Partial Joint Penetration Groove Weld Sizes

[jdgengineer]

I have a question regarding Table 8-2 of AISC 360. I have always assumed that with a PJP weld that you would need approximately 1/8" min of root face (varies by welding process), and 1/8" min neglected groove to obtain your effective weld size (again varies by welding process). With the SMAW, and SAW process this appears to mean that you need to subtract out 1/4" from your material thickness in order to obtain the maximum size partial penetration weld you can do. With the GMAW and FCAW it depends on the welding position and varies between 1/8" and 1/4". Therefore, I've always used 3/8" minimum material and only used a 1/8" minimum effective weld size. To obtain a 1/4" minimum effective weld size I have always used 1/2" material. Am I misunderstanding this?

One of the reasons I ask is the table designates T1 as unlimited for the SMAW process. However, it states that f = 1/8" min, and E = S - 1/8. Therefore, how would you have any effective weld size with a 1/4" minimum thickness that appears acceptable per Table 8-2?

 

[racookpe1978]

If I understand the setup of your question properly, you are adding the worse possible cases together in your calc for joint strength, and then using that to set the joint prep conditions to get the final prep thickness.

But welds are individual events that require the metal to be joined by melting - that thick a joint base is actually harder to weld than a conventional 1/16 inch root face. Using such a thick face means each weld is less likely to be melted through and less likely to be properly consumed by the new joint metal. 1/4 plate, 1/4 bar stock is easily welded with a single pass, full-penetration weld. 1/2 thick plate? Multi-passes, each more likely to have slag or overlap or other problems inside the joint.

 

[jdgengineer]

This is for an HSS section, so CJP is difficult. I'm not trying to put together an especially thick PJP weld, I am just trying to get a sense as to what everyone uses for minimum base material thickness to accomplish a PJP per the prequalified welding details.

 

[nutte]

I agree with you that there is an apparent discrepancy in that table. For that procedure, you need at least 5/16" of base metal thickness to have an effective throat greater than zero.