Numerical simulation study of fatigue damage in high pile cap foundation for offshore wind power

The pile cap part of the high pile cap foundation (HPCF) of offshore wind turbine (OWT) exhibits synergistic deformations and coupling characteristics of steel bar-concrete-steel pipe piles. Structural fatigue damage assessment is relatively complex. This paper conducts a fatigue damage assessment of the HPCF by establishing a refined finite element model including steel bars. The rationality of the model is verified by monitoring data. A fatigue damage assessment method for steel-concrete composite foundation structures considering wave-current loads is summarized. Based on this method, the fatigue damage assessment of the 9 MW HPCF under construction is carried out. The results indicate that the concrete in the foundation is less susceptible to fatigue damage. Annular reinforcing steel bar around the top of the pile and the vertical steel bar inside the pile core concrete exhibit relatively higher fatigue damage, with a damage ratio level of 10_ 3. The prone-to-fatigue damage locations of the steel pipe piles are near the inflection point of the bottom steel plate, with a damage ratio level of 10_2. In the design of wind power HPCF structure, fatigue damage is not the control condition. Locations with significant levels of fatigue damage should be prioritized for monitoring and maintenance.