Looks like the top one is a side of a atlas or? Bridge on atlas piers and the bottom pick looks like another custom bridge using warren bridges. But never seen a item like that from a retailer
Too, the curved bridge structure supported by it would never support anything more than light rail transit. Nonetheless, it looks like a fun railroad.
In the real world, it's unstable and once you cut the top of the girder like that you have effectively reduced it's load carrying capability drastically, to the point of uselessness. But this is a model railroad.
Extremely exceptional. The whole construction is still made up. Since looks as a model already unstable. Sorry........ is just my personal opinion.
It's possible, but the girders aren't compromised like the model. If you were to build something like this, you could use Micro-Engineering girders?
If I were a modeler, I would have made those two structures myself out of scrap wood or other available stuff.
from a structural engineer's point of view 1. the support beam (girder) with the mid cut in the first photo (estimated span about 25-30m) is not realistic. One solution is rearange the track and fit a pier (column) to support the bridge. The bridge carrying the track above the four tracks, is unrealistic too, because is too thin. A solution to this is to make a girder bridge or a truss girder bridge, again with a realistic hight to the span ratio and enough wide for the curved track. The biggest problem to make it looks realistic, if my eyes don't lie to me, is the slope of the track. 2. the bridge carrying the turnout in the second photo looks like more realistic and is achievable, though I dont see all the supports and the girders will have to be a little higher maybe. 3. @Kurt Moose, the beams supporting the bridge in the photo are not cutted and the bridge's beams are connected to the web of the supporting beams. Another difference is that the bridge is connected to the supporting beam near to the support pier and not in the middle of the span. Finally, as already mentioned, you can easy model theese structures from scratch. For the supports placing and to choose the bridges a plan is necessary.
Necessity is the mother of invention when it comes to our hobby. Is it always plausible? No, but if it works and looks half good while doing it...I say go for it !! JMO
Once went to the Naperville prototype modelers convention , and went to a clinic of realistic bridges. We sat through nearly an hour of photos of bridges on guys layouts that, it constructed in real life couldn't support their own weight. He then elaborated on the things necessary to make a realistic bridge. It was a fairly short list and nothing was beyond a entry level scratch builder. And nothing he showed was something that was not obvious to the average high school student.
