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Slip Critical Connections
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Re: Slip Critical Connections By  peach!!

Posts: 0

4/22/2006 5:55:00 AM

interesting reading found here:

http://www.aisc.org/MSCTemplate.cfm?Section=Steel_Interchange2&Template=/CustomSource/Faq/SteelInterchange.cfm&FaqID=2069


   

Re: Slip Critical Connections By  dfrcinspector

Posts: 0

4/23/2006 11:00:00 PM

The need for design of Slip Critical joints are defined in the AISC/ASD Specifications for Structural Joints Using ASTM A325 or A490 Bolts,
5.(a) (1) through (6).
See also the commentary C4 Design for Strength of Bolted Connections
The design drawings should clearly define the type of joints being used and the method of inspection required.
(9(a) Inspector Responsibility

Call the Desgn Engineer if you are not sure of the requirements.
SC is not specificaly identified as being Slip Critical in the AISC......at least I can''t find where it says so?

"I knew if I looked long enough I would find it somewhere in the AISC, See Part 4, Table II-B"

The Research Council on Structural Connections RCSC also identifies "SC" as slip critical.

Upon a little further looking into my reference materials, Steel Structures Technology Center, Inc. has a handbook for Structural Steel Bolting,
where they specifically identify "SC" as slip critical.
"N" as being Shear-bearing, threads included,
"X" being shear-bearing, threads excluded
and "DT" as being direct tension joints.


   

Re: Slip Critical Connections By  dfrcinspector

Posts: 0

4/23/2006 11:53:00 PM

http://www.boltcouncil.org/index.htm


   

Re: Slip Critical Connections By  Loui1

Posts: 0

4/24/2006 7:06:00 AM

It really depends. There are some situations (rare) where full bolt tension is required but the slip critical connection isnt.

Most cases, if SC bolts are indicated, then the engineer wants a slip critical joint to be detailed. The detailer usually automatcially details the faying surfaces per RCSC.

Though, I believe there should be some sort of note specifying the joint to be fully detailed as slip critical, not just a SC bolt designation.

Remember, if the bolts are fully tensioned and the faying surfaces are not preped for a slip critical connection you run the risk of bolt banging....which typically pisses owners off. :)


   

Re: Slip Critical Connections By  rbagnet

Posts: 0

4/24/2006 10:21:00 AM

I believe slip critical connections require a bigger torque on the bolts than bearing connections. AISC has 4 separate hole classifications: standard, oversize, short slot & long slot. The bearing type connection has more restrictions on the type of hole than can be used. Talbe J3.2 of the AISC-89 ASD spec lists allowable loads on bearing type and slip critical type connections. The allowables are the same for tension but the bearing type connection shear allowables are a good bit larger than the slip critical connection shear allowables.


   

Re: Slip Critical Connections By  rbagnet

Posts: 0

4/24/2006 11:09:00 AM

Section J-3.4 of the AISC ASD-89 commentary has an explanation of slip critical vs bearing connectins. To summarize:
1. Connections in shear are either slip critical or bearing type connections.
2. Slip critical connections depend upon the clamping force to prevent slip of the connected parts. Bearing connections depend upon contact of the fasteners against the sides of their holes to transfer load from one part to another.
3. Rivets, A307 bolts & A449 bolts cannot obtain adequate clamping force to be a slip critical connection, therefore they are always bearing connections.
4. The clamping force produced by properly tighetened A325 & A490 bolts is sufficient to assure that slip will not occur at full allowable stress. A325 & A490 bolts can be classified as slip critical or bearing type connections, depending on the hole type.


   

Re: Slip Critical Connections By  henri

Posts: 0

4/24/2006 10:59:00 PM

While most shear-bearing connections are simply tightened up to a "snug-tight" condition and no further, SC and DT connections are first tightened to "snug tight" and then to full pretension.

Slip critical connections are commonly used in moment connections.

The structural drawings should clearly distinguish between slip critical connections (SC), shear-bearing connections (threads included-N or excluded-X), and direct tension (DT) connections.


   

Re: Slip Critical Connections By  14erguy

Posts: 0

4/30/2006 4:07:00 PM

...and...to add to henri....a pretensioned connection. This is an intermediate connection between snug tight and slip critical. A pretensioned connection is installed exactly as a slip critical connection, only it does not require inspection. See the AISC steel spec (and specifically the commentary) for more on this.


   

Re: Slip Critical Connections By  rbagnet

Posts: 0

5/1/2006 8:54:00 AM

This question is also posted on the non-structural issues site.


   

Re: Slip Critical Connections By  rbagnet

Posts: 0

5/1/2006 8:56:00 AM

AISC has 4 classes of hole sizes; standard, oversized, long slot and short slot. A connection can either be bearing or slip critical depending on the hole type. Bearing connections have higher allowable loads than slip critical connections.


   

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