Abstract: In this paper, the general equations of equilibrium for axisymmelrical deformation including the torsional deformation of revolutional shells are derived. It is shown that the shearing stress distribution due to torsion is independent of other stress components including those of membrane stress and bending stress.In this paper, the torsional deformation is considered to he represented by membrane action only, and also by the combined action of bending membrane deformation. It is shown that the main contribution of torsional rigidity is that related to membrane action.

Key words: offshore wind energy project, horizontal axis wind turbine, rotor aerody-namic design, annual usable energy pattern factor, power coefficient, wind turbine rotor, wind turbine blade