Friction connection in tubular towers for a wind turbine

Innovative solution for assembling joints of a tubular tower for wind turbines has been studied by a European consortium since 2005 and the HISTWIN (High-Strength Steel Tower for Wind Turbine) project provides background for design of the friction connection considered. This solution is simpler to produce and 80% less expensive than traditional flange connection. A feasibility study at the production plant indicates that the towers would be easy to assemble in-situ. In addition to the direct costs savings due to technical simplicity of the solution, the higher fatigue endurance than the flange connection is experimentally established. The loss of pretension forces in the friction connection with long opened slotted holes is studied using segment shortterm and long-term static tests, fatigue tests, down-scaled bending tests and by a specimen used in a feasibility study. The total reduction of the costs for tower is estimated to about 10% to 15% compared to the traditional tower with the flange connection.