peteroznewman
Subscriber

If the structure has been built, one method damping can be measured is by using an accelerometer and an impact hammer using the decay of the transient.  See this article: https://en.wikipedia.org/wiki/Logarithmic_decrement

If the structure has not been built, then use values established in the literature. A welded steel structure is going to have different damping parameters than a bolted steel structure or a concrete structure.

Please show the tabular data that is PERMISSIBLE VIBRATION AMPLITUDE 60 microns. Is that a statement about the pump or the pipe?

When I read PERMISSIBLE VIBRATION AMPLITUDE 60 microns, that sounds like a requirement. After you have applied the unbalanced force caused by pump, you would plot a Displacement result and check that no part of the structure had a vibration amplitude exceeding 60 microns.

The pump specification might have a requirement on the maximum unbalance of the rotor calculated from the mass m of the rotor and the radius r of the center of mass from the rotational axis. You can calculate the force F amplitude as a function of rotor angular velocity w using the formula F = mr(w^2).