Comparative study of the influence of kinematic interaction on the seismic response of monopile and jacket supported offshore wind turbines

Abstract

In the last few years, offshore wind energy has been increasing significantly, being the energetic potential of this technology much higher than that of other renewables energies. Most of Offshore Wind Turbines (OWTs) installed in Europe are founded to the sea floor but, due to the increase in offshore wind turbine installations and the visual impact problem, new locations are being considered with greater depths and increasing seismic risk. In this field, jackets substructures are one of the most attractive options. Despite the low natural frequencies that characterise these systems, the effect of the kinematic interaction can be highly relevant in OWTs on monopiles. For this reason, the need arises to analyse the importance of the influence of kinematic interaction on the seismic responses of multi-supported substructures, such as jackets with deep foundations. This paper presents a comparison of the kinematic interaction effects on the seismic response of two types of substructures for OWTs. OpenFAST is used to analyse the dynamic behaviour of OWTs founded either on monopiles or through jacket substructures on deep foundations, taking soil-structure interaction into account. The comparative study shows that the influence of kinematic interaction in both cases is notably different. As expected, in the case of the monopile, the rotational motion has a strong effect on the accelerations and the internal forces in the structure, although the impact of the translational filtered signal is small. However, in the jacket, the influence of the rotational motion is less pronounced.