Deep River Camelback Truss Bridge



This is, without a doubt, one of the most spectacular truss bridges remaining in North Carolina. It is one of two truss road bridges in Chatham County, the other being the Rocky River Truss Bridge. Of the two structures this one is the most significant, both in history and design. The "camelback" truss configuration is not a particularly common one, compared to the Warren and Pratt trusses. Being in a state whose population of truss bridges has shrunk exponentially makes this even more special. It is likely for these reasons that this bridge was nominated to the National Register of Historic Places--the only truss bridge in the state to have this distinction. Left standing after its ugly successor was built, this structure is a unique place to watch the river flow past.

The camelback configuration owes its origins to the Pratt truss, and the two designs are very similar. With the exception of having two extra panels, the order of the diagonal structural members on this bridge are identical to that of the smaller Rocky River bridge. The two center panels, for example, have double diagonals that cross one another to form an "X." The most distinguishing feature, the feature that makes this bridge a camelback and its smaller brother to the north a simple Pratt, is the top chord, the uppermost part of the bridge that runs parallel to the deck (a bridge has two). The Deep River Truss Bridge's top chord has three sections to it. The center section is straight, while the left and right ones angle down to the front posts. Thus, the top chord has four angles to it; this is true for all camelback bridges. The semi-curve to the top chord allows the bridge to span a greater distance using less materials.

This is a pin-connected bridge, meaning that all of the connections between members are made using large steel pins that are then held in place by like-size nuts. The bottom chord is comprised of a series of eyebars, similar to the diagonals, as opposed to a single beam. The vertical members of the bridge use what are referred to as "built-up" beams, meaning that the builders took two lengths of steel and "stitched" them together to form one. This is accomplished with short pieces of steel riveted together across the beam in a "zigzag" pattern. The top chord and front posts are built-up as well, but they employ steel plates called batons. The steel pieces of the bridge are stamped with "Cambria" in many spots, meaning that they came all the way from Johnstown, PA. The bridge does not have its original plaques, which is unfortunate, since there is conflicting information about this bridge's construction dates. Chatham County states that is was originally constructed in 1908, while 1914 is the date stated by the National Bridge Inventory (1). The bridge is very similar to another camelback that once crossed the Dan River between NC and VA:
http://hdl.loc.gov/loc.pnp/hhh.nc0411. The destroyed bridge was built in 1914, by the Virginia Bridge and Iron Company of Roanoke, VA. While of course this is mere speculation it is probable that this bridge was built by the same contractor--a contractor that built other bridges across the state.

This was not the first bridge here, as it makes use of an older pier constructed of course stones, while its Lee County pier is made of reinforced concrete. The 19th Century-looking pier was extended with a concrete cap. The concrete pier is also somewhat odd. Around the time that the bridge was built concrete piers were more likely to be solid, as opposed to being open in the middle like this one. Rather, this pier resembles the NCDOT style used in the 1950s, with its flared square columns and the triangles that are located on the insides of the two corners. I may be wrong though. But if my hunch is correct, then either the bridge was at one time jacked up in order to replace the pier or this is not the bridge's original location.

While I somewhat doubt that this bridge was ever fully rehabilitated, it was modified a little over the years. The wooden deck was paved over with asphalt, as what happens with most truss bridges in the state. Modern guardrails were added in later years; these are supported by their own beams as opposed to being bolted onto the bridge's structural members. A few of the diagonals have been reinforced with parallel cables.

Today this bridge is apart of a small county park, where people can walk out onto this piece of creative 20th century engineering. During this time even a crossing over a non-navigable river could be made to resemble one over a mighty waterway. These departed engineers had to work with various intricate elements of design to create a single span over the river using less material. They spanned the whole distance, from shore to shore, without piers in the water; many pieces working together to form a stronger whole. It is truly a sight to behold. The complexity of this design puts its successor, with its brute-force stringers spanning a shorter distance, to shame.

It does not appear that any significant repairs have been made to this bridge since it was bypassed. In general it appears the same as it probably did in 1992, its deterioration slowed significantly now that traffic has been taken off of it. Overall condition of the bridge appears to be fair, with it retaining most of its silver paint. The part of the bridge that is of the most concern is the steel eyebars that comprise the lower chord, especially around where they connect with the verticals. There appears to be just a minute amount of metal flaking on the eyebars in a few of these locations. Fortunately, without accelerated deterioration caused by vibration from traffic or the application of salt, it is doubtful that this will be a real problem any time soon. When the time to take care of this does come hopefully the respective counties will choose to make a few small repairs rather than waste their money on demolishing it--and in the process deprive us of the sight of this great structure.

During a portion of the 1920s this bridge carried NC 60, the predecessor to US 421 and the highway that followed the Cape Fear River basin, of which the Deep River is apart of, all the way to Wilmington (http://members.cox.net/ncroads/nc060.html). Thus, this bridge, which early in its existence probably carried mostly horse-drawn wagons, was for a little while a piece of the state's transportation network.

This bridge is downstream of the two Cumnock Railroad Bridges, both of which are of the Warren truss configuration.

The Facts:
  • Year Built: 1914
  • Bypassed: 1992
  • Carries: Pedestrians (formally Cumnock Road, SR-2153)
  • Crosses: Deep River
  • Location: Chatham and Lee Counties, North Carolina
  • Design: Eight-panel, pin-connected Camelback truss with steel stringer/timber approaches
  • Length of main span: 160.1 ft. Total length: 365.2 ft.
  • Inside width: 14.8 ft., one lane
  • National Bridge Inventory ID (1992): 37155
  • Coordinates: 35°34'13.38"N, 79°14'28.11"W
Pictures:

  • Left: the main span. Center: looking across the bridge towards Lee County. Right: Portal Shot.
  • Left: a portion of the Chatham approach. Center: the coarse stone pier. Right: the concrete pier and underside.
  • Left: a pinned connection between the lower chord and a vertical member. Center: the same connection, viewed from above. Note the added steel cable. Right: an upper chord / front post connection.
Sources:
  1. VisitChathamCounty.com: Deep River Camelback Truss Bridge


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