In this paper, a description of physical model tests conducted on a newly designed 5-MW TLP Floating Offshore Wind Turbine (FOWT) scale model with failed tendon and its results, are presented. The TLP FOWT is designed for moderate water depths of 60 m. A scale factor of 1:50 is used for the experiments. The free-decay tests, regular and random wave tests, and tendon broken tests are carried out in Dalian University of Technology's wave basin. The natural frequencies, motions of the platform and the corresponding response amplitude operators (RAOs), and forces on the tendons were obtained by the experiments. The results from the experiments show that, after the tendon failure occurred, the tendons adjacent to the broken one suffers from the significant increase of tension force. The outcomes of this research are expected to provide new knowledge towards the design of TLP FOWT with failed tendons.
Tension leg platform (TLP) is seen as a key technology for floating offshore wind turbine (FOWT). As the stability of the platform is provided by the tension forces from its tendons and the excessive buoyancy of the hull, the platform has the potential to significantly reduce structural costs due to the reduced steel weight. The existing TLP FOWT concepts [e.g. Matha (2009), Ding et al. (2016) and Zhao et al. (2012)], were normally designed for water depths larger than 150 m. However, in many countries, for a large part of the ocean, the available water depth for FOWT installation is less than 100 m; therefore, design and analysis of TLP based FOWTs for intermediate water depths is critical and such designs will provide a stable and cost-effective alternative (Ren et al., 2022; Zhao et al., 2021).
For TLP-type FOWTs, one of the particular concerns is the extremely high tension in the tendons. Since the stability of the structure is completely provided by the mooring system, the damage of the tendon, either by accident or fatigue, can lead to serious consequences. Several studies have assessed the effect of mooring failure on different types of FOWT. Bae et al. (2017) revealed that the damage of one mooring line in a semi-submersible FOWT can lead to significant drift of the platform. Wu et al. (2021) investigated the effect of tendon failure on a WindStar TLP FOWT, which showed different outcomes from Bae et al. (2017). It was reported that the change of response as the result of tendon failure is mainly observed in the transient increase of tower top acceleration and the tension force, while the responses in surge and heave are not significantly affected. However, the research in this area is still solely based on numerical modelling, while the reliability of the results may be questioned.
