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RE: Moment Frames with Slip Critical Shear Connection

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It's not a requirement.  Actually, the second edition LRFD (Silver) states
(page 8-15): "Bearing-type connections are typically used for shear, moment,
and diagonal bracing connections in buildings."  In the next paragraph: "...
slip-critical connections are not normally required or used for wind or
seismic loading in buildings."

Since your bolts are in gravity shear only (no load reversal), it looks like
you over designed the connection.  But try not to look like you're "caving"
when you tell the contractor he can use bearing bolts.  Ask how much money
he's going to give back to the owner because his bid was based on drawings
that require SC connections.

If you had a bolted-flange connection (load reversals), the "Specification
for Structural Joints Using ASTM A325 or A490 Bolts" has this to say:

4.2 Pretensioned joints are only required in the following applications:
 (2) Joints that are subject to significant load reversal;

4.3. Slip Critical Joints are only required in the following
 (4) Joints in which slip at the faying surfaces would be detrimental to the
performance of the structure.

I interpret 4.2(2) to require PT bolts in all lateral systems (frames and
drag struts).  Since there are several places that say SC joints are
required where specified by the engineer, I invoke 4.3(4) as needed to help
control frame drift at service-level loads (the slip in bearing connections
increase drift).


Jason Kilgore
Leigh & O'Kane, LLC
Kansas City, Missouri

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