Moment of Inertia of a Circular Section

Moment of inertia of a circular section can be calculated by using either radius or diameter of a circular section around centroidal x-axis or y-axis.

Circular Section

Example

Find the moment of inertia of a circular section whose radius is 8” and diameter of 16”.

Solution

Moment of inertia of a circular section is same around both centriodal axis. This is because of symmetry of a section around both axis.

Therefore, moment of inertia about centroidal x-axis.

[small I_{x_{0}}= frac{Pi R^{4}}{4}= frac{Pi D^{4}}{64}=]

[small I_{x_{0}}= frac{Pi R^{4}}{4}= frac{Pi times 8^{4}}{4}]

[small I_{x_{0}}= 6.28in^{4}]

[small I_{y_{0}}= small I_{x_{0}}= 6.28in^{4}]