Assign rigid diaphragm

[Strep]

Dear All,

I'm modelling a 2D RC frame with 4 floors and 3 Bays. I'm usign fiber section to model the columns and the beams. I want to assign a rigid diaphragm at floor level and since the rigidDiaphragm command is valid only for 3D problems i use the equalDof command.

equalDOF 5 6 1
equalDOF 5 7 1
equalDOF 5 8 1

(Nodes 5,6,7,8 are on the same level)

Is this approach correct?

I have another question too. Is there any way i can get eigen values of my model at every step of a time history analysis?

Thank you in advance

[fmk]

yes.

for eigenvalues:

1. open a file for the eigen values.

2. put the eigen and analyze command inside a loop. at each step only do one analysis step, i.e. analyze 1 $dt, and puts the results of the eiegn command to the file.

3. close the file.

[Strep]

fmk, thank you very much for your help...