Calculating the radius of gyration
To calculate the radius of gyration for the cross-section of the beam in the diagram, start with the values of I that were calculated earlier.
Ixx = 33.3 x 106 mm4
Iyy = 2.08 x 106 mm4
Refer to the diagram for the values of b and d that are used in the calculation of A.
A = Area of cross-section = 50 mm x 200 mm = 10,000 mm2
Substitute I and A into the formula for r to give:
This is the value of the radius of gyration about the x-x axis.