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RE: Staad: Master/Slave Joints

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Title: RE: Staad: Master/Slave Joints


I'm not quite following what you said.  I would expect to see the deflected shape of the diaphragm rotated from its original shape, (based on different stiffness of the frames, or unsymmetrical loading).  This would make the end frames have the most displacement, and the interior frames with the least displacement.  The displacement of the frames in between would vary linearly from frame to frame.  So the frames in this sense would not have equal displacement.  Is this what you mean?

My results are not behaving in this manner.  My results can show the diaphragm appearing to "buckle" at the interior frames.  For example, my building is a plain rectangle shape.  In the longitudinal direction, I made the exterior frames moment type frames.  Down the centerline (ridge) of the building, I have "leaning" columns with simply supported beams.  The results that I would expect is that when load is applied in the longitudinal direction, all columns would have the same deflection (load is applied symmetrically).  However, my results show the center line columns with the most deflection, with the diaphragm deflected shape appearing to buckle. 

To me, this sounds like the program is not working correctly (as others have indicated), or its assumptions do not work well for my model. 

Staad's "rigid" command locks Fx, Fy, Fz, Mx, My, and Mz.  Maybe the correct way to use the master/slave command would be to just lock Fx, Fz?  I'll give that a shot and see what happens.

John Connor

-----Original Message-----
From: EphHirsch(--nospam--at) [mailto:EphHirsch(--nospam--at)]
Sent: Wednesday, August 09, 2000 2:28 PM
To: medeardorff(--nospam--at); seaint(--nospam--at)
Subject: Re: Staad: Master/Slave Joints

Why should all frames have equal displacement in a given direction if their
individual stiffnesses are different?  The rigid body diaphragm linking them
will insure that the dimensions between them will remain invariant but should
not preclude rotational effects on the rigid body which will lead to
differing global translations for each frame.

Ephraim Hirsch, SE