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Re: Masonry Column, Ties Required?

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Will,

As I see it, you can:

1) Just provide ties and avoid any "hassle".
2) Not provide ties, but if/when the plan checker/building
official/inspector flags it just provide the ties as required with no
resistance (kind of what I was suggesting).  If they don't require/flag
it, then no ties needed.  You can even have a detail/design ready to go
that would be per the MSJC requirements.
3) Not provide ties, and if/when the plan checker/building
official/inspector flags it, you could argue why they are not
needed...which could still end up with you "losing" and having to provide
them or maybe you "win" and they won't be required.

#1 and #2 are the path with minimal to no resistance (#1 has is the path
of no resistance, but #2 ain't so bad either).  #3 has the potential for a
not so insignificant amount of hassle/stress and the high potential for
you still having to provide the ties anyway.  In the end, it all becomes a
matter of how strongly you believe that ties are NOT required and how much
hassle/effort you want to deal with.

FWIW, I don't see a compelling reason why there are needed.  If the
maximum shear that you must resist is about 1400 lbs, then that results in
about an applied shear stress of about 5 psi (assuming you make use of the
full 16" square), which per the MSJC's allowable stress values would mean
that no stirrups/transverse steel is required for shear.  And as your
axial load is basically nothing (i.e. self-weight), I don't see a huge
concern for buckling of longitudinal (vertical) bars.  So, at "first
blush" it appears that requiring ties is a bit of an overkill.  But, then
my opinion won't likely mean too much to a code official/plan checker, eh?
<grin>

Good luck.

Scott
Adrian, MI


On Fri, 16 Sep 2005, Will Haynes wrote:

>
> Thanks Scott,
>
> I don't think they are needed either, I have considered trying my luck at
> it making it through the checker and field inpector. I guess one one more
> code argument with these guys will just be another drop in the bucket.
>
>
>
> WILL
>
> ________________________________________________________________________________
> From:  Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu>
> Reply-To:  <seaint(--nospam--at)seaint.org>
> To:  seaint(--nospam--at)seaint.org
> Subject:  Re: Masonry Column, Ties Required?
> Date:  Fri, 16 Sep 2005 08:44:54 -0400 (EDT)
> >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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