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Unreinforced Masonry Building

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David,

Some of the problems with after-the-fact grouting of cmu's is that the webs 
on each side of the cells that were to have been grouted were not mortared, 
the cells probably have not been cleaned *and* mortar fins project into the 
cells.  If some of the stretchers were bond beam block, then the gap at the 
web could be quite large.  Mortar droppings are weak and reduce the strength 
of the walls; fins projecting into the cell provides ledges which can provide 
support for arching of the grout, which, in turn, means that you would have 
questionable grout below the arching, plus, the arching causes premature 
failure of the walls with the arch thrust pushing off the face shell.

I would be very hesitant in using composite fabric to solve the problem until 
it has a history of performance and is not seriously degraded from ultra 
violet rays from the sun.

If these telecommunication buildings are windowless or nearly so, you might 
consider putting expanded metal on the exterior, bolting it thru the wall and 
shotcreting or stuccoing the expanded metal.

Have you talked to the contractor about taking down the walls and doing it 
right? <VVBG>  What was his response?

Good luck!

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

David Hall wrote:

>>A few weeks back I sent out a request asking if anyone knew how to conduct
non-destructive testing to determine if reinforcing and grout was placed in
the voids of an existing masonry building.  I appreciate the responses that I
received from many of you.

Well guess what.  There was only grout and reinforcing in the horizontal bond
beams which were placed at 4 foot centers horizontal, in the lintels, and
vertically at each side of the expansion joints and openings.

Now heres another one for you, there are 15 of these building designed by our
office and from what I recently heard 12 more that were designed by another.  

These buildings are telecommunication building in Texas which is in seismic
zone 0 with a 80 mph wind speed.  I haven't checked yet but I believe that
#4's at 4 feet on center will work vertically.  

Now to retrofit this building I am considering having them saw cut and remove
the inner shell of the block from the inside, embed #4 bars into the upper and
lower bond beams with epoxy grout ,lapping the bars 30 inches, then gluing the
shell back up to the course just below upper bond beam, then filling the void
with grout continuing up carefully and adding the last shell and pointing the
remainder.

What a mess, If anyone has a better idea I would sure like to hear it.  Adding
shotcrete with a grid of steel to the interior is not an alternative.<<