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Welding of HSS to HSS

EngDM

EngDM

Structural
Aug 10, 2021
706
I'm working on the connections in an HSS truss, and I am spot checking with Risa connection when I noticed that, if the width of your branch member width + 2*weld D exceeds the workable flat of the HSS chord, it doesn't allow you to proceed with the calculation. I've screenshotted their report below:

AISC_weld.png

However, we have received structural steel shop drawings (when we are EOR) where the weld does not pass this same check, and fillet welds are still used all around.

Realistically I could groove weld the branch to the chord, but I know I've seen fillets used even though they don't "pass" this check which are much more cost effective.
 
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I think it is a best practice thing, I am not a big fan of RISA connection software, some of its error outputs are difficult to investigate or resolve.
steeltubeinstitute.org

Welding in HSS Corners | Steel Tube Institute

Although it is generally recommended to avoid welding in the rounded corner regions of square and rectangular HSS, it is sometimes required, such as when full-width branch-to-chord truss or frame connections are desired.
steeltubeinstitute.org steeltubeinstitute.org
 
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jhnblgr said:
I think it is a best practice thing, I am not a big fan of RISA connection software, some of its error outputs are difficult to investigate or resolve.
steeltubeinstitute.org

Welding in HSS Corners | Steel Tube Institute

Although it is generally recommended to avoid welding in the rounded corner regions of square and rectangular HSS, it is sometimes required, such as when full-width branch-to-chord truss or frame connections are desired.
steeltubeinstitute.org steeltubeinstitute.org
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Agreed. Hunting down their references is a nightmare. Especially for CSA references, where the page they reference isn't the same for the edition they are running the connection for.
 
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To elaborate a bit more on this, and maybe get a quick sanity check:

I am considering providing groove welds on the sides nearest the rounded edges from the branch to the chord. If I do this, and I am assuming my weld is loading equally, then the fillet weld on the flat face of chord would be my limiting factor (unless of course I exceed the tensile strength of the CJP and gross section).

Do CJP welds still have to use the effective width outline in equation K1-1?
 
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jhnblgr said:

Know Your HSS Welds

www.structuremag.org www.structuremag.org

See if this helps
Click to expand...
Do you know of anything more recent that deals with KT connections? The only thing I have been able to find it a CISC book from Packer that gives a substitute value of Beff to input into the AISC equations, but it is quite old.
 
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jhnblgr said:
AISC design guide 24 discusses it a bit
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Yea I was reading that as well, I couldn't see anything regarding KT connections though unless I missed it. The Packer reference gives transformations to the AISC equations.
 
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skeletron said:
This is a good one to read. Perhaps not exactly related to the exact welding arrangement you've described, but important nonetheless with respect to understanding the effective throat at corners.

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Thank you for this. I was more referring to the case that comes up when welding an HSS to an HSS in a T configuaration. There is the equation for Beff which is like 10/(B/t)*[(Fy*t)/(Fyb*tb)] which reduces your effective weld length on an HSS face presumably since the corners are stiffer and as the face of the HSS gets loaded it tends to bend, and throws the load into the corner/side welds first. I was just wondering if this same trend happened to CJP welds or if it was only applicable to fillets.
 
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Flotsam7018 said:
Still applies. The CJPs don't do anything for the stiffness of the connecting HSS face.
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That's what I figured. I've got one of those "Design to X% member strength" for an HSS truss, and with all of this reduction in area the connection is proving to be a big pain.
 
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What does your truss look like? Maybe there’s an alternative method of connection. Could a gusset plate connection work better?
 
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jhnblgr said:
What does your truss look like? Maybe there’s an alternative method of connection. Could a gusset plate connection work better?
Click to expand...
Simple rectangular HSS truss. Web members are thinner than chords so I can't easily do side gussets.

I got the load reduced by the EOR so it should work fine now with the weld area I have.
 
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