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RE: Levelling plates or shims ?

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Dick,

Good point.  Four bolts is a must!!  The OSHA Subpart R is now the law, and
a good idea.  It is so automatic with me, I did not even mention it.

For narrow bolt configurations that are popular with the 3 hinge arch frames
for pre-engineered metal buildings, it can be even more critical.  I have
seen frames like these blown over, and iron workers killed (Denver 1998).
Engineers who design these structures should run the numbers for wind on the
projected area based on a 5 year wind.  There will be a paper published soon
correlating construction wind velocities to a 5 year wind.

Regards,
Harold O. Sprague

> -----Original Message-----
> From:	Dick_Roberts(--nospam--at)oxy.com [SMTP:Dick_Roberts(--nospam--at)oxy.com]
> Sent:	Wednesday, February 27, 2002 2:25 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	RE: Levelling plates or shims ?
>
> Harold
>
> Any comments on OSHA's requirements on a minimum of 4 anchor bolts
> per column. I believe these went into affect last January
>
> Dick Roberts
>
> > -----Original Message-----
> > From: Sprague, Harold O. [mailto:SpragueHO(--nospam--at)bv.com]
> > Sent: Wednesday, February 27, 2002 1:40 PM
> > To: 'seaint(--nospam--at)seaint.org'
> > Subject: RE: Levelling plates or shims ?
> >
> >
> > As many on this list are aware, I am a former iron worker.  I
> > have set many
> > columns with every method you can imagine.  The shim pack is the most
> > efficient way to set a column.
> >
> > In theory using the leveling nuts makes good sense.  In the
> > land of come
> > alongs, and spud wrenches it does not work that well.
> >
> > The problems with using leveling nuts are as follows.
> > 1.	Because of tolerance problems, you have to use oversize
> > holes in the
> > base plate.  With oversize holes, you have to use a plate
> > washer.  The plate
> > washer will be a minimum of 3/8" thick.  The nut will be
> > about 1" thick
> > (assuming a 1" diameter anchor bolt).  Vertical alignment per ACI 117
> > "Standard Specifications for Tolerances for Concrete Construction and
> > Materials", Sec. 3.3.1.2  is + 1/2" to -2".  This would
> > require an absolute
> > minimum grout space of 1 5/8".  I have had occasion to use
> > leveling nuts,
> > but they are rare, and generally are for base plates that are huge and
> > shipped loose from the column.
> > 2.	They are not as easy to adjust or to plumb the frame as with a
> > single shim pack in the center.
> > 3.	If the floor is cast first and you are working in a pocket, you
> > can't get to the bottom nut.
> > 4.	Most iron workers will either not install the bottom
> > nuts at all or
> > will back them off to the top of the foundation.
> >
> > The procedure in the single shim pack is:
> > 1.	Shoot the level at the center of the bolt group.
> > Knowing the level
> > of the base plate, you set a shim stack that is the height of
> > the difference
> > in elevations.
> > 2.	Set the column on the shim stack, install the plate
> > washers and the
> > nuts, and release the choker for the crane.
> > 3.	Set the rest of the steel frame for the next level up.
> > 4.	Install temporary erection cable bracing and/or
> > vertical braces.
> > 5.	Plumb and square the frame by whacking the bottom of
> > the column with
> > a sledge to move the bottom in place.  Plumb the frame by a
> > combination of
> > rocking the column on the shim stack, tightening and
> > loosening the nuts from
> > the top, and adjusting the bracing.
> > 6.	Grout the base plate.
> >
> > If additional stability is required during construction the
> > iron workers
> > drive wedges in the sides of the base plate.
> >
> > Regards,
> > Harold O. Sprague
> >
> > > -----Original Message-----
> > > From:	EphHirsch(--nospam--at)aol.com [SMTP:EphHirsch(--nospam--at)aol.com]
> > > Sent:	Wednesday, February 27, 2002 12:01 PM
> > > To:	seaint(--nospam--at)seaint.org
> > > Subject:	Re: Levelling plates or shims ?
> > >
> > > To Harold Sprague's response I would add a suggested modification:
> > >        Rather than use shims under the base plate, use a
> > double levelling
> > > nut                  procedure, whereby nuts are placed
> > under the base
> > > plate which allows more accurate levelling as well as
> > clamping action to
> > > secure the base plate and column when the above-plate nuts
> > are installed.
> > >
> > >
> > > HTH,  Ephraim G. Hirsch, SE
> >
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