Ok, I we are not talking about seismic, right?
What kind of connection?
I prefer a knife plate.
Some use a cap plate plus connection plate.
Then the bending of the connection plate would depend on the relative stiffness of the gusset versus the tube. Typically your gusset is going to be more stiff than the tube, so that would put you into simple bending. If you used a thin connection plate you might get into double curvature bending. Note that this would be weird. You'd end up with a pile of bolts and a really large gusset.