Fillet weld sizes for HSS Tube column base plates
Fillet weld sizes for HSS Tube column base plates
(OP)
I am designing a base plate for an HSS tube column. My column is a 10x10x1/4 and my base plate is 1 1/4" thickness. From the AISC design guide 1 for base plate it seems pretty standard to call out a 5/16" fillet weld size. But,I have also seen in the AISC design guide 21 for welds that "The minimum fillet weld size need never exceed the thickness of the thinner part being joined." I have read that 5/16" welds are economical. Is it possible to use a 5/16" weld size for my HSS 10x10x1/4 and my 1 1/4" thickness base plate, even though a 5/16" weld size is greater than my thinnest material? Suggestions/comments are appreciated.






RE: Fillet weld sizes for HSS Tube column base plates
At least that is how it was explained to me.
RE: Fillet weld sizes for HSS Tube column base plates
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Fillet weld sizes for HSS Tube column base plates
RE: Fillet weld sizes for HSS Tube column base plates
However, referring to AISC 13th Table J2.4, it appears you could use even smaller welds than what is being discussed.
RE: Fillet weld sizes for HSS Tube column base plates
It is fine to have a 5/16" weld for the base plate condition you describe. That quote says "the minimum fillet weld size need never exceed ..." If the loads dictate it, you might need more for your scenario.
RE: Fillet weld sizes for HSS Tube column base plates
Likely based on being able to develop the cross section with the weld.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Fillet weld sizes for HSS Tube column base plates
RE: Fillet weld sizes for HSS Tube column base plates
RE: Fillet weld sizes for HSS Tube column base plates
I guess that'd be true if you've never designed a column to anything close to it's tensile or bending capacity.
Pretty sure that would only apply if the load is pure shear. For example, if I have a 1/4" (nominal) HSS wall with Fy=46 ksi, the allowable tensile capacity is 0.233" (design t) x 46 ksi/1.67 = 6.42 k/in. The required weld to develop is D=(6.42 k/in) / (0.928 k/in/D) = 6.92 D ==> 7/16" weld.
So, by my understanding, if you provide a 1/4" weld, you're only providing 57.8% of the bending/tensile capacity. If you follow the 5/4 rule, you're only providing 72.2%.
RE: Fillet weld sizes for HSS Tube column base plates
RE: Fillet weld sizes for HSS Tube column base plates
I was thinking of shear load rather than axial load. I'd assumed that we were talking about a compression column finished to bear at the base plate. If it's a more exotic loading condition than that, OP will have to elaborate. If it's a predominately tension member, OP should rethink that enormous cross section and 1/4" wall thickness.
That said, it would be a pretty rare column that would be so heavily loaded axially that a base plate weld matching the wall thickness wouldn't provide an axial capacity exceeding the buckling strength of the column.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Fillet weld sizes for HSS Tube column base plates
AISC mentions that a weld sized for 5/8 of the plate thickness will develop its strength, in bending, shear, whatever. They have also acknowledged that this doesn't calculate, but it has been verified in testing.
RE: Fillet weld sizes for HSS Tube column base plates
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Fillet weld sizes for HSS Tube column base plates
RE: Fillet weld sizes for HSS Tube column base plates
Check out the attached table from CISC's steel manual which I've just "discovered". They spec a 10 mm fillet weld for shear development. I imagine that they're using calculation rather than the 5/8 / extended shear tab business from AISC. High falutin' technology like that can take a while to make its way across the border.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.