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RE: Leveling Nuts

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Joe,
Small shear loads are those that the anchor bolts can resist. It is a function of the anchor bolt diameter and the applied moment and shear. The moment is dependent on the distance from the plate washer to the concrete. Or (if done with diligence and injected grout) you can use the grout to resist the lateral shear of the anchor bolt. Invariably the shear is less than about 20 kips.

PEMB's do not use grout, and the moment arm is shorter. Never the less, the practice in PEMB's is to use some sort of shear lug if the bolts can not transfer the shear load.

It is easiest to use setting templates with shear lugs and then weld shear transfer bars from the base plate to the setting template. Shear lugs on the column base plate are a pain to erect.

I need to write an article for this.  It is on my to do list.

Regards,
Harold Sprague





From: "Joe Grill" <jgrill(--nospam--at)swiaz.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Leveling Nuts
Date: Fri, 16 Sep 2005 13:22:39 -0700

Harold,
Out of curiosity, what do you consider "small" shear?  I've never done any
structures where I would really consider the shear transfer "large", and am
considering moving more towards shear lugs, but where I work I know I will
catch a lot of flack for doing that.  It doesn't matter what you do here
it's never been done that way before.

Another bad day.

Joseph R. Grill, P.E. (Structural)
Shephard - Wesnitzer, Inc.
Civil Engineering and Surveying
1146 W. Hwy 89A Suite B
Sedona, AZ  86340
PHONE (928) 282-1061
FAX (928) 282-2058
jgrill(--nospam--at)swiaz.com



-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com]
Sent: Friday, September 16, 2005 11:50 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Leveling Nuts

The wedges are generaly removed when you grout.  They are there more for
stability unti the frame is erected.  You can assume an increase in
secondary moments, but a properly designed plate washer should make that
issue moot.

If the applied shears are small, I take the grout space into account for
applied moment on the anchor bolts.  If the shears are larger, I will use
the anchor bolts for uplift only, and use shear lugs to take out the shear.

Regards,
Harold Sprague


>From: Padmanabhan Rajendran <rakamaka(--nospam--at)yahoo.com>
>Reply-To: <seaint(--nospam--at)seaint.org>
>To: seaint(--nospam--at)seaint.org
>Subject: RE: Leveling Nuts
>Date: Fri, 16 Sep 2005 05:52:08 -0700 (PDT)
>
>Harold,
>
>Thanks. Although I have never seen erection of a steel
>frame so far, I suspected that the sequence of steps
>for it would be like what you have described. I guess
>you omitted to state that the very last step is to
>grout the holes created by the removeal of the wedges.
>
>Typically, a 1" grout space is called out on the
>drawing. With the tolerance of + or - 3/4" on top of
>concrete, a 1" nominal grout thickness may not give
>much room (50% chance)for proper grouting. Should this
>not impact the design philosophy for anchor bolts? It
>may be prudent to assume that the bolts may experience
>additional tension from the secondary bending monets
>on them (=Shear * grout space/bolt spacing). Is this
>scenario included in the design equations given in
>Appendix D, ACI 318?
>
>Rajendran
>
>--- Harold Sprague <spraguehope(--nospam--at)hotmail.com> wrote:
>
> > This is iron working 101.
> >
> > The top of concrete foundations is never flat.
> > Concrete tolerances are + or
> > - 3/4".  Steel tolerances are + or - 1/16".
> >
> > 1.  A laser level is set up, and a bucket of 2"x2"
> > of shims of various
> > thicknesses are carried around by an iron worker.
> > He sets up at the
> > theoretical bottom of steel column and shoots in the
> > top of concrete.  The
> > difference is the shim stack which is set in the
> > center of the anchor bolt
> > group
> >
> > 2.  The column is set on the shim stack.
> >
> > 3.  Plate washers and nuts are placed on the anchor
> > bolts.
> >
> > 4.  Set the frame.
> >
> > 5.  The columns are plumbed and aligned.  (Optional
> > and good safety
> > practice.)  Drive shims in between each pair of
> > anchor bolts at the edge of
> > the base plate.
> >
> > 6.  Grout in the base plate leaving the steel shims
> > in place.  Remove the
> > wedges.
> >
> > This is the way that 90% of steel frames are set.
> >
> > Regards,
> > Harold Sprague
> >
> >
> >
> >
> >
> > >From: Padmanabhan Rajendran <rakamaka(--nospam--at)yahoo.com>
> > >Reply-To: <seaint(--nospam--at)seaint.org>
> > >To: seaint(--nospam--at)seaint.org
> > >Subject: RE: Leveling Nuts
> > >Date: Thu, 15 Sep 2005 19:28:01 -0700 (PDT)
> > >
> > >Harold,
> > >
> > >If shim plates are used, how much of the volume
> > below
> > >the base plate is taken up by them? Do they get
> > buried
> > >in the grout?
> > >
> > >Rajendran
> > >
> > >--- Harold Sprague <spraguehope(--nospam--at)hotmail.com> wrote:
> > >
> > > > As a former iron worker, I do not like leveling
> > > > nuts.  Most iron workers
> > > > will not use them even if you show them.  The
> > > > preference is to use shims and
> > > > wedges and nuts with plate washers on the top of
> > the
> > > > base plate only.
> > > >
> > > > That said, if you choose to use them, there is
> > no
> > > > justification in what the
> > > > plan checker is asking.  What he is trying to do
> > is
> > > > get the grout to take
> > > > all of the compression without loading the bolts
> > in
> > > > compression.  The answer
> > > > is so what if they do take a measure of
> > compression.
> > > >  It will not have a
> > > > major impact on the performance.
> > > >
> > > > Regards,
> > > > Harold Sprague
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > >From: "John L. Smart"
> > <smartj(--nospam--at)smartengineers.com>
> > > > >Reply-To: <seaint(--nospam--at)seaint.org>
> > > > >To: <seaint(--nospam--at)seaint.org>
> > > > >Subject: Leveling Nuts
> > > > >Date: Wed, 14 Sep 2005 12:04:42 -0400
> > > > >
> > > > >I have a plan reviewer telling me that if I
> > allow
> > > > leveling nuts, I must
> > > > >specify that the column be leveled, shimmed,
> > then
> > > > the leveling nuts backed
> > > > >off before grouting. The erectors I have asked
> > have
> > > > never heard of this.
> > > > >Has
> > > > >anyone else? I assume the point is to keep the
> > > > column from sitting on the
> > > > >bolts, but so what?
> > > > >
> > > > >
> > > > >
> > > > >John L. Smart
> > > > >
> > > > >Lindsey & Ritter, Inc.
> > > > >
> > > > >smartj(--nospam--at)smartengineers.com

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