Return to index: [Subject] [Thread] [Date] [Author]

Braced Frame Philosophy Question

[Subject Prev][Subject Next][Thread Prev][Thread Next]
	Does anyone know what the rationale for the 1.5 multiplier applied
to the brace force for an OCBF chevron (or V-type) brace is?  This is in UBC
2213.8.2.2, UBC 2211.4 Part I 9.4a Item 1, or 14.4a Item 1 of the Seismic
Provisions for Structural Steel Buildings.  It doesn't seems like this case
would be more severe than a single diagonal brace (with a brace in the
opposing direction in another bay) or than a X-brace (given that the
effective length is probably less for a comparable layout), as long as the
connection to the beam and the beam itself are properly designed and
detailed.  Additionally, since the column design is based on Omega times the
calculated seismic force and not based on the force generated by the brace
specifically, doesn't the 1.5 applied to the brace force make a column
buckling failure more likely than in a similar design without the 1.5
applied to the brace?  Admittedly, I don't do many braced frames, so perhaps
this question is simpler than it seems.  Any insight into the 1.5 would be
appreciated.

Paul Crocker, P.E.

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********