How to find mode shape

[zenginse]

Hi Seismosoft,

I searched forum for finding mode shapes in 3D Structures, I need to find or calculate but I have never tried to find mode shapes before in 3D structures. I solved lots of examples 2D frame or 1D frame by hand. In those examples I always found the mode shapes.

Now, I need to change axes of my capacity curve from Force and Disp. to Spectral Acc. and Spectral Disp.

I am thinking a way to calculate mode shapes. I don't know if it is true but it is something like:

1-) Calculate or sum all the nodes modal mass ( I am not sure whether to sum in Xdir or All directions)

2-) Calculate rigidity of columns in Xdir.

3-) Put these values in mass matrix and rigidity matrix.

[k-w^2*m]=0

with this formula I can calculate. But as I said above I am not sure. And once again I don't know whether I sum nodes mass in Xdir or All direction.

[ruipinho]

Zenginse,

- use the Wizard facility of SeismoStruct to quickly create a 3D eigenvalue analysis

or

- read the Help System/User Manual chapter on eigenvalue analysis

or

- read the Verification Report's eigenvalue examples

Rui

[zenginse]

Hello Rui,

As you said in your answer i looked them up but couldn't find any info.

Thank you.

[ruipinho]

Zenginse,

There must be some misunderstanding here.

You can readily find the mode shapes for 2D, 2D, 3D structures by running an eigenvalue analysis in SeismoStruct and then going to Post-Processor -> Step Output / Deformed Shape Viewer.

Regards,

Rui

[zenginse]

Hi everyone,

Thx for your help. I have solved the problem and discovered that SeismoStruct and other softwares using mm units when finding modal participation factors even though we use meters units in SeismoStruct.

Thx again.