Davidson River Pony Truss Bridge

First of all, I consider this to be a very boring truss bridge, and if it weren't for its beautiful location, construction date, and potential history, I would probably not include it on this site. It is a prefabricated structure, utilizing the same type of components for each section. In essence the bridge is a temporary structure that has somehow become permanent. It lacks the sophistication, the complex engineering of even a simple but permanent pony truss.

The bridge is located in Pisgah National Forest, between US 276 and the Davidson River Campground, a popular location for rafting and swimming in the clear waters of the river. The bridge is barricaded, though pedestrians walk out on it quite a bit, some of whom in the past have carved their names on the steel. The only purpose that the bridge would serve today would be to provide access to a small Methodist church located on the other side. Today the congregation has to pass through the gated campground, which is probably an inconvenience. But considering its limited use, it makes for a poor candidate for rehabilitation.

The span utilizes the Warren configuration and simple bolted connections, as opposed to the vast majority of bridges erected at the time, which used rivets. All structural members are comprised of two rolled steel L-beams that are connected together with either rivets or bolts, depending on the member. The vertical members located at connections involving a floor beam feature buttresses on the inside of the truss, which serve to prevent the trusses from "tipping." Many of the members are stamped with the "Pencoyd" label, meaning that the components were supplied by the Pencoyd Iron Works. Pencoyd had a history of making prefabricated bridges, notably supplying one that was used to cross the Nile (1).

This is the first truss bridge I have been on where I could feel a slight deflection of the deck, so subtle that I had to wonder if I was imagining it. The pulsations, notably, could be felt when cars pass by on US 276 or when I jumped up and down. This leads me to believe that the truss height-to-span length proportion on this bridge is insufficient. The engineers obviously thought that the strength of the structural members would make up for the low height of the trusses. Personally I would not want to drive across it.

The bridge uses stone piers, possibly built out of material taken out of the river. This is very unusual for the 1930s, when concrete had clearly become the predominate material for bridge piers. In all likelihood, this means that the bridge was erected by the Civil Conservation Corps, which had a camp nearby and played an important role in shaping Pisgah National Forest. The CCC was known for using unskilled labor for nearly all tasks, with an emphasis placed on avoiding the usage of heavy equipment. The stone-and-mortar piers could have been erected without large machines, unlike what would be necessary for concrete pouring. Furthermore, the truss span itself could have been erected by a group of less-skilled men with wrenches, requiring only simple falsework to support the span as the pieces were assembled. It is unlikely that heavy machinery like cranes were used, though of course I may be wrong in my assessment.