Reinforcement of wind turbine structures

A method of reinforcing a tubular wind turbine structure using a radially adjustable ring stiffener, the ring stiffener comprising a pair of adjacent ring segments coupled together by a coupling means configured to permit radial adjustment of the ring stiffener by varying an intersegmental separation between adjacent ends of those ring segments, the method comprising:

• positioning the ring stiffener at a reinforcement position within the tubular wind turbine structure;
• adjusting the intersegmental separation between the pair of adjacent ring segments to increase the radius of the ring stiffener;
• and thereby to engage an inner surface of the tubular wind turbine structure with a radial force that holds the ring stiffener at the reinforcement position by means of friction between the ring stiffener and the tubular wind turbine structure;
• and
• securing the engagement between the ring stiffener and the tubular wind turbine structure by fixing the intersegmental separation between the pair of adjacent ring segments.