Return to main page: Cross Arm Parameters

Torsion Constant - Cross Arms

There is no exact formula to calculate the Torsion Constant of a rectangular object however there is an approximation given in by the following formula: 

As an example consider a cross arm that is 2m long, 0.1m wide and 0.2m deep. The long side is 0.2m and hence a = 0.2m, b = 0.1m. Solving the torsion constant gives:

This is the same result calculated by clicking on Derive assuming rectangular cross section.