effective mass

Dear all,

I am doing 3d modal analysis using Ansys. When I checked the "Effective Mass-EM" for rotational dof, it is very large compared with total mass of the model. can you share your ideas for this question.Run simulation upto 90% of EM in all dof or only in translation dof or only for 2 translation dof (any rule of thumb)?

 Thanks in advance.