TRANSFER FORMULA
There are many built-up sections in which the component parts are not symmetrically distributed about the centroidal axis. The easiest way to determine the moment of inertia of such a section is to find the moment of inertia of the component parts about their own centroidal axis and then apply the transfer formula. The transfer formula transfers the moment of inertia of a section or area from its own centroidal axis to another parallel axis. It is known from calculus to be:
Ix = Ic + Ad2
Where:
Ix = moment of inertia about axis x-x (in4)
Ic = moment of inertia about the centroidal axis c-c parallel to x-x (in4)
A = area of the section (in2)
d = perpendicular distance between the parallel axes x-x and c-c (in)
Transfer Formula
Given:
the glued asymmetric built-up cross-section below.
Determine:
the moment of inertia of the composite area about the x axis.
[src:
http://www.totalconstructionhelp.com/momenti.html]
