How to Capture Mode Shapes in X,Y, Z Directions

[MaryAval]

Dear all,

I have modeled a 3D reinforced concrete structure. I wonder how to capture its mode shapes in the three X,Y, Z directions . Is there any command to do so?
I have used the "Node Recorder" command to capture the first 8 mode shapes of the structure, yet I couldn't recognize for which direction they are!

Your help would be highly appreciated.

[selimgunay]

Did you use the eigen command as shown below?

recorder Node -file modeshape1.out -time -node 10 -dof 1 2 3 "eigen 1"

[MaryAval]

Yes I did, I used the following command to capture the first 8th mode shape of the structure, but I do not know for which direction they are, for instance: whether the first mode shape is for X direction or Y or Z directions!

The command I used:
for { set k 1 } { $k <= $numModes } { incr k } {
recorder Node -file "[set folder]/modes/mode[set k].out" -nodeRange 1 24 -dof 1 2 3 4 5 6 "eigen $k";

[selimgunay]

You can figure out the directions of the modes by considering the relative values of modal amplitudes for a floor node. If you are using a rigid diaphragm constraint, you should consider the master nodes.

[MaryAval]

Thank you Selimgunay,

I do not use rigid diaphragm and the structure that I have modeled is 3 dimensional and includes 26 nodes and 156 degrees of freedom. I copied the first captured mode shape below:

-0.146233 0.00021218 0.000449344 -0.000124599 -0.0775583 2.04E-09 -0.144418 0.000195553 0.000428142 -0.000113614 -0.0775583 2.04E-09 -0.13531 0.000208594 0.000139991 -0.000124599 -0.0679577 2.84E-09 -0.133538 0.000190102 0.000135579 -0.000113614 -0.0679576 2.44E-08 -0.146416 0.000202162 -0.000559332 -0.000124599 -0.0740386 2.87E-09 -0.144666 0.000174601 -0.000553436 -0.000113614 -0.0740385 2.42E-08 -0.122599 0.000177727 -0.000277325 -0.000118332 -0.0740382 2.14E-08 -0.111907 0.000219655 0.000278171 -0.000118332 -0.0679574 2.16E-08 -0.428234 0.000655147 0.000752828 -0.000162835 -0.0968337 3.52E-09 -0.425816 0.000626786 0.000731895 -0.000156166 -0.0968337 3.52E-09 -0.411255 0.00066789 0.000273073 -0.000162835 -0.0892246 5.12E-09 -0.408647 0.000642631 0.0002755 -0.000156166 -0.0892245 4.15E-08 -0.425653 0.000630511 -0.00100232 -0.000162835 -0.0924349 5.19E-09 -0.422968 0.000605034 -0.000992727 -0.000156166 -0.0924348 4.11E-08 -0.375625 0.000610346 -0.00042721 -0.000150924 -0.0924345 3.59E-08 -0.360188 0.000661165 0.000428827 -0.000150924 -0.0892243 3.65E-08 -0.72366 0.00116447 0.000902634 -0.000169335 -0.0873555 4.27E-09 -0.721313 0.00113299 0.000882186 -0.000169695 -0.0873555 4.26E-09 -0.709241 0.00118662 0.000406529 -0.000169335 -0.0886805 6.55E-09 -0.706889 0.00115819 0.000410104 -0.000169695 -0.0886805 4.30E-08 -0.724853 0.00115591 -0.00128946 -0.000169335 -0.0944483 6.62E-09 -0.722498 0.00112769 -0.00127758 -0.000169695 -0.0944483 4.25E-08 -0.986317 0.0016861 0.000541652 -0.000144466 -0.0832354 7.24E-09 -0.984086 0.00166068 0.000545267 -0.000157157 -0.0832354 4.37E-08 -1 0.00165527 -0.00142368 -0.000144466 -0.0796448 7.32E-09 -0.997769 0.00163007 -0.00141117 -0.000157157 -0.0796448 4.32E-08

The maximum value is 0.0016861 which associates with the 2nd degree of freedom of the node 23rd. So, the direction of the first mode shape is translational Y.
Is there any way possible that I can only capture specific mode shapes, like 3 mode shapes in X direction?

[Jhno]

"Is there any way possible that I can only capture specific mode shapes, like 3 mode shapes in X direction?"
I guess you could ask for the first 3 mode only using the eigen command :
[eigen 3]
Then use this other command create a list from the response for each node :
nodeEigenvector $nodeTag $eigenvector <$dof>

[selimgunay]

Yes you can capture all mode shapes. After using the commands that you have used (below), you need to plot the mode shapes for different modes. I recommend to plot the translation dof (and not the rotational ones) and you can scale up the values if you want as the listed mode shapes are normalized.

for { set k 1 } { $k <= $numModes } { incr k } {
recorder Node -file "[set folder]/modes/mode[set k].out" -nodeRange 1 24 -dof 1 2 3 4 5 6 "eigen $k";