Modal participation factor variation

[GMarsh]

Hi all,

I am trying to do a frequency extraction step on a structure. I am interested in plotting participation factor for all the modes. Depending on the number of modes extracted I am finding different participation factors for the same mode. For example mode no. 85 has highest participation factor when I extract 140 modes and the same mode is no where to be seen when I extract around 200 modes ! This is true for almost all modes.

Is this possible ?

I read Abaqus analysis manual on this. But the definition of participation factor no where indicates the number of modes as a parameter.

Thank you in advance.

Regards
Geoff

 

[GMarsh]

Just to add - the generalised mass associated with each mode is same irrespective of number of modes extracted. This is as expected.

But effective mass of modes in each direction (which again depends on participation factor) changes with the number of modes extracted.

Any helpful comment would be appreciated.

Geoff