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RE: Steel Connections

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Thanks, Ron for your clarification.

Still more comments and questions.

If one designs the connection based on R=1, I would HOPE it would be
adequate since it would be designed for 4.5 (in the case of OMFs) times the
member design forces instead of a paultry 2.8.

Is FEMA-267 (or it's successor, FEMA-350) officially part of the UBC or is
it just considered prudent to use it for the design of moment connections? I
don't seem to see a reference to this document in the UBC. Based on reading
the UBC *only* (without being familiar with FEMA-267 or FEMA-350), I hope
you can see how one could use the section of the UBC I referenced then go to
the AISC (ASD, of course) and design for Omega-sub-naught times the frame
design forces. I'm not sure if this issue has been clarified in the IBC 2000
or not.

And, finally, what about the exceptions the SEAOC Seismology Committee has
taken to FEMA-350 (see:
http://www.seaint.org/seaosc/ftp/research/Interim_FEMA_350.PDF )? Will this
report generate a new publication by FEMA or addendum by SEAOC?

Without sounding cynical (intentionally), everything published to date
appears to be expert witness fodder unless one succumbs to proprietary
connections.

How much information on this topic will be covered in the Seismic Design
Manual, Volume 3?

For those interested in the SAC seminar, you can download an application by
clicking on:

http://www.seaoc.org/pdfs/SACSeminar.pdf

Regards,

Bill Allen, S.E. (CA #2607)
ALLEN DESIGNS
Consulting Structural Engineers
Laguna Niguel, CA
http://www.AllenDesigns.com
V (949) 365-5696
F (949) 249-2297

||-----Original Message-----
||From: Ron O. Hamburger [mailto:ROH(--nospam--at)eqe.com]
||Sent: Friday, August 18, 2000 8:14 AM
||To: seaint(--nospam--at)seaint.org
||Subject: Re: Steel Connections
||
||
||
||
||Bill-
||
||Here's why you can't just design a connection for 3/8Rw or
||(Omega-0) loads and
||call it quits:
||
||1- The unanticipated fracture damage that occurred in the
||Northridge earthquake
||often occured at elastic or near-elastic response levels.
||
||2- The Omega-0 (and 3/8Rw) overstrength factors provide an
||esimate of the
||maximum strength demands on a structure, presuming that it is behaving
||inelastically.
||
||3- Thus, use of the 3/8Rw or Omega-0 overstrength modifiers
||might not give you
||adequate connections strength to assure that such fractures
||do not occur.
||
||You can however, design a connection using an R of 1; and
||ignore the testing
||requirement, as indicated in FEMA-267.
||
||FEMA-350, the replacement for FEMA-267, and  which is
||currently in publication
||includes a catalog of prequalified connections.  These
||connections have been
||subjected to sufficient testing and analytical evaluation
||that SAC feels
||comfortable recommending their use for general application,
||without further
||testing, as long as the connection detail is used in framing
||that complies with
||the limits of the prequalificaiton.  The prequalifications
||include connection
||details for OMF as well as SMF applications.  Both welded and
||bolted connection
||types are included.  Also included, for OMF service, is a
||connection that is
||similar, although not identical to, the pre-Northridge connection.
||
||SAC will be holding a series of seminars in September in Los
||Angeles, San
||Francisco and Seattle.  FEMA-350 and its companion
||publications will be
||distributed at the workshops.  Those who can not attend the
||workshops will be
||able to obtain copies, free, from FEMA.
||
||


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