This #seismicsaturday we feature a 150ft long bridge over the Ausable River in the Adirondacks Mountains of New York.
The bridge foundation is built from stones piled on top of one another, with cement in between (pic 2). The foundation is built in a hydrodynamic shape with a pointed front, making it look similar to a boat hull. This shape reduces the force on the foundation from the river, and makes it less likely that the foundation would be washed away downstream during heavy flows.
The beams of the bridge are simply two telephone poles, laid from one foundation pier to the next (pic 3). The beams are strapped down to the foundations using strips of steel and anchor bolts (pic 4). You can learn a lot about this pole from its marking (pic 5). “WT” is the sawmill. “97” means it was milled in 1997. SP SK means it is Southern Pine, treated with Vascol 500 SK, an insecticide. And 65 is the length in feet. Learning to read these telephone pole acronyms is a great way to impress you friends!
Guardrail posts are simply installed. Tops of the posts are covered with fake leather, which keep water from seeping into the top and rotting the wood (fig. 4a). The posts are bolted to 2×4 wood joists, and leaned against the telephone poles (fig. 4b)
The use of telephone poles was a resourceful choice by the builders. These poles are cheap and readily available, are treated to withstand the elements, and help the bridge blend into to the forested landscape.