Single Story All HSS moment frame 3

[StrEng007]

What is the preferred method here, run the HSS beam over the top of the column... or have the HSS beam attach to the inside face of the HSS vertical?

I can come up with the individual connection to resolve shear, moment, etc. Just taking a poll on the most accepted method.

 

[MotorCity]

Either method will work. If you want to reduce the edge prep and welding, size either the beam or the columns to be smaller than the other such that you can fillet weld one them together. Otherwise you will end up with flare bevel, PJP, or CJP welds everywhere.

 

[phamENG]

I'd run it over the top. Less welding that way if you can keep the beam continuous. Might be a different story depending on proportions of members, but that's my starting point.

 

[CANPRO]

Is the beam continuous past the column, or do you have a simple single bay moment frame? If a single bay, over the column or face of column doesn't make a huge difference in terms of fabrication, similar weld requirements. If you have other members connecting to the HSS it might change the decision.

Either way, the walls of the HSS that are carrying the bending stresses are going to meet up with some out of plane bending of the adjacent HSS walls. The detail below is one of my preferred details for joining HSS at a corner in these cases. Stiff load path and simple welds. Not always acceptable aesthetically, and won't work well if you have other members framing in at the corners.

 

[milkshakelake]

I run it over the top so I can use cap plates with bolts, and have the framing above use clip angles into each other. If you connect it to the sides, you'll end up using knife plates, which is more cutting/welding and also a tiny bit of accidental eccentricity.

@CANPRO That looks expensive, two miter cuts on HSS pieces and a lot of field welding.

 

[dik]

You want to limit the loading on the HSS sectons to about 70% or 80% of their capacity to make connections easier to design.

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

-Dik

 

[271828]

As dik alluded to, connections are critical. I'd recommend checking those even if you're planning to delegate connection design. You might realize a slight increase in thickness would make a big difference downstream.

 

[bookowski]

Speaking of HSS to HSS moment connections - does anyone have or can point to a good spreadsheet for rectangular hss to hss welded moment connections per ch k?

 

[CANPRO]

milkshakelake, I welcome the criticism and love to discuss a detail. The end cuts of the HSS are not difficult or expensive. We don't know the size of this moment frame so we don't know if it needs to be field welded or if it can be a shop assembly. OP didn't really say it had to be welded, the conversation just kind of went that way. Maybe it can be a bolted moment connection. For a welded option, I don't think square cuts, either beam into face of column or vice versa, is a particularly effective/economical moment connection (if you're looking for any reasonable percentage of the member capacity). For good load transfer between the beam and column the tubes should be PJP or CJP together or the connection proposed above. For a shop weld, the CJP might be preferred because the fit-up conditions are controlled and it would be less weld volume, just need to fit a continuous backing bar into the tube. For a field weld, the plate in the corner is the better option because it is less sensitive to fit up.

StrEng007, to discuss connection options, there are a few questions that need to be asked:

[ul]
[li]How big are the pieces and is a shop assembly feasible?[/li]
[li]Are bolted connections acceptable? For a connection like this, the most economical bolted connection will be ugly and likely not acceptable if exposed to view.[/li]
[li]If it needs to be field welded you really need to look at accessibility on site. Is this a renovation or new build? If welded in place do you have access to all sides of the tubes? Even if a new build there might be access restrictions due to other connection material or already erected components.[/li]
[li]Is there anything else framing into this node that may impact connection choice?[/li]
[/ul]

 

[human909]

Totally agreed with CANPRO here. That corner detail is great, and one that I've used on a couple projects recent. In the last year I've done several moment frame from HSS. Getting efficient and strong connections can a challenge.

Mitre cuts and fillet welds are comparatively cheap compared to alternative moment connections.

Also the connection doesn't have to be field welded. You can do that connection in the shop and then move the bolting away from the corner to a lower moment area.

 

[Tomfh]

Agree with the welded shop moment joint if possible.

Another one we’ve done is pairs of long thick splice plates with a lot of bolts, in cases were chunky end plates weren’t architecturally acceptable.

 

[milkshakelake]

@CANPRO That's very reasonable, thanks for the explanation. I use cap plates generally.

I'm not sure where I can use your detail, because I need to connect a beam from the out-of-plane direction (at the corner) to provide lateral stability to the column. It's required where I practice to provide 10k or 2% of the axial load (whichever is greater) of resistance/stability in the out-of-plane direction. A knife plate or second end plate in the perpendicular direction would be difficult to achieve with this detail. If I didn't have that requirement, I think this detail is pretty cool and thinking out of the box.

I'm thinking that what you mentioned about a full penetration joint could work. And it could avoid field welding by having the bolting at a lower point, like what human909 said. This would allow another beam in the perpendicular direction.

 

[dik]

You would not want that mitred corner with the plate to be field welded under any circumstances.

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

-Dik

 

[StrEng007]

For the sake of the exercise, would either method here result in the same forces in the anchor bolts that hold this moment connection together?

The particular loading scenario I'm considering is for lateral load as shown below:

How big are the pieces and is a shop assembly feasible?
Are bolted connections acceptable? For a connection like this, the most economical bolted connection will be ugly and likely not acceptable if exposed to view.
If it needs to be field welded you really need to look at accessibility on site. Is this a renovation or new build? If welded in place do you have access to all sides of the tubes? Even if a new build there might be access restrictions due to other connection material or already erected components.
Is there anything else framing into this node that may impact connection choice?

1. Not very big. They would be HSS6x6 tubes. Shop assembly is not possible. These frames components would need to be erected in field.
2.Yes, either bolted or welded connections are acceptable.
3. This is a new build. The the aesthetics is not a primary concern for the overall connection. However, a less bulky/cumbersome connection may be preferred.
4. In plan view, it will be a four sided moment frame. So each corner will have (2) beams at a 90° to one another.

 

[jerseyshore]

In general when using HSS beams and columns together, I try to size the column 1 size larger than the beams to make the welding simple where the beams frame into the sides of the column. This is helpful at corners when you have beams coming in from multiple angles too. It's the cleanest detail IMO. Typically when I have to use HSS beams it's because things are tight architecturally and I don't want any plates or bolts sticking out.

 

[CANPRO]

StrEng007, a few follow up comments to your last post:

[ul]
[li]Just me being picky, but words matter - we're talking about bolts here not anchor bolts[/li]
[li]Bolt forces will not be the same. Depending on geometry, you might have similar reactions in the bolts due to the bending moment. But, I'm assuming there is other load transfer at this joint and axial/shear transfer will be very different in the (2) arrangements.[/li]
[li]If this is a (4) sided frame I can appreciate that shop assembly is not possible. What about shop assembling (2) of the sides and bolting the other sides on site? This would simplify the connections[/li]
[li]If aesthetics aren't a concern your best best is to provide bolted connections. They will be ugly (according to architects, I like the look of a big bolted connection).[/li]
[li]Neither of your (2) bolted options will work because you have HSS from both directions. The plates and bolts will foul each other. If you shop weld (2) of the sides I think the beam framing into the side of the column option is back in play.[/li]
[li]See below suggestion. Shop welded stubs are very helpful in this situation to get your bolts away from each other. You get the pre-coffee version of my sketch, apologies for the sloppiness. Keep in mind that when you use the shop welded stubs you're doubling your connections with a shop welded connection and bolted connection for each member end ($$). Use this sparingly.[/li]
[/ul]

 

[StrEng007]

jersey, Thanks for the advice. It looks like I will end up taking that direction due to architectural wraps on the beams and columns.

Canpro, All of your feedback is much appreciated. That's a pretty good pre-coffee detail.

Like you, I also appreciate seeing bolted connections. After some discussions, the Arch. has opted for nice hidden connections. I will be taking an approach of using HSS to HSS welded connections. I can handle the welds. Chapter K of AISC will be completed via the Steel Tube Institute's HSS Connex Tool.

 

[jerseyshore]

Makes sense. Like I said, 95% of the time when I'm using HSS beams it's because they want a clean look (if exposed) or hidden connections so bolts are out the window. I've used various mitered corner details as well with success.

HSS to HSS connections can be extremely costly, so I try to design and detail with that in mind. Fillet welds wherever I can.

 

[ETX]

@StrEng007: If talking anchor bolts, if we can assume the two connection methods provide the same stiffness and rigidity, then the forces in the anchor bolts should be the same. The forces in the connection bolts likely differ as the orientations and axis of loading is different, but the overall moment transfer (assuming same stiffness) should be the same and therefore anchor bolt loads the same. That is in practice, however if diving into the weeds I am inclined to think the second connection detail provides more connection stiffness since both the top and bottom flanges of the beam are restrained versus option one where the top flange is unrestrained. Therefore, the forces on the anchor bolts would vary between the two connections. I think this difference is so small it doesn't functionally matter, but this is my thought just for the sake of the discussion. I am looking at this from simple portal frame behaviour. Just my two cents mate.