I don't see where "the web was cut away". I see shadow.
The cross-section of the assembly does not appear to me to be rail based: the base of the "rail" is too wide for its height, the head of the rail is way too shallow for its width.
I DO find interesting that the part below the car side was flame-cut, and that there are two empty holes showing. And also that I don't find evidence of such holes in the other big-ribs. And that there doesn't seem to be much of any cross-connection of the "hanging" part of those ribs by a cross-member under the car.
'Tis an interesting puzzle.