Spaulding Bridge
Northern overview
Photo taken by Michael Quiet in September 2016
BH Photo #363004
It might be safe to say that this is one of the most visually and technologically interesting pony truss bridge in the entire state of VT. A rare survivor manufactured in 1905, this bridge weathered the great flood of 1927 that destroyed the majority of VT's early metal highway bridges, as well as the inevitable modernization process. As it stands this is the only pin connected Parker pony truss that is still open to automobile traffic and is still functioning as a truss.
Even with all of these attributes we still have not touched the surface of the fascinating nature of this bridge. Its manufacturer, Henry L. Norton of Springfield Massachusetts, was quite an obscure builder with no known extant bridges in New England. Its been suggested that Norton was formerly in the employee of the Hawkins Iron Works, which would give an idea as to where Norton picked up the bridge building trade. No doubt owing to the reality that this was either a one-off or one of a very small production, this bridge has several details that are unique/unusual and thus make it singularly unique among remaining examples in the region.
Starting with a broad view, this is a 98 foot pin-connected 6 panel Parker pony truss. The structure rests on irregular dry laid stone abutments capped in concrete. The bridge has a single lane roadway that is comprised of a wooden deck covered in asphalt. The upstream truss has a pedestrian sidewalk cantilevered outside the truss line, and has a modern 'historical looking' railing. The lower chord is classically composed of paired eyebars, but they are mounted inside the connections of the verticals giving them a very narrow distance between the pair. Also of note is that the lower chord slopes downwards in the first panel, giving it a 'fishbelly' appearance.
The upper chord is a built up box member secured by battens, which why not completely unusual is nonetheless notable as a later example of a bridge fabricated with these, as opposed to the increasingly common V and X lacing. Diagonals are eyebars with smaller adjustable tension rods for the counter braces. Verticals are comprised of V lacing with angled sections riveted together. The upper connection of the verticals is interesting, as they are not directly pinned to the upper chord, but are instead riveted to gusset plate that connects to the upper chord.
The floorsystem has been completely replaced with a modern galvanized steel system, and is the biggest hit to historical integrity (or nearly equal with the loss of almost all the original rivets). The pedestrian walkway is supported by its own timber stringers that were also installed in the 2005 rehab.
Despite the damage to the historical integrity of this bridge with the complete reconstruction of its floor system and loss of rivets, it is a happy note that this bridge operates with no weight restriction without the additional of other load bearing devices. While perhaps not the most ideal solution, it does allow for a historic truss to continue to function in place with no major visual distractions to it.