Safety Evaluation of a Hybrid Substructure for Offshore Wind Turbine

Abstract EN

Towers and rotor-nacelles are being enlarged to respond to the need for higher gross generation of the wind turbines.

However, the accompanying enlargement of the substructure supporting these larger offshore wind turbines makes it strongly influenced by the effect of wave forces.

In the present study, the hybrid substructure is suggested to reduce the wave forces by composing a multicylinder having different radii near free surface and a gravity substructure at the bottom of the multicylinder.

In addition, the reaction forces acting on the substructure due to the very large dead load of the offshore wind turbine require very firm foundations.

This implies that the dynamic pile-soil interaction has to be fully considered.

Therefore, ENSOFT Group V7.0 is used to calculate the stiffness matrices on the pile-soil interaction conditions.

These matrices are then used together with the loads at TP (Transition Piece) obtained from GH-Bladed for the structural analysis of the hybrid substructure by ANSYS ASAS.

The structural strength and deformation are evaluated to derive an ultimate structural safety of the hybrid substructure for various soil conditions and show that the first few natural frequencies of the substructure are heavily influenced by the wind turbine.

Therefore, modal analysis is carried out through GH-Bladed to examine the resonance between the wind turbine and the hybrid substructure.