Mass Participation factors
Mass Participation factors
(OP)
Dear all,
I am reletivly new to vibrational analysis and am trying to work through some of the basics.
I have been doing some basic modal analysis so far successfully and am now about to embark on dynamic random analysis. I have been told by my collegues to look out for mass participation factors in my results and that they have to be above 80%, but so far nobody has been able to tell me what they are or what they signify - not in a way that I can understand anyway!!
So can someone please tell me what is and what the significance of a mass participation factor is.
I find it difficult to 'go do' without understanding.
Regards
I am reletivly new to vibrational analysis and am trying to work through some of the basics.
I have been doing some basic modal analysis so far successfully and am now about to embark on dynamic random analysis. I have been told by my collegues to look out for mass participation factors in my results and that they have to be above 80%, but so far nobody has been able to tell me what they are or what they signify - not in a way that I can understand anyway!!
So can someone please tell me what is and what the significance of a mass participation factor is.
I find it difficult to 'go do' without understanding.
Regards





RE: Mass Participation factors
RE: Mass Participation factors
cloche is correct from what I understand. I would suggest that you post this in the "Finite Element Analysis Engineering" forum. I know someone there can advise you. The mass participation factors are used to distinguish between "local" and "global" eigenvalues. I work with a lot of structural steel skids and we get a lot of local modal frequencies for stiffener plates. The only way to sort these out is to use mass participation. The real trick is to figure out what % = Global...
Hope this helps.
Chris Foley
Midland, TX
RE: Mass Participation factors
The complete explanation of m.p.f. and related matters is somewhat complex, but for sure you can find plenty of good books (e.g. "The Vibration Analysis Handbook", "Theory of Vibration with Applications", "Machinery Vibrations - Measurement and Analysis"...) that will clarify this.
I myself will buy some of these to better understand all implications of this (and other...) matter(s)...
Claudio
RE: Mass Participation factors
Depending on what you're looking at as well (the type of structure, the code you're using, etc.), I'd always go with 90% effective system mass and above to make sure you've captured the response of the system.
Cheers,
-- drej --
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RE: Mass Participation factors
In fact, I can figure out only one exception to this: when you do analytical interpolations based on eigengrequencies in order to calculate "best-fit" Rayleigh damping coefficients Alpha and BEta that would respect an imposed structure response damping factor: in this case it is usualy wanted to take into account all eigenfrequencies whose sum of mpf gives at least 99%.
RE: Mass Participation factors
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Tom Irvine
www.vibrationdata.com
RE: Mass Participation factors
I remember now having already read (perhaps in another life, I don't remember...