Problem ➔Track the degradation of one rotor blade and tower base over over as 10 months period under wind inflow and operational uncertainties Scenario ➔Continuous wind turbine blade and tower stiffness degradation, emulating blade root delamination resulting in dynamic instability, leading to the tower base excess fatigue. Simulation environment and setup in FAST v8 : ➔In the blade input file: modify flap and edge stiffnesses in damage regions, blade root (only 1 in 3 blades is affected). Assumed equal degradation in both edgewise and flapwise directions ➔In the blade input file: modify mode shapes coefficients (1st flap, 2nd flap and 1st edge modes) ➔In the tower input file: modify FA and SS stiffnesses in damage regions, tower base ➔In the tower input file: modify mode shapes coefficients (1st & 2nd FA and 1st & 2nd SS modes) ➔Note that the tower degradation only "shows up" in the last 2 monitoring periods ➔In the turbulence input file: modify wind speed, tuburlence intensity, shear exponent, horizontal and vertical inflow angles. ➔Further complication by assuming that the average input environmental conditions are not stationary over the monitoring period, emulating seasonal variations. ➔This means 120 environmental samples (and consequenly input wind field time series) are sampled from different distributions each period during the degradation process