Column to Base Plate simplified Welds ?

[Jim Jr]

Probably beating a dead horse here but I searched and could not find a dumbed down version. I need a simple answer to the Note I see all the time on contract drawings for Column to Base Plate welds, IF the EOR even puts anything often it is just a note to use AISC Standard min. weld. Where do I find this again? Had an OLD pencil eng. onetime just told use as detailers to "Just use 5/16 Fillet for any column with a base plate 3/4" or thicker and 1/4" fillet for anything less. Looking for more up to date and simplified for a dumb detailer (myself) to understand.

 

[TLHS]

Man, is this what people do?

If you're doing high efficiency engineering where you want to minimize details it seems like you should have a standard detail sheet that you use that includes all the information and welds. Base plate details are super-easy to tabulate.

Otherwise I don't know why you wouldn't just have a base plate detail on your plans.

 

[lexpatrie]

If you're a detailer, RFI the engineer that there's no information on those welds you found on the plans.

"Common" practice hasn't yet evolved much past a weld-all around symbol.

 

[ads0221]

Honestly this is something the engineer needs to be detailing.

 

[Jim Jr]

This is what we get most of the time.

 

[271828]

That's nuts. I just looked at a set of drawings from an EOR that I know produces good drawings. They point at these welds and put the size in the table with the base plate size.

The note on your screenshot refers to the minimum fillet weld size per the AISC Specification Table J2.4. The largest that could ever be is 5/16 in. That weld would provide a lot of strength even for uplift and shear, so it should be plenty the vast majority of the time.

The new AISC Design Guide 1 Section 4.5.2 talks about base plate welding quite a bit, BTW. Might be worth checking out. (aisc.org/dg)

For your screenshot, one new item is the weld strength directional increase [ kds = 1.0 + 0.5 sin(theta)^1.5 ] no longer applies for rectangular HSS.

 

[Jim Jr]

AISC Table J2.4 Basically says to use 3/16 Fillet for HSS8x8x3/8 to 1 1/2" Base plate. Again, I'M NOT an Engineer just a Detailer but my gut says 3/16 won't cut it.

 

[bones206]

Any chance this is meant to be designed by a delegated connection engineer? Might be stated in the general notes.

 

[Jim Jr]

Bones206, No this job was not to be sent to a connection Eng. However even the jobs that are sent through a Connection Eng. they only do beam to beam and beam to column connections never BP connections.

 

[271828]

AISC Table J2.4 Basically says to use 3/16 Fillet for HSS8x8x3/8 to 1 1/2" Base plate. Again, I'M NOT an Engineer just a Detailer but my gut says 3/16 won't cut it.

Because this is at a bracing connection, I'd recommend flagging it on your approval drawings and asking the EOR to confirm.

There is a good chance 3/16 in. is enough, but the presence of the brace makes it a lot less certain. Especially with that many anchor rods. That brace could have a large load in it. Usually the vertical component of the brace force is taken by the gusset-to-HSS column welds, which then gets transmitted to the base plate through the HSS-to-base plate welds. There's a chance this force could be large.

 

[DrZoidberWoop]

From experience, I've barely ever spec'd a 3/16" fillet weld on anything 3/8" thick (nominal) and above.

"Just use 5/16 Fillet for any column with a base plate 3/4" or thicker and 1/4" fillet for anything less."

This line of thinking covers a lot of ground for gravity column base plates. It's probably evolved out of common fabrication-shop preferences. 1/4" fillet welds are often a shop-preferred baseline min weld size because they can be achieved via a single pass w/ various welding processes. Pretty similar situation with 5/16", but why waste the weld wire/electrodes if you don't have to on material 3/4" and thinner?

In East-coast delegated connection design, it's common for the EOR to design the welds btw the column and BP (and BP to shear lug), even at braced frames. It's always perfectly OK to verify this via RFI or email.

 

[lexpatrie]

Usually the vertical component of the brace force is taken by the gusset-to-HSS column welds, which then gets transmitted to the base plate through the HSS-to-base plate welds. There's a chance this force could be large.

Not really on the topic here, but I don't think this is very correct. The HSS load goes into the gusset, the gusset transfers the vertical load (plus) via the weld into the face of the HSS, and the lateral load (plus) into the base plate- UFM. You could probably design it the way you describe, taking the entire load as tension, shear, and bending into the column via the gusset, and arrive at a safe design via some sort of upper bound/lower bound argument, but I don't think that's a typically used load path. It's been a while since I did delegated connection design and that was R=3 anyway, so not seismic, effectively.

Night School 6, Session 2: The Uniform Force Method, Thornton, AISC, 2014

Designing Compact Gussets with the Uniform Force Method, Muir, AISC Eng. Jour, 1st quarter, 2008, currently a free download as of 7/6/24.

Given the nature of this "connection" it suggests to me this could be in a significant seismic zone, at which point the connection design gets a good deal woolier.

I still think this is a cloud by the detailer. "EOR provide weld size" - e.g. Refuse to size this weld and ask for confirmation. Force the EOR to actually provide the design, and ideally, via a revision cloud on the detail, and on the sealed revision 1 plans.....

These sort of coordination problems will proliferate if people other than the engineers don't hold the "our" feet to the fire. This isn't proper connection design procedure, it isn't proper delegated design procedure, and it needs to get at least a little horse medicine (cause the horse pain to diagnose the problem, because if it's the problem it's extremely painful, not just uncomfortable, and you know what the problem is...)

As the detailer has stated, they aren't doing engineering here, and the forces are not disclosed so they physically cannot size the weld (nor could a connection design engineer, unless they want to go the "maximum force the connecting elements can possible endure" approach). At least the work point is where it's supposed to be.

 

[271828]

lexpatrie, I do basically what you typed.

VERTICAL COMPONENT of the brace force goes through the gusset-to-column weld so it ends up in the column-to-BP weld.

Horizontal component ends up in the gusset-to-BP weld.

A typically small moment would need to go somewhere to establish equilibrium of the gusset. Usually put that at the column because the EOR designed the BP and I'm not sure how to check the BP for the upward force.

It's the KISS method mentioned early in Design Guide 29.

 

[phamENG]

Jim Jr - check out the AISC code of standard practice, section 3.1.2. It lays out the 3 options for connection design. It sounds like this project falls under option 2. In that case, the EOR needs to provide a table with appropriate design information for you to pull from, or you need to be able to pull it from a design table in the AISC manual.

"Weld...shall meet AISC requirements" is meaningless. What requirements? That's their job to figure out. You could word your RFI like this: "EOR, please indicated AISC Steel Manual connection design table or figure to be used in selecting weld size." That way they can realize that there isn't one.

 

[canwesteng]

Uniform force puts axial and shear force at each interface. I like the anchorage detail less than leaving the weld details off tbh, that's a decent amount of eccentricity