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curved plate girders - HO

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Jerry Abrams

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Mar 15, 2003, 11:41:48 PM3/15/03
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At the NJ Greenberg show, there was a box of "N" gauge curved plate
girders. Does anyone know if there are similar ones made for HO, of
course they would have to be designed for the different radius tracks.
--

Erik Olsen

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Mar 16, 2003, 5:47:59 AM3/16/03
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If you want to be prototypic, use only straight girder bridge spans. A
succession of straight spans can be used for curved track, the spans
will have to be wider than for straight track, though.

--
Faithfully
Erik Olsen

Mark Mathu

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Mar 16, 2003, 9:26:18 AM3/16/03
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Jerry Abrams wrote...

> At the NJ Greenberg show, there was a box of "N" gauge curved plate
> girders. Does anyone know if there are similar ones made for HO, of
> course they would have to be designed for the different radius tracks.


The only ones I am aware of are from European manufacturers with tight radii
and not often in dealer's stock:

Kibri - Steel Bridge, Curved 14" Radius
http://www.walthers.com/exec/productinfo/405-9682

Noch - Curved Steel Bridge
http://www.walthers.com/exec/productinfo/528-21350

Vollmer - Deck Bridge Kit
http://www.walthers.com/exec/productinfo/770-2507


--
Mark
"I started out with nothing and I still have most of it."


Mark Mathu

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Mar 18, 2003, 9:00:51 PM3/18/03
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Erik Olsen wrote...

> If you want to be prototypic, use only straight girder bridge spans.


That's not true, curved plate girders can be used for railroad bridges.

Most railroad plate girder bridges are straight - mainly because the railroad
on them are straight or of such a broad horizontal curve to not warrant
curving the girders. And because railroad loads are so large the spans are
usually short enough that the girders are just "kinked" at the piers when a
curve is required. But when the situation arises (a combination of sharp
enough curve and long enough spans), plate girders can be designed and
fabricated to a horizontal curve.

The BNSF's Latah Viaduct near Spokane is an example of a North American
curved plate girder bridge.

--
Mark Mathu
The Green Bay Route: http://www.greenbayroute.com/

Erik Olsen

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Mar 19, 2003, 2:43:54 AM3/19/03
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Mark Mathu wrote:
> Erik Olsen wrote...
>> If you want to be prototypic, use only straight girder bridge spans.
>
> That's not true, curved plate girders can be used for railroad
> bridges.

Of course it can be done but not without consideration to the stability
problems that arise, and the curved spans have to be short in any case.
Normally curved girders are considered bad engineering practice, and it
is more cost effective to use short straight spans.

--
Faithfully
Erik Olsen

PEACHCREEK

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Mar 19, 2003, 9:39:32 AM3/19/03
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>Normally curved girders are considered bad engineering practice, and it
>is more cost effective to use short straight spans.
>
>--
>Faithfully
>Erik Olsen
>
Curved girders are NOT bad engineering practice. The reason virtually ALL
railroad and highwaty bridges were straight before the 1960's is that it was
too difficult to calculate the stresses. When the computer became available to
large engineering firms the ability to calculate these stresses became
relatively simple. This is quite evident by the number of curved bridges you
see on moderm highways.

Why don't we see more curved RR bridges? Well there just haven't been many new
RR bridges built and most of those that have been built are replacements for
existing straight bridges.
>
>
>John Glaab
>
>BTW I reall don't expect to see a curved Warrem truss bridge any time soon.
<g>


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