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RE: Short anchor bolt projection

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Harold, thanks for your comments. I don't have those references, but I did
confirm that 
a standard heavy hex nut can develop an A307 anchor rod with 0.8" of thread
engagement 
by comparison of capacities:

Min, tensile capacity of A307 1" bolt = 36.35 kips
Proof load of A563 1" heavy hex nut = 45.45 kips
Height of heavy hex nut = 1"

Required thread engagement = (36.35/45.45)x1" = 0.80"
(assuming linear relationship of thread engagement to capacity of nut)

This seems like a reasonable solution to me. (I will have the recess above
the top of 
anchor rod filled with caulk to prevent standing water, as this is an
exterior 
application.)


> -----Original Message-----
> From: Sprague, Harold O. [mailto:SpragueHO(--nospam--at)bv.com]
> Sent: Monday, October 09, 2000 10:27 AM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Short anchor bolt projection
> 
> 
> William,
> 
> I have run this calculation many times.  Re: Fastener Design Manual by
> Barrett, NASA Ref. Pub. 1228.  I obtained another reference 
> from the IFI,
> The Distribution of Load on The Threads of Screws, Goodier, Journal of
> Applied Mechanics, March, 1940.
> 
> A standard nut can fully develop an A36 anchor rod even with 
> 3/16" short on
> projection.  
> 
> If you are resisting shear I would be inclined to keep the 
> washer, and weld
> the washer to the base plate.  That way the maximum slip to bearing is
> 1/16".
> 
> Regards,
> Harold Sprague
> 
> 
> > -----Original Message-----
> > From:	Sherman, William [SMTP:ShermanWC(--nospam--at)cdm.com]
> > Sent:	Monday, October 09, 2000 10:56 AM
> > To:	SeaInt Listserver (E-mail); 'Charlie Carter'
> > Subject:	Short anchor bolt projection
> > 
> > I have a situation in which the projection of an anchor 
> bolt is about
> > 3/16"
> > less than required for nonshrink grout, base plate 
> thickness, washer and
> > nut
> > (based on field measurements of actual anchor bolt 
> projection and base
> > plate
> > thickness). We are using 1-inch diameter galvanized A307 
> anchor bolts in
> > 1-1/8-inch diameter holes. There is no calculated uplift on 
> the anchor
> > bolts
> > but they are required for shear. 
> > 
> > I am considering three options: 1) delete the washer; 2) 
> use "standard hex
> > head nuts" in lieu of "heavy hex nuts"; 3) allow the anchor 
> bolt to stop
> > short of the top of the nut, using a heavy hex nut. 
> > 
> > As I understand the purpose of a washer, it is intended to 
> be used under
> > the
> > part turned in tightening of high strength bolted 
> connections to prevent
> > galling of the surface, and it helps distribute loads where 
> oversized
> > holes
> > are used in base plates. While an anchor bolt needs to be 
> tightened down,
> > it
> > does not need to be pretensioned to the level of an A325 
> bolt, so galling
> > does not seem to be as big of a problem here. The hole diameter in a
> > washer
> > for a 1-inch bolt is 1-1/8" diameter, the same as in my 
> base plate; so
> > provided that the base plate holes are not enlarged in the 
> field, the
> > washer
> > should not be necessary to distribute load. On this basis, 
> I don't see a
> > need for the washer - any other thoughts on why a washer might be
> > necessary?
> > Elimination of the washer would allow the bolt to extend 
> flush with the
> > top
> > of the heavy hex nut. 
> > 
> > Although heavy hex nuts are provided with the anchor bolts, 
> according to
> > Table X1.1 attached to ASTM A563, standard hex nuts can be 
> used with A307
> > bolts if of the appropriate grade. Unfortunately, this would only
> > eliminate
> > 1/8" vs the 3/16" I need. The base plate is 1/8" thicker 
> than the what was
> > specified, so I could grind down the base plate by 1/16". 
> > 
> > Similarly, if a heavy hex nut was provided but a standard 
> hex nut would
> > suffice, would it be acceptable to allow the bolt to 
> project into the
> > heavy
> > hex nut only the distance as required for the height of a 
> standard hex
> > nut,
> > if of the same grade material? 
> > 
> > Any thoughts on these solutions would be appreciated. 
> > 
> > 
> > William C. Sherman
> > Camp Dresser & McKee, Inc.
> > Denver, CO
> > Phone: 303-298-1311
> > Fax: 303-293-8236
> > email: shermanwc(--nospam--at)cdm.com