Monday, February 11, 2008

RE: CMU Bond Beam at Control Joint

I would say it is highly dependent on the specifics of the project.  I can certainly see #1/#4 being reasonable for a building where you want to put the diaphragm chords in the bond beam.  If the floor diaphragm is tied to the wall at that point anyway, unless you use some special detailing, it is not like the CMU will have much chance to shrink relative to the floor. 
 
I am not sure how well #2 would work.  Depending on how the ledger angle is attached to the wall, it might effectively prevent the CMU from shrinking/moving, thus defeating the purpose of the control joint.
 
#3 could be a good detail if the chord forces are handled in the slab and thus the floor is not continuously tied to the walls in such a way that prevents movement of the CMU.  Could also be a good detail for a flexible (wood) diaphragm depending on how the building is laid out and what the diaphragm segments are.
 
In general, if you are talking seismic situations, the walls is likely going to have so much prescriptive/designed reinforcement that shrinkage cracks will largely be mitigated by the reinforcement, which means that either #1 or #4 will be fine.
 
Regards,
 
Scott
Adrian, MI
-----Original Message-----
From: Michel, Greg [mailto:gmichel@DLRGROUP.com]
Sent: Monday, February 11, 2008 6:48 PM
To: seaint@seaint.org
Subject: RE: CMU Bond Beam at Control Joint

keep the horizontal reinforcing continuous and grout solid
 
Greg
 

From: Paul Blomberg [mailto:paul.blomberg@gmail.com]
Sent: Monday, February 11, 2008 3:34 PM
To: seaint@seaint.org
Subject: CMU Bond Beam at Control Joint

We have another office debate going on and I would like to hear opinions of others.  For a fully grouted wall, what do you do at the horizontal reinforcing (bond beam) at the vertical control joint. 
  • Do you keep the horizontal reinforcing continuous and grout solid (makes for good chord steel)? 
  • Do you break the horizontal reinforcing on each side of the joint (provide chord steel via deck ledger angle)? 
  • Do you replace the deformed bar with a smooth dowel and break the bond on one side of the sleeve?
  • Do you break the horizontal reinforcing except keep it continuous at floors and roof bond beam?
It seems there are as many approaches as there are opinions!
 
Paul.

 

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