Carlton Bridge

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Key Facts

Bridge Name	Type	Road	Location	City	Crossing
Carlton Bridge	Truss	New Lebanon Road	Mercer County, PA	Carlton	French Creek

Technical Facts

Construction Date	Rehabilitation Date	Structure Length	Deck Width	Builder
1898	1990	276 Feet	18.5 Feet	Columbia Bridge Works of Dayton, Ohio

This is one of those truss bridges that has a spectacular plaque. Head over to my photo gallery for some photos. The Columbia Bridge Works used this ornate plaque on all their bridges that I have seen, but I never tire of seeing another one! Each span of this double-span bridge is composed of nine panels. This bridge features the unusual, even bizarre, construction that is characteristic of an older Columbia Bridge structure. The use of i-beams for things like the top chord, and unusual connection details set this bridge far aside from the "average" pin connected truss bridge. This bridge retains good integrity, including original lattice railings, builder plaques and decorative finials, although some of those have gone missing. There is an annoying clearance sign on this bridge, but considering Mercer County's other truss bridges, I supposed I should be thankful that the clearance sign isn't covering up the builder plaques. This bridge is in fair shape, although it is my understanding that PennDOT and Mercer County want to demolish this bridge, which is unsurprising. Here is a revolutionary idea: restore the bridge! There is not a lot of traffic on this bridge, and restorations are generally the same or less than the cost of replacement. Preserving this bridge is important not just because of its beauty but also because of its historic value.

Information and Findings From Pennsylvania's Historic Bridge Inventory

Note: This bridge was surveyed as part of the first historic bridge inventory in 1988, which is not available to me. The comments for this bridge in 1996 were very limited in nature as a result.

Discussion of Bridge

According to the inspection file, the stringers and deck were replaced in 1990. The changes are minor modifications that do not affect the integrity of the truss.

Bridge Considered Historic By Survey: Yes

Information From www.mercercotrussbridges.com Demolition Mitigation Website

The Pratt Through Truss bridge features the distinctive, idiosyncratic details of its fabricator, the Columbia Bridge Works of Dayton, Ohio. Company trademarks include the extensive use of I-beams and bolted connections, such as those on the lower chords, which the company called lap-jointed “Flat Bar Chords.” The company’s designs reflect the experimentation that characterizes early truss bridge designs.

The Columbia Bridge Works of Dayton, Ohio was established in 1852 by David H. Morrison (1817-1882), Dayton’s first city engineer. Morrison ranks among the earliest engineers to recognize the possibilities of metal truss bridge technology, establishing one of the first bridge companies in the nation, and reportedly building the first all-iron bridge west of the Allegheny Mountains. The firm specialized in Morrison’s patented designs, the most successful of which was a bowstring arch-truss built throughout the Midwest in the 1860s and 1870s.

In the early 1870s, the Columbia Bridge Works began to produce variations of the Pratt truss design. Like many bridge builders of the period, Morrison developed a number of distinctive, idiosyncratic details. Trademarks were the extensive use of I-beams, which Morrison correctly believed to be an ideal shape for primary members, and bolted lower chord connections that Morrison called lap jointed “Flat Bar Chords.” He claimed that the chords increased stiffness and reduced vibrations from large moving loads. Morrison passed away in 1882, but his company continued under the direction of his son, Charles Carroll Morrison, who had joined as a partner in 1868. The company remained in operation into the 1890s.