Crystal Springs Bridge

Information and Findings From Ohio's Historic Bridge Inventory

Setting/Context

The bridge carries a trail over a stream in Crystal Springs Park. It is for pedestrian use only.

Physical Description

The approximately 220'-long, riveted Pratt pony truss bridge is supported on ashlar substructure units that predate this superstructure (old bridge lost in 1913 flood). Panels are about 20' long. The upper chords and inclined end posts are built up box sections and the diagonals and verticals are built up with back-to-back angles with lacing. There are original outriggers. Of particular note are the handsome lattice railings set inside the truss lines and the end fill panels with cast iron posts. The steel grid deck is not original. The plaque has been damaged, so it is not possible to read which firm fabricated the bridge if indeed that information was ever part of the plaque mounted to an inclined end post.

Integrity

The bridge maintains the aspects of integrity.

Summary of Significance

The riveted Pratt pony truss bridge was placed in 1914 to replace one lost in the great 1913 flood. It is a complete example of its type, but it is not an early example nor does it have innovative or distinctive details. There are at least 25 older riveted truss bridges in the state Extant riveted truss bridges in Ohio date to the turn of the 20th century, and it is the early examples that chronicle the historical and technological significant of the design. The plaque on this bridge has been damaged, so the fabricator is not readily apparent. The completeness of the bridge makes it a fine example of its type, design, and context.

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design of the last quarter of the 19th century and continued to be built into the 20th century, although eventually superseded in popularity starting about 1900 by the Warren truss design, which was better suited for riveted rather than pinned panel point connections. The Pratt 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, pin-connected 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. 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.

Bridge Considered Historic By Survey: No