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RE: Anchor bolt confinement in pedestals

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Ben:

I agree that in reality one should look at the intent, but one has to
admit that is where things become problematic.  Codes (and laws) are
supposed to be crystal clear.  I should not have to figure out the
intent...the intent and the letter should match 100%.  Otherwise, what I
view as the intent may not be what the code writer (or lawmaker) really
intented.  We are not mind readers, which is why the intent is supposed to
be put down in the "letter".

Regards,

Scott
Adrian, MI


On Wed, 13 Oct 2004, Ben Yousefi wrote:

> This requirement dates back at least to the 76 UBC, Section 2607 (m). It was the result of observed damage from the 1971 Coalinga earthquake where beams framing to columns slid of the top of the column and due to lack of any confinement at the top of the member.
>
> It is stated for "columns" however, like anything else in the code, one needs to look at the intent and not only the letter. If it makes sense to protect the gravity members supported by a column, it probably makes sense to do the same for pedestals.
>
> Ben Yousefi, SE
> Santa Monica, CA
>
> >>> smaxwell(--nospam--at)engin.umich.edu 10/13/04 11:00AM >>>
> Very true.  But, my main point still stands...the provision in ACI 318
> comes by way of the provisions that were in the model building codes
> (BOCA, IBC, UBC).  It appears that ACI 318 decided to specifically call it
> out for columns AND pedestals.  But, otherwise it is the same provision as
> what is in the 2000 IBC.
>
> If you want to pick appart differences, then it should be noted that the
> similar provision for columns (but not pedestals) in the 1996 BOCA applied
> for ALL seismic conditions just like the ACI 318-02 provision (i.e.
> non-seismic to highest seismic) while the provision in the 2000 IBC only
> applies for Seismic Design Categories C or higher.  And strictly
> speaking, the UBC provision only applies for cases where the columns
> would fall under the seismic provisions (section 1921 is the seismic
> concrete provision), which admittedly is all of California (the only
> location that I know that still uses the 1997 UBC).
>
> In addition, the 1996 BOCA only required no less that 2 #4 in the top 4
> inches, while the 2000 IBC provision is 2 #4 or 3 #3 in the top 5 inches
> just like the ACI 318-02 provision.
>
> And, for me, most pedestals that I have dealt with would meet the
> definition of a column.  Of course, I live in an area where frost depth is
> about 42" or more, so most exterior spread footings have to be deep enough
> to be below that.  As a result, many exterior spread footing that I have
> designed end up with a pier/pedestal on it that is about 3+ feet tall, so
> they would either meet that definition or be close enough.
>
> And, finally, while it is not enforceable (if only my opinions were in
> general <grin>) unless I am the EOR, I have always believed that it is
> good practive to place such ties in the top of piers/pedestals/columns
> with anchor bolts.  It certainly helps that I now seem of the same mind as
> ACI 318.  ;-)
>
> Regards,
>
> Scott
> Adrian, MI
>
>
> On Wed, 13 Oct 2004, Dickey, David wrote:
>
> > The original question concerns ties around anchor bolts at the top of a
> > pedestal.  The title of section 1910.4.3 in IBC 2000 is "Anchor bolts in
> > the top of *columns*."  Since a column is defined as "a member with a
> > ratio of height-to-least-lateral dimension exceeding three", this
> > provision won't apply to most pedestals.
> >
> > David Dickey
> > Lexington, KY
> >
> > -----Original Message-----
> > From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
> > Sent: Wednesday, October 13, 2004 12:29 PM
> > To: seaint(--nospam--at)seaint.org
> > Subject: RE: Anchor bolt confinement in pedestals
> >
> >
> > FWIW, this provision which is now in ACI 318 came by way of the model
> > building codes.  There has been such a provision in the BOCA codes since
> > the 1996 edition (too lazy to crack open the 1993 edition to check) in
> > the form of section 1913.1.3 and from there it made into the 2000 IBC in
> > section 1910.4.3.  I don't recall if there such a provision in the 1997
> > UBC or not.
> >
> > Regards,
> >
> > Scott
> > Adrian, MI
> >
> >
> > On Wed, 13 Oct 2004, Wesley Werner wrote:
> >
> > > You can find it in ACI 318-02 section 7.10.5.6.  This section is new
> > to
> > > ACI 318-02. It requires (2)- #4 bars or (3) - #3 bars in the top 5" of
> > > pedestals containing anchor bolts.
> > >
> > > Wesley C. Werner
> > >
> > >
> > > -----Original Message-----
> > > From: Will H [mailto:haynewp(--nospam--at)hotmail.com]
> > > Sent: Wednesday, October 13, 2004 9:55 AM
> > > To: seaint(--nospam--at)seaint.org
> > > Subject: Anchor bolt confinement in pedestals
> > >
> > >
> > > I usually see something like (4)-#3 ties @ 3" o.c. enclosing
> > > anchor bolts at
> > > the top of a concrete pedestal which is supporting axial load
> > > from a column.
> > >
> > > I am having trouble finding something in ACI that describes this as a
> > > detailing/design requirement. Does anyone know where ACI
> > > addresses this or
> > > has designed for this before?
> > >
> > >
> > >
> > > Will Haynes, P.E.
> > >
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