Return to index: [Subject] [Thread] [Date] [Author]

RE: Levelling plates or shims ?

[Subject Prev][Subject Next][Thread Prev][Thread Next]
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
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   without your permission. Make sure you visit our web
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
>

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********