In-situ measurements of fatigue demands on a wind turbine support structure

Fatigue demands often control design and detailing requirements of wind turbine support structures including the tubular steel tower. The in-situ structural demands placed on a community-scale (100kW) wind turbine have been monitored for approximately one year and the fatigue demands quantified using a Palmgren-Miner approach. A rain-flow counting method is used for calculating stress range cycles during turbine response. Demand-to-capacity ratios for a few common fatigue critical steel tower details are presented and can be used for estimation of remaining fatigue life. Future investigations will provide valuable data for evaluating fatigue loading based on aero-elastic analysis and for structural design requirements of wind turbine support structures.