Cardington Denmark Road Bridge

Information and Findings From Ohio's Historic Bridge Inventory

Setting/Context

The bridge carries a 1 lane, unimproved road over a stream in a rural area of active farms. Bridge posted for 4 tons.

Physical Description

The 1 span, 64'-long, pin-connected, half-hip Pratt pony truss bridge is supported on ashlar abutments with concrete toe walls and other repairs. The truss lines are traditionally composed with built up box sections for the upper chords and inclined end posts, and the lower chords and diagonals are eyebars. The floorbeams are salvaged.

Integrity

Lower chord is sprung.

Summary of Significance

The pin connected Pratt pony truss bridge dated stylistically to ca. 1890 is one of 20 examples of the important bridge type in Morrow County with the oldest extant example dating to 1874. Many are undocumented and represent the era of standardization. This example, with no innovative or distinctive details, is not historically or technologically significant. A note in the county records shows that the fabricator was located in Roanoke, VA. Metal truss bridge fabricators were located in Roanoke, VA as early as 1889 (American Bridge & Iron Co reorganized as the Virginia Bridge & Iron Co in 1895).

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. The design, which initially was a combination of wood compression and iron tension members, was patented in 1844 by Thomas & Caleb Pratt. 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'. Prior to about 1890, a variety of panel point connections (including bolts, cast-iron pieces, and pins), end panel floorbeam connections, and lower chord designs were in widespread use. 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. Post-1885 Pratt trusses show a progression toward less variation in their details such that by 1895 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 eclipsed in the highway bridge market by more rigid, rivet-connected truss designs, particularly the Warren design, but also the Pratt design as well. The transition to riveted field 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, there are 185 Pratt trusses dating from ca. 1874 to 1945 with at least 140 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. Post-1890 examples are less technologically significant.

Bridge Considered Historic By Survey: No