Mooring line fatigue damage evaluation for floating marine energy converters: Field measurements and prediction

Thies, Philipp R.; Johanning, Lars; Harnois, Violette; Smith, Helen; Parish, David

doi:10.1016/j.renene.2013.08.050

Cited by 52 publications

(23 citation statements)

References 16 publications

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“…Christiansen et al [153] use system identification techniques to train neural networks on a FEM MM output to allow efficient mooring line fatigue assessment. Thies et al [209] present a method to analyse annual fatigue conditions from a limited number of experimental tanks tests, and from field measurements [210].…”

Section: Fatigue Analysismentioning

confidence: 99%

Mathematical Modelling of Mooring Systems for Wave Energy Converters—A Review

2017

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Mathematical analysis is an essential tool for the successful development and operation of wave energy converters (WECs). Mathematical models of moorings systems are therefore a requisite in the overall techno-economic design and operation of floating WECs. Mooring models (MMs) can be applied to a range of areas, such as WEC simulation, performance evaluation and optimisation, control design and implementation, extreme load calculation, mooring line fatigue life evaluation, mooring design, and array layout optimisation. The mathematical modelling of mooring systems is a venture from physics to numerics, and as such, there are a broad range of details to consider when applying MMs to WEC analysis. A large body of work exists on MMs, developed within other related ocean engineering fields, due to the common requirement of mooring floating bodies, such as vessels and offshore oil and gas platforms. This paper reviews the mathematical modelling of the mooring systems for WECs, detailing the relevant material developed in other offshore industries and presenting the published usage of MMs for WEC analysis.

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Section: Fatigue Analysismentioning

confidence: 99%

Mathematical Modelling of Mooring Systems for Wave Energy Converters—A Review

2017

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“…These have begun to provide some guidance on the calibration of design factors when considering fatigue in a WEC and have also allowed for some more refined estimates of reliability and maintenance [107]. Thies et al [108] investigated mooring fatigue in WECs, which is known to be an important consideration for some WEC designs. Thies et al found large uncertainties in the spread mooring system's line fatigue loads.…”

Section: Fatiguementioning

confidence: 99%

A Survey of WEC Reliability, Survival and Design Practices

Coe

Rij

2017

Energies

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A wave energy converter must be designed to survive and function efficiently, often in highly energetic ocean environments. This represents a challenging engineering problem, comprising systematic failure mode analysis, environmental characterization, modeling, experimental testing, fatigue and extreme response analysis. While, when compared with other ocean systems such as ships and offshore platforms, there is relatively little experience in wave energy converter design, a great deal of recent work has been done within these various areas. This paper summarizes the general stages and workflow for wave energy converter design, relying on supporting articles to provide insight. By surveying published work on wave energy converter survival and design response analyses, this paper seeks to provide the reader with an understanding of the different components of this process and the range of methodologies that can be brought to bear. In this way, the reader is provided with a large set of tools to perform design response analyses on wave energy converters.

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“…This short period of 400 seconds correspond with the moment where the vessel manoeuvred at the vicinity of the targeted site. The methodology used to quantify the fatigue load during transit is similar to the method reported in [18]. The rainflow cycle counting method [19] was used to quantify the number of load cycles for different load range intervals.…”

Section: Modelling Of the Load Experienced By The Polyester Line Durimentioning

confidence: 99%

Abrasion process between a fibre mooring line and a corroded steel element during the transit and commissioning of a marine renewable energy device

Herduin

Banfield²,

Weller

et al. 2016

Engineering Failure Analysis

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SummaryThis paper brings together two experiences from TTI (Tension Technology International) and the UoE (University of Exeter) and aims to quantify the damage that could be experienced by fibre mooring lines during the transit and commissioning phase of Marine Renewable Energy (MRE) devices.1. While deploying a new prototype of anchoring system for a MRE device, UoE experienced the failure of a new polyester mooring line during transit to site (90 minute duration). A thorough visual inspection supported by Scanning Electron Macroscopy (SEM) analysis and tensile test have established the physical conditions of the fibre rope before its failure.2. Wear testing led by TTI has investigated and established a relation between the degree of abrasion sustained and the residual strength of Dyneema ® fibre ropes. The ropes were submitted to friction forces via cycling over a roller and a fairlead with different abrasive surfaces (from 7.6 to 254.3μm). Negligible wear occurred with the low roughness surfaces and very high wear at the higher roughness surfaces.The load experienced by the polyester line during the deployment of the anchoring system was simulated with the software OrcaFlex TM . Dynamic modelling using representative conditions indicates that the polyester mooring line was loaded between 3 and 20% of its Minimum Breaking Load (MBL) which is well below the design load of the rope. IntroductionTo date there are only a few MRE designs which have achieved a pre-commercial development status. Experience in deploying such devices and specific guidance are missing. The approach of designers is thus conservative and based on the offshore oil and gas industry and anecdotal evidence [4].The use of synthetic fibre ropes for mooring systems has seen a sudden rise in marine applications over the last two decades [5] albeit mainly for deep water mooring [6]. Experience and feedback from the use of polyester ropes for MRE device moorings is still limited in terms of publications produced. This paper focuses on the commissioning phases of MRE devices, with a specific focus on the deployment of a novel anchoring system. Handling, lifting and rigging of mooring lines could result in damage during transport or installation as discussed in [7] and [8]. The strength of a rope will inevitably degrade from mishandling. Several research programs have been carried out to investigate the abrasion and twisting damage by rope manufacturers for towing systems. For example incorrect handling during transport could cause significant damage to the rope due to abrasion and the application of sudden high loads is one of the most severe conditions that a rope can experience [9].Certification standards and specific test methods have been developed to test the abrasion resistance of yarns [10] - [11]. The abrasion mechanism was described in [12] as a sequence of fibre peeling induced by surface shear forces. However the abrasion resistance of a fibre rope is not determined by standards and knowledge is only based on empirical test data.The exte...

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Mooring line fatigue damage evaluation for floating marine energy converters: Field measurements and prediction

Cited by 52 publications

References 16 publications

Mathematical Modelling of Mooring Systems for Wave Energy Converters—A Review

Mathematical Modelling of Mooring Systems for Wave Energy Converters—A Review

A Survey of WEC Reliability, Survival and Design Practices

Abrasion process between a fibre mooring line and a corroded steel element during the transit and commissioning of a marine renewable energy device

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