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Single angle tube connection?

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SteelPE

SteelPE

Structural
Mar 9, 2006
2,759
I have a bunch of columns in my structure that are HSS8x8 (1/4-5/16). In looking at the reaction and my beam to column interface, it appears that I may be able to use single angle connections to support my floor girders.

I can use AISC tables 10-10 and 10-11 to calculate the capacity of the single angle connection. I can also calculate the minimum thickness of the tube = 3.09D/Fu. As I am manipulating AISC table 10-10 and 10-11 is there anything else I would need to consider when calculating the strength of the connections?
 
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connectegr

We had this discussion a few weeks ago (I must be forgettable).


My columns are 1/4" and 5/16" thick. For a single tab to work a my column would need to be 3/8" thick. Can you think of any reason why I could use the method I described above?

Hopefully we are discussing the same thing.
 
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For an 8" column the minimum wall thickness, for a 3/8" plate with 1/4 fillets is only 1/4".

But, single angles are acceptable. Note that the outstanding leg must less than 3" or trimmed to avoid welding at the radius of the column. Also provide only a return across the top.

 
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I am confused, I thought the minimum tube thickness for 1/4" fillet welds on a single tab was:

tmin = 6.19D/Fu
tmin = 6.19*4/58
timn = .426"

therefore you would need to use a 1/2" thick tube for a single tab. This calculation in done in reference to the AISC example K.6 you referenced in the other post.
 
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That would explain it..... I don't have AISC design guide 24.

I find it a little odd that the AISC give a design example on how to calculate the capacity of the connection and then contradicts themselves with a design guide.
 
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I have the HSS connection manual where in table 4-9 they list the minimum HSS thickness for welds on single-plate connections.

For a 5/16" plate with a 1/4" weld they list a minimum tube thickness of .22". I just thought they revised this table with the AISC 13th edition. Now I am really confused.
 
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Not to confuse you further, but there are several differences in the single plate design procedure and additional errata in the HSS Manual. My copy is painted in red pen. The quick reference I attached above is correct.

 
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SteelPE, use the other tmin equation, since each shear plane on the HSS will only see one weld.

tmin = 3.09D/Fu = 0.21"
 
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nutte.

This is something I though of in the previous thread but since the AISC design example was so specific I didn't bother.

Are you telling me that the AISC Steel Construction Manual CD Companion example K.6, which references the above equation (6.19D/Fu) which references HSS shear rupture strength at the welds, is incorrect?
 
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Hmm, allow me to rant a bit.

Yes, the example K.6 is in error. Look at version 13.1 of the design examples. They use the equation with 3.09.

But that's not all that's wrong with the first example, in version 13.0. First of all, they use a 5/16" shear tab. Does anybody really use that plate size? Isn't a 3/8" shear tab the common starting point?

Then, with the wrong tmin equation, they decide to decrease the weld size, so that tmin is not violated. But in doing this, their weld size, 3/16, is less than the minimum weld size for the 5/16" shear tab. That minimum weld size is 5/8*5/16=0.195", a bit more than 3/16. By using a weld less than 1/4, they've violated the shear tab procedure.

So yes, this example is wrong.
 
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Nutte,
Good catch on the weld check. I rarely use the design example CD, and attached the single plate example to a previous post without review. I agree with all of the issues you point out.

Sorry SteelPE, I had hoped the K.6 example would resolve your original questions. I should have attached my own calculation.

The good news is that the single plate design procedure has changed again in the 14th Ed manual. So I am sure we will have this discussion again in a few months when more people receive the new manual. The changes are related to bolt shear strength, not your current HSS issues.

 
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nutte-
Can you explain a little further what you mean by "each shear plane on the HSS will only see one weld"?

 
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For the 6.19 factor to apply a weld would have to be placed on both sides of the tube wall (with one inside the tube). Similar to shear plates located on both sides of a beam web. In this case two welds are applied to one side of the HSS wall and separated by the thickness of the shear plate. The shear plate experiences two shear planes, with a weld on opposing sides. But the HSS wall has only one shear plane. Therefore the 3.09 factor is correct for verifying the wall thickness relative to the weld.

 
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Toad, for the HSS wall to fail in shear rupture, there will be two shear planes formed, one on each side of the shear tab. Each shear plane corresponds to one weld, which is why you'd use the equation with 3.09.
 
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