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Re: Double Nuts on Anchor Rods

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Steve,

I agree that for bolts accessible to the public it may be better to stake the threads so they are not easy to remove but for all other cases I would go with double nutting.  If you have ever double nutted bolts you would see that finger tight is enough to lock them together, i.e., very little torque is required and for cases of slotted connections that may be high up in a structure it is easier to verify.  I guess I would have to ask what specifications do you have staking threads; three whacks on a 7 inch screwdriver with a 10 lb hammer  <;-).

Thomas Hunt, S.E.
Fluor



"S. Gordin" <mailbox(--nospam--at)sgeconsulting.com>
01/12/2006 12:54 PM
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        Subject:        Re: Double Nuts on Anchor Rods

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Tom,
 
I agree, for removable equipment staking may be a problem.  At the same time, the new equipment is unlikely to have the same footprint, and the anchor bolts are likely to be torched anyway.  
 
I usually specify double counter-tightened nuts on the anchor bolts of the pedestrian bridges.  However, I also specify staking to prevent the removal of these exposed and accessible nuts by vandals.  Similarly, I also specify staking in some structural (A307) bolt applications, where the nuts can be removed (say, "accessible" components of a bridge at the school grounds).  
 
Specification-wise, I am not sure what is more practical.  How do you specify/verify the torque on the double nuts?  At the same time, staking appears doable, visible/verifiable, and effective.
 
Steve Gordin SE
Irvine CA

----- Original Message -----
From: Tom.Hunt(--nospam--at)fluor.com
To: seaint(--nospam--at)seaint.org
Sent: Thursday, January 12, 2006 11:29 AM
Subject: Re: Double Nuts on Anchor Rods


Steve,


My personal opinion is that staking/spiking the threads is least preferred method for both structural bolts and anchor bolts.  Double nutting is very positive and easily inspectable.  The effectiveness of staking threads is questionable and makes it difficult to remove the nuts especially for equipment that may require removal for maintenance.  Lock washers should never be used in structural applications.


Thomas Hunt, S.E.

Fluor



"S. Gordin" <mailbox(--nospam--at)sgeconsulting.com>
01/12/2006 10:01 AM

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        Subject:        Re: Double Nuts on Anchor Rods

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Tom,

 

The only reference to double nuts in the referenced source appears to be that of the embedded nuts for QT rods (I may have been looking not thoroughly enough).  According to AISC Manual "Column Base Plates", it is generally "better to spike the threads of double nuts than to use lock washers."  That manual also indicates that "use of lock nuts on anchor bolts is rarely justified" and the split-ring washers are"ineffective."

 

IMO, "Spiking" ("staking") can be easily specified and implemented, and may represent the only practical and almost fool-proof way to assure the long-term intactness of the bolted assembly.  

 

Steve Gordin SE
Irvine CA

 

----- Original Message -----
From:
Tom.Hunt(--nospam--at)fluor.com
To:
seaint(--nospam--at)seaint.org
Sent:
Thursday, January 12, 2006 9:18 AM
Subject:
Re: Double Nuts on Anchor Rods


Ken,


Yes, double nuts are often used for vibrating equipment and tall vertical vessels anchor bolts.  I do not have a copy in front of me but you might want to look at ASCE, "Wind Loads and Anchor Bolt Design for Petrochemical Facilities".


Thomas Hunt, S.E.

Fluor


"Ken Peoples" <kspeoples(--nospam--at)lvta.net>
01/12/2006 07:35 AM

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        Subject:        Double Nuts on Anchor Rods

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When we are doing structural steel detailing, we sometimes see double nuts on anchor rods - especially for industrial work.  I am curious if any of you know of any particular recommendations from AISC (or any other authority) regarding using double nuts for anchor rods.  I often see them where there are vibrations (screens), cranes, towers or stacks.


Best regards,



Kenneth S. Peoples, P. E.


LVTA
Lehigh Valley Technical Associates, Inc.
1584 Weaversville Road
Northampton, PA 18067


Phone: 610-262-6345
Fax: 610-262-8188



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