AISC Table 8-2 (TUBE) & Table 10-13 1

[MacGruber22]

I am reviewing shop drawings for shear tabs welded to 6" and 8" SCH40 pipe columns. In the past, I have noticed that detailers often miss providing larger fillet welds (or switching to PJP welds) to make up for the acute angle on skewed shear tabs. The questions are:

1. Does Table 8-2 for tubes apply to shear tabs welded to round HSS/pipe? If so, am I correct that you must always use PJP welds for this condition?
2. Or - can you still use fillet welds and verify with Table 10-13 by increasing the skew base on the additional angle between the end of the fillet leg and pipe/HSS wall?

Sketch attached.

Thanks a bunch!

p.s. - the attached sketch certainly doesn't have the worst case shown.

 

[48v]

I'm not an expert in AISC, but in AWS D1.1, which it follows for most weld details, if your dihedral (95.1 in your sketch)angle is between 80 and 100, you can just treat it as a fillet with no adjustments. Between 60 and 80 degrees (or over 100 degrees), you have to adjust for the diagrammatic throat. Less than 60 degrees, you have to consider a 'Z-loss' to account for the possibility that they may not have been able to weld all the way at the bottom of the acute angle. In these cases, it stops being a fillet weld and is classified as a 'Skewed T Joint."In D1.1:2008, the sections that explains this are 2.3.2.6 and 2.3.3. In table 8.2 of AISC SCM does include the prequalified details for skewed T joints. in the 13th edition, it's on page 8-36.
Hope that helps.

 

[MacGruber22]

Thanks, 48v.

Maybe I didn't explain myself well enough. I understand table 8.2 doesn't include the prequalified details for skewed t joints - the title of the table is what I am wondering about (whether it categorically disallows fillet welds for a shear tab on pipe/round tube)

As you mentioned the AWS classifies the more dramatic angles as "Skewed T joints", which may not use fillet welds - thus, you are using partial joint penetration welds, as qualified for the application. Again, table 8-2 on page 8-63 of the AISC 13th seems to indicate their are not any qualified fillet welds for connecting to the face of pipe/round tube.

Thanks!

 

[48v]

As I understand it, that page refers only to TYK connection, which are tube-to-tube. In your case, tube-to-plate I believe you can treat it as you would a plate-to-plate shear tab, provided the dihedral angles work out for either a fillet or a skewed T. AWS D1.1 clarifies the issue in the commentary. See C-4.7.1 and Figure C-4.1 (p 463 in the 2008 ed.)

 

[MacGruber22]

I think I agree. Thanks, 48v.