Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Experimental study of a TLP-type Floating Offshore Wind Turbine with Tendon Failure
Yajun Ren1, Vengatesan Venugopal1, Yiming Zhou2, Wei Shi3
1

Institute for Energy Systems, the University of Edinburgh
Edinburgh, UK2

Huaneng Clean Energy Research InstituteBeijing, China

3

Deepwater Engineering Research Centre, State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology
Dalian, China

For TLP-type FOWTs, one of the particular concerns is the extremely
high tension in the tendons. Since the stability of the structure iscompletely 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 ofFOWT. 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). Itwas reported that the change of response as the result of tendon failure
is mainly observed in the transient increase of tower top acceleration andthe tension force, while the responses in surge and heave are notsignificantly affected. However, the research in this area is still solely
based on numerical modelling, while the reliability of the results may bequestioned.

ABSTRACTIn this paper, a description of physical model tests conducted on a newly
designed 5-MW TLP Floating Offshore Wind Turbine (FOWT) scalemodel 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 Universityof Technology’s wave basin. The natural frequencies, motions of theplatform and the corresponding response amplitude operators (RAOs),and forces on the tendons were obtained by the experiments. The resultsfrom the experiments show that, after the tendon failure occurred, thetendons adjacent to the broken one suffers from the significant increaseof tension force. The outcomes of this research are expected to provide
new knowledge towards the design of TLP FOWT with failed tendons.

Model testing is one of the most reliable approaches for the investigationof FOWT. It has been demonstrated in the literature that model testing
can effectively calibrate and validate the numerical model and thus
support the assessment of FOWT performance (Zhang et al., 2020).
Several experimental studies have been carried out on FOWT in the past[e.g. Sethuraman and Venugopal (2013), Oguz et al. (2016), Zhao et al.
(2018), and Xu et al. (2019)], whereas mooring/tendon failure test has
been hardly conducted.

KEY WORDS: TLP Floating Offshore Wind Turbine; scale model,tendon failure; regular waves; motion responses

INTRODUCTION
Tension leg platform (TLP) is seen as a key technology for floating
offshore wind turbine (FOWT). As the stability of the platform isprovided 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 TLPFOWT 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 iscritical and such designs will provide a stable and cost-effectivealternative (Ren et al., 2022; Zhao et al., 2021).

To fill the knowledge gap stated above, we carried out an experimental
campaign on a scale model of TLP FOWT in a wave basin testing tendon
failure for different wave and wind scenarios. This paper describes thestructural parameters of the model and its setup in the wave basin toinduce tendon failure, wave generation, equipment setup ， datameasurements and analysis. The natural frequencies, RAOs, andmooring restoring curve of the floating platform etc. are obtained fromthe tests. The effects of tendon failure on the tension forces are presented
and discussed.

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