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Re: Staad: Master/Slave Joints

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John,
Did you check diaphragm rotation? Deflection of each
slave joint is equal to master joint deflection in
that direction plus multiplication of diaphragm
rotation by distance between slave and master joints,
e.g. Uxs=Uxm+Rzm*Dy.
So deflection of each node in a general 3-D model will
be different in this way. 
There is no analytical limitation for such
formulation, however diaphragm shall be practically
rigid to make anlysis results reliable. For instance
in a L-shape diaphragm, one may notice that such
formulation is not applicable for all of joints.
Hope it helps, 
(By the way, I'm SAP user!!)
Have a good time,
Frank


--- "Connor, John A NWK"
<John.A.Connor(--nospam--at)nwk02.usace.army.mil> wrote:
> According to Staad's user manual, you can use the
> master/slave joints to
> model a rigid diaphragm.  Does anybody know its
> limitations/assumptions?
>  
> I'm playing with an example, and the results do not
> make much sense.  I made
> a 3d model for a 3 story structure.  I have moment
> frames evenly spaced in
> each direction.  I gave each frame a different
> stiffness.  Some frames are
> all W10's and others are W12 members.
>  
> Using the master/slave to make a rigid diaphragm, I
> would expect that each
> frame would have the same deflection, and the
> differences between each frame
> would be their stresses.  However, the results are
> showing each frame with
> varying deflections.
>  
> Anybody have any insight to this?
>  
> Is there a better way to make a 3d model?   (please
> don't say..."don't use
> Staad").
>  
> Thanks,
> John Connor, PE
> Kansas City, MO
> 


=====
Fariborz Tehrani,                      Phone: (310)509-8826
Civil Engineer                           Fax: (530)481-9532
BSCE, MSCE, PE                    Voice Mail: (877)743-6206
email: fmtehrani(--nospam--at)msn.com
web: www.fmtehrani.com

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