Ballasted deck girder bridges

[OldEastRR]

Wondering if there are/were these bridges with turnouts on them -- even just part of the turnouts. These are the bridges with the plate girders under the rails. If so, would they have separate girder structures for each track or a set of them connected laterally for a double-track main, what with the switches being on them? I want to use the ME bridges but wonder if I need to modify them.

[nkalanaga]

The girder design would probably depend on how the turnout fit the bridge.  If only the switch portion was on the bridge, there wouldn't be any need to change anything.  If the entire turnout was on the bridge, I don't know how they'd do it.  My guess would be to use at least three girders, either parallel, or with the third one angled, close to the second at the point end, and spread far enough to support the diverging track at the frog end.

I've never seen such a bridge, but they were probably common on big-city elevated railroads.  Maybe look for pictures there?

[Chris333]

Ballasted deck bridges have a deck. Do whatever you want on a deck.
https://www.google.com/maps/@41.4224541,-79.6986057,278m/data=!3m1!1e3

The tracks are gone, but you can't see the water through the bridge. The deck is still there, probably concrete. And there was a crossover on the truss bridge.
https://www.facebook.com/photo?fbid=10222415564870706&set=pcb.3900601179984110

https://bridgehunter.com/pa/venango/oil-city-railroad/

[nkalanaga]

Yes, but the girders still have to support the load.  If there's a full turnout on the bridge, the load will be wider at one end than at the other.  So, the only two options are:

1:  Make the entire bridge structure wide enough for the turnout, basically a double-track bridge, or

2:  Build a "V" shaped structure, wider at the wide end of the turnout.

Either will be structurally sound, but I have no idea what a given railroad would choose.

[OldEastRR]

With the girders under the solid deck, really only need to have the outer plate girders showing without needing extra girders hidden behind them, at least for a model.  Right? As long as nobody can see the underside.

[nkalanaga]

True.  For a model, one can run the regular roadbed right across the gap, and glue the girders to the outside.  As long as the underside isn't visible, it doesn't matter.  If the girders are deeper than the roadbed, one can fake the bottom portion of the center girders, so even if the underside is somewhat visible, it will look good.

For a through girder bridge, a solid floor could be prototypical.  There are a couple bridges in Catlettsburg, KY, on CSX with solid floors.  Instead of center girders and cross beams, the underside is closely spaced crosswise small I-beams, with a solid floor above them.  Its a ballasted deck bridge, and I think they did it that way to maximize clearance over the streets.

Those are double-track bridges, on a fairly sharp curve, so the same design should work for a turnout on a bridge.

[m_nanson]

Two very important bridges in Canada have turnouts on them.  First is the New Westminster Bridge in New Westminster in the Lower mainland of BC.

https://www.google.ca/maps/@49.2089709,-122.8968925,120m/data=!3m1!1e3?hl=en

The second is the Victoria Bridge in Montreal
This one is Double tracked and splits in to four lines to cross over the St Lambert locks of the St Laurent Seaway.  The line is Quad tracked over the locks, Two tracks over each end so that the rail line is never interrupted when ships are transiting into or out of the locks.  It is also a major road crossing to the South shore of Montreal and the road way also snakes over each end of the lock in a spaghetti like fashion allowing two way traffic to never be interrupted.

https://www.google.ca/maps/@45.4930139,-73.5211736,914m/data=!3m1!1e3?hl=en

In answer to your question, I think both decks are solid and ballasted where the turnouts are located.

[fire5506]

Since you asked about a ballasted bridge, Here is one.

https://www.google.com/maps/@40.3871128,-79.8535222,100m/data=!3m1!1e3


Richard

[Jbub]

Since you asked about a ballasted bridge, Here is one.

https://www.google.com/maps/@40.3871128,-79.8535222,100m/data=!3m1!1e3


Richard

Looks like a freeway interchange