Fillet weld/ Groove weld Combination

[FWQ]

How can I calculate de strength of a PJP (partial penetration) groove weld with reinforcing fillet weld. In tfis case I have a 1-in thick plate connecting a 1-in perpendicular plate, with 1/4-in groove each side and a 3/8-in fillet. Is just the sum off both effects? In this particular case it's not possible to achieve complete penetration because of the welded zone is not easy accessible. Thanks.

 

[gtaw]

Find the shortest failure path through the weld (graphically) and use that to calculate the area through the weld (shortest distance through the cross section of the combination weld times the witdth of the joint). The code you are using is going to stipulate how to calculate the allowable stress. I in this case I assume its AWS D1.1, so multiply the electrode tensile strength by 0.33 multiplied by the area of the weld.

Remember that the weld size is 1/8 inch less than the depth of the groove preparation if the groove angle is less than 60 degrees.

However, don't take my word on this, check AWS D1.1 and the AISC Steel Construction Manual to verify I haven't lead to down the wrong road. I could be a raving crazy man for all you know.

Best regards - Al

 

[HgTX]

D1.1 section 2.6.4 and associated commentary say that the reinforcing fillet weld does not count toward the PJP throat. The fillet weld is only there to reduce the stress concentration at a re-entrant corner.

Hg

Eng-Tips policies: faq731-376

 

[gtaw]

I don't disagee with your comment when the main load carrying weld is the bevel groove, but in this case it appears the fillet weld is larger than the groove weld and qualifies as a combination weld.

What edition of AWS D1.1 are you looking at? I have the 2002 edition handy and paragraph 2.6.4 says you can consider each of the welds in a combination weld separately, each carrying a portion of the load. As an alternative, Annex I shows a method of determining the "throat" of the weld as I described.

Different editions of the code have different requirements, that's what keeps life interesting!

Best regards - Al

 

[HgTX]

If it's a combination weld, then it's not a "reinforcing fillet".

D1.1-2006, C-2.6.4:
"Fillet welds deposited over groove welds do not directly increase the effective throat of the joint; therefore the strength of the joint may not be taken as the sum of the strength of the groove weld and the fillet."

Again, if what's being talked about isn't really a "reinforcing fillet", then language regarding reinforcing fillets doesn't apply. 1/4" groove and 3/8" fillet doesn't make a whole lot of sense to me.

But you're absolutely right about it being the distance to the face of the weld and not simply a sum of the capacities of the individual welds.

Hg

Eng-Tips policies: faq731-376

 

[gtaw]

I believe the commentary is simply stating that a small reinforcing fillet minimizes the stress concentration at the corner formed by the bevel groove weld in a tee or corner joint. As such, it isn't contributing to the strength of the weld because it isn't typically included in the shortest (straight line) failure path from the weld root to the weld face. However, in those cases where the bevel weld size is small compared to the fillet weld, the shortest (straight line) failure path can be through a portion of the fillet and it (the fillet) will contribute to the strength of the weld by increasing the "throat" dimension. If the fillet weld is about equal to the bevel groove weld, the failure path may be along the "short" fusion face if that is the shortest distance through the weld.

A great discussion when there's cold brew and peanuts to share.

Best regards - Al

 

[arto]

ASME UW-15c give Joint Efficiencies of 74% Groove Weld Tension, 60% Groove Weld Shear, & 49% Fillet Weld Shear.

So your Equivalent Thickness would be:
2x[1/4*0.49 +3/8*0.60]= 0.70" in Shear
&
2x[1/4*0.49 +3/8*0.74]= 0.80" in Tension

With equal-sized welds, for equivalent strength:
t = 1"/{2*(0.60+0.49)} = 0.46" in shear
t = 1"/{2*(0.74+0.49)} = 0.41" in tension
[thus the old t/2 & cjp]

[don't forget lamellar tearing for T-joints]