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Re: Application of 3Rw/8 - How to apply

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Dennis,
Your assumption is absolutely correct, 
but you should use Rw = 6 to get the frame forces and 
also for magnification of moment and shear of the joint. 

Karim Hosseinzadeh, SE
----------
> From: Dennis S. Wish PE <wish(--nospam--at)cwia.com>
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Application of 3Rw/8 - How to apply
> Date: Wednesday, September 23, 1998 1:26 PM
> 
> Dick,
> I'm still not clear on this one. You have stated pretty much what is
written
> in 2211.6 and the wording of this is what is confusing to me. I need a
> practicle example. I would assume that you would first determine the
> appropriate member size based upon applying the original load to the
frame.
> The 3Rw/8 term would be applied to the design of the beam to column
> connection and therefore would be applied to the moment and shear at that
> node. The initial load is not increased only the stress in the joint.
> Is this a correct assumption?
> 
> Dennis
> 
> -----Original Message-----
> From: Horning, Dick/CVO [mailto:dhorning(--nospam--at)CH2M.com]
> Sent: Wednesday, September 23, 1998 1:02 PM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: RE: Application of 3Rw/8 - How to apply
> 
> 
> Rw = 6, not 8, for steel OMRF.  Framing elements not part of the lateral
> force resisting system must be able to support gravity loads under a
> displacement of 3Rw/8 times the calculated displacement of your moment
> frame.  You don't need to multiply your moment frame forces by it.
> 
> > ----------
> > From: 	Dennis S. Wish PE[SMTP:wish(--nospam--at)cwia.com]
> > Sent: 	Wednesday, September 23, 1998 12:38 PM
> > To: 	SEA International List
> > Subject: 	Application of 3Rw/8 - How to apply
> >
> > I design very little steel so I apologize up front for my lack of
> > understanding regardless of the number of posts which have been sent on
> > this issue. I am in need of a fast answer and would appreciate any
> > responses.
> >  
> > I have designed a simple (Ordinary) moment frame for a seismic
retrofit.
> > The frame is one bay - 25 feet between columns and 12 feet in height. 
The
> > lateral load applied from the results of the UCBC design is 10.57 Kips.
> > The frame is pinned at the base and therefore develops moment in the
> > connection of beam to column.
> >  
> > Do I apply 3Rw/8 to the moment at the connection or is it applied to
both
> > the moment and the shear at the end of the beam?
> >  
> > Also, is it correct to assume Rw is equal to 8 for use with an Ordinary
> > Moment Frame?
> >  
> > I appreciate any fast responses.
> >  
> > thanks
> > Dennis Wish PE
> >  
> >
> 
> 
> 
> 
>