1) What code are you referencing?
2) Do you have an example of the type and orientations of your connections?
3) Do you use AISC's Manual of Steel Construction? It does a great job these days of providing connection details especially tubing and pipes. AISC also provides a manual for Seismic regions, so the connection type may differ given the seismic folks like a little more joint movement for energy dissipation. I have not had the pleasure of using the Seismic manual.
Back when AISC had the red book (guess how long ago that was) I spent weeks researching the effectiveness of steel tubing sections when connected to other sections. AISC addresses all those types of connections. A great reference book is Blodgett's Design of Welded Structures. One of the most brilliant engineers I ever knew, R. Krumpen, introduced Blodgett to a lot of us young engineers starting out. It was a jewel. I used my Blodgett so much that it has duct tape holding it together.
[Note: Some may have businesses that provide consulting services, so a detailed answer may not be readily available.]
Steel plates aka gusset plates, stiffeners, chock plates or simply plates. Plates connected or embedded in one, both or multiple members.
However, in some cases you will not be able to obtain 100% and have to reduce the effectiveness of your connecting member.
By the way, in this era of modeling structures being able to produce a solid model of the connection and applying a unit axial, shear, torsional and bending forces individually should provide great reference numbers as well as the visual of stress concentrations easily identifying the effective regions.