A Numerical Study on the Behaviour of Suction Bucket Foundations for Offshore Wind Turbines under Cyclic Loading

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2021-5-24
Yılmaz, Seyit Alp
Suction bucket foundations simply consist of a cylinder skirt and a top plate, usually made of steel and installed by the assist of suction are a relatively new and economically favorable solution for offshore wind turbines which are exposed to high lateral loads from winds and waves both of which have cyclic characteristic. Understanding the behaviour under the effect of complex cyclic load environment is essential to assess the design requirements of bucket foundations. Deformations and pore pressures may accumulate up to irrecoverable range under cyclic loadings. In this research, a 3D finite element model is developed with ANSYS v.18 software to investigate the behaviour of bucket foundations in sandy soils under cyclic axial compressive and cyclic lateral loads. Hypo plastic constitutive material model with intergranular strain which is appropriate to use with non-cohesive soils is adopted to simulate the material behaviour in cyclic load environment. Special attention was given to the pore pressure accumulation in and around the foundation. A fully coupled two-phase finite element model is adopted in which soil consists of a solid phase, the skeleton, and a fluid phase that fully saturates the skeleton. Coupled pore fluid-structure interaction is solved by the fluid flow by Kozeny-Carman poro-permeability relations and equilibrium conditions. The frictional behavior at the soil-structure interface is modeled by contact elements. The effect of the bucket dimensions, cyclic loading amplitude and frequency, relative density of the soil on the deformation and pore pressure behavior was investigated with a numerical parametric study. A set of design charts are developed according to the findings of the parametric study.
Citation Formats
S. A. Yılmaz, “A Numerical Study on the Behaviour of Suction Bucket Foundations for Offshore Wind Turbines under Cyclic Loading,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.