Seismosoft | Earthquake Engineering Solutions

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.

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

Hello Rui,

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

Thank you.

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

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.