# Curved steel bridges--they exist

On Fri, 12 May 2006 05:56:34 GMT, I said, "Pick a card, any card"

Like highway curves, my bet is they're also banked to allow higher transit speed but increasing friction at the same time. An engineer's nightmare but as the photos show, can be accomplished.

They compensate by making the boxcars and other load bearing cars straight.

Mathematically speaking, all curves are an infinite number of straight line segments formulaically defined in this link Remember, this is analytical geometry. Nothing on this page is easy. http://www.answers.com/topic/curve-1
An arc, which is what is really being discussed in this thread, is a segment of the circle defined above which is mathematically explained in that link.
Here's an arc definition and description. http://mathworld.wolfram.com/Arc.html and last, a chord: http://mathworld.wolfram.com/Chord.html
A thousand or so years ago, as a young engineering student, we had to be multi disciplined after a fashion by being exposed to a variety of engineering subjects. I was an Electronics Engineer but had to suffer through some Mechanical, Civil, Hydraulic and Electrical before I was allowed to choose my final discipline.
We designed bridges of all types but none of them were curved, I'm afraid. I know it can be done as we have seen proof in the photos. It strikes me as odd that in the face of evidence, we still cannot agree that a curve bridge can and does exist.
It reminds me of the Flat Earth Society in a strange way. -- Ray
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I used to read reports of a "Man Will Never Fly" group in Kitty Hawk NC (site of Wright brothers' first flights) with the motto: "Birds fly, Men drink"!
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And Northwest Airlines pilots do both!
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On Fri, 12 May 2006 17:55:08 +0800, Ray Haddad

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Ah, it's just a semantic problem. Most people think of the deck when they think of a bridge, is all. What we actually have is:
a) straight spans, straight decks, straight track --> a straight bridge b) straight spans, curved decks, curved track --> a curved bridge c) straight spans, straight decks, curved track --> a straight bridge (usually single span***), or a curved trestle bridge d) curved spans, curved decks, curved roadway or track --> a curved bridge
I think I've covered all cases.
***MR some years ago published a photo of a wide through girder bridge with a curve over it. Span looked to be about 40ft, inside width about 20ft. An overpass carrying a spur into a factory, IIRC.
HTH
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On Fri, 12 May 2006 10:55:47 -0400, I said, "Pick a card, any card"

In the photos in the links provided in he original post, we only have one case. Curved bridge, curved track and curved girders. Oh, and very straight rolling stock.

How would it help if all you can do is suggest that it's so with the disclaimer of IIRC? Besides, there were some perfectly good photos of a curved bridge in this very thread. -- Ray
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[...]
Sorry, the IIRC refers to the destination or purpose of the bridge, not the bridge itself. It was shown in a pic I encountered when I was clipping stuff out of my MR collection before sending the remainder to the recycler. I may have kept it, but I'm not about to go looking for it -- I waste enough time on this NG as it is. ;-)
FWIW, and risking diversion of this thread into another endless exchange, MR and RMC have both published pics of switches (turnouts) located partly or wholly on bridges (and I don't mean the Keddie Wye bridge.)
HTH
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Ken wrote:

Weight. A curved-girder span would have to built much more robustly for a RR bridge than for a road bridge. So it's usually cheaper to build many short straight spans than a few longer curved spans. You might have to build a curved span if clearances under the bridge require it, but if it's longer than a 100ft or so, it would be cheaper to realign the track to enable a straight span instead, even at the cost of tighter curves leading into that straight span.
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To get back to the original post, if the bloke, regardless of all the arguments of whether there are bridges with the main spans curved, want to build such a bridge, how would he do so? If in HO, assume that the main span is a box girder of say ten feet deep and eight feet wide. How is he to replicate this in model form? If a good tinsmith he could solder up an actual box girder out of tinplate or sheet brass. If that's not on, the box girder could be done in solid wood. Cut from a big plank with a bandsaw, not too many people could get this done. If access to a boatbuilder, a suitable section of timber could be steamed to a radius, again, not too many people can get this access. No, all too hard, replace the curved steel bridge with a masonry one, or even an embankment. Regards, Bill.
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