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Re: Steel Connections

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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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