On the basis of ice- induced forced vibration model, ice- induced displacement responses of offshore fixed platforms are investigated in both time domain and frequency domain. The relationships of ice-induced displace...On the basis of ice- induced forced vibration model, ice- induced displacement responses of offshore fixed platforms are investigated in both time domain and frequency domain. The relationships of ice-induced displacement responses with ice breaking modes, ice acting directions and platform structures are analyzed and determined. The results lead to an important conclusion obtained for the first time that ice breaking frequency and the natural frequency of the first mode of the platform are the two main factors that dominate the degree of vibration. The present work provides a firm basis for both design and operation of fixed platforms against ice loading.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
A three-dimensional fixed offshore platform in deep water modeled by the finite element method is studied in this paper. Analysis of the dynamic response of the MDOF structure is realized taking the non-linearity of t...A three-dimensional fixed offshore platform in deep water modeled by the finite element method is studied in this paper. Analysis of the dynamic response of the MDOF structure is realized taking the non-linearity of the wave drag force and the wave-structure interaction into account. The structural response statistics, which have Gaussian distributions, are used to evaluate the vibration effect of the structure without TMD and with TMD. And an optimal method to design TMD controlling the first mode of the multi-mode structure is proposed. Moreover, the probabilities of occurrence of sea states at the platform site are considered for prediction of the long-term effect of a TMD. Simulation results demonstrate that the long-term effect of a well-designed TMD is good and the practical use is possible due to the good stability of its optimal parameters under different sea states.展开更多
Objective To compare the preliminary clinical outcome between fixed platform and rotating high-flexion prosthesis following total knee replacement(TKR).Methods Form January 2007 to December 2009,68 patients with osteo...Objective To compare the preliminary clinical outcome between fixed platform and rotating high-flexion prosthesis following total knee replacement(TKR).Methods Form January 2007 to December 2009,68 patients with osteoarthritis of展开更多
An approach to seismic response reduction for offshore platforms by the use of the tuned liquid damper is presented in this paper. First of all, the effects of the tuned frequency ratio and excited frequency ratio on ...An approach to seismic response reduction for offshore platforms by the use of the tuned liquid damper is presented in this paper. First of all, the effects of the tuned frequency ratio and excited frequency ratio on the seismic response reduction of the platform structure are investigated. Based on the results, a mechanical model and equation of motion for the TLD-platform system are established. And then effectiveness of the appraoch is verified by numerical calculation.展开更多
In this paper, the control method for fixed offshore platforms using semi-active tuned liquid column damper (TLCD) is presented. The equation of motion for the platform-TLCD control system is given and the semi-active...In this paper, the control method for fixed offshore platforms using semi-active tuned liquid column damper (TLCD) is presented. The equation of motion for the platform-TLCD control system is given and the semi-active control strategy is established. A back propagation artificial neural network (ANN) is used to adjust the orifice opening of TLCD because of the nonlinear motion of liquid in TLCD. The effectiveness of the control method is verified by numerical examples.展开更多
Fatigue design method is usually used for estimating whether a platform structure meets the requirements of fatigue resistance. It is described in API RP-2A and ZC rules for fixed offshore platforms, in which the allo...Fatigue design method is usually used for estimating whether a platform structure meets the requirements of fatigue resistance. It is described in API RP-2A and ZC rules for fixed offshore platforms, in which the allowable stresses for fatigue design are defined. In this paper discussed are the allowable stresses related factors, such as wave climate, structural response, fatigue behaviour of structural members.展开更多
This paper analyzes the seismicity in Bohai Sea,introducing a shape factor K to characterize the seismic risk distribution in sub-regions of the sea. Based on the seismic design ground motions for 46 platforms located...This paper analyzes the seismicity in Bohai Sea,introducing a shape factor K to characterize the seismic risk distribution in sub-regions of the sea. Based on the seismic design ground motions for 46 platforms located in the Bohai Sea,a statistical analysis was performed for different peak ground acceleration (PGA) ratios at two different probability levels. In accordance with the two-stage design method,a scheme of two seismic design levels is proposed,and two seismic design objectives are established respectively for the strength level earthquake and the ductility level earthquake. By analogy with and comparison to the Chinese seismic design code for buildings,it is proposed that the probability level for the strength level earthquake and ductility level earthquake have a return period of 200 and 1000 - 2500 years,respectively. The validity of these proposed values is discussed. Finally,the PGAs corresponding to these two probability levels are calculated for different sub-regions of the Bohai Sea.展开更多
基金The project was financially supported by China Postdoctor Science Foundationthe Key Project Foundation of the Chinese Academy of Sciences and China National Offshore Oil Corporation
文摘On the basis of ice- induced forced vibration model, ice- induced displacement responses of offshore fixed platforms are investigated in both time domain and frequency domain. The relationships of ice-induced displacement responses with ice breaking modes, ice acting directions and platform structures are analyzed and determined. The results lead to an important conclusion obtained for the first time that ice breaking frequency and the natural frequency of the first mode of the platform are the two main factors that dominate the degree of vibration. The present work provides a firm basis for both design and operation of fixed platforms against ice loading.
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.
文摘A three-dimensional fixed offshore platform in deep water modeled by the finite element method is studied in this paper. Analysis of the dynamic response of the MDOF structure is realized taking the non-linearity of the wave drag force and the wave-structure interaction into account. The structural response statistics, which have Gaussian distributions, are used to evaluate the vibration effect of the structure without TMD and with TMD. And an optimal method to design TMD controlling the first mode of the multi-mode structure is proposed. Moreover, the probabilities of occurrence of sea states at the platform site are considered for prediction of the long-term effect of a TMD. Simulation results demonstrate that the long-term effect of a well-designed TMD is good and the practical use is possible due to the good stability of its optimal parameters under different sea states.
文摘Objective To compare the preliminary clinical outcome between fixed platform and rotating high-flexion prosthesis following total knee replacement(TKR).Methods Form January 2007 to December 2009,68 patients with osteoarthritis of
文摘An approach to seismic response reduction for offshore platforms by the use of the tuned liquid damper is presented in this paper. First of all, the effects of the tuned frequency ratio and excited frequency ratio on the seismic response reduction of the platform structure are investigated. Based on the results, a mechanical model and equation of motion for the TLD-platform system are established. And then effectiveness of the appraoch is verified by numerical calculation.
文摘In this paper, the control method for fixed offshore platforms using semi-active tuned liquid column damper (TLCD) is presented. The equation of motion for the platform-TLCD control system is given and the semi-active control strategy is established. A back propagation artificial neural network (ANN) is used to adjust the orifice opening of TLCD because of the nonlinear motion of liquid in TLCD. The effectiveness of the control method is verified by numerical examples.
文摘Fatigue design method is usually used for estimating whether a platform structure meets the requirements of fatigue resistance. It is described in API RP-2A and ZC rules for fixed offshore platforms, in which the allowable stresses for fatigue design are defined. In this paper discussed are the allowable stresses related factors, such as wave climate, structural response, fatigue behaviour of structural members.
基金the 2007 Special Research Project 8-55 of the Department of Finance and the State Science and Technology Support Project 2006BAC13B02
文摘This paper analyzes the seismicity in Bohai Sea,introducing a shape factor K to characterize the seismic risk distribution in sub-regions of the sea. Based on the seismic design ground motions for 46 platforms located in the Bohai Sea,a statistical analysis was performed for different peak ground acceleration (PGA) ratios at two different probability levels. In accordance with the two-stage design method,a scheme of two seismic design levels is proposed,and two seismic design objectives are established respectively for the strength level earthquake and the ductility level earthquake. By analogy with and comparison to the Chinese seismic design code for buildings,it is proposed that the probability level for the strength level earthquake and ductility level earthquake have a return period of 200 and 1000 - 2500 years,respectively. The validity of these proposed values is discussed. Finally,the PGAs corresponding to these two probability levels are calculated for different sub-regions of the Bohai Sea.
