Floating Wind Structure Pre-FEED

  • Client Marine Power Systems
  • Year 2022
  • Business unit Offshore Renewables


Apollo completed a Pre-FEED study for Marine Power Systems for the structural design of a floating wind structure which is configured to house a 15MW wind turbine.

To house such a turbine with a blade diameter of 240 metres demanded a sizeable structure with an approximate displacement of 5,000 tonnes. The work involved taking an initial concept and evolving it to enable sizing of members and to identify required stiffening with the objective of minimising design changes in the subsequent FEED stage.

Apollo managed to deliver this with ease through our prior experience in floating structures for both carbon energy and marine renewable structures. A small and efficient team of experienced engineers were assigned to the project. The FEA work was completed on ANSYS, owing to the considerable size of the structure, shell elements were used for a global model, with local models devised to analyse the joints and transition piece. This combined approach to modelling enabled a global picture of the structural behaviour with in-depth results being interpreted at critical locations.


Marine Power Systems required an experienced contractor to conduct structural studies for the Pre-FEED design of their 15MW floating wind platform.

The high-level scope of work was comprised of the following elements:

🚀 Parametric Finite Element Analysis (FEA) models
🚀 Structural assessment of the lateral and diagonal braces
🚀 Design and structural verification of the transition piece and lower joints
🚀 High-level full platform structural assessment

In support of the above elements, Apollo viewed the following smaller fields of study to be value-adding, aiding the development of future follow-on studies, these included:

🚀 Design and verification of stiffeners, mooring line pad-eyes and thicknesses of main elements for lower joint and transition piece
🚀 Develop 3D Inventor model of the lower joint and transition piece
🚀 Adjustments to the 3D Computer Aided Design (CAD) model to include designed sections and relevant stiffeners
🚀 FEA model analysis of geometries to relevant code standards
🚀 Structural assessment of lateral and diagonal braces, identifying any areas of high stress such as the transition of thicknesses and interfaces of braces with stiffening rings
🚀 Structural assessment and verification of transition piece and lower joints, identifying regions of high stress and concentrations
🚀 Structural assessment of load paths, stresses and deformations with representative load cases
🚀 A comprehensive description of results in an overall structural report


The client benefitted from a diverse and experienced engineering team which looked at an array of initiatives for design optimisation whilst always prioritising weight reduction without impairing structural integrity or performance.

Using the findings from the study the client was able to accelerate the design into FEED having already sized all major members including locating and sizing the required stiffening.

Stress concentration factors were identified and kept to acceptable levels which reassured the client that fatigue will not be overly restrictive on design highlighting the key areas that will require further refinement whilst the design develops.

Inventor models and drawings were issued to the client to enable the next phase to begin without duplication of pre-FEED work.

Throughout the project Apollo kept Marine Power Systems informed with weekly technical meetings where challenges were discussed, enabling feedback on design features to be efficiently incorporated.

If you are looking for help with a Pre-FEED or FEED study, contact us today.