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RE: Short anchor bolt projection

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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
>