Issued in 2016, DNVGL-ST-0126 is a design standard by DNV GL, the leading certification agency in the wind energy industry. It can be downloaded for free from the DNV GL website.
The ASCE/AWEA RP2011 is a North American recommended practice for compliance of large land-based wind turbine support structures. It is meant as guidance in interpreting and applying North American engineering standards to the design of wind turbine towers and their foundations. It can be downloaded for free from the ASCE or AWEA websites.
Currently in its edition 3, the IEC61400-1 is the international standard defining loads and load cases necessary to design wind turbine support structures. As of October 2018, Edition 4 of this standard is in final balloting by various national committees before being issued as an FDIS (Final Draft International Standard). Edition 3 can be ordered from the ANSI web store.