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Re: Masonry Column, Ties Required?

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You are right on point in my opinion, but then so is Will in his response
to this message.  While you are technically correct in terms of how
members are typically described from a structural point of view, Will is
also correct in that the MSJC's (ACI 530) definition does not talk about
things like flexure vs. axial load, etc but only defines a column in terms
of its relative cross-section dimensions and length.  So, Will is 100%
correct (in my opinion) that by the MSJC's definition, he is dealing with
a column.  As a result, his "concern" that a code official will thus
require the ties is a valid question/concern.

Will:

The commentary might help a little.  First, it does kind of help with the
arguement of a column is an axial load element...but then it also says
that columns can have flexure too (which is true...but many times
structural engineers then may call it a "beam-column").  Unfortunately,
while I agree that what you have is really primarily what I would call a
beam (i.e. something overwhelming governed by flexural/shear loads), the
commentary is still not specific enough to even say that the INTENT is
that the column provisions in the MSJC may not apply.

The second are is that section 2.1.6.5 of the commentary does talk about
WHY ties are required.  The first reason is just as mention in ASQuilala's
post...to prevent buckling of the vertical bars under axial compression.
So, at first blush, this would potentially provide you with an arguement
as to why ties are not required.  But, then the second reason given is to
provide diagonal tension resistance when loaded in shear.  And, thus, you
are back to "square one" in that this requirement would "reinforce" (pun
intended) the thought that you must provide ties.

The options that I would explore that could "eliminate" the tie
requirements are:

1) Design the "grouted" core as a reinforced concrete vertical
cantilevered beam and just have the brick be a veneer.  This would first
require a close look at your X-section dimensions (you would want a "gap"
between brick and the concrete so that the connection between the two
would minimize composite behaviour...and whether or not something around
8" will work per ACI 318).  You could then design per ACI 318 (assuming
there is nothing in ACI 318 that would prevent it...i.e. such as minimum
dimensions...but I don't recall any such limitations).  If so, then it is
possible that the shear is small enough that stirrups/ties would not be
needed for shear resistance.

2) Argue that "building code" requirements are not required for a "fence
post".  I believe that we had such a discussion in the past on the list.
I tried looking in the archives some, but could not locate it (sorry, only
willing to look so long).  I don't recall exactly how the discussion
went/ended up, but I do recall discussing a similar issue (i.e. must fence
posts be required to meet building code structural requirements).

Now, my final "suggestion" is why not do what you think is appropriate
(i.e. if you think ties are not needed, then don't provide them).  If you
don't think ties are needed, but the plan checker disagrees, then it is
not much effort to "add" them in (after all, I would have to believe that
the odds of you getting NO plan check comments [from what I have
seen/heard relative to what typically happens with plan checks...at least
on the West Coast] is pretty nill, so it is not like you "gain" anything
by avoiding this potential comment).  This is assuming that your only
concern is that you will get a plan check comment and that you are
completely fine with the idea that ties are NOT really required.  If you
are not SURE if you believe ties are not required, then that is a whole
other matter.

Regards,

Scott
Adrian, MI


On Fri, 16 Sep 2005 ASQENGG2(--nospam--at)aol.com wrote:

>
> The word column and beam are terms to describe structural members.  Beams
> generally are subjected to flexure while columns are those that carry  large
> axial loads.  Since the member you describe does not carry large  axial loads but
> instead is subjected to bending moment then it should be  treated as a beam.
> The main function of ties is to prevent buckling of the  reinforcement.  Since
> there is no chance that the reinforcement will buckle  in the absence of
> large axial loads, then there is no need for  ties.  Structural members should not
> be designed for their name  or call outs but on the nature of forces or loads
> they are being subjected  to.
>
> ASQuilala Jr., P.E.
>
>
> In a message dated 09/15/05 1:56:55 P.M. Pacific Standard Time,
> gtg740p(--nospam--at)hotmail.com writes:
>
>
> I have an equipment yard with 16" brick columns (4" brick  around perimeter
> with an 8" solid grouted  core). They are about 9ft tall  and at 10ft spacing
> with a nearly solid metal fencing between them. The only  axial load the
> pilasters are taking is their own self weight.
>
> Are ties required?  It appears ACI 530 requires ties for  "columns" no matter
> if they are taking vertical load or not. The "columns"  seem to be acting
> more like cantilevered beams to me. The wind shear is only  about 1400 lbs at the
> base of the columns.
>
>
> Will
>
>
>
>
>
>

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