Through Girder Bridge - Abutment and Shoes

I think you are correct.

http://www.johnmarvigbridges.o...ange%20Rail%20Bridge.html

https://www.structuralguide.com/plate-girder/

Atlas Bridge install. Not prototypical, focus was on the bridge as a lift-out piece, and the correct track height to match at both ends.  Click on the underlined phrase to link, then click on Start slideshow.

The model is made with (4) steel flat bars as part of the base.  The model bridge is self supporting, in addition to being a pretty good model of a Pratt Truss bridge. IMO, Mike CT.  Bridge with the grey abutments 40.5".

The girders sit on the abutments.

(My Photo)

Then what dictates if girders need bridge shoes or not?

As already stated, the girders carry the load to the abutments.  Rail bears on stringers, stringers transfer load to girders, girders transfer load to the abutments. 

I would submit that most sit on some sort of bearing shoe or plate.  Normally one end is a pinned (aka hinged) connection, while the other end has the ability to roll, rock, or slide.  This arrangement accommodates the change in length due to expansion and contraction (rolling or sliding end), and also the lifting or settling of the abutments (pinned or hinged end). 

In the case of the typical bridge shoes used on railroad bridges, both shoes look very similar.  It's actually only the base that is dissimilar.  They look enough alike that it's reasonable to use the same shoes on both ends of the bridge.

I know that Scale City Designs offered bridge shoes, or alternatively they are a detail that would be pretty easy to scratchbuild from styrene sheet and rod, or 3d print.

Jim

Thanks for the education guys. So I need to find a wider set of abutments to accommodate the girders.

Still, I haven’t seen a girder bridge (at least not a through girder bridge) on shoes. I’ve seen the girders resting on what I would refer to as skid plates (or slide plates) on the top of the abutment, but not on shoes (yet).