Slip-Critical Joint Inspection

[Heldbaum]

Hello everybody,

Can someone tell me how does the inspection of slip-critical joints look like? My understanding is, according to AISC, that "faying surfaces shall be verified that they meet the requirements as specified in the contract documents prior to assembly of the joint.." I am gonna have a project (shop drawings), working for steel fabricator, where EOR specified all connections as slip-critical..it's a 4 story steel frame 50'x100'. So inspection wise, does that mean that all plates have to be inspected prior assembly ? Bolts pretensioning is clear to me. I've got to say I've never seen SC bolts specified as typical bolt for the frame..Anyways, Thanks in advance !

 

[BridgeSmith]

Yes, the faying surfaces will have to inspected to ensure they are free of grease, road grime, etc. and paint overspray. If the surfaces have a primer or coating of any kind, it must meet the coating class that provides the slip coefficient used in the design. Commentary in the new 8th Edition of the LRFD Bridge design specs indicates that surface rust is not detrimental to the slip resistance of the joint, but some types of metallized coatings do substantially reduce the slip coefficient.

 

[dik]

In these environs, it's not common for all joints to be spec'd as slip critical... only some... connections to exterior columns, X-bracing, where there can be load reversals... most connections are snug tight, unless the engineer made an oversight and spec'd slip critical for all. You may want to contact the EOR for clarification.

Dik

 

[Dinosaur]

I would think SC joints were common but not omnipresent. When designing joints that incorporate welding and bolting, SC bolts have to be used unless things have changed since I received my degree.

 

[BridgeSmith]

"When designing joints that incorporate welding and bolting, SC bolts have to be used unless things have changed since I received my degree."

Are you talking about a connection where the load is shared between bolted and welded portions of the connection? If so, I don't know that we ever discussed joints that in any of my classes. In designing the connections for bridges, we certainly don't ever use both. If you were to use both in the same connection, certainly the bolted portion would be SC, otherwise it would not add any resistance until after the welded part of the connection had failed. Even with SC bolting, I'm not sure you'd get full load sharing.

For all of our connections, each connection is either welded or bolted with fully tensioned high-strength bolts and blast-cleaned SSPC-SP6) faying surfaces. Alternately, they can opt to do a Near-white blast cleaning (SSPC-SP10) and a Class B coating. Either should provide a slip coefficient of 0.5, but we have been using 0.33 for design.