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RE: CMU Column Ties (horizontal)

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There might be a demand on the fence if anything, but I was told that
the stanchions would be placed adjacent to the columns and that the
columns were decorative. Besides, these are not structural and not
subjected to wind loads (other than those against the masonry itself
since the fence is wrought iron and has no real load against it. Even if
I assume the same issues for a balcony railing or stair railing, then it
is only a 200-pound concentrated load applied laterally at mid-span or
100-pounds reaction on each side of the columns (which are tied to the
foundation by nature of the vertical steel.
Being a non-structural component, I don't see where any temperature
steel or ties (used for brick) would be necessary to secure the masonry
block together. 
Another engineer suggested in a private e-mail that ACI 530-99 / MSJC,
C-12, Section 1.13.5.2.2 and 3 which require reinforcing in "either" the
horizontal "OR" vertical directions. In this case, the vertical is
covered and any wind loads against the columns would affect the vertical
steel in fully grouted cells. Lateral loads other than wind would be due
to the weight of the column (seismic lateral) alone and the anchorage of
the vertical steel to the foundation would be sufficient.
Dennis

-----Original Message-----
From: Charley Hamilton [mailto:chamilto(--nospam--at)uci.edu] 
Sent: Saturday, November 15, 2003 11:28 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: CMU Column Ties (horizontal)

Dennis -

Is there any load path (intentional or unintentional) from the
fencing to the columns?  This may place some demand on the
columns if someone loads the fence, making the columns
more than just decorative features.  However, I can't imagine
this demanding more lateral capacity than provided by the
fully-grouted CMUs, especially with rebar.  Unless someone
crashes a car into it.  ;-)  Depending on what fronts on
the pool, this might actually be a problem.

The other concern about omitting the ties would come not
from the issue of fencing loads on the columns, but seismic
demand.  You might check the columns as either non-building
structures or non-structural components of buildings per
UBC'97 (or whatever is current in the jurisdiction).  Just
check the shear demand, and show whether or not the ties are
necessary.  Even at 1g lateral, back of the envelope suggests
there's no real problem.  However, my copy of the UBC is at
the office, and I can't recall if there is a provision for
minimum lateral reinforcing that might open you to
substantial liability if you recommend against the ties.


Charley

-- 
Charles Hamilton, PhD EIT               Faculty Fellow
Department of Civil and                 Phone: 949.824.3752
     Environmental Engineering           FAX:   949.824.2117
University of California, Irvine        Email: chamilto(--nospam--at)uci.edu




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