Proposal and application of onshore lattice wind turbine support structure and integrated multi-scale fatigue assessment method

Abstract

To accommodate the development of wind turbines in areas with weak wind speeds, an upright ultra-high lattice support structure is proposed for the large wind turbine, which is prefabricated and assembled mainly from thin-walled circular hollow steel (CHS) tube elements. As a practical example, a 180 m wind turbine support structure is presented. To evaluate the fatigue performance of the new structure type with modular assembly, a new integrated multi-scale fatigue assessment method is proposed to address the shortcomings of the equivalent fatigue load method commonly used in engineering design. For any fatigue load condition, the integrated multi-scale fatigue assessment method enables accurate and efficient calculation of the relationship curve between fatigue load and hot spot stress, and identification of the locations in the structure where fatigue accumulation damage is the greatest. Furthermore, fatigue damage accumulation and fatigue life can also be predicted accurately and efficiently by the proposed method. The results show that for the maximum fatigue cumulative damage of the proposed new structural systems, as the effect of average stress is not considered and the assumption of superposition of principal stresses, the traditional equivalent fatigue load method is too conservative compared to the proposed integrated multi-scale fatigue assessment method, detrimental to cost decreasing and benefit increasing of the wind turbine structures.