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CMU Wall Removal

TRAK.Structural

Structural
Dec 27, 2023
264
I have a potential project where the client wants to remove a portion of a CMU wall that separates different areas of an industrial building. The CMU wall is part of the lateral system for each side of the building so I am envisioning using either steel moment frames (or braced frames if I can convince them) in place of the wall in the final condition. The tricky part is that the upper portion of wall is going to remain. See my sketches below for the current condition and the proposed new condition. Design of the shoring and sequencing of the work will be up to the contractor but obviously I would have to come up with something that can indeed be built. Does this look reasonable? What pitfalls am I not thinking of?

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Seems reasonable. Personally, I've never seen shear studs used as you show them, but of course that doesn't mean it isn't done, or it wouldn't work. I imagine it'd be quite difficult to install and inspect. I'd potentially look at post-installing anchors to the side of the CMU course, fastened to the beam flange with an angle or similar. I think that would give me a better feeling about it if I could get it to work--easier to inspect at a minimum--but that's just me.
 
Seems reasonable. Personally, I've never seen shear studs used as you show them, but of course that doesn't mean it isn't done, or it wouldn't work. I imagine it'd be quite difficult to install and inspect. I'd potentially look at post-installing anchors to the side of the CMU course, fastened to the beam flange with an angle or similar. I think that would give me a better feeling about it if I could get it to work--easier to inspect at a minimum--but that's just me.
I agree. Anytime we have a retrofit we always try to use Hilti's into the side of the block.

OP how big is this opening going to be? And how long is the overall length of wall?
 
is there a concern with creating a "hinge" at the top of the new moment frame?
 
I agree. Anytime we have a retrofit we always try to use Hilti's into the side of the block.

OP how big is this opening going to be? And how long is the overall length of wall?
I think the height of the opening will be about 15 feet. The client wants to remove basically the entire length of wall (around 100 feet).

is there a concern with creating a "hinge" at the top of the new moment frame?
Initially my gut says that the diaphragm connection to the low roof will brace the wall/frame at that level. I could possibly brace the steel to the low roof structure with some kickers.
 
If the sketch is ~to scale, that little angle connecting the low roof to the wall looks rather wimpy. Kickers sound like a good idea.
 
The angle at each roof is continuous. It will engage the diaphragm, kickers still may be justified though.
 
One problem I've had with anchors in the top of block is masonry crushing when the loads are high. TEK 12-03C is a great document to reference for that. I've wasted time designing walls that can't be connected to transfer the shear load. Usually it's the top of the masonry shear wall connecting to floor slab, but similar concept here.
 
I have a potential project where the client wants to remove a portion of a CMU wall that separates different areas of an industrial building. The CMU wall is part of the lateral system for each side of the building so I am envisioning using either steel moment frames (or braced frames if I can convince them) in place of the wall in the final condition. The tricky part is that the upper portion of wall is going to remain. See my sketches below for the current condition and the proposed new condition. Design of the shoring and sequencing of the work will be up to the contractor but obviously I would have to come up with something that can indeed be built. Does this look reasonable? What pitfalls am I not thinking of?

View attachment 4200 View attachment 4201
Though about offsetting the support column to the side of the wall and supporting the remainh masonry wall on the side?
 

Attachments

  • BeamModification.jpg
    BeamModification.jpg
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How is the connection between the existing wall and shear stud made? I don’t understand that part of it.

Overall, this makes sense though
 
Though about offsetting the support column to the side of the wall and supporting the remainh masonry wall on the side?
Not sure what the advantage to doing it this way would be? Looks like a lot more bending induced in the column this way.
How is the connection between the existing wall and shear stud made? I don’t understand that part of it.

Overall, this makes sense though
The intent would be that the bottom course of the CMU would be grouted to make the transfer of load happen.
 
Stage 1 - Prepare to support the remaining masonry block wall by grinding out part of the horizontal mortar joint and inserting an angle iron.
Stage 2 - Install the new vertical steel column. You may have to beef up the new columns to accommodate the moment induced by the remaining block wall, but you are only supporting the weight of the remaining block wall, the new columns and beams are supporting the roof weight.
Stage 3 - Weld the angle iron to the new steel columns.
Stage 4 - Remove the lower block wall in sections and add temporary support, if needed.
Stage 5 - Add a smaller beam to support the remaining block wall supported on brackets added to the new roof columns or add another column next to the roof columns.

Involve an experienced contractor in the design process, you will be surprisedBeamModification4.jpg how innovative they can be on constructability issues.
 

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