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RE: BOLT TORQUE/TENSION RELATIONSHIP

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I think that Charlie Carter's morning cup of coffee has kicked in now enough
for spell check to work, but his point is correct.  The front of the AISC
"Specification for Structural Joints Using ASTM A325 or A490 Bolts" states
that it was prepared by RCSC Committee 15.  The recommendations by AISC are
the same as the RCSC.  

Aside from Charlie's spell check lapse, there are 4 methods listed in the
RCSC that are intended to "pretension" a bolt.  None of them will allow you
to just use a torque wrench and pretension bolts.  The closest thing is the
Calibrated Wrench in Sec. 8.2.2.  It states that "... Torque values
determined from tables or from equations that claim to relate torque to
pretension without verification shall not be used."  The commentary is also
a good read when it comes to this topic.  Frankly the effort to properly
install and inspect bolts using the Calibrated Wrench method are so
difficult, I don't allow it in the specifications that I write, and I can't
even recall a project in the last 20 years in which Calibrated Wrench was
used.  

The torque wrench is allowed ONLY as a means of arbitration.  The torque
wrench is NOT allowed as a method of  installation, nor is it allowed for
inspection.

The goal is to provide a pretension in the bolt per RCSC Table 8.1.  Torque
is irrelevant. Now with all of that, I must confess that I have used torque
as a method to provide a pretension force on some anchor bolts.  But I was
conservative, it was not all that critical of an application, and I required
some serious inspection.  On critical anchor bolts, I require hydraulic
tensioners.  

Regards,
Harold O. Sprague


-----Original Message-----
From: Christopher Wright [mailto:chrisw(--nospam--at)skypoint.com] 
Sent: Wednesday, July 09, 2003 11:37 PM
To: ?
Subject: RE: BOLT TORQUE/TENSION RELATIONSHIP


>Torquing bolts is not an accepted method of bolt pretensioning by the 
>RCSC. The only "torque" method discussed in the RCSC is for arbitration 
>ONLY.
Why do you suppose RCSC takes this position so much different than that 
taken by the AISC? Have safety issues been uncovered, using the AISC 
calibrated wrench or turn-of-the-nut methods been founf defective?

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw


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