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Re: Shear-off bolted connection

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For anyone interested in talking with manufacturers about gauging tension,
it seems to me that (like a guitar string) the tighter the bolt is - the
higher the frequency it would give off.  I seem to remember an article in
NASA Tech Briefs about gauging bolt tension with ultrasonics - might be
worth looking into.

                                                                Greg Smith
-----Original Message-----
From: WILLIAM R. KEEN <wrk(--nospam--at)clarknexsen.com>
To: mail@ih {seaint(--nospam--at)seaint.org} <seaint(--nospam--at)seaint.org>
Date: Monday, January 18, 1999 1:22 PM
Subject: RE: Shear-off bolted connection


I think we need to balance the theoretical aspects of this issue with the
practical aspects. Erectors and fabricators are telling us they like the
twist-off bolts because they are easier to install and they can maintain
higher quality. Usually, if it's hard to do something in today's
construction
industry, there's very little likelihood that it will be done well without:
a) a LOT of involvement by the SER,
b) more field inspection,
c) a contractor who cares about quality and
d) someone with enough chutzpa to tell the contractor it's not right and do
it over again

I agree with Charlie - they all CAN perform well if installed properly. The
question is, how hard is it for all parties involved to make sure that
happens.

I like the twist-off bolts. I've experienced problems with DTIs myself. The
biggest problem I've seen is that they "squish" too late in the torque
process and bolts break off. Over-tensioning worries me more than
under-tensioning. I'd much rather have a bolt tensioned to 50% of proof when
90% was required vs. 110%.

Bill Keen




-----Original Message-----
From: Charlie Carter On Behalf Of Charlie Carter
Sent: Sunday, January 17, 1999 10:02 PM
To: mail@ih {seaint(--nospam--at)seaint.org}
Subject: Re: Shear-off bolted connection


It's not surprising that a manufacturer of DTI's would claim
emphatically that DTI's are the best method. But the facts are that any
of the four methods approved by RCSC (the Research Council on Structural
Connections) will provide acceptable bolt installation for pretensioned
applications when used properly.

The four methods are:

turn-of-nut method
calibrated wrench method
alternative design fastener method (such as a twist-off bolt)
direct tension indicator method

Any of these methods can produce unsatisfactory results if not applied
properly. All can be used successfully if applied properly. Refer to the
RCSC Specification (particularly Section 8 and it's Commentary) for a
discussion of these four methods.

Charlie