Important challenges must be addressed to make wind turbines sustainable renewable energy sources.A typical problem concerns the design of the foundation.If the pile diameter is larger than that of the jacket platform...Important challenges must be addressed to make wind turbines sustainable renewable energy sources.A typical problem concerns the design of the foundation.If the pile diameter is larger than that of the jacket platform,traditional mechanical models cannot be used.In this study,relying on the seabed soil data of an offshore wind farm,the m-method and the equivalent embedded method are used to address the single-pile wind turbine foundation problem for different pile diameters.An approach to determine the equivalent pile length is also proposed accordingly.The results provide evidence for the effectiveness and reliability of the model based on the equivalent embedded method.展开更多
The dynamic responses of offshore fixed platforms under ice loads are analysed in this paper. The responses calculated include the displacement and the hot spot stresses on the basis of a dynamic equation of ice-induc...The dynamic responses of offshore fixed platforms under ice loads are analysed in this paper. The responses calculated include the displacement and the hot spot stresses on the basis of a dynamic equation of ice-induced forced vibration for offshore structures. The results obtained can be cited and used for the design and operation of offshore fixed platforms against ice loading.展开更多
The problems of ice-induced vibration have been noticed and concerned since the 1960s, but it has not been well resolved. One reason is that the dynamic interaction between ice and structure is so complicated that pra...The problems of ice-induced vibration have been noticed and concerned since the 1960s, but it has not been well resolved. One reason is that the dynamic interaction between ice and structure is so complicated that practical ice force model has not been developed. The recent full-scale tests conducted on jacket platforms in the Bohai Sea presented that ice could cause intense vibrations which endanger the facilities on the deck and make discomfort for the crew. In this paper, the strategy of mitigation of ice-induced offshore structure vibration is discussed. Based on field observations and understanding of the interaction between ice and structure, the absorption mitigation method to suppress ice-induced vibration is presented. The numerical simulations were conducted for a simplified model of platform attached with a Tuned Mass Danlper （TMD） under ice force function and ice force time history. The simulation results show that TMD can fa- vorably reduce ice-induced vibrations, therefore, it can be considered to be an alternative approach to utilize. Finally, the application possibilities of utilizing TMDs on other miniature offshore structures in ice-covered areas of marginal oil fields are discussed.展开更多
In this paper,we established the equation of motion of a platform structure with four legs by way of Hamilton' s Principle and obtained the nonlinear dynamical model of platform struc...In this paper,we established the equation of motion of a platform structure with four legs by way of Hamilton' s Principle and obtained the nonlinear dynamical model of platform structures. By using Laplace transformation we obtain the mode shapes of the system. The nonlinear model of the platform structure in this paper provded an accurate way of analysis for the engineering prediction of the dynamical characteristics of the platform and the understanding of its vibrational mechanism.展开更多
This paper deals with several hot topics in ice related problems. In recent years, advances have been made on ice breaking modes, dynamic ice loads on offshore structures, ice-induced structural vibrations, Fatigue an...This paper deals with several hot topics in ice related problems. In recent years, advances have been made on ice breaking modes, dynamic ice loads on offshore structures, ice-induced structural vibrations, Fatigue and fracture by ice-structure interaction, and design of jackets in the Bohai Gulf.展开更多
A series of tests of a full-scale river icebreaker was conducted to investigate the characteristics of ice-induced hull vibration.The test was conducted when the river icebreaker was operating in an ice-covered river ...A series of tests of a full-scale river icebreaker was conducted to investigate the characteristics of ice-induced hull vibration.The test was conducted when the river icebreaker was operating in an ice-covered river at temperatures of-4 to 0°C with ice thicknesses of 300 to 400 mm.In the tests,the ice condition and icebreaker speed were chosen as the main influence factors.By analyzing the measured test data,we identified some important points regarding ice-induced hull vibration.When the river icebreaker navigates in an area with complete ice coverage,the peak value of the acceleration amplitude spectrum is highest.Also,the vibration response excited by the icebreaking load in an area with complete ice coverage exhibits more frequencies.With an increase in icebreaker speed,the vibration acceleration response gradually increases.However,habitability of the bow region on the main and driving decks is maintained due to the harmless vibration levels.In addition,the icebreaking operation of the river icebreaker causes violent local vibration of the grillage on the main deck.展开更多
The sea ice is idealized as an elastic-brittle material. When an ice sheet moves toward a structure, the dynamic interaction between ice and the structure is analyzed by the DDA (Discontinuous Deformation Analysis) ap...The sea ice is idealized as an elastic-brittle material. When an ice sheet moves toward a structure, the dynamic interaction between ice and the structure is analyzed by the DDA (Discontinuous Deformation Analysis) approach, where the ice sheet and the structure, are considered as assemblages of blocky masses. This has the advantages that the whole process of collision between the ice and structure can be shown visually with a series of pictures. Meanwhile, the dynamic response of the structure at each time step after the bumping of the ice against the structure is calculated. And with the aid of inverse analysis developed by the authors, the time history of the resultant ice force exerting on the structure is evaluated. A numerical example shows that the proposed approach is suitable to the simulation of the ice-breaking process and reasonable result of ice force acting on the structure can be obtained.展开更多
Sea ice can attenuate wave energy significantly when waves propagate through ice covers.In this study,a third-generation wave model called simulating wave nearshore(SWAN)was advanced to include damping of wave energy ...Sea ice can attenuate wave energy significantly when waves propagate through ice covers.In this study,a third-generation wave model called simulating wave nearshore(SWAN)was advanced to include damping of wave energy due to friction in the boundary layer below the ice.With the addition of an eddy viscosity wave-ice model,the resulting new SWAN model was applied to simulate wave height in the Bohai Sea during the freezing winter.Its performance was validated with available buoy data near the ice edge,and the new model showed an improvement in accuracy because it considered the ice effect on waves.We then performed a wave hindcast for the Bohai Sea during a freezing period in the winter of 2016 that had the severest ice conditions in recent years and found that the mean significant wave height changed by approximately 16.52%.In the Liaodong Bay,where sea ice concentration is highest,the change reached 32.57%,compared with the most recent SWAN model version.The average influence of sea ice on wave height simulation was also evaluated over a five-year(2013-2017)hindcast during January and February.We found that the wave height decrease was more significant in storm conditions even the eddy viscosity wave-ice model itself showed no advantage on damping stronger waves.展开更多
Some problems concerning the ice forces and ice response spectra are studied from both theoretical and practical points of view. On the basis of structural analysis,the analysis method of ice response spectra is propo...Some problems concerning the ice forces and ice response spectra are studied from both theoretical and practical points of view. On the basis of structural analysis,the analysis method of ice response spectra is proposed, since it plays an important role in the prediction of maximum structural response in cold regions. And it is illustrated that it is easy to study the structural response to ice using the ice response spectra.展开更多
As the Arctic Channel continues to be developed,collisions between polar navigation vessels and sea ice are inevitable,which will directly affect structural safety and vibration comfort.However,the numerical analysis ...As the Arctic Channel continues to be developed,collisions between polar navigation vessels and sea ice are inevitable,which will directly affect structural safety and vibration comfort.However,the numerical analysis method of ship-ice collision-induced vibration is not perfect,and the effect of fluid coupling is not typically considered.In this paper,a simplified numerical analysis method for ship-ice collision-induced vibration is proposed,in which a reliable ice load is obtained by first performing ship-ice-water-air coupled collision calculations,followed by ship-ice-water coupled vibration calculations to obtain the vibration response of the structure.In addition,this paper investigates the full coupling method and the modeling ranges and meshing sizes involved in the analysis ship-ice collision-induced vibration,and the computational efficiencies of the traditional ALE algorithm and S-ALE algorithm are compared.The results indicate that the simplified simulation analysis method and gradient meshing model improve the calculation accuracy and efficiency in ship-ice collision and vibration response analysis.Moreover,the modeling range of the water and air models cannot be less than 6 times the ship width,2 times the ship length,and 1 times the ship depth,and the S-ALE algorithm saves 47.86%time compared to the ALE algorithm.The research results in this paper can provide a reference for the numerical simulation of ship-ice collision-induced vibration.展开更多
基金supported by the National Natural Science Foundation of China (52071055)the Fundamental Research Funds for the Central Universities (Grant No.DUT22QN237).
文摘Important challenges must be addressed to make wind turbines sustainable renewable energy sources.A typical problem concerns the design of the foundation.If the pile diameter is larger than that of the jacket platform,traditional mechanical models cannot be used.In this study,relying on the seabed soil data of an offshore wind farm,the m-method and the equivalent embedded method are used to address the single-pile wind turbine foundation problem for different pile diameters.An approach to determine the equivalent pile length is also proposed accordingly.The results provide evidence for the effectiveness and reliability of the model based on the equivalent embedded method.
文摘The dynamic responses of offshore fixed platforms under ice loads are analysed in this paper. The responses calculated include the displacement and the hot spot stresses on the basis of a dynamic equation of ice-induced forced vibration for offshore structures. The results obtained can be cited and used for the design and operation of offshore fixed platforms against ice loading.
基金the National High Technology Research and Development Program of China(863 Program,Grant No. 2001AA602015)the National Natural Science Foundation of China (Grant No.10672029)
文摘The problems of ice-induced vibration have been noticed and concerned since the 1960s, but it has not been well resolved. One reason is that the dynamic interaction between ice and structure is so complicated that practical ice force model has not been developed. The recent full-scale tests conducted on jacket platforms in the Bohai Sea presented that ice could cause intense vibrations which endanger the facilities on the deck and make discomfort for the crew. In this paper, the strategy of mitigation of ice-induced offshore structure vibration is discussed. Based on field observations and understanding of the interaction between ice and structure, the absorption mitigation method to suppress ice-induced vibration is presented. The numerical simulations were conducted for a simplified model of platform attached with a Tuned Mass Danlper （TMD） under ice force function and ice force time history. The simulation results show that TMD can fa- vorably reduce ice-induced vibrations, therefore, it can be considered to be an alternative approach to utilize. Finally, the application possibilities of utilizing TMDs on other miniature offshore structures in ice-covered areas of marginal oil fields are discussed.
文摘In this paper,we established the equation of motion of a platform structure with four legs by way of Hamilton' s Principle and obtained the nonlinear dynamical model of platform structures. By using Laplace transformation we obtain the mode shapes of the system. The nonlinear model of the platform structure in this paper provded an accurate way of analysis for the engineering prediction of the dynamical characteristics of the platform and the understanding of its vibrational mechanism.
文摘This paper deals with several hot topics in ice related problems. In recent years, advances have been made on ice breaking modes, dynamic ice loads on offshore structures, ice-induced structural vibrations, Fatigue and fracture by ice-structure interaction, and design of jackets in the Bohai Gulf.
基金This study was funded by the National keyResearch and Development program (2016YFC0303406)FundamentalResearch Funds for the Central University (HEUCFD1515,HEUCFM170113)+2 种基金High Technology Ship Funds of Ministry ofIndustry and Information of China, Assembly Advanced Research Fundof China (No. 6140210020105)China Postdoctoral Science Foundation(No. 2014M552661)Major innovation projects of High TechnologyShip Funds of Ministry of Industry and Information of China, Navalpre-research project, National Natural Science Foundation of China(Nos. 51209052 and 51 709 063).
文摘A series of tests of a full-scale river icebreaker was conducted to investigate the characteristics of ice-induced hull vibration.The test was conducted when the river icebreaker was operating in an ice-covered river at temperatures of-4 to 0°C with ice thicknesses of 300 to 400 mm.In the tests,the ice condition and icebreaker speed were chosen as the main influence factors.By analyzing the measured test data,we identified some important points regarding ice-induced hull vibration.When the river icebreaker navigates in an area with complete ice coverage,the peak value of the acceleration amplitude spectrum is highest.Also,the vibration response excited by the icebreaking load in an area with complete ice coverage exhibits more frequencies.With an increase in icebreaker speed,the vibration acceleration response gradually increases.However,habitability of the bow region on the main and driving decks is maintained due to the harmless vibration levels.In addition,the icebreaking operation of the river icebreaker causes violent local vibration of the grillage on the main deck.
基金financially supported by the National Natural Science Foundation of China(Grant No.50179003)National Outstanding Youth Foundation of China(Grant No.59725919)
文摘The sea ice is idealized as an elastic-brittle material. When an ice sheet moves toward a structure, the dynamic interaction between ice and the structure is analyzed by the DDA (Discontinuous Deformation Analysis) approach, where the ice sheet and the structure, are considered as assemblages of blocky masses. This has the advantages that the whole process of collision between the ice and structure can be shown visually with a series of pictures. Meanwhile, the dynamic response of the structure at each time step after the bumping of the ice against the structure is calculated. And with the aid of inverse analysis developed by the authors, the time history of the resultant ice force exerting on the structure is evaluated. A numerical example shows that the proposed approach is suitable to the simulation of the ice-breaking process and reasonable result of ice force acting on the structure can be obtained.
基金Supported by the National Key Research and Development Program of China(No.2016YFC1402001)the Fundamental Funds for the Central Universities(No.201713026)
文摘Sea ice can attenuate wave energy significantly when waves propagate through ice covers.In this study,a third-generation wave model called simulating wave nearshore(SWAN)was advanced to include damping of wave energy due to friction in the boundary layer below the ice.With the addition of an eddy viscosity wave-ice model,the resulting new SWAN model was applied to simulate wave height in the Bohai Sea during the freezing winter.Its performance was validated with available buoy data near the ice edge,and the new model showed an improvement in accuracy because it considered the ice effect on waves.We then performed a wave hindcast for the Bohai Sea during a freezing period in the winter of 2016 that had the severest ice conditions in recent years and found that the mean significant wave height changed by approximately 16.52%.In the Liaodong Bay,where sea ice concentration is highest,the change reached 32.57%,compared with the most recent SWAN model version.The average influence of sea ice on wave height simulation was also evaluated over a five-year(2013-2017)hindcast during January and February.We found that the wave height decrease was more significant in storm conditions even the eddy viscosity wave-ice model itself showed no advantage on damping stronger waves.
基金this work was financially supported by the National Natural Science Foundation of China under contract No.50678033.
文摘Some problems concerning the ice forces and ice response spectra are studied from both theoretical and practical points of view. On the basis of structural analysis,the analysis method of ice response spectra is proposed, since it plays an important role in the prediction of maximum structural response in cold regions. And it is illustrated that it is easy to study the structural response to ice using the ice response spectra.
文摘As the Arctic Channel continues to be developed,collisions between polar navigation vessels and sea ice are inevitable,which will directly affect structural safety and vibration comfort.However,the numerical analysis method of ship-ice collision-induced vibration is not perfect,and the effect of fluid coupling is not typically considered.In this paper,a simplified numerical analysis method for ship-ice collision-induced vibration is proposed,in which a reliable ice load is obtained by first performing ship-ice-water-air coupled collision calculations,followed by ship-ice-water coupled vibration calculations to obtain the vibration response of the structure.In addition,this paper investigates the full coupling method and the modeling ranges and meshing sizes involved in the analysis ship-ice collision-induced vibration,and the computational efficiencies of the traditional ALE algorithm and S-ALE algorithm are compared.The results indicate that the simplified simulation analysis method and gradient meshing model improve the calculation accuracy and efficiency in ship-ice collision and vibration response analysis.Moreover,the modeling range of the water and air models cannot be less than 6 times the ship width,2 times the ship length,and 1 times the ship depth,and the S-ALE algorithm saves 47.86%time compared to the ALE algorithm.The research results in this paper can provide a reference for the numerical simulation of ship-ice collision-induced vibration.
