Bearing and Slip Critical Connections.....

[Ron]

AISC says that if there is a significant stress reversal, the connection should be designed as slip critical. This is clear for connections that have wind uplift reversing gravity loads; however, should this also include lateral force reversals such as for shear walls? I have my thoughts on this, what are yours?

 

[sandman21]

Per AISC 341 connections part of the SFRS, drags, collectors, chord, are required to be pretensioned bolts with a class A faying surface. Projects in high seismic typical have ALL bolts as A325 and class A faying.

 

[dik]

I use slip critical for all bracing where there can be stress reversal... as well as beam connections to exterior columns.

Dik

 

[Ron]

I posted this to create a discussion....which it apparently did.

One of the issues we deal with in construction is the lax procedural methods of "snug tight". Faying surfaces are to be brought into full contact! I see many times that unless there is greater specificity in the tensioning specification, this does not occur. ALL high strength bolts are to be tightened to a "snug tight" condition, at least. A non-specific requirement at best, other than the faying surface requirement.

I ran into a condition where TC bolts were used for numerous connections; however, they were not tensioned as required for TC bolts. The plans were vague and the fabricator could not provide shop drawings. An interesting condition at least. Why would a fabricator use bolts that cost 3x the normal bolt cost, yet not use them for their purpose? Further, TC bolts are very difficult to tighten to a snug tight condition without using a TC bolt tool (TC bolts do not have hex heads, so they are prevented from rotating during tightening with the spline engagement of the tensioning tool.) Does it make sense?