Mass moment of Inertia according to SAP2000

[Germandsc]

thread801-353850

Hi all!, im doing some research on Isolated Structures, in wich I had to model them on MATLAB software. In order to verificate my results, had to compare them with a comercial software, wich I choosed as SAP2000.

All values were okey, except for one: the Mass Moment of Inertia. I realiced that SAP2000 calculated this values as: m*(Lx^2+Ly^2)/4, but according to all literature its: m*(Lx^2+Ly^2)/12. And its important, cause the research has a highly important rotational behaviour.

When i used the (....)/4 value, my global results where identic to the SAP2000 ones, and now i have the doupt if sticking on to whats teorically correct (....)/12 or what appears to be correct from a well known and respected program.

Any help on this matter would be very greatfull. Thanks!

 

[BeFEA]

Hi!

Please explain which element you are checking the mass moment of inertia for. How did you find out that sap2000 calculates the mass moment of inertia as (...)/4? The questions above will help me understand the issue.

Best regards

 

[Sannyboy]

@Germandsc : How did you infer it uses m*(Lx^2+Ly^2)/4

mass moment of inertia by formula is m*(Lx^2+Ly^2)/12.
Even i am interested to know more.