rigidDiaphragm and fix

[Mohammadf]

Hi dear all
when we want to define a rigid floor in a 3D frame we have to use rigidDiaphragm command and also we have to define a node as a center of mass. my question is is it necessary to define fix command afrer rigidDiaphragm or is not important? what is the rule?
best

[xxlsunshine]

I guess you have to fix your masternode of the rigiddiaphragm in those restrained dof. I don't why, but i read the example on the opensees home page. maybe the following website could help you.

http://opensees.berkeley.edu/wiki/index ... _W-Section

[fmk]

if center of mass has no elements framing into it, then yes .. you need to constrain dof not in the constraint, e.g. vertical dof and 2 rotational dof out of plane if 3d model with 6 dof

[Mohammadf]

Many thanks for your kindly reply
but my question is that we have to put fix command of center of mass node BEFORE rigidDiaphragm command or AFTER it?

1-
fix 9001 0 0 1 1 1 0
rigidDiaphragm 3 9001 101 102 103 104 105 106 107

2-
rigidDiaphragm 3 9001 101 102 103 104 105 106 107
fix 9001 0 0 1 1 1 0


which one is correct with transformation constraints?

Best

[fmk]

does (should) not matter