Stability of Floating Offshore Wind Turbine Structures

Overview

This presentation explores the principles used to assess the stability of ships and floating offshore structures, drawing on the foundational concepts of metacentric height (GM), restoring moments and energy balance developed by Bouguer, Euler and Mosely.

These principles continue to underpin the intact stability criteria adopted by the International Maritime Organisation (IMO) and classification societies and form the basis of quasi-static stability assessments used across the marine and offshore industries.

The session will examine the role of mooring stiffness in stability assessments, highlighting the limitations of conventional commercial software that typically considers only buoyancy-related stability effects.

While this approach may be suitable for turret-moored FPSOs, where mooring stiffness has little influence on stability, it may not be adequate for other moored offshore structures where mooring systems can have a significant impact.

Focusing on floating offshore wind turbine structures (FOWTs), the presentation will review how catenary, semi-taut and taut mooring systems are incorporated into stability assessments under current industry rules and regulations.

It will also present intact and damage stability analysis results for a FOWT under various operating conditions, demonstrating that partial consideration of mooring effects can be detrimental to stability, whereas a full assessment can reveal a positive contribution from the mooring system.