Dear Anuj,
A similar question has been answered in the forum topic found here: RotThrust, LSSTipMya, TwrBsMyt (particularly my Mar 13, 2013 post). Of course, this forum topic applies to a turbine with a rigid tower and fixed platform. For a flexible tower or moveable platform, inertia forces (due to tower deflection or platform motion) and additional moment arms due to tower deflection or platform motion would also contribute to the tower-base moments.
Best regards,