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RE: Design of knee braced steel frame for support of a crane on a trolley

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Rafael 

You apparently misunderstood the posting. Nobody claimed this is an OCBF.
The original posting asked if this type of frame could be considered as
"other Structures" in table 16-p for non-building structures, my answer was
yes. The second portion was how you fit it into design requirements for
steel frames. Since it is a non-concentric brace the requirements of section
2213.8.4.2 and 2213.8.4.3 apply in my opinion. Keep in mind that With an
R=2.9 and the frame and all the members designed for omega (2.0) times the
calculated base shear I think the stability of the frame is receiving due
consideration.

Ben Yousefi, SE
San Jose, CA


	-----Original Message-----
	From:	Rafael Sabelli [SMTP:Sabelli(--nospam--at)dasse.com]
	Sent:	Tuesday, December 07, 1999 10:18 AM
	To:	'SEAINT'
	Subject:	RE: Design of knee braced steel frame for support of
a crane on a trolley

	Dear Ben Yousefi:

	I think your reply is in error.  The categorization of a structural
system should be based on its expected behavior, including its yield
mechanisms.  No doubt the braces in the knee-braced frame will resist axial
load, but the yield mechanism will almost certainly be flexure of the beams
or columns.  If the designer treats this system as an OCBF he or she will
perform pointless checks on compactness and slenderness of the knee braces,
but will not pay attention to compactness of the flexural members nor to
their lateral stability.
	Respectfully,
	Rafael Sabelli

	ORIGINAL MESSAGE:
	From:	"Yousefi, Ben" <Ben.Yousefi(--nospam--at)ci.sj.ca.us
<mailto:Ben.Yousefi(--nospam--at)ci.sj.ca.us> >
	To:	"'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org
<mailto:seaint(--nospam--at)seaint.org> >
	Subject:	RE: Design of knee braced steel frame for support of
a crane on a

	I would treat it as a K brace per section 2213.8.4.2 along with the
requirements for Nonconcentric brace per 2213.8.4.3.


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