Weld in tension 2

[McSEpllc]

I have two HSS10x10 beams 90 degrees turned from each other and one hung from the other with an 11 k tension load and minor bending. The Architect does not want any connection hardware. Usually I set up welds to be in shear. In this case though welding the four interfacing sides would be all in tension. It should be no different then a bending moment on a welded connection though. By the numbers it works fine. Has anyone of you done something like this?
Thanks!


Eric McDonald, PE
McDonald Structural Engineering, PLLC

 

[paddingtongreen]

I don't see why not, but how do you make the welds at the sides? The outside curve radius is twice the thickness of the material. At best you can get a J groove weld but that separation is too much.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[dhengr]

An 11k tension/(4x10") = .28k/in., a shear flow, on the welds. The moment causes shear stress on the weld on two sides, and the moment is resolved over about 9" of weld top&bot. with a lever arm of about 9.5", that is... (M in inch kips)/ 9.5" lever arm = force in kips/9" long weld = another shear flow on the weld, these are actually all shear stresses in the weld, the way the weld sees them, and they are algebraically additive, for a max. weld stress at two corners. On the leg of the Tee joint you have fillet welds on two sides, and a nasty groove weld on the top&bot., at the corner radius of the HSS which is the top of the Tee. As long as this is not a fatigue sensitive structure, this connection should be no problem. The groove weld just shouldn’t be considered a full pen. groove weld, because of the poor root consitions.

 

[McSEpllc]

Thanks both of you.

All four sides are groove welds. I am considering adding two "shear tabs" in tension placed on top of the lower beam and sandwiching the upper beam. That will remove two of the four groove welds.

This is for a residential deck structure, so no major cyclycal loads

Eric McDonald, PE
McDonald Structural Engineering, PLLC

 

[dhengr]

McSE:
Lower beam and on top of and left and right don’t mean a thing from here, I can’t see what you’re looking at. A sketch would really be helpful, with moments and forces and their orientations, if you want help. Imagine the number of picture that could be drawn from your description, each a slightly different design problem. Your bending condition must be inducing one hell of a moment and shear, if you need intentional (prepared) grooves along two of the edges. The other two grooves are your fault for having chosen HSS’s, but ask your fabricator how to handle these grooves. Paddington must have pulled out a catalog, and I don’t doubt his open radius area comment. The fabricator will probably lay a filler bar in that opening, and just fill the groove over it, with the corner transition from this groove to the side fillets requiring a bit of welding finesse. Now, let’s see which of the welds is loaded by tension/compression from the moment, but you can’t make a small enough weld on those tubes to be over loaded by the 11K tention.

 

[connectegr]

We weld HSS the HSS all the time in structural steel construction. More information on your detail would be helpful. Are you cutting both members at 45* and welding the intersecting wall for a 90* corner? For only 11kips this should be no problem. A backing bar can be used to provide CJP (BL1a, I think I am typing on my iPhone). All the tension can be taken in the side walls at the CJP welds. The outside and inside corners can be seal welded for cosmetics. For other details and design requirements see AISC Chapter K and Design Guide 24.

http://www.FerrellEngineering.com

 

[McSEpllc]

Is there a way to upload a sketch into eng-tips?
connectegr: are you by any chance Tony or Doug so I could e-mail a pdf?

Eric McDonald, PE
McDonald Structural Engineering, PLLC

 

[connectegr]

Doug

http://www.FerrellEngineering.com

 

[KENAT]

"Is there a way to upload a sketch into eng-tips?"

If you look at the little box below where you type your posts you'll see a link to "...or upload your file"

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[paddingtongreen]

I have yet to see a legal weld, for one tube welded to the side of a tube of the same size, unless the end cut is very special. You cannot get an effective backup strip behind the side. You end up with a J bevel groove weld with a huge root gap.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[connectegr]

BTC-P10 flare bevel groove.

http://www.FerrellEngineering.com

 

[McSEpllc]

Thanks for all your feedback sofar. At the link below you can see a sketch that clarifies what is going on. This is for a deck for a high-end residence. The Architect wants to use HSS10x10 beams for appearance.

Eric McDonald, PE
McDonald Structural Engineering, PLLC

 

[connectegr]

The detail as shown should be more than adequate for the loads shown. Technically the weld symbol in not correct. Also technically the two E = 3/16 welds are adequate for the moment and tension load, which would eliminate the overhead field welds.

http://www.FerrellEngineering.com

 

[McSEpllc]

Thanks for the feedback connectegr. What is the correct weld symbol?

Eric McDonald, PE
McDonald Structural Engineering, PLLC

 

[connectegr]

I attached a sketch.

http://www.FerrellEngineering.com

 

[McSEpllc]

The sketch did not get uploaded

Eric McDonald, PE
McDonald Structural Engineering, PLLC

 

[McSEpllc]

NOW I SEE IT THNAKS

Eric McDonald, PE
McDonald Structural Engineering, PLLC

 

[paddingtongreen]

@connectegr, Oops I missed OP's sketch. I was thinking end of tube on side of tube, plus there was mention of a back up strip and a back-up strip couldn't fill the gap at the bevel.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[dhengr]

Paddington.... You and I were on the same page as to what the joint looked like. I would never have come up with the sketch the OP’er shows from his original description. Welding and stress transfer at and around the corners of HSS’s has always been a problem. So are the welds Connecteng shows, even though they are approved ,all because of less than ideal root conditions, once you rationalize that issue away everything is just fine. I probably wouldn’t do what I proposed in a fatigue sensitive or highly stressed joint. But, I also had a couple welders, out of dozens, that I’d go to when I wanted something done in a special way, not always a prequalified weld, but they were real artists and understood what I wanted. I probably woulda said, get a good backer bar in there, be sure it’s fused well to both members, then fill er up, I don’t want a bunch of chicken sh!t at the root. Stresses allowing, I would have him us a lesser, softer, welding rod to minimize cracking. And, I would have done the grooves first alternating sides, and then finished the side fillets and corner transitions.

 

[Duwe6]

Major Concern: D1.1 leaves NDT up to the Engr-of-Record. Industry standard is 100% UT [shearwave] of all tension groove welds. Strongly recommend the UT, and an MT [magnetic particle] test of these welds also. MT will find surface-breaking defects, UT will find everything else.

If nothing else, very cheap liability insurance.