In the design of structural members subjected to torsional moments two possible cases may apply after cracking:

  1. The equilibrium torsion case occurs when the torsional moment is required for the structure to be in equilibrium and torsional moment cannot be reduced by redistribution of moments.
  2. The compatibility torsion case occurs when the torsional moment can be reduced by the redistribution of internal forces after cracking while compatibility of deformation is maintained in the structural member.