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RE: OMF Connection Design

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Bill,

Interesting point, I had not noticed that clarification before. So it
appears that the panel zone does not have to be designed for the higher
forces. Do you then think it is appropriate to use the panel zone
strength, as designed per the LRFD specification, to determine the
maximum moment that can be delivered by the system? My feeling is that
it is still part of the connection, but I'm not sure there would be any
point in designing the rest of the connection for a higher moment if the
panel zone is going to yield before those forces can ever be developed. 

-Matt

-----Original Message-----
From: Bill Allen [mailto:T.W.Allen(--nospam--at)cox.net] 
Sent: Tuesday, June 29, 2004 2:17 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: OMF Connection Design

Matt -

You're right.

However, in the AISC 2002 Seismic Provisions, section 11.3 is titled
Panel
Zone of Beam-to-Column Connections (beam web parallel to column web) and
the
entire text reads: "No additional requirements beyond the AISC LRFD
Specification" which is the section I cited. I believe this is one area
that
was not very clear in the 1997 Seismic Provisions and was clarified in
the
2002 version. See also FEMA 350 requirements where there is no comment
on
panel zone requirements for OMFs (which are AISC Seismic Provisions
IMFs). I
believe this would leave the reader to use the section I cited as a
design
guide.

If you have to have the panel zone meet the same requirements as a SMRF,
the
only other "freedom" an OMF/IMF has is the column depth, I believe.

Just my two cents.

Bill

-----Original Message-----
From: Hood, Matthew O. [mailto:HoodMO(--nospam--at)ci.anchorage.ak.us] 
Sent: Tuesday, June 29, 2004 3:01 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: OMF Connection Design

Bill,

Thank you for you input, but check out the 1997 seismic provisions for
OMF. (I'm including supplement #1 per the IBC 2000) Section 11.2a.1
indicates that this provision applies to OMF as well.

-Matt

-----Original Message-----
From: Bill Allen [mailto:T.W.Allen(--nospam--at)cox.net] 
Sent: Tuesday, June 29, 2004 1:28 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: OMF Connection Design

I know I'm in dangerous territory here particularly since I do very
little
steel design (every time I do - once a year or so - I have to "relearn")
and
I know there are smarter people on the list than I.

However, I'm under the impression that the 1.1*Ry*Mp panel zone
requirement
is for SMRFs only. For OMFs (and IMFs), one "only" has to design for the
actual forces. See AISC Eqn. K1-12, p. 15.1-76, LRFD, 3rd. ed.

If this is the case (and I *think* it is), then the moment limitation of
the
panel zone strength is not appropriate for OMFs.

Regards,

T. William (Bill) Allen, S.E. (CA #2607)

-----Original Message-----
From: Haan, Scott M. [mailto:HaanSM(--nospam--at)ci.anchorage.ak.us] 
Sent: Tuesday, June 29, 2004 1:52 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: OMF Connection Design

Matt:

My opinion is that the panel zone is part of the connection and needs to
be designed to be at least as strong as 1.1*Ry*Mp, but will yield to
superior wisdom.

Respectfully,
Scott Haan P.E.
Deputy Building Official

-----Original Message-----
From: Hood, Matthew O. 
Sent: Tuesday, June 29, 2004 12:40 PM
To: seaint(--nospam--at)seaint.org
Subject: OMF Connection Design



I am currently plan checking the connections of an OMF in a
Pre-engineered metal building. I have indicated to the Engineer that the
connections need to be designed in accordance with the '97 AISC seismic
provisions so that they resist a moment equal to 1.1*Ry*Mp of the beam
or the maximum moment that can be delivered by the system. The Engineer
has indicated that the maximum moment that can be delivered by the
system is governed by the panel zone shear strength of the column. The
Engineer cites the commentary to FEMA 350 section 3.2.1 as justification
where it states: "for Ordinary Moment Frame systems, fully restrained
connections that permit development of plastic hinges at locations other
than within the beam span, e.g. in the panel zone or in the column, are
permitted."

It is the opinion of my office that the panel zone is interior to the
connection and should, itself, be designed for the maximum moment, not
determine the maximum moment. Meaning that something else (e.g. Lateral
torsional buckling of the beam) should be the failure mode used to
determine the maximum moment. The panel zone should then be designed to
resist those forces. I'm reading FEMA 350 section 3.3.3.2 and section
3.6.1.1 specific to bolted end plate connections which says: "The
connection shall be designed so that yielding occurs either as a
combination of beam flexure and panel zone yielding or as beam flexure
alone."

Any thoughts/opinions?

-Matt



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