Assuming that I have a C-Channel When the load acts along the X-X axis, we take Iyy for the Bending moment calculations. Similarly, when load acts along the Y-Y axis, we take Ixx. But if i have a load that acts on Z-Z axis, how do I calculate the Moment of Inertia? PLS SEE THE ATTACHMENTS in the following SEQUENCE FIRST : Attchmnt : TOP VIEW SECOND : Attchmnt : DETAIL A THIRD : Attchmnt : ELEVATION My specific Doubts: Do I have to take Izz? If yes, is Izz=Ixx+Iyy (applying Perpendicular Axes Theorem) Can Anyone help me?