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RE: Master-Slave Joint

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The master/slave relationship in STAAD is a tool to model a rigid diaphragm.
A rigid diaphragm does not imply that all displacements on a given level are
the same.  One must add translations with rigid body rotation to arrive at
the final displacement for points located on a rigid diaphragm.  A rigid
diaphragm is used to model a rigid floor (poured concrete, composite
concrete & steel deck, etc.).   The diaphragm (floor)is used to transmit
lateral loads to vertical elements that transfer these loads to the
foundations.  Additionally, if you search the SEAINT Archives there is an
excellent technical thread on this topic that thoroughly discusses the
master/slave relationship. 

Unfortunately, about 6 months ago, I had many conversations with the
technical representatives of STAAD III / R23 and found out that it does not
correctly handle rigid diaphragm behavior.  The discussions where prompted
as I was looking at the results of one of my 3-D model; the translations and
rotations did not appear to be characteristic of rigid diaphragm behavior.
Bottom line is that the program did not take into account diaphragm
rotations properly.  This problem used to be posted on their web site but I
don't believe that it is there now.  Whether this has been corrected in the
current version of STAAD\Pro I do not know.  We have STAAD\Pro but I have
not had the need recently to model a rigid diaphragm.  Hope this helps.
Contact me at my E-Mail if you have any other thoughts or questions.

Robert Rogers, PE <> 
ph:  937-461-5660
fax: 937-461-0743
Woolpert LLP
409 East Monument Avenue
Dayton, Ohio 45402

-----Original Message-----
From: Francis.Ang(--nospam--at) [ mailto:Francis.Ang(--nospam--at)
<mailto:Francis.Ang(--nospam--at)> ]
Sent: Thursday, October 07, 1999 10:43 PM
To: seaint(--nospam--at)
Subject: Master-Slave Joint

I need some advice here. There is a feature in STAAD3 about master-slave
joints. I have seen some use it but in my 3-D models , I have never used the
option. Well basically, I know it has something to do with the rigidity of
joints . I heard that when this option is used, the lateral displace ment of
joints in one story would be the same ??? Am I on the conservative side if I
did not use it ? What are its advantages / disadvantages.

Thanks !!!!

Allan Yango