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RE: Steel Moment Connections

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You have raised an interesting point.  Following the Hyatt walkway collapse, I inspected several shopping centers in Kansas City that had been in service for several years .  On one, I found a connection supporting an escalator (vibration, high load, etc.) that had 14 - A307 3/4" bolts snug tight in unpainted steel.  The connection was designed for and required A325 SC bolts.  

The interesting part came when the bolts were replaced.  Only one of the bolts had slipped into bearing.  Thirteen of the 14 bolts were removed by hand without the aid of a hammer.

The point:
Bill's caution is justified.  Don't count on the bolts slipping with dead load only.

Harold Sprague, PE
Krawinkler, Luth & Assoc.

-----Original Message-----
From:	Bill Sherman [SMTP:SHERMANWC(--nospam--at)]
Sent:	Tuesday, June 30, 1998 8:26 AM
To:	seaoc(--nospam--at)
Subject:	Re: Steel Moment Connections

I asked a similar question "in reverse" several weeks ago.  I asked why AISC
permits bearing type bolts in combination with welds in such connections,
since slippage of the web connection bolts would cause additional stress in
the flange welds.  The response I got was that AISC assumes that the bolts
will be in bearing due to dead load during erection and the examples shown
intended for non-high seismic conditions.  Personally, I feel that
slip-critical bolts should be used in such connections to prevent
the welds.

It should be noted that the LRFD commentary suggests torquing the bolts
performing welding when using slip-critical bolts in combination with welds
(see commentary for Section J1.7).