Re: This defies logic -DSPP station location

WOW!

What caught my eye was the picture of the bridge in the link. Typically, early truss bridges were of the Howe truss design where wood timbers were used for spans and posts. Iron vertical rods held it together. The wood beams were primarily in compression while the iron rods were in tension.

Look at this bridge! It has wood beams forming the top and angled end chords and stringers like a Howe truss. It also appears to be a "pony" design, the trusses being shorter than the equipment going over it (versus a through truss). The rest is a "pin connected" design with iron flat bars and rods tying it all together and connecting at several pins. The I beams and U channel braces look out of place making me question if they were original or part of a later replacement or strengthening?

I don't think I've ever seen such a truss bridge as this combining wood and iron in such a unique arrangement, at least for rail service.

Pin connected truss bridges had the advantage in that they could be built at a factory, easily assembled in the field from a kit, and if necessary disassembled and used again elsewhere. They fell out of favor circa 1900 since a failure or damage to a single component could lead to catastrophic failure. I-beams riveted together at each joint in the truss were far less prone to failure, plus could be both in compression and tension. But there are still plenty still around and still in service. I occasionally still run trains over a steel pin connected truss that was relocated decades ago to it's present location by the NP.