Where's the steel in a concrete viaduct?

[snowplough]

I plan to model a (curved) concrete viaduct, but I'm not sure what, in the way of steel beams, plates, etc. might typically be exposed on such a viaduct. I'm especially interested in learning what the platform (where the track is laid) looks like. Do exposed steel beams bridge the gap between the viaduct walls, or does the platform actually have a solid floor (made of plates or concrete)? Are the ties actually part of the viaduct structure, or are they simply laid on top of the platform? (Surely a track on a viaduct isn't ballasted, is it?)

Also, should I use bridge track (with a guardrail) on a viaduct, or regular track?


snowplough

[steemtrayn]

The concrete is poured around the steel reinforcing rods and is not visible on a completed viadust. The deck should be ballasted, so regular track can be used.

[brucejob]

You might find these books informative:

"Bridge & Trestle Handbook" by Paul Mallery,
published by Boynton & Assoc

"Model Railroad Bridges & Trestles" (Model Railroad Handbook No. 33)
published by Kalmbach Books

Both books present an overview of engineering and building practices with details of specific designs.