Many structural components in bridges and buildings subject to significant torsional moments that are critical in designing. Box girder bridges, beams in eccentrically loaded frames of multi-deck bridges, edge members in shells, and spandrel beams in buildings are typical examples of such elements. If external loads act far away from the vertical plane of bending, the beam is subjected to Twisting about its longitudinal axis, known as torsion, in addition to the shearing force and Bending moment.
Torsion on structural elements may be classified into two types; statically determinate, and statically indeterminate. Since shear and moment usually develop simultaneously with torsion, a reasonable design should logically account for the interaction of these forces. However, variable cracking, the inelastic behavior of concrete, and the intricate state of stress created by the interaction of shear, moment, and torsion make an exact analysis unfeasible.