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I don't know about others on this list, but I have always used slip
critical bolts for wind and seismic connections (the way I was taught).  I
don't do it for the "fatique" issue per se.  It is because of the
possibility of load reversals...if a true bearing connection is used (i.e.
"snug tight"), then the connection can slip within the constraints of the
bolt hole (slightly larger than the bolt) which could result in "popping"
at the joint.  This could be un-nerving to occupants of the building.
While not truely along the same line, someone told be about column splices
that were done with bearing bolts that slipped into bearing after the
building was in service.  Sounded like a bunch of guns going off and
scared the crap out of the building occupants.

Also, a slip critical connection gives you some "reserve" capacity since
if the "slip" value is exceeded, then the bolts just go into bearing.

Scott Maxwell, PE, SE


On Mon, 10 Jul 2000, Arvind K. Bisarya wrote:

> Can   someone  help  me  with  this  please ,   thanks  in  advance.
> 
> AISC, ASD Ninth Edition/LRFD 1St Edition, Volume II - Connections :
> 
> Referring to Specifications Section K which says: "The occurrence of full 
> design wind or earthquake loads is too infrequent to warrant consideration 
> in fatigue design.", goes on to say -(p 1-11) "Consequently, slip critical 
> connections are not normally required or used by engineers for wind or 
> seismic loads for buildings."
> 
> However - AISC's Seismic Provisions, dated April, 1997, section 7.2.a says: 
>  "Connections may use bearing values, but nevertheless - the faying 
> surfaces are to be a minimum of Class A friction condition."
> 
> This seems somewhat of a contradiction to me, but the requirements are 
> clearly stated.  
> 
> Anyone having some insight into why AISC would require a friction capacity 
> faying surface for bolts intended to withhold their seismic load via 
> bearing - I would like to hear it.
> 
> 
> Thankyou
> 
> Arvind  Bisarya
> Phone  314  -  539  -  0471
> Fax       314  -  539  -  8321
> E - Mail       arvind_bisarya(--nospam--at)mk.com
> 
> 
> 
> 
> 
> 
> 
> 
> 
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