Research On Fatigue Damage Of Offshore Wind Turbine Bucket Foundation

As a new type of wind turbine foundation, offshore wind turbine bucket foundation is long-term in complicated oceanic environment, mainly under the influence of dynamic loads generated from both operation of the upper structure and complex marine environment such as wind and waves. Strain accumulation of concrete material will give rise to the process of internal damage, affected by many variables, which eventually results in macro crack until the whole structure is destroyed. Duo to the unexpected and heavy losses, fatigue damage calculation of concrete structure has attracted a great deal of concern in the domestic and international academic or engineering field.According to the linear and nonlinear calculation methods,3MW offshore wind turbine bucket foundation was taken as the prototype into three-dimensional finite element to be calculated by the method of static calculation and dynamic calculation, using the method of comparative analysis in order to ensure the correctness of results. Concrete damaged plasticity model was used in the dynamic analysis to define concrete materials. Cloud of tensile damage and compressive damage about the whole model and the various components of the overall structure in the calculation results can be visually observed.Combined Norske Veritas DNV standards and the German GL standards with the finite element software creatively, theσmax、σmin was provided, which was needed by the specification validation formulas of concrete fatigue properties. The calculation results were analyzed by the fatigue verification for concrete under compression based on EUROPEAN STANDARD. The computation results show that this type of bucket foundation satisfies the requirement of avoiding fatigue damage under compressive load. The method of fatigue damage accumulation basing on S-N curve and Miner linear cumulative damage criteria was introduced and fatigue load spectrum compiled method-rain flow method was described in detail. The academic term related to concrete fatigue damage was also defined in system.The computation results show that this type of bucket foundation satisfies the requirement of avoiding fatigue damage under compressive load, but do not have enough resistance to tensile fatigue damage.It is necessary to take certain measures to make up for lack of the defect of concrete tensile strength. Considering a series of advantages of bucket foundation such as simple, economical and recyclable, this new kind of foundation should be widely applied.