is a rail line carried over Seven Mile Road by an overpass with a 9'6" vertical clearance. The bridge's western approach roadway is a sharp S-curve.

Physical Description

The 1-span, 155'-long, pin-connected Pegram thru truss bridge is composed of built-up compression members and eyebar tension members. The upper chords are toe-out channels with cover plate and lacing. The compression members in the web are toe-out channels with lacing. The tension members in the web and the lower chords are eyebars. The upper laterals are angles with lacing. The bridge has A-frame portals with builders plaques. The plaques read, "1906, Indianapolis Bridge Co., Muncie, Ind., S. C. Richie, Isaac Ulrich, J. E. Flora, Commissioners." There are original lattice railings. The floorbeam hangers are pin plates from the web members; the hangers do not connect to the lower chords, a characteristic of the Pegram design. There are rolled floorbeams, rolled stringers (with channel fasciae beams), and a wood deck. The bridge is supported on concrete abutments.

Integrity

Deck replaced, 1985. Welded stiffeners have been added at the floorbeam hangers.

Summary of Significance

The 1906 Pegram truss is a rare type/design in Ohio that is technologically significant (Criterion C). There has been no change in the bridge's status since the prior inventory. The eligible recommendation remains appropriate.

This is Ohio's only identified example of a design that was patented by George H. Pegram (1855-1937) in 1885. The truss, which is characterized by the equal-length sloping upper chords, no verticals, and steeply sloped diagonals (60-75 degrees) was designed to economize on the amount of steel being used and allow for ease of disassembly and re-use. Pegram worked for the Missouri Pacific and Union Pacific RRs, and the design gained popularity in the Midwest and Rocky Mt. regions where most surviving examples can be found today (e.g. Idaho had seven at latest report). The primary objection to the bridge type was the difficulty of making riveted connections, and it had largely fallen out of use by the 1910s.

Justification

The design is rare with this being the only example. It has exceptional significance.

Bridge Considered Historic By Survey: Yes

View PDF Historic Bridge Management Plan