Context

Synthetic ropes offer a promising mooring solution for floating systems, in particular wind turbines, with lower loads and reduced seabed footprint. However, they show complex tension-elongation behaviours which differs for instantaneous and long-term loadings, in function of the material used. Among these synthetic fibres, polyamide is of interest to lower the peak tension in the mooring lines, especially in shallow waters. During previous projects, the understanding and modelling of the complex mechanical behaviour of polyamide ropes was significantly improved. However, some questions still need to be solved for a long-term use with high level of reliability.

Objectives

To improve the modelling of short- and long-term behaviour of nylon ropes and expand the knowledge on fatigue and degradation mechanisms

Scientific content

• In-depth modelling of polyamide ropes
  • Development of a meso-scale model
  • Enhancement of 1D behaviour law for rope
  • Experimental campaigns
• Investigations on fatigue mechanisms
  • Extension of the fatigue curve at low tension range
  • Fatigue prediction method using self-heating approach
  • Investigation on the influencing parameters of the fatigue curve
  • Challenge a new criterion for fatigue prediction
• Validation of polyamide rope behaviour law and degradation
  • Laboratory validation of behaviour law on a full-scale rope
  • Impact of selected rope model on mooring design
  • Extended sea trials, review of degradation rope mechanisms, ropes inspection and tests after dismantling

Expected results

• Validated meso-scale model for different construction patterns
• Fatigue prediction method using self-heating approach, including a new challenged fatigue criterion
• Fatigue curve extended towards high number of cycles, and assessment of parameters influencing fatigue
• Validated polyamide rope behaviour law after 1 year of mooring service, numerical study on optimisations made possible by this law
• State of the art and feedback on degradation mechanisms

Resources

BAMOS Project Sheet (PDF)

Partners and funding

This project is led by ENSTA Bretagne and France Energies Marines.

The total project budget is €2,255K.

This project receives funding from France Energies Marines and its members and partners, as well as French State funding managed by the National Research Agency under the France 2030 investment plan. It also benefits from the financial support of Bretagne, Pays de la Loire and SUD Provence-Alpes-Côte d’Azur regions.

Photo credit: France Energies Marines