I have created the model ran on dynamic analysis.
First, I modelled based on ASME B31.8 code, and the modal analysis results (%Total captured mass) equal to about 80%,
and then I changed the code to DNV offshore, but the modal analysis results (%Total captured mass) equal to about 40%.
My question is
1. Why the modal results in two different code are different? (My perception is frequency results depends on stiffness and mass of the system)
2. I noticed something in dynamic analysis box when I'm using DNV offshore code, pressure stiffening is closed box, is this factor affect to the frequency results?
I got this. I found that the shear modulus is different.
That means the shear modulus will affect modal analysis results, doesn't it?
Answer Verified By: Mike Dattilio
Congratulations, on resolving this...
Yes, anything that changes the stiffness matrix will ultimately change the modal analysis results.
Regards, Mike Dattilio Design Analysis Engineering Group Senior Analyst Bentley Systems Inc=============================================================================