Framework for Multi-Level Optimisation of Offshore Wind Jacket Foundations

Abstract

Abstract This paper presents Wood Thilsted’s in-house developed framework MORPHEUS for structural optimization of jacket structures. The approach is based on a hybrid model consisting of 3D Timoshenko beam elements, combined with stiffness and mass representation of non-trivial details like the transition piece (TP) and tubular joints using 3D FE shell or solid models. For tubular joints, the 3D solid FE-models are automatically generated based on the beam geometry and offsets in the global model. The associated stiffness and mass contributions are then evaluated and used to adjust the local joint flexibility. Additionally, the 3D FE models are used for detailed stress evaluation by so-called local influence matrices. These provide relations between incoming member section forces and local stresses at relevant hotspots along the intersection weld in the tubular joints, thereby ensuring full consistency between stiffness representation and stress evaluation at detailed level. It is illustrated how the framework enables multi-level optimization, automatically adjusting both the global member sizing (thicknesses) in the beam model and the thicknesses in the tubular joints. This is achieved by alternating between the global beam-based model and the individual 3D solid FE models.