Analytic equation to calculate the XY inertia moment in relation to the origin

[hmalfs]

Hello All,

I am modelling a structure in ANSYS APDL and I need to compare the Inertia moment of the structure given by ANSYS with analytical calculations. My structure can be considered as several rectangular parts. I know that I=b*h^3/12 in relation to the center of mass. But for this case, in ANSYS,the relevant Inertia moment is the one that is "XY in relation to the origin". Do you know how can I calculate analytically this inertia moment?? what is the expression?

thanks,
Hugo

 

[kranmeste]

Hi,

from what i understand you should read up on Parallel-Axis Theorem for Moment of inertia, if you want to find the Moment of inertia around an axis which is not the centre of the x-section.

Also see the link:

http://en.wikipedia.org/wiki/Second_moment_of_area

Regards

 

[kranmeste]

Hi,

i were a little quick in my earlier reply. I didn't notice you wanted an example. See the attached file.

Also i noticed that you write "I=b*h^3/12 in relation to the center of mass". This is not correct. Is should be in relation to centre of cross-sectional area. A plane (Surface) does not have any mass .

Regards