What is Radius of Gyration

If cross-sectional geometry of column is other than simple shapes like circle, square, rectangle etc. Then radius of gyration is required for the calculation of ultimate load that column can carry.  Minimum value of radius of gyration is adopted during the design of columns. For getting minimum value, use minimum value of moment of inertia in the formula.

Radius of gyration is directly proportional to the moment of inertia.

Radius of Gyration is the minimum radius from the centroid of column cross-section. It is denoted by “K” or “r’’.  It is measured in millimeter, centimeter, inches etc..,


K = √(I/A)

Mathematically, Radius of gyration can be represented as;


K = Radius of Gyration

I = Moment of Inertia

A = Cross-sectional Area.


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