Amplitude value from Vibration modal analysis

Dear Members,

I did a slug flow analysis by maintaining the first natural frequency of piping system above 5Hz using the dynamic modal analysis. My query is i need to provide the allowable amplitude value corresponding to 5Hz of the piping system to the commisioning team.

From Caesar-II dynamic modal analysis, where i can get the amplitude value of the piping system.

Please provide the solution.

Hi Dave and Richard,

Please reply or comment on the above query?

Thank you.

You can't. By definition, a modal analysis is the free undamped vibration of a system. You don't obtain real displacements until you apply a load.

The numeric values (for displacement) that are obtained during the modal solution are therefore normalized to 1.0.

You can however provide the displacements from your slug flow analysis. These displacements represent the total response from all of the modes included in the analysis.

Thanks for your reply. You mean the slug flow analysis using force spectrum analysis type.