US Patent 7802412 Method of constructing large towers for wind turbines

In order to transport large size windmill towers, the invention suggests a steel tower (1) for a windmill, comprising a number of cylindrical or tapered tower sections (2), at least the wider sections (2) of which being subdivided into two or more elongated shell segments (3), which combine into a complete tower section (2) by means of vertical flanges (6) tightened together, e.g., by bolts (10), said shells being also provided with upper and lower horizontal flanges (4), respectively, to allow interconnection of tower sections (2) one on top of the other.