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Re: AISC 341 7.2 slip critical? pre-engineered metal bldg end plates, shear plates as drag struts

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> From: "Haan, Scott M POA" <Scott.M.Haan(--nospam--at)>

> AISC 341 7.2 Bolted Joints has a couple of sentences for bolted
> connections that are part of the seismic resisting systems which read:
> "All bolts shall be pretensioned high-strength bolts.  All faying surfaces
> shall be prepared to as required for a Class A or better Slip Critical
> Joints...."

> Does this mean all connections resisting seismic forces need to meet
> slip critical requirements?  I thought they could be fully pretensioned
> but someone at work is making a contractor sand blast all the contact
> surfaces between beams and shear plates where the connections are double
> dipping as drag strut connections.

They do not need to be DESIGNED as slip critical (e.g. "reduced" shear
capacity). The faying surfaces must be clean to meet the Class A
requirements, minimum, and the bolts must be fully tightened. I believe
blast cleaning is required in combination with Class A coatings. So,
unless they plan to paint after blasting, then blasting is not required.

> Also I cannot think of a pre-engineered metal building end plate moment
> connection I have seen that did not have a shop primer on it.  I am
> pretty sure those resist seismic forces and also that the shop primers do
> not meet Class A requirements.  Is paint being omitted under
> pre-engineered metal building end plate moment connection faying surfaces
> in other states?

Some shop primers are Class A compatible. Ask for the manufacturer's
confirmation or test report. I could take a guess at how many simply
ignore the prep requirements.

Realistically, the shears are very low in the rigid frame moment
connections relative to the number of fully tightened bolts AND
compression flange bearing area. Something else will probably be
redistributing forces or failing before the connection has any slip,
with or without Class A preparation.

It is up to the EOR to determine level of enforcement.

R. Paul Ransom, P. Eng.
Burlington, Ontario, Canada
<mailto:ado26(--nospam--at)> <>

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