harryagain wrote
Brian-Gaff wrote

But it might bend of course, more than the actually specified item. One
really needs to know such things in case it cracks the building by its
lack of rigidity.

After all it is load bearing in a different way. also if you are indeed
using old lines, the how do you know metal fatigue has not started?

A railway line is probably about 20 times stronger than needed.
The axle loading of a steam locomotive could be over 20 tons.

But those don’t have a ****ing great hole under the rail.

Your little triangle of masonary wieghs nothing by comparison.
Especially if two are fitted side by side as was the normal trick.