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RE: pretensioned HS bolts

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I'm told that buildings with non-pretensioned bolts at bracing connections
sometimes "creak" or make popping sounds when subject to wind loads. I
assume that wind reversals cause the bolts to slide into bearing on the
opposite side of the hole. Thus, I consider connections subject to load
reversal due to wind to be "slip-critical connections". I would consider all
seismic connections subject to load reversal also to be slip-critical. 

Since RCSC requires bolts subjected to direct tension to require
pretensioning, the Table appears to be written to reinforce that
requirement. In reality, the bolt should have the same tensile capacity
regardless of application of pretensioning. 

> -----Original Message-----
> From: Casano, Karen [mailto:Karen.Casano(--nospam--at)dgs.ca.gov]
> Sent: Wednesday, August 14, 2002 11:51 AM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: pretensioned HS bolts
> 
> 
> Hello,
> 
> I am hoping to get some input or guidance from all of you 
> structural steel
> experts about the use of fully-tensioned or slip critical, high
> strength(A325SC or A490SC)bolts. I have always specified them 
> for use on all
> seismic connections including drag lines and any joints 
> subject to direct
> tension, but I'm noticing that other engineers don't do this.  
> According to the RCSC Specification for Structural Joints 
> Using A325 or A490
> Bolts, SC bolts should be used for joints "subject to significant load
> reversal", and "joints in which, in the judgement of the 
> Engineer, any slip
> would be critical to the performance of the joint or 
> structure..".  Do these
> apply to seismic resisting systems (or wind)?  In FEMA 350 
> and AISC Chapter
> 4, the bolted MF connections show use of "pretensioned" 
> bolts, however, in
> the HSS manual Moment connections, I don't see mention of 
> tensioning the
> bolts.  
> In regard to the direct tension connections, Chapter J in the AISC ASD
> manual (Table J3.2)indicates that the allowable tension for a 
> high strength
> bolt is independent of the intial tightening force (listed as 
> 44 ksi for
> A325 and 54 ksi for A490); however, the RCSC specification (Table 2)
> indicates that applied static tension allowables are only for 
> pretensioned
> bolts (footnote b).  ??
> 
> 
> karen casano, PE 
> san diego
> 
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