MONON BOARD
MONON Activity Post Merger => CSX - Monon Sub => Topic started by: Jim Davis on July 13, 2012, 07:43:31 pm
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The bridge over the Tippecanoe River.
JD
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Looks like this photo was shot during one of the times the lake was lowered 10-12 feet for repair work on the dam
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That is a very unusual bridge design. I am not sure to even call it. A Girder/truss combination of some type. But I have never seen girders on top of a truss structure of that configuration. Maybe Bob Wheeler can identify the type.
Pete
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I think that's a standard Pratt truss. The girders aren't anything special - the trusses are loaded only at the joints, so there needs to be a beam/girder grid to carry the tracks between the joints. You just don't normally notice them because it's hidden down at the base of the truss.
The top-loaded truss was probably used because of the high banks. A conventional bottom-loaded truss would have towered over the area, and there was obviously sufficient clearance underneath for a top-loaded truss.
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Thanks for posting the photos Jim. I have never seen a closeup of the South end as you have it in the 2nd. photo. All of the stone and foundation were removed just a few years ago.
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I realilze the girders are only bearing at the pier points or end of the girders. Making the piers taller to the bottom of the girders would be a lot more preferable than the steel truss to keep maintained.
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Pete & All:
To qualify the comments below I am a roadway engineer and not a structural (bridge)engineer.
I agree, I’ve never seen one like this anywhere or even in my bridge picture books. Usually the truss is under the track and doubles as the floor beam.
It looks like a truss bridge that they forgot to turn over to make it a â€deck†truss instead of a “thru†type.
A SWAG is that they designed a Thru Curved Chord Pratt Truss beyond “the point of no return†in the design. To save 1880-1901 design costs they decided to moved the floor beams to the “topâ€, made the top chord straight and put the curve in the bottom chord.