Modal analysis problems in Abaqus
 

Hello everyone,

I'm doing modal analysis in Abaqus (step type: frequency).

Yet the results seem to have some problems.

The picture below is mode 1 shape.

https://imgur.com/bMzpCTO

The result is wrong, it seems that most elements are not deforming.

Normally, it should be like this:

https://imgur.com/HFOdUEU

Boundary condition at the bottom: (fixed)

https://imgur.com/KM6gx9t

I've checked everything, boundary conditions, interactions,....

Still I couldn't find where the problem is.

Need your kind suggestion and guidance, thank you very much!

You have some parts that are not connected to the main structure. These parts can move freely and exhibit rigid body modes.
Carefully check deformed mode shape and determine what part is not connected to structure and fix it.