Analyzed are the merits and demerits of catenary mooring system and taut mooring system, which are commonly used nowadays. As falling somewhere between these two systems, a new mooring system integrating catenary with...Analyzed are the merits and demerits of catenary mooring system and taut mooring system, which are commonly used nowadays. As falling somewhere between these two systems, a new mooring system integrating catenary with taut mooring is proposed. In order to expound and prove the advantages of this new system, the motion performance of a semi-submersible platform is simulated by employing full time domain coupled analysis method. A comparison of the result of new mooting system with that of taut mooring system shows that the movement of the platform using the new type mooting system is smaller than that using the taut mooring system, which ensures a better working condition. Furthermore, the new mooring system is also compatible with the characteristics of catenary mooting system, which eliminates the requirement of anti-uplift capacity of the anchors.展开更多
Precisely predicting the fatigue life of taut-wire mooring systems has become an interesting and important problem for scientists and engineers since there are still difficulties in the inspection and maintenance of m...Precisely predicting the fatigue life of taut-wire mooring systems has become an interesting and important problem for scientists and engineers since there are still difficulties in the inspection and maintenance of mooring lines in a rough sea environment especially in deep waters. In this paper, a comprehensive fatigue analysis is performed for a polyester taut-wire mooring system of an FPSO based on the time domain dynamic theory, rainflow cycle counting method and linear damage accumulation rule of Palmgren-Miner. Three influential factors in the fatigue analysis including the pre-tension, dynamic stiffness and T-N curve are investigated in detail. Two polyester T-N curves, one is from the DNV- 0S-E301 and the other is from the API-RP-2SM, are adopted in the calculation. The fatigue analysis of the mooting system after one-line failure is also carried out. The calculation results indicate that the fatigue life is significantly affected by the T-N curve. The fatigue life decreases with increasing pre-tension, and is largely reduced if taking into account the dynamic stiffness caused by cyclic loading. The analysis also proves that one-line failure has remarkable effects on the fatigue lives of other mooting lines. The present parametric and comparative study is believed to be meaningful to further understanding of the taut-wire mooting system for deepwater applications.展开更多
Mooring system failure can lead to largely different dynamic response of floating structures when compared to the response under the condition of intact mooring system.For a semi-submersible platform with taut mooring...Mooring system failure can lead to largely different dynamic response of floating structures when compared to the response under the condition of intact mooring system.For a semi-submersible platform with taut mooring system under extreme environmental conditions,the typical mooring system failure includes anchor line breaking failure due to the broken anchor line,and the anchor dragging failure caused by the anchor failure in the seabed soil due to the shortage of the anchor bearing capacity.However,study on the mooring failure caused by anchor failure is rare.The current work investigates the effect of three failure modes of taut mooring system on dynamic response of a semi-submersible platform,including one line breaking failure,two lines breaking failure,and one line breaking with one line attached anchor dragging failure.The nonlinear polynomial mooring line model in AQWA was used with integrating the load and displacement curve from the anchor pulling study to characterize the anchor dragging behavior for mooring system failure caused by the anchor failure.The offsets of the platform and the tension of mooring lines were analyzed for mooring system failure with 100-year return period.It is found that the mooring failure of one line breaking with one line attached anchor dragging is a case between the other two mooring failures.The traditional mooring analysis considering only the damaged condition with one line breaking is not safe enough.And the simple way of mooring analysis of two lines breaking is too conservative for the costly offshore engineering.展开更多
The taut mooring system using synthetic fiber ropes has overcome the shortcomings such as the large self-weight of the mooring lines and provides better mooring performance for the floating structures.The polyester ro...The taut mooring system using synthetic fiber ropes has overcome the shortcomings such as the large self-weight of the mooring lines and provides better mooring performance for the floating structures.The polyester rope has attracted much attention among numerous synthetic fiber rope materials due to its lightweight,low price,corrosion resistance,and high strength.Thus,the mooring characteristics of it are worth studying.Polyester mooring lines are flexible in deep water,when a marine structure is moored by them,the geometric nonlinearity such as large displacement,large stretch,and large bending deformation,and the material nonlinearity like viscoelastic of the polyester ropes become complex integrated problems to be studied.Considering the nonlinear phenomenon,the simulation and calculation of a polyester line were carried out by the absolute nodal coordinate formulation(ANCF)in this paper since the ANCF method has advantages in dealing with the significant deformation problems of the flexible structures.In addition,a chain mooring line was also simulated for comparison,and the results show that the polyester ropes reduce the self-weight of the mooring lines and provide sufficient mooring strength at the same time,and the nonlinear phenomenon of the polyester ropes is different from that of the chain mooring lines.展开更多
Based on the theory of impact dynamics, the motion equations for a mooring line-floating body system before and after impact loading are established with consideration of the viscoelastic property of mooring lines. Th...Based on the theory of impact dynamics, the motion equations for a mooring line-floating body system before and after impact loading are established with consideration of the viscoelastic property of mooring lines. The factors that influence the taut-slack conditions of a mooring system are analyzed through classifying the taut-slack regions, which are defined by non-dimensional ratios of displacement, frequency, and damping of the system. The mooring system of Jip spar platform is analyzed, and the snap tension characteristics of mooring lines are given. The factors that influence the maximum tension in mooring lines, including the mass of the floating body, length of mooring lines, frequency and amplitude of external excitation, and pretension in mooting lines, are also analyzed through computing the dynamic response of system and parametric study. It is shown that the maximum tension increases with the increasing mass of the floating body, external excitation and pretension. Also, it is found that the influence of the non-dimensional ratio of damping increases with the increase of the pretension in mooring lines.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 51079065)the Science and Technology Support Project Plan of Jiangsu Province (Grant No. BE2010159)A Project Funded by Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Analyzed are the merits and demerits of catenary mooring system and taut mooring system, which are commonly used nowadays. As falling somewhere between these two systems, a new mooring system integrating catenary with taut mooring is proposed. In order to expound and prove the advantages of this new system, the motion performance of a semi-submersible platform is simulated by employing full time domain coupled analysis method. A comparison of the result of new mooting system with that of taut mooring system shows that the movement of the platform using the new type mooting system is smaller than that using the taut mooring system, which ensures a better working condition. Furthermore, the new mooring system is also compatible with the characteristics of catenary mooting system, which eliminates the requirement of anti-uplift capacity of the anchors.
基金supported by the Key Project of the National Natural Science Foundation of China (Grant No. 50639030)the National High Technology Research and Development Program of China (863 Program, Grant No. 2006AA09Z348)
文摘Precisely predicting the fatigue life of taut-wire mooring systems has become an interesting and important problem for scientists and engineers since there are still difficulties in the inspection and maintenance of mooring lines in a rough sea environment especially in deep waters. In this paper, a comprehensive fatigue analysis is performed for a polyester taut-wire mooring system of an FPSO based on the time domain dynamic theory, rainflow cycle counting method and linear damage accumulation rule of Palmgren-Miner. Three influential factors in the fatigue analysis including the pre-tension, dynamic stiffness and T-N curve are investigated in detail. Two polyester T-N curves, one is from the DNV- 0S-E301 and the other is from the API-RP-2SM, are adopted in the calculation. The fatigue analysis of the mooting system after one-line failure is also carried out. The calculation results indicate that the fatigue life is significantly affected by the T-N curve. The fatigue life decreases with increasing pre-tension, and is largely reduced if taking into account the dynamic stiffness caused by cyclic loading. The analysis also proves that one-line failure has remarkable effects on the fatigue lives of other mooting lines. The present parametric and comparative study is believed to be meaningful to further understanding of the taut-wire mooting system for deepwater applications.
基金financially supported by the National Natural Science Foundation of China(Grant No.51809165).
文摘Mooring system failure can lead to largely different dynamic response of floating structures when compared to the response under the condition of intact mooring system.For a semi-submersible platform with taut mooring system under extreme environmental conditions,the typical mooring system failure includes anchor line breaking failure due to the broken anchor line,and the anchor dragging failure caused by the anchor failure in the seabed soil due to the shortage of the anchor bearing capacity.However,study on the mooring failure caused by anchor failure is rare.The current work investigates the effect of three failure modes of taut mooring system on dynamic response of a semi-submersible platform,including one line breaking failure,two lines breaking failure,and one line breaking with one line attached anchor dragging failure.The nonlinear polynomial mooring line model in AQWA was used with integrating the load and displacement curve from the anchor pulling study to characterize the anchor dragging behavior for mooring system failure caused by the anchor failure.The offsets of the platform and the tension of mooring lines were analyzed for mooring system failure with 100-year return period.It is found that the mooring failure of one line breaking with one line attached anchor dragging is a case between the other two mooring failures.The traditional mooring analysis considering only the damaged condition with one line breaking is not safe enough.And the simple way of mooring analysis of two lines breaking is too conservative for the costly offshore engineering.
基金Supported by the Specialized Research Project for LS17-2 Semi-submersible Production Platform(LSZX-2020-HN-05-0405).
文摘The taut mooring system using synthetic fiber ropes has overcome the shortcomings such as the large self-weight of the mooring lines and provides better mooring performance for the floating structures.The polyester rope has attracted much attention among numerous synthetic fiber rope materials due to its lightweight,low price,corrosion resistance,and high strength.Thus,the mooring characteristics of it are worth studying.Polyester mooring lines are flexible in deep water,when a marine structure is moored by them,the geometric nonlinearity such as large displacement,large stretch,and large bending deformation,and the material nonlinearity like viscoelastic of the polyester ropes become complex integrated problems to be studied.Considering the nonlinear phenomenon,the simulation and calculation of a polyester line were carried out by the absolute nodal coordinate formulation(ANCF)in this paper since the ANCF method has advantages in dealing with the significant deformation problems of the flexible structures.In addition,a chain mooring line was also simulated for comparison,and the results show that the polyester ropes reduce the self-weight of the mooring lines and provide sufficient mooring strength at the same time,and the nonlinear phenomenon of the polyester ropes is different from that of the chain mooring lines.
基金supported by the National Natural Science Foundation of China (Grant Nos .50679051 and 50639030) the National High Technology Research and Development Program of China (863 Program, Grant No.2007AA09Z304)
文摘Based on the theory of impact dynamics, the motion equations for a mooring line-floating body system before and after impact loading are established with consideration of the viscoelastic property of mooring lines. The factors that influence the taut-slack conditions of a mooring system are analyzed through classifying the taut-slack regions, which are defined by non-dimensional ratios of displacement, frequency, and damping of the system. The mooring system of Jip spar platform is analyzed, and the snap tension characteristics of mooring lines are given. The factors that influence the maximum tension in mooring lines, including the mass of the floating body, length of mooring lines, frequency and amplitude of external excitation, and pretension in mooting lines, are also analyzed through computing the dynamic response of system and parametric study. It is shown that the maximum tension increases with the increasing mass of the floating body, external excitation and pretension. Also, it is found that the influence of the non-dimensional ratio of damping increases with the increase of the pretension in mooring lines.
