AISC Fillet Encroachment 1

[STR04]

All,

Can I frame a beam (tw = 3/8") into a column (W8x31) at its web using a double clip (2)-L4x3x5/16 (Long Leg Back-to-Back) with the use of Figure 10-4, LRFD Third Edition or Figure 10-3, Thirteenth Edition? According to this figure k=6.125", tf=0.435, Kdet - tf = 0.69 thus Encr. = 1/4". This leaves me with k+2(Encr)=6.625". Any thoughts?

TIA

 

[swearingen]

I'm a little confused on your nomenclature. I'll have to make an assumption:

The 6.125" dimension that you call "k" seems to be a misnomer. It's closer to a T dimension, but that's the T dimension for the W8x28 and W8x24, not the 31.

The quick way to do this stackup is to add 6" (2-3" angle flanges) to your tw of the beam coming in. In your case this would be 6 3/8". Then compare that to the T dimension for the column you're framing into. The T for a W8x31 is 5 3/4", so it won't fit. Note that it also will not fit in a W8x28 or W8x24 either.

 

[STR04]

Sorry, T not k. I disagree with your statement. For a W8x31 T+2*Encr = 6.25" thus providing you a 1/4" web thickness. For a W8x28 or W8x24 T+2*encr = 6.5" thus providing you a 1/2" web thickness. Your assumption is correct based on older AISC versions but without newer references listed above you struggle to understand my issue.

 

[swearingen]

I have my 13th LRFD/ASD sitting open right here and every number I wrote on the earlier post checks out.

I was not taking advantage of what's called "riding the fillet". You do indeed get an extra 1/2" of space for this member bringing you up to 6.25" of room which is just enough for your clips and a 1/4" web. Also, you can get a larger web with the same angle clips into the W8x28 and W8x24 as you stated.

 

[WillisV]

As a followu-p to swearingen - further information for "riding the fillet" can be found on p10-8 of the 3rd Ed, LRFD along with a table of allowable encroachments.