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Re: Adding Storefront to Existing CMU Wall

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Rich,
I've actually done a couple of those Wal-Marts here in TX.  No seismic helps.
Down side: I'm afraid if you punch every cell, you may find it hollow.  Many are actually unreinforced masonry. How these things stand the test of time is beyond me. I've done post-construction, reinforcing and grouting w/ structural Steel supports, pretty much as you describe.
 
IMHO, I've not considered it a good idea to detail a sequence of construction as you are laying out.  I've gone with a performance spec (no masonry cracks, etc) with limitations such as 15 ft or 30 ft sections at a time as parameters dictate.    I've discovered that a good Contr'r can come up w/ a much better approach than I could dream of.
 
Then have the Cont'r submit a detailed plan of sequence/ methods for record purposes.  When I could, I would require certain things (shoring, supports, etc) to be stamped by 3rd party Engr.  Only intervene by rejecting if you see something potentially disasterous.
 
On other buildings, I've also re-build walls, either CMU or stud/ steel.
 
Side notes: Shore the entire wall.  Might saw in a few extra control joints in the brick veneer to minimize crack propagation.
 
Just recently, I watched some masons working on an existing tilt-up w/ veneer building.  They were putting in a continuous window, about 50 ft long and 18" tall, about 15 ft above grade.  They were sawing out and removing the brick.  About every 6-8 ft, they would support the brick above w/ a 2X8 cut to the height of the opening.  No cracks.
 
JDC

>>> On 11/13/2007 at 10:07 PM, "Rich Lewis" <seaint04(--nospam--at)lewisengineering.com> wrote:

This post is associated with my other Walmart post.  I’m working on designing the framing to put in storefront windows and was wondering how others had tackled it.

 

I have an 18’-8” high bearing wall.  It is 12” CMU and 4” brick.  I have no drawings so I don’t know if it is partially reinforced or not.  All the holes that were poked in the wall showed hollow cores so far.

 

The owner wants to put a storefront strip window 9’-0” high the length of the building.  About ½ the length of the wall has steel beams and columns supporting the roof framing.  Some sections have just a masonry bearing wall. 

 

I have given some thought as to how to support the wall.  I’m considering using a 16”x?” tube lintel to carry the 16” wide wall.  I haven’t sized it yet so I don’t know the height.  I will have steel posts directly below the tube header, probably at 15’ on center.  I will have some type of ‘strong back’ column behind this to provide the lateral support of the wall from foundation to roof framing.

 

Construction sequencing as I see it is to cut a hole at the floor line to install the column footing.  I see the wall being able to arch over the hole cut for the footing.  I then see wood needle beams poked through the wall above the steel header to support the wall while the section below is demolished.  The new header and posts would be installed.  Steel shims would then be wedged between the tube beam and the masonry to load the beam as much as possible before releasing the needles.  A non-shrink grout needs to be packed in the gap made by the shims.

 

My preference is to see this done a section at a time, whether 15’ or 30’ lengths.  I know what will happen though is any contractor who is doing this will want to shore it all up at once and tear it all out at once and install the steel framing.

 

I’m looking for critique or suggestions as to what I have proposed.  Any steps left out?  Any suggestions to improve on what is proposed?

 

Thanks.

 

Rich