Concurrent Design on Three-Legged Jacket Structure and Transition Piece of Offshore Wind Turbine by Exploiting Topology Optimization

The jacket structure and transition piece comprise the supporting structure of a bottom-fixed offshore wind turbine (OWT) connected to the steel tower, which determines the overall structural dynamic performance of the entire OWT. Ideally, optimal performance can be realized by effectively coordinating two components, notwithstanding their separate design processes. In pursuit of this objective, this paper proposes a concurrent design methodology for the jacket structure and transition piece by exploiting topology optimization (TO). The TO for a three-legged jacket foundation is formulated by minimizing static compliance. In contrast to conventional TO, two separated volume fractions are imposed upon the structural design domain of the jacket structure and transition piece to ensure continuity. A 5 MW (megawatt) OWT supported by a four-legged or three-legged jacket substructure is under investigation. The external loads are derived from various design load cases that are acquired using the commercial software platform DNV Bladed (Det Norske Veritas).Through a comparative analysis of the fundamental frequency and maximum nodal deformation, it was found that the optimized solution demonstrates a reduced weight and superior stiffness. The findings demonstrate the present concurrent design approach using TO can yield significant benefits by reducing the overall design cycle and enhancing the feasibility of the final design.