I am curious - does any code specifically address or state the applied stresses on backing?

Picture a vertical tubular structure. The weldment - done on one end only - is a CJP single bevel groove weld with backing. This backing is a 2.00" tall "ring" inside the tubular shaft and "seal" welded with a fillet weld.

The question is - while this structure is standing in a vertical position - the "seal weld" on the inside of the shaft - on the backing is approx 1.5" above the completed CJP weldment.

Does this fillet weld on the inside of the shaft see any type of stresses? Does it qualify as a Structural weld?

A related question --- the same tubular structure - but with a reinforcing "ring" on the outside of the shaft - instead of the ring inside. How do the stresses on this differe ( if at all) from the first example?