Load effects from breaking waves on offshore structures may be a driving point for the design. It is hence important to assess the likelihood of occurrence along the magnitude of the loads in the event of an impact. Traditionally, loads are predicted using wave theory combined with a load model such as the Morison. This paper features an alternative approach in determining the loads from wave breaking. It is demonstrated how the structural response can be used for (indirectly) estimating the magnitude of the loads caused by wave breaking. The theory is applied to an experimental setup in a wave flume, where a flexible model is subjected to loads from breaking waves. The dynamic properties are mapped using operational modal analysis and it is consequently shown that the loads can be identified using the vibration measurements.
{"title":"Estimating Loads From Breaking Waves Using Operational Modal Analysis","authors":"M. Vigsø, C. Georgakis","doi":"10.1115/omae2020-19170","DOIUrl":"https://doi.org/10.1115/omae2020-19170","url":null,"abstract":"\u0000 Load effects from breaking waves on offshore structures may be a driving point for the design. It is hence important to assess the likelihood of occurrence along the magnitude of the loads in the event of an impact. Traditionally, loads are predicted using wave theory combined with a load model such as the Morison. This paper features an alternative approach in determining the loads from wave breaking. It is demonstrated how the structural response can be used for (indirectly) estimating the magnitude of the loads caused by wave breaking. The theory is applied to an experimental setup in a wave flume, where a flexible model is subjected to loads from breaking waves. The dynamic properties are mapped using operational modal analysis and it is consequently shown that the loads can be identified using the vibration measurements.","PeriodicalId":297013,"journal":{"name":"Volume 2A: Structures, Safety, and Reliability","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125539400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ricardo Soares Gomes Junior, P. Videiro, P. Esperança, L. Sagrilo
This paper presents a procedure for reliability analysis of mooring lines of floating units for oil and gas production considering corrosion and material degradation over time. The proposed procedure is limited to the ultimate limit state (ULS) and considers mooring lines made up of chain and polyester rope segments, although the same methodology can be applied to cases with steel wire segments. The proposed procedure can also be applied for mooring lines connected to any other type of floating offshore structure. For reliability assessments, it is necessary to consider the distributions and the probabilistic aspects of the random variables involved in the process. The weakest link system is used to model the strength of a mooring line segment. Simplified time-dependent probabilistic models for chain corrosion and polyester degradation are adopted to predict the strength degradation over time. The annual failure probability for different years is estimated by approximating the degraded strength by a piecewise constant model in order to perform a time variant reliability analysis. Monte Carlo simulations are used to determine the failure probability. A study case is also presented, where annual extreme top tension is obtained from long-term statistics considering Brazilian offshore environmental conditions acting on a turret moored floating, production, storage and offloading unit (FPSO).
{"title":"Reliability Analysis of Mooring Lines of Floating Structures Under Corrosion and Material Degradation","authors":"Ricardo Soares Gomes Junior, P. Videiro, P. Esperança, L. Sagrilo","doi":"10.1115/omae2020-18306","DOIUrl":"https://doi.org/10.1115/omae2020-18306","url":null,"abstract":"\u0000 This paper presents a procedure for reliability analysis of mooring lines of floating units for oil and gas production considering corrosion and material degradation over time. The proposed procedure is limited to the ultimate limit state (ULS) and considers mooring lines made up of chain and polyester rope segments, although the same methodology can be applied to cases with steel wire segments. The proposed procedure can also be applied for mooring lines connected to any other type of floating offshore structure.\u0000 For reliability assessments, it is necessary to consider the distributions and the probabilistic aspects of the random variables involved in the process. The weakest link system is used to model the strength of a mooring line segment. Simplified time-dependent probabilistic models for chain corrosion and polyester degradation are adopted to predict the strength degradation over time. The annual failure probability for different years is estimated by approximating the degraded strength by a piecewise constant model in order to perform a time variant reliability analysis. Monte Carlo simulations are used to determine the failure probability.\u0000 A study case is also presented, where annual extreme top tension is obtained from long-term statistics considering Brazilian offshore environmental conditions acting on a turret moored floating, production, storage and offloading unit (FPSO).","PeriodicalId":297013,"journal":{"name":"Volume 2A: Structures, Safety, and Reliability","volume":"264 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130514201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An improved understanding of the present and future marine climatology is necessary for numerous activities, such as operation of offshore structures, optimization of ship routes and the evaluation of wave energy resources. To produce global wave information, the WW3 wave model was forced with wind and ice-cover data from an RCP8.5 EC-Earth system integration for two 30-year time slices. The first covering the periods from 1980 to 2009 represents the present climate and the second, covering the periods from 2070–2099, represents the climate in the end of the 21st century. Descriptive statistics of wind and wave parameters are obtained for different 30-year time slices. Regarding wind, magnitude and direction will be used. For wave, significant wave height (of total sea and swell), mean wave period, peak period, mean wave direction and energy will be investigated. Changes from present to future climate are evaluated, regarding both mean and extreme events. Maps of the theses statistics are presented. The long-term monthly joint distribution of significant wave heights and peak periods is generated. Changes from present to future climate are assessed, comparing the statistics between time slices.
{"title":"Assessing Climate Change in the North Atlantic Wave Regimes","authors":"M. Bernardino, M. Gonçalves, Carlos Soares","doi":"10.1115/omae2020-18697","DOIUrl":"https://doi.org/10.1115/omae2020-18697","url":null,"abstract":"\u0000 An improved understanding of the present and future marine climatology is necessary for numerous activities, such as operation of offshore structures, optimization of ship routes and the evaluation of wave energy resources.\u0000 To produce global wave information, the WW3 wave model was forced with wind and ice-cover data from an RCP8.5 EC-Earth system integration for two 30-year time slices. The first covering the periods from 1980 to 2009 represents the present climate and the second, covering the periods from 2070–2099, represents the climate in the end of the 21st century.\u0000 Descriptive statistics of wind and wave parameters are obtained for different 30-year time slices. Regarding wind, magnitude and direction will be used. For wave, significant wave height (of total sea and swell), mean wave period, peak period, mean wave direction and energy will be investigated. Changes from present to future climate are evaluated, regarding both mean and extreme events. Maps of the theses statistics are presented.\u0000 The long-term monthly joint distribution of significant wave heights and peak periods is generated. Changes from present to future climate are assessed, comparing the statistics between time slices.","PeriodicalId":297013,"journal":{"name":"Volume 2A: Structures, Safety, and Reliability","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131899370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The fatigue strength of thin-walled structures can be reduced significantly by non-linear secondary bending effects resulting from geometrical imperfections such as axial and angular misalignments. The welding-induced distortions can cause a critical increase of the structural hot-spot stress in the vicinity of the weld. Traditionally, the classification society rules for the fatigue strength assessment of welded ship structures suggest an analytical formula for a stress magnification factor km for axial and angular misalignment under axial loading condition. Recently, the well-known analytical solution for the angular misalignment has been extended to account for the curvature effect. The present paper analyses the effect of non-ideal, intermediate boundary conditions between fixed and pinned ends. In this regard, the fixity factors ρ (with 0 ≤ ρ ≤ 1 from ideally pinned to clamped conditions) are introduced in order to model the actual constraint on the rotation close to the ends. Under tension, a non-negligible decrease of the km factor is observed in relation to the reduction of the fixity factor at the welded end, while the fixity factor related to the loaded end has a minor effect on the km factor. Under compression, the reduction of the beam end fixity factors results into lower buckling resistance.
{"title":"A Stress Magnification Factor for Plates With Welding-Induced Curvatures","authors":"Federica Mancini, H. Remes, J. Romanoff","doi":"10.1115/omae2020-18094","DOIUrl":"https://doi.org/10.1115/omae2020-18094","url":null,"abstract":"\u0000 The fatigue strength of thin-walled structures can be reduced significantly by non-linear secondary bending effects resulting from geometrical imperfections such as axial and angular misalignments. The welding-induced distortions can cause a critical increase of the structural hot-spot stress in the vicinity of the weld. Traditionally, the classification society rules for the fatigue strength assessment of welded ship structures suggest an analytical formula for a stress magnification factor km for axial and angular misalignment under axial loading condition. Recently, the well-known analytical solution for the angular misalignment has been extended to account for the curvature effect. The present paper analyses the effect of non-ideal, intermediate boundary conditions between fixed and pinned ends. In this regard, the fixity factors ρ (with 0 ≤ ρ ≤ 1 from ideally pinned to clamped conditions) are introduced in order to model the actual constraint on the rotation close to the ends. Under tension, a non-negligible decrease of the km factor is observed in relation to the reduction of the fixity factor at the welded end, while the fixity factor related to the loaded end has a minor effect on the km factor. Under compression, the reduction of the beam end fixity factors results into lower buckling resistance.","PeriodicalId":297013,"journal":{"name":"Volume 2A: Structures, Safety, and Reliability","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131047299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Tang, Ray-Yeng Yang, Tzu-Chieh Wen, P. Yeh, Chai-Cheng Huang
Up to date, the mooring system failure of aquaculture net cage remains a continuing problem, especially the domino effect, which often leads to huge economic losses. Thus, this study aims to investigate the domino effect of a mooring system of a net cage under waves and currents. In this study, a time-domain numerical model based on the Morison equation and the lumped mass method is applied. A full-scale net cage system widely used in a local sea area is adopted. A 50 years return period waves with a strong following current is considered to be the design condition. It can be expected that the tension on the remaining upstream anchor increases dramatically when an upstream anchor is lost. Then, the domino effect occurs if the maximum tension on the remaining anchor exceeds its design condition. Therefore, in this simulation, the initial failure is considered to be a man-made event at a preset time, but the rest failures are resulted from exceeding the breaking strength of a rope. Both the current-only condition and the wave-current condition have been examined. The results including mooring line tension, volume reduction coefficient and rigid body motion are discussed. In addition, the results show that the failure sequence of anchor is different between the current-only condition and the wave-current condition.
{"title":"Numerical Simulation of the Domino Effect of Mooring System Failure for an Aquaculture Net Cage Under Waves and Currents","authors":"H. Tang, Ray-Yeng Yang, Tzu-Chieh Wen, P. Yeh, Chai-Cheng Huang","doi":"10.1115/omae2020-18232","DOIUrl":"https://doi.org/10.1115/omae2020-18232","url":null,"abstract":"\u0000 Up to date, the mooring system failure of aquaculture net cage remains a continuing problem, especially the domino effect, which often leads to huge economic losses. Thus, this study aims to investigate the domino effect of a mooring system of a net cage under waves and currents. In this study, a time-domain numerical model based on the Morison equation and the lumped mass method is applied. A full-scale net cage system widely used in a local sea area is adopted. A 50 years return period waves with a strong following current is considered to be the design condition. It can be expected that the tension on the remaining upstream anchor increases dramatically when an upstream anchor is lost. Then, the domino effect occurs if the maximum tension on the remaining anchor exceeds its design condition. Therefore, in this simulation, the initial failure is considered to be a man-made event at a preset time, but the rest failures are resulted from exceeding the breaking strength of a rope. Both the current-only condition and the wave-current condition have been examined. The results including mooring line tension, volume reduction coefficient and rigid body motion are discussed. In addition, the results show that the failure sequence of anchor is different between the current-only condition and the wave-current condition.","PeriodicalId":297013,"journal":{"name":"Volume 2A: Structures, Safety, and Reliability","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125470570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Technology qualification (TQ) has been employed to perform assessments to verify whether a new technology performs within pre-specified functional limits after an application. If a best available technology (BAT) is used in a new environment, it is considered as a new technology. The TQ is vital in the implementation of best available technology (BAT) in a new environment. Risk based technology qualification provides an optimal approach for performing TQ of a BAT when it is necessary to implement in a new environment. This manuscript first demonstrates the standard TQ process. Secondly, it presents development of a risk matrix for failure mode identification and consequence risk ranking (FMI&CRR). Thirdly, it demonstrates the use of FMI&CRR in a risk-based technology qualification process. Finally, it presents use of the risk matrix to perform TQ on moorings solutions that have been selected as a BAT for a floating wind turbine sub-system. Fuzzy inference system has been used to assess the risk rank to minimize the variability that causes due to experts’ performance variability. Illustrative risk based TQ assessment has been performed and presented. The developed risk based TQ process (TQP), fuzzy inference system supported risk rank estimation, and illustrative risk based TQ recommendation are significantly important for practitioners while performing FMI&CRR in larger scale offshore floating wind turbines’ TQ projects.
{"title":"On the Necessity for Minimizing Risk Based Technology Qualification Variability: An Application to Offshore Floating Wind Turbines","authors":"S. Samarakoon, R. Ratnayake","doi":"10.1115/omae2020-18139","DOIUrl":"https://doi.org/10.1115/omae2020-18139","url":null,"abstract":"\u0000 Technology qualification (TQ) has been employed to perform assessments to verify whether a new technology performs within pre-specified functional limits after an application. If a best available technology (BAT) is used in a new environment, it is considered as a new technology. The TQ is vital in the implementation of best available technology (BAT) in a new environment. Risk based technology qualification provides an optimal approach for performing TQ of a BAT when it is necessary to implement in a new environment. This manuscript first demonstrates the standard TQ process. Secondly, it presents development of a risk matrix for failure mode identification and consequence risk ranking (FMI&CRR). Thirdly, it demonstrates the use of FMI&CRR in a risk-based technology qualification process. Finally, it presents use of the risk matrix to perform TQ on moorings solutions that have been selected as a BAT for a floating wind turbine sub-system. Fuzzy inference system has been used to assess the risk rank to minimize the variability that causes due to experts’ performance variability. Illustrative risk based TQ assessment has been performed and presented. The developed risk based TQ process (TQP), fuzzy inference system supported risk rank estimation, and illustrative risk based TQ recommendation are significantly important for practitioners while performing FMI&CRR in larger scale offshore floating wind turbines’ TQ projects.","PeriodicalId":297013,"journal":{"name":"Volume 2A: Structures, Safety, and Reliability","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133447489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Andreas F. Haselsteiner, A.F.M. Sander, J. Ohlendorf, K. Thoben
Applications such as the design of offshore wind turbines requires the estimation of the joint distribution of variables like wind speed, wave height and wave period. The joint distribution can then be used, for example, to define design load cases using the environmental contour method. Often the joint distribution is described using so-called global hierarchical models. In these models, one variable is taken as independent and the other variables are modelled to be conditional on this variable using particular dependence functions. In this paper, we propose to use dependence functions that offer physical interpretation. We define a novel dependence function that describes how the median of the zero-up-crossing period increases with significant wave height and a novel dependence function that describes how the median significant wave height increases with wind speed. These dependence functions allow us to reason about the physical meaning, even when we extrapolate outside the range of a given sample of environmental data. In addition, we can analyze the estimated parameters of the dependence function to speculate which kind of sea dominates at a given site. We fitted statistical models with the proposed dependence functions to six datasets and analyzed the estimated parameters. Then we calculated environmental contours based on these estimated joint distributions. The environmental contours had physically reasonable shapes, even at areas that were outside the datasets that were used to fit the underlying distributions.
{"title":"Global Hierarchical Models for Wind and Wave Contours: Physical Interpretations of the Dependence Functions","authors":"Andreas F. Haselsteiner, A.F.M. Sander, J. Ohlendorf, K. Thoben","doi":"10.1115/omae2020-18668","DOIUrl":"https://doi.org/10.1115/omae2020-18668","url":null,"abstract":"\u0000 Applications such as the design of offshore wind turbines requires the estimation of the joint distribution of variables like wind speed, wave height and wave period. The joint distribution can then be used, for example, to define design load cases using the environmental contour method. Often the joint distribution is described using so-called global hierarchical models. In these models, one variable is taken as independent and the other variables are modelled to be conditional on this variable using particular dependence functions. In this paper, we propose to use dependence functions that offer physical interpretation. We define a novel dependence function that describes how the median of the zero-up-crossing period increases with significant wave height and a novel dependence function that describes how the median significant wave height increases with wind speed. These dependence functions allow us to reason about the physical meaning, even when we extrapolate outside the range of a given sample of environmental data. In addition, we can analyze the estimated parameters of the dependence function to speculate which kind of sea dominates at a given site. We fitted statistical models with the proposed dependence functions to six datasets and analyzed the estimated parameters. Then we calculated environmental contours based on these estimated joint distributions. The environmental contours had physically reasonable shapes, even at areas that were outside the datasets that were used to fit the underlying distributions.","PeriodicalId":297013,"journal":{"name":"Volume 2A: Structures, Safety, and Reliability","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123637286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Maturana, Victor Rafael Souza, Valentina Clavijo Mesa, M. Martins, A. Oshiro, A. Schleder
Currently, most offshore oil exploration operations are performed by Dynamically Positioned (DP) units; in Brazil, the use of these units is traditional in drilling operations (DP drilling rigs). The advent of DP systems, which allow the vessel to maintain a certain position without the need for anchor lines, has brought great flexibility to the oil field; however, usually in drilling areas, there are a large number of operations being performed simultaneously and subject to weather conditions and a failure of the DP system may cause these vessels to drift, which may occasionally result in a collision with other field equipment or vessels, causing material, personal and environmental damage. In this context, it is necessary to analyze what would be the best positioning points for these units according to the configuration of potential obstacles present in the area (such as risers, anchor systems and floating production systems), the characteristics of the DP unit and the expected environmental conditions. It is vital to know the risk of collision associated with the positioning of these units. The risk of collision will depend mainly on the meteo-oceanographic variables of the operating region, the hydrodynamic characteristics of the unit, the DP system reliability and its repair time, and the distribution of obstacles in the area. The objective of the ongoing research is the development of a methodology to define the risk associated with the positioning of the DP units, through a statistical method and a validated drift mathematical model under the influence of environmental agents. The proposed methodology allows us to demonstrate compliance with a widely accepted RAC (Risk Acceptance Criterion). The developed methodology proposes the use of two instruments: Location Iso-Probability Maps (MIL) and Operational Iso-Risk Maps (MIRO), to synthesize the information to the decision making about the operation of the DP units at a specific location, considering the overall collision risk (at MIRO) and the probability of the rig being at a specific location (at MIL).
{"title":"MIL and MIRO Diagrams for Risk-Based Positioning of Drilling Rigs With Dynamic Positioning System","authors":"M. Maturana, Victor Rafael Souza, Valentina Clavijo Mesa, M. Martins, A. Oshiro, A. Schleder","doi":"10.1115/omae2020-18834","DOIUrl":"https://doi.org/10.1115/omae2020-18834","url":null,"abstract":"Currently, most offshore oil exploration operations are performed by Dynamically Positioned (DP) units; in Brazil, the use of these units is traditional in drilling operations (DP drilling rigs). The advent of DP systems, which allow the vessel to maintain a certain position without the need for anchor lines, has brought great flexibility to the oil field; however, usually in drilling areas, there are a large number of operations being performed simultaneously and subject to weather conditions and a failure of the DP system may cause these vessels to drift, which may occasionally result in a collision with other field equipment or vessels, causing material, personal and environmental damage. In this context, it is necessary to analyze what would be the best positioning points for these units according to the configuration of potential obstacles present in the area (such as risers, anchor systems and floating production systems), the characteristics of the DP unit and the expected environmental conditions. It is vital to know the risk of collision associated with the positioning of these units. The risk of collision will depend mainly on the meteo-oceanographic variables of the operating region, the hydrodynamic characteristics of the unit, the DP system reliability and its repair time, and the distribution of obstacles in the area. The objective of the ongoing research is the development of a methodology to define the risk associated with the positioning of the DP units, through a statistical method and a validated drift mathematical model under the influence of environmental agents. The proposed methodology allows us to demonstrate compliance with a widely accepted RAC (Risk Acceptance Criterion). The developed methodology proposes the use of two instruments: Location Iso-Probability Maps (MIL) and Operational Iso-Risk Maps (MIRO), to synthesize the information to the decision making about the operation of the DP units at a specific location, considering the overall collision risk (at MIRO) and the probability of the rig being at a specific location (at MIL).","PeriodicalId":297013,"journal":{"name":"Volume 2A: Structures, Safety, and Reliability","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121226927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Taeyoon Park, Jeon Junhwan, Kim Jung, Sangbae Jeon, Bongjae Kim, Dongyeon Lee
In this paper, a pile mooring system is introduced as an alternative mooring solution for FSRU. Also, the methodologies of mooring analysis and structural analysis to verify a design of pile mooring system are introduced. The mooring performance of pile mooring system can be assessed by coupled mooring analysis considering stiffness of pile, resistance of soil and hull interface mechanism. The structural integrity of pile, foundation and hull interface can be assessed by non-linear contact finite element analysis. Using these methods, the basic design of pile mooring system for 160,000-CBM large scale FSRU is developed considering practical environmental conditions.
{"title":"Development of a Pile Mooring System for Large Scale FSRUs","authors":"Taeyoon Park, Jeon Junhwan, Kim Jung, Sangbae Jeon, Bongjae Kim, Dongyeon Lee","doi":"10.1115/omae2020-19179","DOIUrl":"https://doi.org/10.1115/omae2020-19179","url":null,"abstract":"\u0000 In this paper, a pile mooring system is introduced as an alternative mooring solution for FSRU. Also, the methodologies of mooring analysis and structural analysis to verify a design of pile mooring system are introduced. The mooring performance of pile mooring system can be assessed by coupled mooring analysis considering stiffness of pile, resistance of soil and hull interface mechanism. The structural integrity of pile, foundation and hull interface can be assessed by non-linear contact finite element analysis. Using these methods, the basic design of pile mooring system for 160,000-CBM large scale FSRU is developed considering practical environmental conditions.","PeriodicalId":297013,"journal":{"name":"Volume 2A: Structures, Safety, and Reliability","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126581114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shock waves from underwater and air explosions are significant threats to surface and underwater vehicles and structures. Recent studies on the mechanical and thermal properties of various phase-separated elastomers indicate the possibility of applying these materials as a coating to mitigate shock-induced structural failures. To demonstrate this approach and investigate its efficacy, this paper presents a fluid-structure coupled computational model capable of predicting the dynamic response of air-backed bilayer (i.e. elastomer coating – metal substrate) structures submerged in water to hydrostatic and underwater explosion loads. The model couples a three-dimensional multiphase finite volume computational fluid dynamics model with a nonlinear finite element computational solid dynamics model using the FIVER (FInite Volume method with Exact multi-material Riemann solvers) method. The kinematic boundary condition at the fluid-structure interface is enforced using an embedded boundary method that is capable of handling large structural deformation and topological changes. The dynamic interface condition is enforced by formulating and solving local, one-dimensional fluid-solid Riemann problems, which is well-suited for transferring shock and impulsive loads. The capability of this computational model is demonstrated through a numerical investigation of hydrostatic and shock-induced collapse of aluminum tubes with polyurea coating on its inner surface. The thickness of the structure is resolved explicitly by the finite element mesh. The nonlinear material behavior of polyurea is accounted for using a hyper-viscoelastic constitutive model featuring a modified Mooney-Rivlin equation and a stress relaxation function in the form of prony series. Three numerical experiments are conducted to simulate and compare the collapse of the structure in different loading conditions, including a constant pressure, a fluid environment initially in hydrostatic equilibrium, and a two-phase fluid flow created by a near-field underwater explosion.
水下和空中爆炸产生的冲击波对水面和水下交通工具和结构构成重大威胁。最近对各种相分离弹性体的力学和热性能的研究表明，应用这些材料作为涂层来减轻冲击引起的结构破坏的可能性。为了证明这种方法并研究其有效性，本文提出了一种流固耦合计算模型，该模型能够预测空气支撑双层结构(即弹性体涂层-金属衬底)在水中对静水和水下爆炸载荷的动态响应。该模型采用FIVER (finite volume method with Exact multi-material Riemann solvers)方法将三维多相有限体积计算流体力学模型与非线性有限元计算固体动力学模型耦合在一起。采用能够处理大的结构变形和拓扑变化的嵌入式边界方法来实现流固界面的运动边界条件。动态界面条件是通过建立和求解局部一维流固Riemann问题来实现的，该问题非常适合于传递冲击和脉冲载荷。通过对内表面涂覆聚脲的铝管的静水压和激波破坏的数值研究，验证了该计算模型的有效性。结构的厚度由有限元网格显式求解。采用修正的Mooney-Rivlin方程和prony级数形式的应力松弛函数的超粘弹性本构模型来解释聚脲的非线性材料行为。通过三个数值实验，模拟和比较了结构在恒压、初始静水平衡流体环境和近场水下爆炸形成的两相流体流动等不同加载条件下的倒塌过程。
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