Brick veneer isolation in Seismic Design Category D

[bnickeson]

I'm working on a three-story wood-framed apartment-style building down in Charleston, SC. We have anchored brick veneer going up at least two stories around a majority of the building. In the central "Core" portion of the building, the lateral system is a special moment frame, and on the "Wing" portions of the building, the lateral system are standard plywood framed shear walls. Section 6.2.2.10.1.2 of the 2011 ACI530 (and older versions as well) states to "Isolate the sides and top of anchored veneer from the structure so that vertical and lateral seismic forces resisted by the structure are not imparted on the veneer." I'm wondering how exactly this is commonly accomplished? The only way I can think of is to provide expansion joints at every corner of the veneer. These expansion joints would have to be sized based on the elastic deflection of the structure at the brick's highest level times the deflection amplification factor, correct?

Is that the only way to isolate the veneer or am I missing something? For our structure, especially the Core, the amplified seismic deflection can get up in the 3" range due to the flexibility of the moment frame. It seems pretty crazy that we would have to provide a joint in the veneer accommodating 3" of movement at every corner of the building. And at the Wings, we have a much lower deflection but an extremely high number of jogs and re-entrant corners of the building. We would have dozens of joints in each Wing that might be around an inch in size.

For anyone that deals with this typically, are there other methods of isolating the veneer that I'm not thinking of? I'm looking for several opinions before I inform the architect and get my head bitten off...

 

[manstrom]

Brick veneer in SDC D sucks for exactly the reasons you list.

There was a good woodworks seminar that discussed this. They isolated the brick into panels supported at each floorline. The joints were fairly big, but maybe not 3". The detailing on this will probably drive you nuts. Is there any way to massage numbers back into SDC C?

Do you need to apply the deflection amplification factor for non structural veneer?

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[bnickeson]

The brick isolation requirement is actually listed for Category C and carries over into Category D. So even if we were C it would still apply.

And yes, I would assume you would still need to apply the Cd factor for non-structural veneer.

 

[JAE]

Anyone else have any thoughts?

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[XR250]

maybe use adhered thin brick?

 

[bnickeson]

XR250, we already are using thin brick on a large portion of the structure. There are many areas though where the veneer was desired. We got this job after the architect had essentially completed nearly all of his design. Plus the design review board down in Charleston is a nightmare to go through apparently, so they won't be changing any of the architectural design for the most part.

It was a good suggestion though. On another project very similar to this in Memphis, we went to adhered brick on the entire building due to seismic concerns there.

 

[wannabeSE]

Here is a link for information for brick veneer on metal studs

http://www.google.com/url?sa=t&rct=...cd=1&cad=rja&uact=8&ved=0CB4QFjAA&url=http://

http://www.brick-wscpa.org/cms/down..._LcyI-kfoLoTYygQQ&sig2=21EdyXdMub6VencTDezwvA

from the Western States Clay Products Association. Even if your walls are different, it may give you some ideas.

 

[XR250]

@BNickeson;

I hear you on their review board. My in-laws have a house in downtown Charleston and just to get approval to replace their front door was a headache.

 

[mike20793]

Support the brick at each level. It's really the only way to have drift compatibility between the deflecting elements and the veneer. As mentioned above, the detailing is pretty intense, but there are details out there available to show how to do it. Typically, we tell the architect that we need lipped brick at each relief angle to help with the joint. See attached (note: this sketch is not from me and I do not take credit for it).

 

[bnickeson]

Mike, that doesn't address what happens at the corners of the first level though. You have brick attached to walls when seismic forces acts in the out-of-plane direction (to that particular wall) that wants to deflect with the structure, but it has to be isolated from the brick around the corner that is in-plane with the load/deflection. Meaning you would still need a joint at the corner presumably.

For a taller structure with brick going up multiple levels I'd completely agree with you that it'd need to be supported at each level, but for brick only going up two stories in some areas, the juice just really isn't worth the squeeze when you still have isolation issues at the first level.