{'fraction_non_alphanumeric': 0.016142050040355124, 'fraction_numerical': 0.004035512510088781, 'mean_word_length': 5.2, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Position Specific Monopile Fatigue Load in the Frequency Domain


 This article presents a method for frequency domain calculations of fatigue loads for offshore wind turbines from wave loading on the monopile foundation. The method is used to estimate position-specific loads to lower the inherent conservatism to optimise the monopile design compared to the conventional approach where a conservative load envelope is applied for the whole or selected parts of the wind farm. The loads are calculated by transforming a wave spectrum into a stress spectrum, used for frequency domain rainflow counting. The remaining fatigue load is then determined by comparing the wave-only fatigue loads to the loads from an integrated loads analysis including all aero-dynamics associated with the turbine. The remaining contributions to fatigue loading are demonstrated to be nearly constant between positions and can thus be used to calibrate the wave-only load, estimated by frequency domain analysis, which subsequently enables the calculation of position-specific loads. When applying the method on site specific data, load reductions up to 12.5% are obtained on individual positions, while a 1–2% saving is achieved on the overall monopile mass.