Patent-family-89619023

A tower section for a wind turbine is provided. The tower section comprises an annular wall portion defining a tower section axis and having an annular connecting flange portion, wherein the annular connecting flange portion defines a first array of bolt holes. An annular flange strengthening device is located on the annular connecting flange portion, the annular flange strengthening device defining a second array of bolt holes, each bolt hole of the first array of bolt holes being alignment with a respective bolt hole of the second array of bolt holes. A plurality of mechanical fasteners are provided, each of which extends through respective bolt holes in the first and second array of bolt holes. Beneficially, the annular flange portion and the annular flange strengthening device are configured to define an annular-shaped void between them. The annular shaped void provides the annular flange strengthening device with a degree of flexibility which changes the ratio of stiffness between the flange portion and the mechanical fasteners. Beneficially, this improves the stress capacity of the interface between the mechanical fasteners which clamp the annular flange strengthening device to the annular flange connecting portion.