F1852 TC Bolts Weathered

Date 01-29-2011 20:19 Edited 01-29-2011 20:25

cepennington

Touchy Subject to say the least.

Fastener Design/Lubrication is the key to an achieved pretension procedure.

Research Council on Structural Connections

Specification for Structural Joints Using ASTM A325 or A490 Bolts, June 30, 2004

9.2.3. Twist-Off-Type Tension-Control Bolt Pretensioning: The inspector shall observe
the pre-installation verification testing required in Section 8.2.3. Subsequently, it
shall be ensured by routine observation that the splined ends are properly severed
during installation by the bolting crew. No further evidence of conformity is
required. A pretension that is greater than the value specified in Table 8.1 shall not
be cause for rejection.
Commentary:
The sheared-off splined end of an installed ASTM F1852 twist-off-type
tension-control bolt assembly merely signifies that at some time the bolt was
subjected to a torque that was adequate to cause the shearing. If in fact all
fasteners are individually pretensioned in a single continuous operation without
first properly snug-tightening all fasteners, they may give a misleading indication
that the bolts have been properly pretensioned. Therefore it is necessary that the
inspector observe the required pre-installation verification testing of the fastener
assemblies, and the ability to apply partial tension prior to twist-off is
demonstrated. This is followed by monitoring of the work in progress to ensure
that the method is routinely and properly applied within the limits on time between
removal from protected storage and final twist-off of the splined end.

Tell them that for this fastener to maintain it's designed performance the lubricant/assembly can not be compromised by the effects of weather.

Most are a water soluble lubricant anyway it ain't rocket science but any dummy should realize the ill affects.

If you want to go to page 125 of this paper it starts there with the conclusions of this research paper that
RCSC is doing on stuff like you ask
http://www.boltcouncil.org/files/FinalReportonTCBoltsPhase1.pdf

"Delayed Installation of ASTM F1852 Fasteners - 2nd Phase"

University Of Toronto
Dr. Peter C. Birkemoe

Earlier research had shown that bolts placed in the steelwork and left for a period of time, prior to
the final installation to a residual tensile force, experience degradation in the achieved tensile force
that is attained and this is delay phenomenon forms the principal parameter of concern in this
investigation. Other important parameters that were identified are the temperature of and moisture
present in and around the fastener assembly at the time of final installation, the strength of the
assembly and the configuration of the assemblies during atmospheric exposure.

If you want to really do something get the Engineer of Record in on it.

My ¢¢'s
( Unless the connections are slip Critical or the initial tightening does not at least bring about a Snug-tight condition, I wouldn't worry about it)

But If I was the TPI I would have to put a stop to it for non-conformance.

Either way
Good Luck
Marshall

By cepennington (*)

Date 01-30-2011 20:59

Thanks for the link to the article. The problem I run into the most is that the ironworkers put the steel up, install the bolts, but can't snap them until they rack and plumb the building. Therefore, the bolts hang out in the iron for days or weeks prior to being snapped. I usually don't worry about it on snug tight jobs, but most of the projects I have worked lately are all pretensioned. I wish there was a paragraph in RCSC that would just make it easy and say they have 24 hours to snap bolts once installed. The last sentence in the commentary reads, "This is followed by monitoring of the work in progress to ensure that the method is routinely and properly applied within the limits on time between removal from protected storage and final twist-off of the splined end". So what are the limits on time between removal from protected storage and final twist-off? Where does this information come from? I can't find the time limit anywhere. I was hoping they would put it in the 2009 editon of the RCSC spec, but they didn't. So, what are they refering to in the last sentence in the commentary.
Any help is appreciated.

By 803056

Date 02-25-2011 19:49

There may not be a time limit because site conditions vary from job to job, season to season.

You can hang your hat on something as simple as asking the EOR to request a "preinstallation" test at the time of tightening the bolts using a bolt that has been exposed to the job conditions. That could be accomplished as easy as removing a bolt from a connection and tightening it in a tension gage (Skidmore) on the day the erector intends to tighten the bolts. If you obtain the proper tension, all is good. If there is a problem, change the bolts. It will not happen a second time on the same project.

Best regards - Al

By FabsForLife (*)

Date 10-04-2011 17:45

Yes, Al is correct. You will be required to do a verification test just prior to pre-tensioning in the bolts exsisting condition. Most erectors now are all using TC bolts wheather the connection is pre-tension or snug tight. Its always a good idea to establish what the connection is even requried to have. If it is only snug tight you need not verify tension or worry about the rusty condition. But somewhere in the RCSC I believe stated if the spleend end is severed in a joint only required to be snug tight it shall be a the engineers discrestion but I could be worng about that.

By MBSims

Date 10-05-2011 02:05