HSS welded to HSS 6

[McMichael05]

Need some help in determining if this connection adequate for the given loading. Its a HSS6x6x1/4 beam welded to another HSS6x6x1/4 beam. Calls for a 3/16 fillet weld around the whole member. Has a constant shear of 4.5k and a torsion of 0.365k-ft. Having a hard time determining the required depth of the weld needed. Any help would be appreciated. Thanks

 

[spieng89]

You won't be able to fillet weld all the way around given the HSS shapes are the same size. Can you make the beam members smaller? This will simplify the conenction calculation

 

[McMichael05]

No i can't change the size unfortunately

 

[phamENG]

Then you need to change your welds. Fillets where appropriate and flare bevels where appropriate.

For calculating capacity, do you have access to Blodgett's Design of Welded Structures? Very easy elastic analysis techniques that are straightforward and related to more general concepts.

Otherwise, take a look at the "Weld" tab in the Steel Construction Manual. It gives all the equations you'll need to to figure out minimum weld strength/inch, and then the equations in the specification in conjunction with the effective throat numbers from the various weld types in the weld tab will give you the strength/inch in the joint. If it's good, great, if not, try again.

 

[McMichael05]

Yes i do have Blodgetts design. I've been looking through it for help.
Would you then just find the capacity for the fillet welds using o.928DL (ASD)?
Then you would add the capacity of the flare bevel welds to that to get the total?
Also, could you give some direction where to look for these equations?
Thanks

 

[phamENG]

In elastic weld analysis, the simplifying assumption is that all weld segments have a width of 1in for calculating geometric properties to determine minimum strength per inch. Then you figure out the actual effective throat that gives you that strength.

One thing to keep in mind: unless Blodgett's book was rewritten for strength design (and yes, ASD now means Allowable Strength Design, not Allowable Stress) you can't use it all the way to the end. My copy is very much allowable stress based.

So...take a look at Table 4 on page 7.4-6 (I'm going to assume your pages are numbered as mine are). You can determine the "treating the weld as a line" force in lbs/in. To do it, you'll need the Aw and Sw values, which come from Table 5 - Properties of Weld Treated as Line.

Now that you have that, you'll want to go to AISC 360. You're in North Carolina, so you're still using 2010 (me, too - makes it easier). Flip to Chapter J - Design of Connections. You'll need to check the weld metal and the base metal separately. Table J2.5 gives guidance on what to check for various weld types.

Use J2-2 to check your base metal, and J2-3 for the weld metal. You'll want to adjust the equations to get the units right. As written, they'll give the total strength of the weld based on the full area. Modify it to be "area/inch" or something like that so you can compare it to the required strength per inch of weld from the elastic weld as a line analysis.

Effective throat of a fillet weld is measured as the shortest distance from the root to the surface (for an equal leg weld it's .707*Leg). For the flare bevel, you'll need to look at page 8-61 and use the table to determine the achievable weld size for your configuration.

Once all that is done...be sure to discuss it with your supervisor because welded joints are not to be taken lightly.

 

[BAretired]

No i can't change the size unfortunately

Why not?

BA

 

[RPMG]

Yeah, why not?

 

[r13]

The ARCHITECT, who else?

 

[CANPRO]

Is there any bending in the HSS at the connection? Having just shear and torsion at a joint seems unusual to me. If the HSS to HSS is also transferring moment then this becomes a bit more cumbersome. Check out AISC Design Guide 24.

 

[RPMG]

There are lots of red flags here from the member sizes, welds, and no bending moment.

But for the sake of discussion, the HSS wall strength 46/1.67*1/4 = 6.9 kip/inch, and the weld specified is 0.928*3 = 2.7 kip/inch. I would question whether it's a good idea to connect such a large section with a little weld. Why not try 5/16" welds first, since they're both single pass? For that matter, I don't think that it's unreasonable to specify 1/2" welds, given the errors and inexperience.

 

[BAretired]

If the column shown in section occurs at the same location as the members shown in plan, there isn't enough room to make the weld.

BA

 

[XR250]

But for the sake of discussion, the HSS wall strength 46/1.67*1/4 = 6.9 kip/inch, and the weld specified is 0.928*3 = 2.7 kip/inch. I would question whether it's a good idea to connect such a large section with a little weld. Why not try 5/16" welds first, since they're both single pass? For that matter, I don't think that it's unreasonable to specify 1/2" welds, given the errors and inexperience.

RPMG,

The loads here a tiny unless I am misinterpreting things (4.5k shear, 365 ft-lb torsion (or moment - don't really know). Seems like JB weld would be suffice.

 

[RPMG]

Where is the 4.5k? It's 1" offset to the plan north or south, and not cantilevered.

-OR-

The analysis is wrong. How could that connection have zero moment?

I don't disagree, XR, that those forces are tiny, but McMichael is going to specify a weld that he doesn't know how to analyze, design, or detail, and you just told him to glue it.

 

[phamENG]

To be fair, he could have told him to duct-tape it.

 

[RPMG]

Fair Play. Walmart Engineering.

 

[CANPRO]

XR250, I think you are missing something. I can't imagine a practical situation where this joint sees shear and torsion, but not a bending moment. Assuming the 4.1k load is applied at the end of the 25" stub, you'll have almost 10k-ft in bending at the joint.

This guy created an account on E-tips and logged in only once to ask this question, which is a pretty basic question. Based on how basic the question was, I wouldn't take the forces provided by the OP at face value. Even with the bending moment, the loads are still very manageable - but I think its a slippery slope giving this guy the confidence to just write-off the weld design at this joint as unimportant. I respect your opinion, and I've been around E-tips long enough to know that you know what you're talking about - but I think you might have armed the OP with a dangerous level of confidence.

 

[DrZoidberWoop]

If your given load forces are accurate, even treating it as 2 parallel weld-lines is more than strong enough.

HSS6x6x1/4 max fillet weld the wall can handle (assuming A500B material) is 0.75*0.6*58ksi*0.233in/0.928k/in/16th=6.55 sixteenths.

 

[XR250]

I can't imagine a practical situation where this joint sees shear and torsion, but not a bending moment. Assuming the 4.1k load is applied at the end of the 25" stub, you'll have almost 10k-ft in bending at the joint.

This guy created an account on E-tips and logged in only once to ask this question, which is a pretty basic question. Based on how basic the question was, I wouldn't take the forces provided by the OP at face value.

That's fair, CANPRO. The forces did seem unusual. Thanks for the feedback.
On a side note, my local steel fabricator carefully cuts the attaching tube so that it matches the profile of the column to keep him from having to build up welds as much.

 

[phamENG]

XR250 - if only everyone were so conscientious in their work. But how is that much of a benefit in this application? You end up with a little "blade" of steel sticking off that will surely be melted off in welding. Aside from that, it alters the geometry of the joining faces such that it is no longer technically prequalified, is it?

My question now is: where is the OP? Hopefully he wasn't just looking for a quick answer and then run away without engaging in the conversation.