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FW: Structural Bolt Torquing Question

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I believe that the proper requirements are spelled out in the "Specification for Structural Joints Using ASTM A325 or A490 Bolts".  To summerize; all bolts that are tightened to a fully tensioned condition under the four methods allowed must prove the ability to achieve the proper bolt tension by testing in a device capable of indicating bolt tension.  If the method used to install the bolts also indicates the torque used for the installation, it has no direct bearing on whether the bolt was properly installed unless verified by tension testing. There are too many variables that affect bolt torque to make that an accurate gauge of installed bolt tension.

Curt La Count
Jacobs Engineering
Portland, OR

-----Original Message-----
From: Eric Green [mailto:EGreen(--nospam--at)]
Sent: Thursday, October 10, 2002 1:01 PM
To: seaint(--nospam--at)
Subject: RE: Structural Bolt Torquing Question

This is where the question came about. The specification gives torque
information when using the turn of the nut method (Table 8.2), but gives
no information for torque when using torque control.

I realize the specification does state that the minimum tension should
be equal to 70 percent of yield and I certainly understand how to
calculate pre-stress from torque. I guess my question more accurately
stated would be:

Who specifies K so that the relationship between torque and tension can
be determined? Surely one does not depend on the contractor for this
information? Is it determined by the testing lab for each type of bolt,
nut and thread compound (if used)?

Eric Green
- Fighting my ignorance since 1964.

-----Original Message-----
From: LaCount, Curt [mailto:Curt.LaCount(--nospam--at)] 
Sent: Thursday, October 10, 2002 1:33 PM
To: Seaint (E-mail)
Subject: FW: Structural Bolt Torquing Question


The answer is that nobody specifies torque.  The engineer should however
specify the tension by referencing the "Specification for Structural
Joints Using ASTM A325 or A490 Bolts".  This is commonly done from the
structural notes or in the specifications.  The installation is also
subject to special inspection.

Curt La Count
Jacobs Engineering
Portland, OR

-----Original Message-----
From: Eric Green [mailto:EGreen(--nospam--at)]
Sent: Thursday, October 10, 2002 8:59 AM
To: seaint(--nospam--at)
Subject: Structural Bolt Torquing Question

Excuse me for what is probably an obvious question for those of you who
deal with these connections on a regular basis:

Who normally specifies the required bolt torque for a slip-critical
connection? The bolt supplier, steel fabricator or the engineer? Or is
it some other party?

Eric Green
- my ignorance is my own, not my employers.

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