HSS post extension 2

[VA-Struct-Engr]

Hello,
I have several HSS 5x5x3/8 posts that were not fabricated to the correct length. The fabricator would like to reuse the existing posts and weld a new piece at the bottom of the posts while avoiding CJP welds. The posts need to extend 1ft-0”. The posts only support gravity loads in the order of 20kips to 50kips total load. I am thinking of using a “sleeve” to attach the two pieces together. The post above will bear directly on the piece below. Let me know what you guys think.

Thanks for your help in advance.

 

[XR250]

My guess is it is fine without the sleeve. Also, I would be surprised if you can get an HSS 6 x 6 x 1/2 sleeve to fit over the 5x5 pipe due to different bend radiuses and fabrication tolerances.

 

[Once20036]

In my experience, fabricators don't want to use CJP welds in this instance due to the backing bar requirements.
In the past I`ve used PJP welds for this application.
The PJP joint penetration is 1/8" less than the material thickness, so I`d analyze that low section as an HSS 5x5x1/4 instead of HSS 5x5x3/8.
It's a much easier weld to produce.

To XR250's point, there's also probably a bead inside the tube that will interfere with the slip fit that you`re envisioinig.

 

[phamENG]

Of course they want to avoid the expense. But they messed it up, and they need to fix it. What they provide needs to be at least as good as what they were contracted to provide.

So I would make them either provide full length columns or CJP to extend these. But be careful. This is very near the base. What is this supporting? You're in Virginia, but even around here we still have to detail for seismic at times. This is close to the protected zone of some seismic force resisting systems which may preclude repairs of any kind.

 

[XR250]

Would an internal 4x4 sleeve act as a perimeter backer bar?

 

[dold]

Stick a plate between the new and existing and just fillet weld all around. You end up with the same amount of weld.

 

[dik]

BAR stock is good... make sure the grade is the same as the HSS. Often BAR stock is lower fy.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[phamENG]

dik - not anymore. For one, there's virtually no differentiation between bar and plate anymore. You can run plate on a continuous caster and then cut it down to narrower widths as and when needed. Most plate coming out of the mills these days is 50ksi.

 

[GC_Hopi]

Here are the recommendations from the Steel Tube Institute. Link

 

[WinelandV]

Before you direct a splice fix, if this is going to be visible, someone (you, GC, architect) should run the fact that these need to be spliced by the owner. They may not take kindly to the idea that "well, the fabricator messed up, so you're getting a splice column." From the owner's perspective, they are paying for a new structure, so it shouldn't need to be spliced before it's even used. It's also possible that they don't care. But someone should find out before moving forward.

Please note that is a "v" (as in Violin) not a "y".

 

[DrZoidberWoop]

Several HSS as in 3? or 20? Don't take on the unnecessary expense and design responsibility for the fabricator's mistake. I'd make them eat the cost and CJP or get me the correct steel.

The sleeve is roughly equivalent to the intact HSS in compression only. It creates a weak point in bending/rotation, shear, and tension. That might leave you wide open if a forensic investigation is ever invoked.

 

[dik]

dik - not anymore.

Sorry pham... but I often encounter projects in Canada where the BAR and plate material is spec'd as ASTM A36. I have no idea of what the supplied material is, but I consider it as A36 for my calculations. In Canada, you can get both CSA G40.12-44W as well as -50W, and not be guaranteed that it will will all be -50W. I've checked with the fabricators on this.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

Hopi...

I've been a member of the STI for a couple of years now. Membership is inexpensive and the benefits are great. Their webinars are some of the best when it comes to HSS. Well recommended. I've not used 'bolts' with HSS, yet.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[phamENG]

No - I'm the one who should apologize. I failed to think of the difference in market. You're right, of course.

AISC has modified their recommended material specs. They still call out A36 - it remains widely available - but they list A572 Gr. 50 right along side it as a preferred material. I worked briefly in a plate mill - even the A36 stuff was coming in at or above Gr. 50 specs, but the community is slow to change our design specs so they were selling it with the spec that was called for.

 

[dik]

pham... I have no idea of what the material supplied is... it just a matter of selecting the spec'd material in my SMath programs

and it all comes out in the wash...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[XR250]

It creates a weak point in bending/rotation, shear, and tension. That might leave you wide open if a forensic investigation is ever invoked.

True, but where is that demand coming from? Unless it is part of a braced frame, the only non-trivial loads it is going to likely see are compression and tension. I seriously doubt a perimeter PJP weld is going to fail in tension in this scenario.
The risk here seems to be small and if the owner is ok with it, and I was getting compensated sufficiently, I would try to play ball with the fabricator. What goes around comes around.

 

[DrZoidberWoop]

Perhaps. We don't know the full story though. God forbid a forklift bang into it or something.

 

[MotorCity]

This seems like a perfect application for a Shuriken connection by Atlas tube. I've seen this product advertised all over the place but have never used them myself or heard anything good or bad about them. Anybody ever used these?

 

[phamENG]

Neat. I'd be interested in seeing if they have published capacities or if the expectation is to design it like you would any other bolted plate splice. Inspections would be interesting, of course.

Shuriken

 

[jayrod12]

Bolted splice based on my read of the FAQs/Info. They essentially are just there to hold a bolt in place with enough "slop" to accommodate erection tolerances. They replace welding the bolt in place to the inside face of the HSS/splice plate.