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RE: Slip Critical Connections

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Title: RE: Slip Critical Connections

>Is there any situation where the design of a slip critical
>bolted connection would not be required to address
>bearing requirements?

No. There has long been a misconception that slip-critical connections behave differently than bearing connections. In fact, both types initially resist load through friction. At some undefined level, a bearing connection will slip into bearing. At a more definable level of service load (approximately, just above the calculated slip resistance of the joint) a similarly proportioned slip-critical connection will also slip into bearing. In both cases, the ultimate strength of the connection is then larger than the slip load and controlled by some "bearing" limit state such as bolt shear, bolt bearing, etc.

There's one catch, though. Some joints may have slip resistances that are lower than other bearing limit states. Particularly when thin plies and Class B coatings are used and the slip resistance is much higher.

Slip resistance is simply a serviceability criterion masquerading as a strength check. The real strength of the joint still has to be there, though for when (if) slip does occur. So it is required that SC connections always be checked as bearing connections.

For the official specification requirements, see RCSC Specification Section 5. That spec is available as a free download from http://www.boltcouncil.org/.

Charlie