Research on the strain response of offshore wind turbine monopile foundation through integrated fluid-structure-seabed model test

During the service period, the offshore wind turbine (OWT) must withstand multiple fluid loads of wind, waves and ocean currents. While the dynamic characteristics of OWT are affected by the coupling effect between the wind turbine structure, foundation, and fluid environment. Therefore, a complete model with geometrical scaling of 1:100 of the NERL-5MW wind turbine was manufactured and a series of model tests were conducted in the integrated Wind Tunnel-Flume-Foundation experimental system. The strain response characteristics of the monopile foundation were studied for the first time while the OWT under real fluid conditions. The strain response characteristics of OWT monopile foundation in the real fluid were studied for the first time. The experimental results revealed that the loading state, load intensity, and OWT operating state have significant effects on the dynamic strain response of the monopile. Under the coupling effect of complex fluid loads, the effect of waves enhances the strain response in the top region of the monopile foundation, which is attributed to the fact that the deformation of the foundation has amplified the effect of wind load acting on the upper part of OWT. Moreover, the dominant role of aerodynamic loads on the dynamic response of the OWT becomes more pronounced as the load intensity increases. Therefore, coupling effect between the influence of aerodynamic loads acting on the top and the impact of the hydrodynamic load acting on the foundation cannot be ignored.