Longitudinal Seam Weld - ASCE 48-19

[structural-eng]

Can someone please explain to me what the last sentence in section 7.2.3 of ASCE 48-19 means? It states "Longitudinal seam weld shall have 60% minimum penetration (except as specified in Sections 6.3.4, 6.3.5 and 6.4.1 in this standard)." I understand that the exceptions listed require full penetration welds in certain locations. Is that section stating that the remaining portions of the seam weld that aren't required to have full penetration welds should have 60% (minimum) partial penetration welds? What is the equivalent size of a 60% partial penetration weld? In the case I'm reviewing the base material is (2) 1/4" plates oriented to form a 45° vee).

If a fabricator says every longitudinal seam weld is fabricated with 100% CJP for the top and bottom 6" and a minimum of 80% PJP for the remainder of the seam weld does that meet the requirements in section 7.2.3 of ASCE 48-19? I don't see anything in ASCE 48-19 about sizing the longitudinal weld, just these welding requirements which makes me think you can design the tapered pole per ASCE 48-19 as long as it's welded as noted.

 

[JStephen]

A 60% partial penetration weld, welded from one side only, would have a weld size of 60% of the thickness.
A 60% partial penetration weld could also refer to a weld double butt-welded from each side with an unwelded portion in the middle. "Weld size" in that case would be two different numbers for the weld on either side.
I think in some of our applications (more ASME type stuff), partial-penetration welds are also required to have a strength of that percent of the strength of the base metal as well. I don't if the Structural Welding Code or other welding codes have that requirement.

 

[dauwerda]

Is that section stating that the remaining portions of the seam weld that aren't required to have full penetration welds should have 60% (minimum) partial penetration welds?

Yes.

What is the equivalent size of a 60% partial penetration weld? In the case I'm reviewing the base material is (2) 1/4" plates oriented to form a 45° vee).

If you were to cut the pole in half and inspect the welded seam, you should be able to observe a fully fused welded area (weld throat) that is at least 60% of the total steel thickness. So in your case of 1/4" thick steel, the welded portion would be a minimum of 0.15" deep.

If a fabricator says every longitudinal seam weld is fabricated with 100% CJP for the top and bottom 6" and a minimum of 80% PJP for the remainder of the seam weld does that meet the requirements in section 7.2.3 of ASCE 48-19?

Yes, except that the exception for 6.4.1 has to do with slip joints. If a pole section is the female section of a slip joint the longitudinal seam weld needs to be full penetration for the entire length of the slip joint. The reason for that is the tensile hoop stress that is generated when the two sections are jacked together. So, as long as the pole section is not part of a slip joint, 6" of CJP meets the requirements, if there is a slip joint, the seam weld of the outside section would need to be a CJP for more length than 6" (it would be a minimum of the slip joint length).

 

[structural-eng]

Thank you @dauwerda! This condition is not a slip joint, the pole is bolted at the joints. If what the fabricator proposes meets the requirement of 7.2.3 am I able to check the pole strength based on Chapter 5 or do I need to consider a reduced strength of the pole since the seam weld is only 0.8*0.25"=0.2" effective?

 

[dauwerda]

There is no reduced strength, checks are per chapter 5.
The longitudinal seam weld is essentially acting as a brace connection between the two flats of the pole section. A 60% penetration weld is more than adequate to transfer the forces for that bracing effect. The main stress on these poles is axial (tension/compression couple due to bending), so the seam weld doesn't directly see those forces. Instead, it is bracing one flat with another to prevent local buckling of that flat.

 

[structural-eng]

Thank you!