Torsion is an important structural action that increases member shear strength. It occurs when it is twisted causing twisting force acting on the member, known as torque, and the resulting stress is known as shear stress. This stress is added to the existing shear stress due to vertical and lateral applied loads.
The design of members to resist the torsional shear stress depends on the rigidity of the member cross-section. Therefore, edge beams should consider torsion in their design. Vertical members such as columns and shear walls should be designed to resist dynamic loadings such as earthquake and wind.
The importance of considering the extra shear stresses caused by torsional actions will provide stability and resistance against structural failure.
Torsion means twisting.If you are applying a force to a manual screwdriver, you are applying torsion.Similarly, a rod being turned by a mechanism around its longitudinal axis is experiencing a torsion force.
Effects Of Torsion-
The effects of a torsional load applied to a bar are
(i) To impart an angular displacement of one end cross-section with respect to the other end.
(ii) To setup, shear stresses on any cross-section of the bar perpendicular to its axis.