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RE: brick monuments

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Another option might be to use Kla-All or similar brick masonry unit.  They look like brick, but they can be grouted and reinforced like CMU.  I used them once to build a free-standing elevator tower next to another building.  

Paul Crocker, PE, SE


>>> Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu> 03/24/05 02:04AM >>>
Mark,

I will ask the dumb question...from a structural point of view
(discounting things like water penetration/trapping of moisture, other
architectural reasons, etc), is there really a need to put ANYTHING in the
middle of the brick pier?  In otherwords, why not just do a hollow brick
monument (i.e. a single width of brick with a 24"x24" hollow center)?

A quick calc (unless I screwed something up - nah...can't happen <grin>)
would seem to indicate that unreinforced brick under the worst case the
MSJC (masonry cement or air entrained portland cement/line mortar that was
type N) would result in an allowable surface pressure (i.e. wind pressure)
on the momument of about 74 psf (this is based upon 9 psi allowable
tension in the unreinforced, ungrouted masonry with "worst case" mortar
per the MSJC).  This neglects the benefitial effect that you would get
from the self-weight (which effectively increasing the allowable tensions
stress by basically providing some "pre-compression"/prestressing force).
I doubt that you will have a wind pressure that gets that high, and even a
equivalent seismic load would be more than likely be lower that than 74
psf.  And this assumes worst case mortar.  To do, really worst do a worst
case, consider it as the above worst case but per the 97 UBC with no
inspection.  The permitted value with full inspection is still 9 psi, but
I believe per the 97 UBC if there is no inspection you use half the
value...thus 4.5 psi.  If so, then you still end up with an allowable load
of 37 psf.

Now, your biggest problem will be overturning.  Since you are likely using
solid brick or at best brick with cores, you likely will not be able to
dowel the brick to the fountation with reinforcing if you do not provide
anything in the center of monument.  But, this still checks out.  Using
the maximum allowable load determined from above (74 psf) and checking
against overturning due to self-weight resisting the overturning, you
still end up with a FS of about 1.7.

The point is that it seems that structurally you could get a hollow,
unreinforced brick monument to work.

Now, this does not account for whether or not code might require you to
grout it solid (i.e. for seismic reasons) nor does it account for other
reasons such as possible water intrusion and trapping or just a hollow
"dead" spacing that could create other non-structural problems.

If for what ever reason, you don't want to use the brick as the structural
element (i.e. hollow, unreinforced), then I think Harold's suggestion is a
good one...use a CMU core.  This leaves everything under one trade (other
than the foundation).  Of course, you could do a reinforced concrete core
that is formed (either as a square with wood or metal forms or maybe as a
circle with sonotubes...although, I don't know if a sonotube form will
hold a 8 ft column of wet concrete without blowing out since you will not
have earth to help confine it unless it is "reinforced" in some
manner)...this would be done by the same trade that does the foundation
work most likely.  You could pontentially build up the hollow brick
monument and then grout solid the inner core (with some bars in it that
are dowelled into the foundation), but care would have to be taken with
the grout mix (i.e. you may not want to use a typical masonry grout [i.e.
really high slump] but instead use something more in between a masonry
grout slump and a concrete slump).

HTH,

Scott
Adrian, MI


On Wed, 23 Mar 2005, Mark Pemberton wrote:

> Would there be any problem with using a hollow sonotube core?  I could reinforce the portion of concrete between the brick and sonotube (vertical bars at interior corners?) creating a boxbeam, and include brick ties extending into this grouted area.  This would reduce the amount of concrete fill by over 50% and no forming would be required.  Does anyone see any problems with this configuration?  Thanks.
>
> Mark Pemberton, S.E.
> Pemberton Engineering
> Davis, CA
>
> Harold Sprague <spraguehope(--nospam--at)hotmail.com> wrote:
> Build a 16" square CMU pedistal with cavity wall ladder reinforcement in the
> bed joints. Check out Hohman and Bernard's web site
> http://www.h-b.com/home/index.html. It is the same as the reinforcement you
> would use for a standard cavity wall with 2" rigid insulation and 2" air gap
> except you don't need the insulation. Do not forget the drainage and the
> weeps. I prefer Mortar Net drainage and head joint weeps.
> http://www.mortarnet.com/ 
>
> I do not liike to mix trades if possible. Everything should be installed by
> the masonry trade above the foundation. Carpenter trade installs stud
> walls.
>
> Regards,
> Harold Sprague
>
> >From: Mark Pemberton
> >Reply-To:
> >To: SEAOC
> >Subject: brick monuments
> >Date: Tue, 22 Mar 2005 16:11:45 -0800 (PST)
> >
> >I'm doing some brick monuments that are about 32" square and 8' tall. I
> >was thinking of doing a standard brick exterior and filling with reinforced
> >concrete, but that seems overkill. I'm worried about using a metal stud
> >wall framework because of some really cracked up site walls around here
> >that used metal studs (although these used a stucco finish), and I'm not
> >sure how to transfer the overturning with that configuration. Any
> >suggestions?
> >
> >Mark P.
>
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