Torsion

Torsional forces, shown in 図 1, are calculated using the relations:
図 1.
M x 1 = f x x ( θ x ) + C x x θ ˙ x
図 2.
M x 2 = − M x 1

Where,

θ x = θ x 2 − θ x 1 is the relative rotation of node 1 and 2.

f x x ( θ x ) is the function defining the force-displacement relationship.
図 3. Beam Type Spring Torsion