CSA S16-19 cl13.13.4.3 when does it apply? 1

[leetse]

The clause 13.13.4.3 (a) in S16-19 states. If you are confident of the loads and you want to design the HSS weld for the actual forces in the weld you must design the weld for a minimum 50% yield of the connected wall. This clause seems very vauge? Does it apply only in HSS to HSS branch connections due to the unknown stress distribution in the joint. If there was a HSS to a Cap or base plate with a moment would it apply in that situation also? The commentary does not really help much either.

 

[canwesteng]

I would apply to a base plate connection as well. Essentially any time there is compression in the weld.

 

[EngDM]

I agree that this is pretty vauge. If you need to design the weld for 50% of the yield then the minimum weld now governs over the sizes shown on 6-188.

If we take 1/4" thick tube (pretty standard) @ 350MPa, our Tr per mm works out to 0.9*350*1*6.35*50% = 1kN/mm (might even be best to not factor by phi if it wants yield strength) which exceeds a 1/4" fillet weld's capacity at 0°. I'd really rather not have to use the 90° to get this to work, for most things I just take the lower value conservatively unless I need to get it to work pretty tightly.

Edit: This also makes guardrail connections absurdly heavy as well.

 

[leetse]

I really think this only applies to HSS branch connections, because the clause in the previous revision sent you off to w59, but it is really open ended and vague.

 

[jayrod12]

I'd really rather not have to use the 90° to get this to work

Except that this clause specifically is intended for loads normal to the weld axis, therefore it is the 90[sup]o[/sup]. Which even a 5mm weld can provide. So I don't necessarily see the issue.

 

[EngDM]

Except that this clause specifically is intended for loads normal to the weld axis, therefore it is the 90o. Which even a 5mm weld can provide. So I don't necessarily see the issue.

Yes, I realize that. Refer to the second half of that sentence...

 

[jayrod12]

Yeah. Sorry if it came across wrong. Was more just pointing it out for clarity to others. Probably should have started a new line for my last sentence so it didn't come across as accusatory.

 

[leetse]

(Structural)8 May 24 17:05
Quote (EngDM)
I'd really rather not have to use the 90° to get this to work
Except that this clause specifically is intended for loads normal to the weld axis, therefore it is the 90o. Which even a 5mm weld can provide. So I don't necessarily see the issue

This is 100% my understanding, however the commentary for that clause states directional factor not to be used for HSS fillet welds. So it contradicts the clause and Packers paper. The specific problem I have is a colleague has a HSS brace with a Tee end, brace is tension and compression, long so it is thick walled but very lightly loaded. So for the tension case you need a small weld, but for the compression case you need a much bigger weld if you interpret the code literally, when the HSS is bearing against the cap plate. How can you need a bigger weld for the compression case than the tension case?