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Re: Plate Washers

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One more thing on the grout.  If you have a high shear load on the
anchor rods, try to use a minimum amount of grout.  The more grout
you use, the more bending you will get in the rods from the shear load.

We investigated a failure awhile back that was directly related to this.

Dan Goodrich, P.E.


----- Original Message -----
From: "Effland, Greg" <geeffland(--nospam--at)butlermfg.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, June 07, 2001 11:59 AM
Subject: RE: Plate Washers


> Assuming the washers are going on the anchor rods... and the holes are not
> typical anchor bolt/rod holes i.e. they are oversized, field modified, or
> slotted...
>
> Thickness:
> I would use a washer AT LEAST the thickness of the base plate.  This is to
> prevent the anchor rod and nut from being pulled through the slot/hole.  I
> have seen cases where the erector field adjusted the holes to accommodate
> bad AB placement and placed a std "hardware store" washer under the nut.
> That particular building was blown over during construction due to lack of
> adequate temporary bracing.  Most of the rods, nuts, and washers were
pulled
> straight through the base plate without damaging the base plate at all.
> Left a nice cupped washer over the anchor rod nuts though.  For that
reason,
> on oversized holes (above standard oversized AB holes) use a minimum
> thickness equal to the base plate.
>
> Size:
> The size of the washer is up to engineering judgment.  If you have slots
> that you are worried about then provide a rectangular washer that is +-
1/2"
> past the slot edges and edge of the anchor rod nuts then field weld the
> washer to the base plate with fillet welds.  Size the welds per shear
> requirements.  I would assume the min. AISC/AWS welds would be adequate in
> most of the cases.
>
> Grout:
> For most cases I would not have a problem with 1" to 2" of non-shrinking
> grout.  One thing to keep in mind is to have enough room for leveling nuts
> or plates (if used).  If there is much force reversal in the bolts you
might
> consider "double nutting" the base plate... put a nut (typ. called a
> leveling nut) under the base plate and another nut on top of the base
plate
> at each bolt/rod.  This will help eliminate any slop in the connection
> caused by the shrinking of the grout.  Downside is this can also put
> compression in the anchor rods... might be a problem if they were not
> designed for that load... This compression force could also affect how
much
> grout is acceptable.  Another tip on the nuts is if the bolts see much
> force/stress reversal than I would recommend doing something to upset the
> threads on the anchor rods to prevent the nuts from backing off or
loosening
> up.  I would definitely upset the threads and consider the use of leveling
> nuts/plates and grout on T-shaped frames like you are describing.
>
> HTH,
> Greg Effland, P.E.
> KC MO
>
> -----Original Message-----
> From: Nicholas Blackburn [mailto:nblackburn(--nospam--at)fdgoak.com]
> Sent: Thursday, June 07, 2001 11:37 AM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: Plate Washers
>
>
> I have a steel framed canopy with a single row of columns and an inverted
> gull wing (think of the WW2 Corsair wing) roof.  The columns are anchored
to
> drilled piers with 3/4" threaded rods.  The threaded rods were cast into
the
> pier foundations at an earlier time than the design/construction of the
> canopy and were designed by a different company.  There is no record of
the
> grade and type of rod used so I assumed A36 to be conservative.
>
> AISC section J3.2.e indicates the use of washers that completely cover the
> slot and that they should be 5/16" thick min when using high strength
bolts.
>
> I am looking for some suggestions as to the size and thickness of the
> washers.
>
> On a similar line, how much of a grout pad would you allow below the base
> plate?
>
>
> Thanks
>
> Nicholas Blackburn, PE
>
>
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