HSS-Plate Weld In-Plane Bending

[jreit]

I am welding a connection angle to a HSS vertical member. The weld will be subject to in-plane bending.
I am specifying a 4" long 5/16" fillet weld that fits on the workable flat (4.25") of the HSS member.
As per the design requirements for HSS welds - there is an effective weld length that needs to be calculated and I can't find a good reference in AISC Steel Manual or the Design Guide 24 as the weld is discontinuous and those examples don't cover that. I can't use the full 4" length of the weld on all 4 sides.
Apparently, the STI HSS Design Manual, Volume 3, Example 3-7.5 covers this but I don't have that reference.

Would anyone have any ideas on how to analyze this?
Also, in your experience would an all-around flare bevel groove weld be a better detail here?

Sketch attached. The moment in red goes in and out of the page.

 

[SteelTubes]

If you are just looking to determine effective weld length, could you use AISC 360-22 Table K5.1, transverse plate to rectangular HSS? And then subsequently, Equation K1-1 to get your branch effective width and K5-4 to get effective weld length?

The Steel Tube Institute's Effective Weld Length Calculator will also do this calculation. You do need a professional membership to use it. There is a transverse plate to HSS connection.

https://steeltubeinstitute.org/resources/hss-effective-weld-length-calculator/