Why Is a Minus Term Used in the Moment of Inertia Calculation for a T-Beam?

[teodorakis]

Hi i tried to understand an old report about a beam, in the report maximum normal force due to bending is investigated , the normal procedure is applied nothing special actually they calculate the moment of inertia of a t-beam part by part and from m.c/I they solve the problem. I want to ask that in the calculation of moment of inertia an extra minus term which they added all the first moment of inertias and multiplied it by the center of mass value, what's this term is all about? i really doesn't see this term in any kind of inertia calculation.
Thank you for your help.

 

[OldEngr63]

It would help if you would present this calculation in full, just copy is down even if you don't fully understand it.

It sounds like this may be an application of the parallel axis theorem in order to combine all of the individual area MOI values into a single value referred to the area centroid.

 

[teodorakis]

It would help if you would present this calculation in full, just copy is down even if you don't fully understand it.

It sounds like this may be an application of the parallel axis theorem in order to combine all of the individual area MOI values into a single value referred to the area centroid.

thank you for your kind response, i think it's like you said related with paralle axis theorem and they neglect the square and take only the term that i mention, it's nothing new:), i mean.