This International Standard specifies requirements and general principles to be used in assessing the structural integrity of onshore wind turbine support structures (includes foundations). The scope includes the geotechnical assessment of the soil for generic or site specific purposes. The strength of any flange and connection system connected to the rotor nacelle assembly (including connection to the yaw bearing) shall be designed and documented according to this standard or according to IEC 61400-1. The scope includes all life cycle issues that may affect the structural integrity such as assembly and maintenance. The assessment assumes that load data has been derived as defined in IEC 61400-1 or -2 and using the reliability level and partial safety factors for loads. The principles included in this edition may be applied to the sections of the tower of an offshore fixed structure above the splash zone if the loading has been calculated according to IEC 61400-3. A later edition will consider offshore fixed structures more specifically.