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Re: FW: Min. masonry reinf

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In a message dated 12/5/98 3:01:06 PM EST, Curt.LaCount(--nospam--at) writes:

 The only reason that I've fully grouted a wall, besides axial strength
 reasons, is for achieving a fire rating.  Grouting a nonreinforced cell adds
 much more weight with little gain in flexural capacity and the increased
 inertia forces can have a ripple affect throughout the building.
 I am not aware of any testing or research that shows the performance of a
 fully grouted wall is any better than a partially grouted wall.  Maybe
 someone else on this listserve can help us out.
 From my experience here on the West Coast, partially grouted walls are much
 more common than fully grouted walls.  In Malaysia, they prefer unreinforced
 brick and the plaster coat that you mentioned.  I never understood how those
 walls calc'd out.  Must be in the tensile capacity of the plaster :-).
 Curt La Count
 Jacobs Engineering
 Portland, OR

What about in-plane shear for a fully grouted wall as oppose to a reinforced
cells only grouted wall.  For high in-plane seismic loads, I would think you
would have problems making joint reinforcing work in a reinforced cells only
grouted as oppose to horizontal rebar in fully grouted walls, especially if
you have concrete floors.  To my knowledge, about the only time you ever see
"reinforced cells only grouted" called for on the plans for masonry buildings
in California is if the engineer is from out-of-state.  And who's to say that
the contractor still won't grout all the cells anyway since this is a common
practice, especially if the plans call for all cells with inserts to be
grouted, which I have seen happen.

My understanding is that in the midwest,  "reinforced cells only grouted" is
typically used to help reduce construction costs.  I remember seeing an old
video tape of some research done at one of the universities in Texas about
tornados and flying projectiles.  In the testing they shot a telephone pole
from a cannon at both a unreinforced wall concrete block wall and a fully
grouted concrete block wall to approximate the impact that might occur during
a tornado.  The unreinforced c.m.u. wall shattered when the telephone pole hit
it, while the  solid grouted wall broke the telephone pole into pieces.  I
would think that this might be a reason to encourage the use of solid grouted
walls, even if the tornado pulls the roof off of the building.

Michael Cochran
Brian L. Cochran Associates
Los Angeles, CA