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?