Bridges

[Anonymous]

Does anyone know the circumstances when the prototype would use which style of bridge for a particular span. I'm most interested in the various types of deck girder and thru girder types, ballasted or unballasted , length of span etc?

[DTomajko]

Kalmbach and Carstens publications both carry softcover books about the types, uses, and placement of bridges. Your local hobby shop should carry them or be able to get them for you or you could go online for a copy,(this site would carry the Kalmbach book.).Good luck and good modeling.

[Anonymous]

Generally, the railroads build/built the cheapest crossing they can get away with, taking into account the cost of maintenance and so on. In the long run, a fill is the cheapest thing, so that's why a lot of trestles got "buried". They built a cheap and quick trestle to get across, and then filled in.

I would second the recommendation for a book, or at least a bit more research on your specific needs and prototype.

Andrew

[Anonymous]

The style of bridge would also depend on the required clearance beneath it, and the potential for intermediate supports. A deck truss or deck girder reduces the clearance substantially, and trestles (whether wood or steel) require solid footing for their bents. If the bridge passes over something which must be protected from fuel or other spills, then a ballasted deck might be used; if it's just over a creek, it might be an open deck. There's a prototype for everything, I am sure, so you can go with your gut and use the bridge you feel like using, as long as it seems plausible.

[Anonymous]

If you are looking for a nice girder bridge Auel Industries has a nice one for sale
e-mail address [e-mail]

[dehusman]

The decision is based on the height of the bridge, the clearance required under it and the amount of clear span urequired under it.
Short depressions with little or no running water can have a trestle. 100 ft or less clear spans will usually be either a deck or through girder, depending on the clearance under the bridge. Spans between 100 and 200 feet will tend to be a truss bridge. Longer bridges will be combinations of the types.

Dave H.

[DSchmitt]

Note also that most railroad bridges are simple span. That is each span is supported by an abutment or a pier at each end. Modern highway bridges are often have cantileved spans.

[CBQ_Guy]

QUOTE: Originally posted by aueltrainlady

If you are looking for a nice girder bridge Auel Industries has a nice one for sale
e-mail address [e-mail]

Speaking of bridges for sale, I just discovered this site last night...brass yet!

http://jpstructures.com/