An integrated finite element model(FEM)of offshore wind tower-foundation-soil is established by ABAQUS, where a large-scale composite bucket foundation with seven compartments inside is applied to supporting the upper wind tower. The dynamic response of the structure-foundation system is studied under three seismic waves with the same peak ground acceleration of 0.035 g. It can be seen that the dynamic response increases at the beginning with the structure height, then it decreases because the structural damping increases due to the mass effect of the upper wind turbine generator system. It is shown that the anti-liquefaction capacity of the soil inside and underneath the foundation is improved owing to the high overburden pressure of the upper structure and the constraint effect of the bucket skirt and subdivisions. Moreover, the liquefaction resistance of the soil inside the middle compartment is improved to a higher degree than that inside the side compartments.
The composite bucket foundation(CBF) is a new kind of foundation which has been applied in the offshore wind industry. A reasonable connection pattern between the tower and the CBF top cover is crucial for load transmissions from the superstructure. Therefore, it is essential to choose an optimum structure type for the transition section. The line type and the arc transition section models were established by ABAQUS, and the internal forces of cross section were extracted along the height direction. Specifically, the force transfer mechanism for different types of the transition sections was investigated comparatively with monotonic as well as composite loadings. The results show that the curved transition structure exhibits the better mechanical characteristics under the monotonic and composite loadings, and the reason can be illustrated that its specific arc-shape structure can effectively convert the tremendous bending moment from the turbine tower into the limited tensile and compressive stresses downwards, without the occurrence of force concentration.
Puyang ZhangZhi ZhangJunjie MaHongyan DingRuiqi Hu
The platform with bucket foundations can penetrate and migrate by underpressure/positive pressure technique caused by pumping water out/in the bucket. However, the construction process of bucket foundations cannot be clearly observed and effectively controlled due to the special nature of sea environment. By using an advanced simulation development tool of Multigen Creator, the visual construction simulation program for the platform with bucket foundations was developed to set up the virtual reality system with interaction control and observation in every view angle based on the secondary development technology of Vega platform. The application results show that the method is feasible and effective by simulating the whole construction process for the platform with four bucket foundations.
