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Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

(OP)
I'm trying to come up with a detail for the following condition:

A joist parallel to an existing CMU (assume ungrouted or partially grouted) with brick veneer and an air space between. I'd like to transfer deck shear into the existing CMU wall. My first thought was to use a bent plate say 8" long at 48" oc bolted to the existing CMU and welded to the joist (see attached). This would require removal and replacement of the brick at those locations. I'm wondering though if there are any other suggestions for this situation?

EIT
www.HowToEngineer.com

RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

I'll start with the easy stuff that surely isn't possible:

1) Could you brace the new steel line without engaging the CMU wall at all?
2) Must you restore/preserve the brick above the low roof? If not, you could run the deck right to the block.
3) Is the existing steel roof beam shear connected to the block in any way?

I'm concerned that, with your detail, the clip angles will torque the heck out of the joist top chord.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

Don't know what your lateral forces are, but I would seriously consider removing the brick below the steel deck and extending the deck to as ledger angle where it could be welded to the a=ledger and the ledger bolted to the CMU wall. The brick above could then be set on a new angle ledger just above the new deck and replaced.

Mike McCann, PE, SE (WA)


RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

Here's an alternate form of your detail to consider RFreund. It eliminates the joist top chord torquing issue. You'd have to give some thought to the deck fastening at the last two joists.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

Thought:

How much will the last joist deflect under full roof load? You might want to consider doubling up that last joist if you cannot compensate for the deflection of the deck in your details.

Mike McCann, PE, SE (WA)


RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

Better still: omit the last joist.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

That would work too.

Mike McCann, PE, SE (WA)


RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

V2.0 incorporating latest discussion attached. Kinda depends on your feelings about locking the buildings together perpendicular to the block wall.

I assumed that the low brick needed to stay to make it sexy architect space. Warm and retro... If it doesn't matter then, certainly, I agree with Mike: run the deck out.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

(OP)
Thanks for the suggestions and I appreciate your time to sketch those Kootk.

To answer some questions:

Quote:

1) Could you brace the new steel line without engaging the CMU wall at all?
Possibly but I'm not sure which is going to be more costly and or is a better outcome. Maybe it makes sense to brace the steel line separately in this case.

Quote:

2) Must you restore/preserve the brick above the low roof? If not, you could run the deck right to the block.
Yes right now the goal is to keep the brick above (and below for that matter). Although we can possibly get rid of the brick below. I'm sure as soon as I ask to remove it, they will probably want to keep it.

Quote:

3) Is the existing steel roof beam shear connected to the block in any way?
That part is also a mystery at the moment but I should be getting more information on this. I assuming it is somehow shear connected.

Quote:

I'm concerned that, with your detail, the clip angles will torque the heck out of the joist top chord.
Yeah me too, I wasn't thrilled with it. I like your adjustments, thank you.

This is a relatively small addition that is tucked into the corner of an existing Cross shaped building. Low seismic area and we are not increasing the wind load on the existing structure, so I'd like to utilize the existing lateral system. Normally when I have an addition I look at the structure as if it were being built new and then ask the question, should there be an expansion joint here? If not then I am inclined to connect the buildings. However for this situation, it's possible that it makes more sense to design the addition as a separate structure, if I can get some lateral bracing in easy enough. But it still is nice try and hammer out a detail for this situation for future reference.

EIT
www.HowToEngineer.com

RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

I'll probably come to regret saying this out in the open but could you use the brick wall as your shear wall?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Shear Transfer at Joist Parallel to Existing CMU and Brick Wall

(OP)
Honestly I thought the same thing. It is a solid stretch of wall with no openings and not much load. And I am not one to assume brick is just some flimsy veneer, having had to Demo it before, it doesn't come down easy. I think it could do the job but I'll have to think about it some.

EIT
www.HowToEngineer.com

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