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Erik Falkenberg - One of the best experts on this subject based on the ideXlab platform.

  • Best Practice for Analysis of Polyester Rope Mooring Systems
    Day 3 Wed May 03 2017, 2017
    Co-Authors: Erik Falkenberg, Vidar Ahjem, Limin Yang
    Abstract:

    The objective of the SyRope JIP has been to improve the methods for safe and reliable design of Fibre Rope mooring systems. Normal, conservative, design practice for polyester Rope mooring systems is to use an upper and a lower bound axial stiffness of the polyester. The use of a more advanced, but still manageable design practice allows for a more optimized design. Only polyester lines have been covered by the work, but the principles are assumed to have a general validity. Extensive testing on change-in-length behavior has been performed on subRopes. Testing has covered recommended test procedures from different standards and recommended practices and more realistic load sequences. Based on test results a conceptual model for the behavior of polyester Ropes has been developed. The mean length of a Rope depends on the preceding highest mean tension in the Rope and the actual tension, including its mean value. The response to wave-frequency and low-frequency loads is described by a dynamic stiffness which increases with the mean load in the line. Recommended change-in-length testing of subRopes is described, and principles for analysis of such tests for identification of parameters in the model are presented. Finally, guidance for use of the model in mooring system analyses is given.

  • GLOBAL PERFORMANCE OF SYNTHETIC Rope MOORING SYSTEMS – FREQUENCY DOMAIN ANALYSIS
    2015
    Co-Authors: Erik Falkenberg, Vidar Ahjem, Kjell Larsen, Karl E. Kaasen
    Abstract:

    For deep and ultra-deepwater applications, synthetic Fibre Ropes are considered an enabling technology due to their higher strength-to-weight ratio as compared to steel wire Ropes and chains and due to their superior station-keeping performance. The advantages of synthetic Fibre Rope mooring systems include: • A higher floater payload and reduction in structural costs due to lower vertical load from mooring lines. • A reduction in vessel offsets and associated riser loads due to taut mooring system. • A potential reduction in installation costs due to lighter installation and handling equipment. • Superior endurance under cyclic loading compared to steel moorings

  • Global Performance of Synthetic Rope Mooring Systems: Frequency Domain Analysis
    Volume 1: Offshore Technology; Polar and Arctic Sciences and Technology, 2011
    Co-Authors: Erik Falkenberg, Vidar Ahjem, Kjell Larsen, Halvor Lie, Karl E. Kaasen
    Abstract:

    For deep and ultra-deepwater applications, synthetic Fibre Ropes are considered an enabling technology due to their higher strength-to-weight ratio as compared to steel wire Ropes and chains and due to their superior station-keeping performance. The advantages of synthetic Fibre Rope mooring systems include: • A higher floater payload and reduction in structural costs due to lower vertical load from mooring lines. • A reduction in vessel offsets and associated riser loads due to taut mooring system. • A potential reduction in installation costs due to lighter installation and handling equipment. • Superior endurance under cyclic loading compared to steel moorings. Synthetic Fibre Ropes have visco-elastic stiffness and stretch characteristics. The change-in-length response of a Fibre Rope is non-linear, load-path dependent (different unload-reload stiffness), and the length varies with the rate and duration of loading (due to elongation and contraction). The commonly accepted analysis approach is a simplification where a lower-bound and an upper-bound stiffness is used. This practice is primarily based on two factors: 1. The industry at large does not at present have a common, well-defined understanding of Fibre-Rope change-in-length performance. 2. There is a lack of commercially available mooring analysis programs with the capability to simulate the non-linear change-in-length response of the synthetic Fibre Rope. Individual designers may however have more advanced analysis procedures, but these are not commonly accepted yet. This paper presents results from the SyRope pilot study, Ref. /5/ and /6/, which has used Rope testing to determine the characteristics of the elements in the spring-dashpot model. On this basis a strategy for software implementation in the frequency-domain has been proposed. A case study was performed for a semi-submersible production unit in deep water and harsh environment. The paper focuses on the differences between a commonly accepted, hereafter called traditional analysis approach and the proposed new frequency domain approach. The results show that there are large differences in extreme tensions and offsets as well as fatigue results. Hence, the new approach is considered to represent a significant improvement.Copyright © 2011 by ASME

Karl E. Kaasen - One of the best experts on this subject based on the ideXlab platform.

  • GLOBAL PERFORMANCE OF SYNTHETIC Rope MOORING SYSTEMS – FREQUENCY DOMAIN ANALYSIS
    2015
    Co-Authors: Erik Falkenberg, Vidar Ahjem, Kjell Larsen, Karl E. Kaasen
    Abstract:

    For deep and ultra-deepwater applications, synthetic Fibre Ropes are considered an enabling technology due to their higher strength-to-weight ratio as compared to steel wire Ropes and chains and due to their superior station-keeping performance. The advantages of synthetic Fibre Rope mooring systems include: • A higher floater payload and reduction in structural costs due to lower vertical load from mooring lines. • A reduction in vessel offsets and associated riser loads due to taut mooring system. • A potential reduction in installation costs due to lighter installation and handling equipment. • Superior endurance under cyclic loading compared to steel moorings

  • Global Performance of Synthetic Rope Mooring Systems: Frequency Domain Analysis
    Volume 1: Offshore Technology; Polar and Arctic Sciences and Technology, 2011
    Co-Authors: Erik Falkenberg, Vidar Ahjem, Kjell Larsen, Halvor Lie, Karl E. Kaasen
    Abstract:

    For deep and ultra-deepwater applications, synthetic Fibre Ropes are considered an enabling technology due to their higher strength-to-weight ratio as compared to steel wire Ropes and chains and due to their superior station-keeping performance. The advantages of synthetic Fibre Rope mooring systems include: • A higher floater payload and reduction in structural costs due to lower vertical load from mooring lines. • A reduction in vessel offsets and associated riser loads due to taut mooring system. • A potential reduction in installation costs due to lighter installation and handling equipment. • Superior endurance under cyclic loading compared to steel moorings. Synthetic Fibre Ropes have visco-elastic stiffness and stretch characteristics. The change-in-length response of a Fibre Rope is non-linear, load-path dependent (different unload-reload stiffness), and the length varies with the rate and duration of loading (due to elongation and contraction). The commonly accepted analysis approach is a simplification where a lower-bound and an upper-bound stiffness is used. This practice is primarily based on two factors: 1. The industry at large does not at present have a common, well-defined understanding of Fibre-Rope change-in-length performance. 2. There is a lack of commercially available mooring analysis programs with the capability to simulate the non-linear change-in-length response of the synthetic Fibre Rope. Individual designers may however have more advanced analysis procedures, but these are not commonly accepted yet. This paper presents results from the SyRope pilot study, Ref. /5/ and /6/, which has used Rope testing to determine the characteristics of the elements in the spring-dashpot model. On this basis a strategy for software implementation in the frequency-domain has been proposed. A case study was performed for a semi-submersible production unit in deep water and harsh environment. The paper focuses on the differences between a commonly accepted, hereafter called traditional analysis approach and the proposed new frequency domain approach. The results show that there are large differences in extreme tensions and offsets as well as fatigue results. Hence, the new approach is considered to represent a significant improvement.Copyright © 2011 by ASME

Johanning L - One of the best experts on this subject based on the ideXlab platform.

  • Round robin testing of synthetic Fibre Ropes for application in marine renewable energy
    'Informa UK Limited', 2020
    Co-Authors: Khalid F, Pr Thies, Halswell P, Lacotte N, Johanning L
    Abstract:

    This is the author accepted manuscript. The final version is available from CRC Press via the DOI in this recordRENEW 2020: 4th International Conference on Renewable Energies Offshore, 12-15 October 2020, Lisbon, PortugalThe unique design requirements of mooring systems in Marine Renewable Energy (MRE) installations re-quire detailed numerical and empirical investigations as well as offshore experience to adopt and certify fi-bre Ropes in the marine renewable energy industry. Laboratories provide a controlled environment for quick, inexpensive and repeatable testing compared to field deployment and enable a range of parameters to be studied. Uncertainties may be introduced in the laboratory test results because of effects associated with in-dividual facilities (such as instrumentation accuracy, control system and analysis methods) despite following the same protocol. This paper presents the outcomes of a round robin testing campaign conducted at two test facilities to conduct a comparative analysis by monitoring the implementation of the test program and ana-lysing the results to highlight differences between facilities and suggest best practice for Fibre Rope testing in the MRE industry.EuRopean Union Horizon 202

  • Reducing Peak & Fatigue Mooring Loads: A Validation Study for Elastomeric Moorings
    EWTEC, 2017
    Co-Authors: Dn Parish, Pr Thies, Herduin M, Gordelier T, Johanning L
    Abstract:

    This is the author accepted manuscript. The final version is available from EWTEC via the link in this record.Fibre Ropes are often specified for floating wave and tidal energy device mooring systems. The relatively low axial stiffness goes some way towards mitigation of the peak and fatigue mooring loads. However, the minimum breaking load (MBL) of a Fibre Rope dictates its axial stiffness and hence the free selection of low axial stiffness is not possible with conventional Rope. The resulting mooring stiffness is often sub-optimal, giving rise to elevated peak and fatigue loads. Elastomeric, nonlinear mooring elements solve this by partially de-coupling the axial stiffness from the MBL and offering an initial soft response with increasing stiffness for higher strains. These nonlinear elastomeric moorings have the potential to reduce the peak and fatigue mooring loads as indicated by numerical studies. This work uses a validated numerical model to quantify the load reduction achievable by substituting a novel elastomeric tether in place of a conventional Fibre Rope. Field data is used to validate the base case model of the highly dynamic South West Moorings Test Facility (SWMTF). The base case mooring design utilises Nylon Ropes which are subsequently replaced with elastomeric tethers in the validated model. The results show that the peak mooring loads are reduced substantially upon substituting the elastomeric tethers for the conventional Ropes. Subsequently this allows a downward iteration of MBL and axial stiffness towards an optimal condition, providing the lowest achievable load case. In most instances, the optimum iteration outcome also allows a reduction in catenary chain weight. The reduction in peak tension is accompanied by an increase to the buoy excursion in surge. However, the mean peak excursion increase is 21% whilst the mean peak tension reduction is 66%.This work was partly funded by the EPSRC (UK) grant for the SuperGen United Kingdom Centre for Marine Energy Research (UKCMER) [grant number: EP/P008682/1]. The development of the Exeter Tether was partly funded by the Open Innovation Platform, supported by the Higher Education Council for England. The authors would also like to acknowledge the support from Lankhorst Ropes throughout the technology development

  • Fibre Ropes for Taut Mooring Lines for Marine Energy Converters (Fibre Taut 2)
    MARINET, 2016
    Co-Authors: Dorenbusch J, Canedo J, Leao A, Rodríguez Arias R, Glez. De Lena, Johanning L, Pr Thies, Parish D, Weller S
    Abstract:

    PublishedOne immediate challenge for the Marine Energy Converters (MECs) industry is solving the cost and weight problems of mooring lines in deepwater (>75m). Fibre Rope taut mooring lines represent a new and interesting option for the mooring of MECs in deepwater. Synthetic Fibre Ropes offer a solution to the weight problems of using steel lines in deepwater as they have a very low weight in water. Also, compared to steel, there are a large number of synthetic Fibre material compositions with a wide range of material pRoperties. A synthetic Rope can therefore be designed to have pRoperties that match the mooring requirements. Several materials have potential for mooring line application. Yarns of these synthetic materials can be made into Ropes using a number of constructions, some of which are suited to particular Fibres. As with any new application, research must be conducted to determine how well the Fibre Ropes satisfy the performance requirements. The effects of aging of Fibre Ropes will be characterized in the proposed tests. Test facilities at the University of Exeter are unique in the MARINET consortium, as they allow the extensive testing of mooring lines in water. Their testing infrastructure will help us to determine which prospective innovative Fibre Rope mooring line is best suited for deepwater MECs. Also, the technological and scientific support offered by the well experienced staff is another reason to propose the access to these two tests facilities.The work described in this publication has received support from MARINET, a EuRopean Community - Research Infrastructure Action under the FP7 “Capacities” Specific Programme

  • Fibre Ropes for Taut Mooring Lines for Marine Energy Converters (FibreTaut1)
    MARINET, 2016
    Co-Authors: Dorenbusch J, Leao A, Rodríguez Arias R, Glez. De Lena, Johanning L, Pr Thies, Parish D, Canedo A, Weller S
    Abstract:

    PublishedOne immediate challenge for the Marine Renewable Energy Converters (MRECs) ind ustry is solving the cost and weight problems of mooring lines in deep water (>75m). Synthetic Fibre Ropes already offer a solution to the weight problems of using steel lines in deep water offshore oil and gas installations as they hav e a very low weight in water. Also, compared to steel, there are a large number of synthetic Fibre material compo sitions with a wide range of material pRoperties. A synthetic Rope can therefore be designed to have pRoperti es that match the mooring requirements. Several materials have potential for mooring line application. Yarns of t hese synthetic materials may be built into Ropes using a number of constructions, some of which are suited to particular Fibres. As with any new application, research must be performance conducted to determine how well the Fibre Ropes satisfy the performance requirements. The testing infrastructures at the University of Exeter (UoE) are unique in the MARINET consortium, as it allows for extensive testing of mooring lines in sea water. Its testing infrastructure will help the consortium to determine which prospective innovative Fibre Rope mooring line is best suited for deep water MECs. Also, the technological andscientific support offered by the well experienced staff is another reason to propose the access to this kind of facilities. The present study of international partners, WireCo WorldGroup (Lankhorst‐Euronete Portugal), Fundación Centro Tecnológico de Componentes ‐ CTC (Spain), and University of Exeter ‐ UoE (UK) as facility provider, focuses on obtaining knowledge of the applicability of Fibre Ropes in Marine Energy Converters ( MEC), both in laboratory and sea conditions.The work described in this publication has received support from MARINET, a EuRopean Community - Research Infrastructure Action under the FP7 “Capacities” Specific Programme

Vidar Ahjem - One of the best experts on this subject based on the ideXlab platform.

  • Best Practice for Analysis of Polyester Rope Mooring Systems
    Day 3 Wed May 03 2017, 2017
    Co-Authors: Erik Falkenberg, Vidar Ahjem, Limin Yang
    Abstract:

    The objective of the SyRope JIP has been to improve the methods for safe and reliable design of Fibre Rope mooring systems. Normal, conservative, design practice for polyester Rope mooring systems is to use an upper and a lower bound axial stiffness of the polyester. The use of a more advanced, but still manageable design practice allows for a more optimized design. Only polyester lines have been covered by the work, but the principles are assumed to have a general validity. Extensive testing on change-in-length behavior has been performed on subRopes. Testing has covered recommended test procedures from different standards and recommended practices and more realistic load sequences. Based on test results a conceptual model for the behavior of polyester Ropes has been developed. The mean length of a Rope depends on the preceding highest mean tension in the Rope and the actual tension, including its mean value. The response to wave-frequency and low-frequency loads is described by a dynamic stiffness which increases with the mean load in the line. Recommended change-in-length testing of subRopes is described, and principles for analysis of such tests for identification of parameters in the model are presented. Finally, guidance for use of the model in mooring system analyses is given.

  • GLOBAL PERFORMANCE OF SYNTHETIC Rope MOORING SYSTEMS – FREQUENCY DOMAIN ANALYSIS
    2015
    Co-Authors: Erik Falkenberg, Vidar Ahjem, Kjell Larsen, Karl E. Kaasen
    Abstract:

    For deep and ultra-deepwater applications, synthetic Fibre Ropes are considered an enabling technology due to their higher strength-to-weight ratio as compared to steel wire Ropes and chains and due to their superior station-keeping performance. The advantages of synthetic Fibre Rope mooring systems include: • A higher floater payload and reduction in structural costs due to lower vertical load from mooring lines. • A reduction in vessel offsets and associated riser loads due to taut mooring system. • A potential reduction in installation costs due to lighter installation and handling equipment. • Superior endurance under cyclic loading compared to steel moorings

  • Global Performance of Synthetic Rope Mooring Systems: Frequency Domain Analysis
    Volume 1: Offshore Technology; Polar and Arctic Sciences and Technology, 2011
    Co-Authors: Erik Falkenberg, Vidar Ahjem, Kjell Larsen, Halvor Lie, Karl E. Kaasen
    Abstract:

    For deep and ultra-deepwater applications, synthetic Fibre Ropes are considered an enabling technology due to their higher strength-to-weight ratio as compared to steel wire Ropes and chains and due to their superior station-keeping performance. The advantages of synthetic Fibre Rope mooring systems include: • A higher floater payload and reduction in structural costs due to lower vertical load from mooring lines. • A reduction in vessel offsets and associated riser loads due to taut mooring system. • A potential reduction in installation costs due to lighter installation and handling equipment. • Superior endurance under cyclic loading compared to steel moorings. Synthetic Fibre Ropes have visco-elastic stiffness and stretch characteristics. The change-in-length response of a Fibre Rope is non-linear, load-path dependent (different unload-reload stiffness), and the length varies with the rate and duration of loading (due to elongation and contraction). The commonly accepted analysis approach is a simplification where a lower-bound and an upper-bound stiffness is used. This practice is primarily based on two factors: 1. The industry at large does not at present have a common, well-defined understanding of Fibre-Rope change-in-length performance. 2. There is a lack of commercially available mooring analysis programs with the capability to simulate the non-linear change-in-length response of the synthetic Fibre Rope. Individual designers may however have more advanced analysis procedures, but these are not commonly accepted yet. This paper presents results from the SyRope pilot study, Ref. /5/ and /6/, which has used Rope testing to determine the characteristics of the elements in the spring-dashpot model. On this basis a strategy for software implementation in the frequency-domain has been proposed. A case study was performed for a semi-submersible production unit in deep water and harsh environment. The paper focuses on the differences between a commonly accepted, hereafter called traditional analysis approach and the proposed new frequency domain approach. The results show that there are large differences in extreme tensions and offsets as well as fatigue results. Hence, the new approach is considered to represent a significant improvement.Copyright © 2011 by ASME

Jacquemin F. - One of the best experts on this subject based on the ideXlab platform.

  • Tension fatigue failure prediction for HMPE Fibre Ropes
    2018
    Co-Authors: Humeau C., Davies P., Smeets P., Engels T.a.p., Govaert L.e., Vlasblom M., Jacquemin F.
    Abstract:

    In order to predict the lifetime of Fibre Rope mooring lines it is essential to be able to predict their behaviour under tension fatigue. Creep failure is known to be a major contributor to fatigue in synthetic Fibres and models to predict creep failure are well-established. We show that expansion of such models to varying loading conditions allows the prediction of the fatigue performance. However, it is difficult to design tests to quantify the fatigue performance for HMPE Ropes since often premature failure occurs due to external abrasion and viscous heating due to too high testing frequencies or amplitudes. This paper presents a testing methodology which allows tensile fatigue lifetime to be evaluated by testing at higher temperature to avoid premature abrasion failure. We also show that when the temperature evolution due to viscous heating is pRoperly accounted for the modelling framework presented can be effectively used to describe the premature failure occurring due to this heating effect. Results from tests on yarns and small Ropes are presented, and a predictive model for Rope fatigue lifetime has been validated

  • Tension fatigue failure prediction for HMPE Fibre Ropes
    'Elsevier BV', 2018
    Co-Authors: Humeau C., Smeets P., Vlasblom M., Davies, Pl Laurie, Engels, Tap Tom, Govaert, Le Leon, Jacquemin F.
    Abstract:

    \u3cp\u3eIn order to predict the lifetime of Fibre Rope mooring lines it is essential to be able to predict their behaviour under tension fatigue. Creep failure is known to be a major contributor to fatigue in synthetic Fibres and models to predict creep failure are well-established. We show that expansion of such models to varying loading conditions allows the prediction of the fatigue performance. However, it is difficult to design tests to quantify the fatigue performance for HMPE Ropes since often premature failure occurs due to external abrasion and viscous heating due to too high testing frequencies or amplitudes. This paper presents a testing methodology which allows tensile fatigue lifetime to be evaluated by testing at higher temperature to avoid premature abrasion failure. We also show that when the temperature evolution due to viscous heating is pRoperly accounted for the modelling framework presented can be effectively used to describe the premature failure occurring due to this heating effect. Results from tests on yarns and small Ropes are presented, and a predictive model for Rope fatigue lifetime has been validated.\u3c/p\u3