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RE: 2000 IBC seismic design category D - orthogonal effect requi rement

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Do you need to consider orthogonal effects now when calculating story drift
and building separations with the new 2000 IBC?  This is pertinent to a 10
story building that I am reviewing under the IBC.

> -----Original Message-----
> From:	Haan, Scott M. [SMTP:HaanSM(--nospam--at)ci.anchorage.ak.us]
> Sent:	Monday, March 12, 2001 5:09 PM
> To:	Seaint list (E-mail); Se-Practice List (E-mail)
> Subject:	FYI: 2000 IBC seismic design category D - orthogonal effect
> requi rement
> 
> --------------------------------------------------------------------------
> Your following message has been delivered to the list
>   seaint(--nospam--at)seaint.org at 18:19:51 on 12 Mar 2001.
> --------------------------------------------------------------------------
> 
> 
> 1997 UBC 1633.1 required orthogonal effects to be considered in seismic
> design for columns at intersecting LFRS grids when Pu_seismic>.2*f*Pn.
> The
> 20% column capacity rule appears to be gone in the 2000 IBC.  The The 2000
> IBC now appears to require orthogonal effects to be considered for seismic
> design category D for all conditions.
> 
> For seismic design category D, IBC 1620.3.5 indicates that considering
> each
> direction independently per IBC 1620.1.10 is not considered acceptable.
> 
> Also for design category D, IBC 1620.3.5 indicates for any structure that
> considering SSRS or 1*EQx+.3*EQy or 1*EQy+.3*EQx per 1620.3.5 is
> acceptable.
> 
> In English: orthogonal effects need to be considered in design category D
> for columns, braces and beams.
> 
> 
> Scott M Haan  P.E.
> Plan Review Engineer
> Building Safety Division http://muni.org/building, 
> Development Services Department,
> Municipality of Anchorage
> phone: 907-343-8183   fax: 907-249-7399
> mailto:haansm(--nospam--at)ci.anchorage.ak.us
> 
>