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Re: tightness of anchor bolts

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Without any guidance in your drawing notes or specifications they are likely to be just hand tightened by a couple of tugs with whatever wrench is used for installation.  AISC defines snug tight for structural bolts as "...a few impacts of an impact wrench or the full effort of an ironworker using an ordinary spud wrench to bring the connected plies into firm contact".

Torque is a very lousy method of trying to tension a bolt especially anchor bolts.  Actual pre-tensioning of anchor bolts is typically only done for tall/slender vertical vessels (or other tall/slender cantilever type structures), large vibrating compressors, and other specialty applications.  The big problem with trying to pre-tension an anchor bolt, compared to a structural bolt, is that you are likely to loose your pre-tension due to concrete shrinkage and creep.

Thomas Hunt, S.E.

10/14/2010 06:17 AM
Please respond to seaint
tightness of anchor bolts

What is the standard amount that foundation anchor bolts are tightened unless specified?  What is the definition of snug tight - first contact or contact plus turns?  
If subjected to tension loads from lateral forces (wind or earthquake) is there a certain torque that should be applied and if so what is it?
Thanks for any input.
Paul Franceschi
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