HSS Transverse T-Connection Weld (AISC 360-10, K4)

[P1ENG]

I have a 5.5" wide by 5/8" thick TRANSVERSE plate welded to an HSS8x8x3/8, because I am creating a W-flange beam to HSS moment connection.

Per equation K4-4, my calculated effective weld is 3.42" even though there will be 11" of weld (5.5" across top and bottom of plate). Based on my load and this effective length, I need a 1/2" fillet weld. This seems like a lot for a 3/8" thick wall tube. The last paragraph in section K4 (before the User Note) says:

"The weld checks in Table K4.1 are not required if the welds are capable of developing the full strength of the branch member wall along its entire perimeter (or a plate along its entire length)."

I think this will let me reduce my weld size, but I need help deciphering this statement. I don't understand what "developing the full strength" means. If my weld strength is equal to my plate's base metal strength, I don't need to calculate le per K4-4? Is "full strength" nominal or LRFD/ASD?

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[P1ENG]

I think I understand now. I would have to develop the Fy*Ag strength of the plate in a single line of weld equal to the length of the plate(5.5" long), but that weld would have to be along both sides (11" total). There is no way that the paragraph I quoted will ever be less than the value of table K4.1. If I want a smaller weld, I just have to make my plate thinner as long as the plate can handle the loads.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant