Inspection planning optimisation for offshore energy structures using digital twin

Inspection and maintenance are integral elements within the structural integrity management of offshore energy structures. This allows the identification and remediation of progressive structural degradation such as fatigue cracks, ensuring fitness-for-service of critical offshore assets throughout their service lifetime. In view of optimising the offshore retrieval/intervention and eventually reducing the life-cycle costs, risk-based inspection and maintenance planning is highly relevant. However, conducting a comprehensive risk assessment requires gaining a thorough knowledge of the as-built design and actual operational profile whereby accurately predicting its performance. Although design specifications and assumptions can serve as guidelines, a high degree of uncertainty may arise due to the disparity between the actual operational profile and the design assumptions. This paper studies the application of digital twin approach whose virtual monitoring feature coupled with fatigue load updating algorithm enables the derivation of more realistic loading spectrum. Probabilistic fracture mechanics-based model is utilised to simulate the fatigue crack growth. An optimisation of future inspections is performed with an objective to minimise the life cycle expected total cost due to fatigue failure, inspection and repair. For demonstration purpose, a case study using an offshore wind support structure is presented to illustrate this digital twin-enabled proposal. Furthermore, areas open future research in this field are discussed.