ABSTRACT
The resistance of a structural member to torsional loading may be considered to be the sum of two components. When the rate of change of the angle of twist rotation is constant along the member (see Figure 10.1a), it is in a state of uniform (or St Venant) torsion [1, 2], and the longitudinal warping deflections are also constant along the member. In this case, the torque acting at any cross-section is resisted by a single set of shear stresses distributed around the cross-section. The ratio of the torque acting to the twist rotation per unit length is defined as the torsional rigidity GIt of the member.
