Return to main page: Cross Arm Parameters

Section Modulus

The Section Modulus takes the Second Moment of Area (measure of the stiffness of a object due to its geometric shape) and divides this by the distance from the Neutral Axis to the outer surface of the object.

For a cross arm that is 0.1m wide by 0.15m deep the second moment of area vs horizontal is 1,250cm^4 and the second moment of area vs vertical is 2,812.5cm^4  (See article Cross Arm Parameter - Second Moment of Area for working).

The y dimension would be given as per the below diagrams of the cross arm:

Hence:

Note that these two values above match what Neara calculates using the button Derive assuming rectangular cross section as can be seen below.