Seabed scour is a common phenomenon that causes the loss of lateral support at bucket foundations. In order to investigate the influence of seabed scour on the seismic response of the offshore wind turbine structure, four integrated finite element models of the soil, bucket foundation, and superstructure were established. The four finite element models corresponding to four scour conditions were subjected to an acceleration time history, so as to assess the seismic response of the wind turbine structure and foundation soil for various scour depths. It is found that with the increase of scour depth, the dynamic response of the wind turbine structure increases. In addition, the plastic deformation area and liquefaction range of the soil around the bucket foundation also increase with the scour depth increasing.
Wind energy has gained popularity worldwide as many countries aim to increase the production of clean energy. In recent years, many countries have begun to develop offshore wind power resources because onshore wind resources are limited. Offshore wind turbines have become an attractive solution to harvest offshore wind energy resources. Suction caissons have been considered as possible foundations for offshore wind turbines (Houlsby et al., 2005). According to the geological characteristics and hydrometeorological conditions, a new type of wide-shallow composite bucket foundation has been examined by Tianjin University (Ding et al.,2012; Zhang et al., 2013).
As a foundation for offshore wind power structures, the seismic response research is very important for the bucket foundation. Although the probability of an earthquake is very low, a relatively low structural stiffness and damping of the foundation and tower can lead to a strong dynamic response under seismic action. In addition, depending on the intensity of shaking and soil conditions, liquefaction of near surface soils may occur, which can significantly affect the safety of offshore structures. There has been considerable amount of research conducted to study the seismic response of wind turbines and their support structures (e.g. Bazeos et al., 2002; Witcher, 2005; Ishihara et al., 2008; Prowell et al., 2009). The related interest is the work of Bhattacharya (2011) who have considered the influence of the soil-structure interaction on the seismic response of the offshore wind power turbines. These studies show that uneven distributions of mass and stiffness along the height of a structure can intensify the dynamic response of the structure and lead to its failure. What is more, soil liquefaction caused by earthquake would seriously threaten the stability of the structure. However, the composite bucket foundation can improve the liquefaction resistance of soil inside and directly below the bucket (Zhang et al., 2014a, 2014b).
