Walk-to-work accessibility assessment for floating offshore wind turbines

Abstract

This paper presents a methodology to assess the walk-to-work accessibility of a floating wind turbine. The system composed by the vessel and the platform is modelled in the frequency domain as a rigid, possibly constrained multibody system. Non-linear actions, such mooring and viscous forces are linearised. Extreme maxima for the response variables are calculated assuming that crests are Rayleigh distributed. Two vessels are studied: a catamaran equipped with fender, and a supply vessel mounting a motion-compensated gangway. For the catamaran, accessibility is possible when no-slip conditions between the vessel fender and the ladder landing platform are ensured. For the supply vessel, accessibility is possible when the gangway motions are below the hydraulic system compensation limits. The catamaran is able to handle wave heights up to 2m, provided that it can work under head sea conditions and take advantage of the shielding effect of the platform. The supply vessel allows personnel transfer with wave heights up to 5m, but it is important that roll motions are not excited. The proposed methodology and the calculated maps are a valuable source of information for decision-making during personnel transfer to and from offshore floating platforms.