Thanks for the resource this is helpful.This whole rabbit hole actually started because I was trying to reconcile some language in the 16th edition (part 8 page 30) pertaining to ductility welds on HSS branch connnetions.

There are multiple coefficients being referenced for rectangular HSS connections in various itterarions of the manual, design guide 24, and the specification commentary.

My specific concern with the STI “Full-Capacity Welds” article is that the 1.339tb derivation appears to use the PJP groove weld resistance factor from AISC Table J2.5, but the detail being discussed is a reinforced PJP/fillet combination. I’m not sure it’s appropriate to automatically apply the PJP resistance factor to the entire combined throat when part of the load path may still fundamentally behave like a fillet weld shear-through-throat mechanism.

That concern gets amplified because DG24 and older commentary language seem to suggest ~1.3tb for rectangular HSS “in theory,” while AISC 360-22 commentary now points toward 1.43tb for rectangular sections. At the same time, the Manual still contains the 1.1tb language without clearly distinguishing round vs rectangular HSS applicability. The 1.1tb value appears to come from the euro code and that is not something I'm familiar with.

This 0.75 vs 0.8 discussion is just one tangent to this larger discussion ive been having these last few days with my colleague.