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CR-76 Bridge

Monroe Road 819 Bridge

CR-76 Bridge

Primary Photographer(s): Nathan Holth and Rick McOmber

Bridge Documented: July 3, 2009

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Key Facts

Facility Carried / Feature Intersected
CR-76 (Monroe Road 819) Over Long Branch Creek
Location
Rural: Monroe County, Missouri: United States
Structure Type
Metal 3 Panel Rivet-Connected Warren Bedstead Pony Truss, Fixed and Approach Spans: Metal Stringer (Multi-Beam), Fixed
Construction Date and Builder / Engineer
1910 By Builder/Contractor: Unknown

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
48 Feet (14.63 Meters)
Structure Length
81 Feet (24.69 Meters)
Roadway Width
12 Feet (3.66 Meters)
Spans
1 Main Span(s) and 2 Approach Span(s)
NBI Number
14816

Historic Significance Rating (HSR)

Bridge Documentation

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

This bridge is an extremely unusual and rare example of a bedstead truss bridge with riveted connections and also a Warren truss configuration. Most surviving bedsteads across the country have pinned connections and  a Pratt truss configuration. For the most part, by the time field riveting took off, the bedstead was determined to be a type of bridge with too many problems in its design to be useful. However, the bedstead enjoyed popularity in Missouri, enough so that  there are even examples like this one with riveted connections. The bridge is historically significant as a surviving bedstead truss, and even more significant on account of the riveted connections, which makes it stand out as something unusual and noteworthy. In addition, the bridge is in great condition for its age, and could easily be restored, either in place or relocated, and for light vehicular traffic or non-motorized traffic. Preservation of this bridge should be given priority.

There is a ford next to this bridge, probably used by farm equipment that may be too heavy or wide to cross here. A truck was observed on-site during field  documentation of this bridge, but it crossed on the bridge.

The bedstead truss is a rare form of  truss bridge that was mostly built between 1890 and 1915, usually using pinned connections and a Pratt configuration. In Missouri however, they continued to be built after that  date for a while, with riveted connections and a Warren truss configuration. The bedstead truss (also known as a truss leg bedstead) was a design in which the end post was vertical and this end post extended down below the bottom chord to act as a substructure (bridge-supporting structure). The design was an economical one, since it reduced abutment costs, since the legs of  the bedstead did most of the job of the abutments. Bedstead truss bridges were marketed to local governments as a less expensive alternative to more traditional truss bridge forms. Bedstead truss bridge construction did not last long however, since it was found that  the design had some functional problems. The truss legs made the bridge susceptible to flooding, since flood debris could collide with the truss legs and damage them, drastically reducing their support strength. Worse, the bridge might be picked up completely and pushed away into the river. Another problem was with the way the forces act on a bridge with vertical endposts, which is a reason why truss bridges of any kind with vertical end posts is rare. One feature that bedstead truss bridges sometimes have to try to counteract these problems is a compression member for the first panel of the bottom chord.

To label a truss bridge as a bedstead, the vertical endpost must extend below the bottom chord to be considered a bedstead. A vertical endpost along is insufficient for a bridge to be called a bedstead. In some cases, a bedstead truss's legs may be encased in a concrete abutment or pier. Close examination of such bridges in the field is often needed to confirm whether or not such bridges are bedsteads or simply truss bridges with vertical end posts.

The bedstead truss is one of the rarest type of truss bridges today. Many states today do not have a single example within their borders, and others might have less than a handful. Neighboring Arkansas has only one example listed. In contrast, Missouri has perhaps the largest number of bedstead truss bridges in the entire country. When the first Historic Bridge Inventory was completed, there were in fact over one hundred examples! The problem with this is that at that time the inventory found most of them non-historic because there were so many. However many years have passed since that initial inventory, and while Missouri may still have the largest number of bedsteads in the country, the current number is nowhere near where it was initially since many of these bridges have been demolished. It is unclear if the Historic Bridge Inventory has been updated to reflect the rarity of the bedstead truss bridge: on a relative scale within the state and on an absolute scale on a national level. If the surviving examples in Missouri are not determined Eligible For the National Register of Historic Places like they should be, this will increase the difficulty of preservation. The high level of integrity, rarity of the design on the national level, and increasing rarity on the state level make the preservation of each surviving bedstead something that should take a high level of priority. In addition, the small size of the bedstead truss makes it  conducive to relocation and preservation in a park or on a non-motorized trail if it is considered insufficient for its current use. In addition, the smaller size makes a preservation project less costly and easier to tackle. Sadly however, the CR-214 Bridge demonstrates that these bridges are still being demolished in Missouri. This must end before it is too late.

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