Mystery Bridge Nr. 79: How To Reconvert A Truss Bridge- Going From Deck To Through Truss In Oklahoma

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Photos courtesy of Mark W. Brown

Our 79th Mystery Bridge takes us to Oklahoma; specifically to Whitesboro in LeFlore County and this bridge. Spanning the Kiamichi River at Township Rd. 4044C south of Whitesboro, this bridge is one of the most unusual through truss bridges a person will ever see in the United States. According to the data from Bridgehunter.com, the total length of the bridge was 270 feet with the largest span being 127 feet, the width of the bridge is around 13-14 feet and the vertical clearance is 13.3 feet. Yet despite the date of construction being ca. 1940, this bridge is unusual as it is a pinned connected through truss, thus bucking the standards of truss bridge construction. As many resources have indicated, most truss bridges built at this time had riveted or welded connections, making the structure sturdier and able to carry heavier loads. Pinned connections had a tendency of dislocating or even having the bolts connecting the beams to break off, causing bridge failure. This resulted in many of the structures being taken off the state highway system and relocated onto less-used township roads beginning in the 1920s and extending well into the 1950s, especially as the US was lacking materials and engineers as a result of World War II. Judging by the appearance of the bridge, it appears to have been built between 1910 and 1915 as this was the cut-off period for constructing truss bridges with pinned connections. It was congruent to the time standardized bridges were approved by the state governments, which included not just focusing on truss bridges with riveted connections and either Howe lattice or lettered portal bracings (namely, A, X, M and West Virginia framed), but also the key truss designs, which were the Pratt, Parker, K-truss, Warren, Polygonal Warren and in some cases, Pennsylvania petit.

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The Whitesboro Bridge features a Warren through truss, but looking at the structure further, it appeared that in its former life, it was a deck truss bridge that had many spans, totaling at least 500-600 feet. One can see how the overhead bracings were added, which consisted of thin cylindrical steel beams. Furthermore, there is no portal bracing, like other truss bridges, and lastly, when looking at the joint where the upper beam and the diagonal end posts meet, the upper beam appears to have been sawed off.  According to observation by fellow pontist, Mark W. Brown, the piers are 2-3 feet wider on each side and 1-2 feet higher, thus creating a slight slope when entering and crossing the structure. Two theories go along with the piers: either they were installed when the bridge was built or they were reinforced after the bridge sustained structural damage because of flooding.

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It is possible that this crossing was the first to have been built as the town expanded because of the baby boomer population. But the expansion did not last as many people moved to bigger cities for job opportunities. As of the 2008 Census, the population of the town incorporated in 1908 and named after one of the founders is only 1298. The hunch is that the highest population of Whitesboro was about 3,400 by 1960.

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The Whitesboro Bridge has a design that is not like any unusual designs developed by the engineers at all. It is neither a Pegram nor a Kellogg, now is it a Schaper truss, which you can see in many truss bridges built in Germany and other parts of Europe. This bridge is definitely a repurposed truss bridge, having gone from its previous life as a deck truss spanning one of the state’s greatest rivers, like the Red and the Canadian, to one spanning a smaller river but on whose width justified a through truss span.

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This leads us to the following questions:

  1. When exactly was this bridge built and was there a previous structure?
  2. Who was the mastermind behind this repurposing project and why did the engineer choose this?
  3. Where did the bridge originate from?
  4. When was this built and who was the bridge builder?
  5. Are there other remnants of that bridge left besides the one at Whitesboro?
  6. What do we know about Whitesboro aside the facts and figures presented in wikipedia?

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Got any leads, please share in the comment sections here as well as in the Chronicles’ facebook pages. You can also contact Jason Smith at the Chronicles, using the link here. As this bridge is eligible for the National Register of Historic Places, any information you have or can find will help build a solid case for its nomination, let alone preserving it for future generations. As Oklahoma is losing historic bridges in large quantities in the past 8 years, the time is ripe to preserve what’s left of its culture, especially when it comes to unusual designs like this bridge in Whitesboro.

Special thanks to Mark W. Brown for bringing this to the author’s attention and for providing some interesting pics of this bridge.

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