| dc.description.abstract | Floating offshore wind turbines (FOWTs) are remotely located structures that are operating without humans on board. The technicians are expected to be on board from time to time throughout the life cycle of FOWTs for maintenance activities such as regular inspections, fault-findings, component changing etc. Due to their remote location, FOWTs are usually subjected to harsh environmental conditions that may cause large motions on the platform. Such motions may obstruct access to the platform and the maintenance work that is going to be conducted on the platform by the technicians. To address the problem and define the objectives, a literature study is conducted on the maintenance process of the FOWTs, the effects of platform motions on the humans located on the structure. The standards and regulations regarding the seakeeping performance of the vessels for human effectiveness and health are demonstrated. Then the motions of the floaters, modelling of the offshore sea conditions and the working principle of the software used are covered with a compact theory. A methodology is developed for the frequency domain to simulate the motions of the floaters in offshore conditions and model the motion exposure of the personnel on the structure. The developed methodology is utilised for three chosen study case floaters. OC3-Hywind, CSC-Semisubmersible and WindFloat are selected for comparative simulation studies where the workability of the technicians on each floater is investigated under different loading conditions. The load cases are modelled with both the JONSWAP and the Torsethaugen wave spectra based on hindcast data from two locations that are relevant for FOWT deployment. The conducted research is presented as a journal paper within this thesis. Additional results which were not included in the paper such as the investigation of the developed methodology and the expected extreme accelerations on the floaters are presented within the thesis. Instantaneous accelerations expected on each floater are graded regarding criteria for the human comfort reactions to vibration environments. Conclusions are made based on the findings from the comparative studies. The thesis is finalised with recommendations for further work. | |
