Re: Curved bridge or tressle



But that's the way most "curved" bridges are.
Curved structural members (stringers, beams and girders) introduce torsion and warping into the calculations, and are extremely difficult to analyze by hand. It wasn't until the advent of the computer that these members could be efficiently analyzed and designed. (Not to mention fabrication costs.)
So, in days gone by, bridges at curves were designed straight, but wider to accomodate the curved track.
--Dan
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On Mon, 30 Jun 2003 21:33:25 GMT, Ernie Fisch wrote:
=>I have a drawing of a deck girder bridge on the Espee. I don't know =>where it is located but... the bridge is straight, the track is =>curved. It looks a bit strange.
Well, maybe, but that's the normal way of doing it. To my eyes a curved grider bridge looks more than a bit strange. :-)
--

Wolf Kirchmeir
Blind River, Ontario, Canada
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On Mon, 30 Jun 2003 22:50:25 UTC, "Wolf Kirchmeir"

As has been pointed out most track across bridges is straight. Seeing a curved track is a bit strange.
I also have a drawing of a curved trestle. The layout of stringers is quite interesting. Each stringer spans two bents. It is perpendicular to the middle bent. The next stringer is offset by one bent so that the space between the stringers is not uniform. Looks complicated but is not. The outside stringers are actually curved which makes the deck look as if it is curved.
--
ernie fisch


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Fellas, On a fan trip to Sri Lanka we went over a curved brick built viaduct, and I'm sure that there is another famous one on one of the Scottish lines, but are viaducts bridges? I reckon that they are, being a series of bridge spans. Regards, Bill.
wrote: 2000

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William Pearce wrote:

There is a famous curved viduct in Switzerland, and a less well-known one on the privately owned tourist section of the line through the Dordogne from Martel to St Denis. Nothing strange about them.
Dave
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You are probably thinking of the Glenfinnan Viaduct on the West Highland Line. Its main fame lies not in being curved, which is fairly common on arched masonry or brick built viaducts, but in being built of mass concrete.
A Google Image search for "Glenfinnan Viaduct" yields about 60 images of which this one http://www.srps.org.uk/railtours/ archive/rh-99b07.jpg shows well the concrete and the curvature.
The contractor for the line, Robert McAlpine, later known as "Concrete Bob" gained his reputation by using that material extensively for bridges and some other structures. A brief history of the construction of the line is at
http://www.nas.gov.uk/education_high.htm
For a really spectacular curved masonry viaduct, have a look at
http://ourworld.compuserve.com/homepages/heimoaga/Luxurytrains3.JPE
which shows the Landwasser Viaduct on the Raetian Railway in Switzerland. The track emerges from a tunnel mouth high up a vertical cliff face directly onto the viaduct. Again, a Google image search on "Landwasser Viaduct" will yield nearly thirty images.
Hope this helps,
Alex. W. Stirrat
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Thank you for the post of the link to the Raetian photo. In the true literal sense of the word, that is awesome.
I had long ago seen a 3 or 4 part "travel log" on PBS of a sort of "circle route" trip in Switzerland of the meter gauge roads, and the Raetian was prominent in the shows, but there were no photos from below the Landwasser Viaduct.
Wow!
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Dan O'Connor wrote:

For the most part they still are. While it's possible to analyze and fabricate curved girders for railroad loads, there's generally no good reason to.
Chris Johnson
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<dan[at]ferrarishields.com> by "Dan O'Connor" <dan[at]ferrarishields.com> dropped his wrench, scratched his head and mumbled,

The asymmetrical loading at the center of each span must lead to enormous overbuilding of the stringers or some super elevation to keep the load on the center line between the stringers. Otherwise the angular moment would either tear out the bearing on the inner supports (bridge)or twist the bents out of the ground (trestle). Straight has got to be worlds easier, if not better.
Bob
--
The goal of driving is to miss the maximum possible number of objects.

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That is the most common kind of curved-track bridge, and not at all rare. Most of them are quite short.
Mark Alan Miller
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Mark Alan Miller wrote:

For a (not so good) photo of a train moving in such a bridge, you could see at http://mercurio.iet.unipi.it/pix/gr/narrow_gauge/steam/pix.html (the so-called "De Cirico bridge"). I hope this gives you an idea (not so unusual for a narrow gauge line which had to contend with extreme curvatures etc.)
Regards from hot and humid Athens (*NOT* the one in Georgia!), Nick Fotis.
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rare.
There is a famous wooden curved uphill trestle in the canyou at highrolls between Almagordo and Cloudcroft New Mexico.
Jim Stewart
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On Fri, 4 Jul 2003 17:28:06 +1000, "William Pearce"

The more usual design is to have the arches with constant span, ie same on each side and make the piers take up the difference, ie the piers are not of constant thickness. Much easier to build like that. Keith
Make friends in the hobby. Keith Visit <http://www.grovenor.dsl.pipex.com/ Garratt photos for the big steam lovers.
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Keith, Yes, that would certainly seem to be the easier way to build such a bridge. The trouble with travelling over these curved bridges by train is that one can only see one side of the structure so one would have to inspect them from both sides on the ground to see this feature. Photos aren't usually of much help, as they too usually show only one side. Regards, Bill.
wrote:

could
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