In this paper, reliability analysis for the offshore jacket platform with the interaction of structure- pile- soil under extreme environmental loads is carried out. The inherent uncertainties of the environmental load...In this paper, reliability analysis for the offshore jacket platform with the interaction of structure- pile- soil under extreme environmental loads is carried out. The inherent uncertainties of the environmental load, foundation soil, platform itself, and calculating models are evaluated. The action of extreme loads on the offshore platform is modeled as a function of extreme wave height. The system capacity of the whole platform is determined by nonlinear pushover analysis, and the relevant probability property is obtained by the simulation method. The reliability model for the whole jacket platform is described as the relationship between the load and resistance based on the offshore design codes. The reliability of whole platform is calculated by the analytical method and the importance sampling method on the basis of a case study for a tripod jacket platform.展开更多
Innovative features of wind turbine blades with flatback at inboard region,thick airfoils at inboard as well as mid-span region and transversely stepped thickness in spar caps have been proposed by Institute of Engine...Innovative features of wind turbine blades with flatback at inboard region,thick airfoils at inboard as well as mid-span region and transversely stepped thickness in spar caps have been proposed by Institute of Engineering Thermophysics,Chinese Academy of Sciences(IET-Wind)in order to improve both aerodynamic and structural efficiency of rotor blades.To verify the proposed design concepts,this study first presented numerical analysis using finite element method to clarify the effect of flatback on local buckling strength of the inboard region.Blade models with various loading cases,inboard configurations,and core materials were comparatively studied.Furthermore,a prototype blade incorporated with innovative features was manufactured and tested under static bending loads to investigate its structural response and characteristics.It was found that rotor blades with flatback exhibited favorable local buckling strength at the inboard region compared with those with conventional sharp trailing edge when low-density PVC foam was used.The prototype blade showed linear behavior under extreme loads in spar caps,aft panels,shear web and flatback near the maximum chord which is usually susceptible to buckling in the blades according to traditional designs.The inboard region of the blade showed exceptional load-carrying capacity as it survived420%extreme loads in the experiment.Through this study,potential structural advantages by applying proposed structural features to large composite blades of multi-megawatt wind turbines were addressed.展开更多
This paper studies the effect of non-symmetric flood and rigidity loss of damaged ship hulls to external loads. Based on the calculation method of ultimate strength of damaged ship hulls under non-symmetric bending, t...This paper studies the effect of non-symmetric flood and rigidity loss of damaged ship hulls to external loads. Based on the calculation method of ultimate strength of damaged ship hulls under non-symmetric bending, the effect of collision, grounding and explosion damage on the ultimate strength of ship hull is also analyzed. Then, residual strength index of damaged ship hulls is given based on extreme loads and ultimate strength calculations. The critical sea state of damaged shin hulls is also predicted.展开更多
With the development of cutting-edge sciences and new technologies,we have to consider the size,the density,the hardness,the stiffness and other properties of engineering materials and structures beyond the convention...With the development of cutting-edge sciences and new technologies,we have to consider the size,the density,the hardness,the stiffness and other properties of engineering materials and structures beyond the conventional ranges,as well as their mechanical behavior in extreme environments,such as ultra-conventional temperature,speed,physical and chemical fields,and severe weather,and more effective theories and methods of mechanics are required.This paper first gives the fundamental definition and the scientific connotation of extreme mechanics,then reviews the studies of extreme mechanics from three aspects:the extreme properties,the extreme loads,and the discipline development,as well as major engineering and scientific challenges.The characteristics of extreme mechanics and major challenges in the aspects of mechanical theory,computational methods and experimental techniques are discussed.Prospectivei developments of extreme mechanics are suggested.展开更多
In this study, the aerodynamic characteristics of tall buildings with corner modifications (e.g., local wind force coefficients, mean pressure distributions, normalized power spectrum density, and extreme local pressu...In this study, the aerodynamic characteristics of tall buildings with corner modifications (e.g., local wind force coefficients, mean pressure distributions, normalized power spectrum density, and extreme local pressure) were examined. Wind tunnel experiments were conducted to measure the wind pressures on building models with different heights and recessed corners of different ratios. At a wind direction of a = 0° (i.e., wind blowing on the front of a building), corner modifications effectively reduced wind forces in all cases. Specifically, small corner modification ratios reduced wind forces more effectively than their larger counterparts. However, corner modifications resulted in extreme local pressure on building surfaces. In addition, for small corner modification ratios, the probability of extreme local pressure occurring at a = 0° was high. This probability was also high for large corner modification ratios at a = 15° (i.e., wind blowing slightly obliquely on the front of a building) because wind blowing obliquely creates substantial vortex shedding on one side surface and extreme negative pressure over one building side surface. Results of computational fluid dynamic modeling were adopted to determine details of the aerodynamic characteristics of tall buildings with corner modifications.展开更多
应用有限元仿真技术,以我国南海使用的深水半潜式海洋钻井平台为原型建立模型,进行极限工况下波浪参数搜索工作.依据ABS(American Bureau of Shipping)和DNV(Det Norske Veritas)规范,应用随机性设计波法搜索并确定深水半潜式平台两浮...应用有限元仿真技术,以我国南海使用的深水半潜式海洋钻井平台为原型建立模型,进行极限工况下波浪参数搜索工作.依据ABS(American Bureau of Shipping)和DNV(Det Norske Veritas)规范,应用随机性设计波法搜索并确定深水半潜式平台两浮体之间分离力最大工况、纵向剪切力最大工况、绕横轴扭矩最大工况以及总纵垂向弯矩最大工况共四种极限工况下的波浪参数,并通过所得波浪参数计算平台表面载荷分布.展开更多
The traffic condition of Taizhou Yangtze River Bridge is obtained to a certain extent, according to the traffic investigation nearby Taizhou Bridge. The statistical characteristics of the traffic conditions are acquir...The traffic condition of Taizhou Yangtze River Bridge is obtained to a certain extent, according to the traffic investigation nearby Taizhou Bridge. The statistical characteristics of the traffic conditions are acquired by statistical analysis. Simulation of the extreme vehicle loads and the sensitive analysis of load parameters are carried out based on these data complemented, which would guide the determination of the frictional coefficient between the main cables and the saddle.展开更多
For the global and structural fatigue strength analysis of a semi-submersible platform, wave loads under design conditions are calculated by use of the three-dimensional boundary element method. Methods for calculatin...For the global and structural fatigue strength analysis of a semi-submersible platform, wave loads under design conditions are calculated by use of the three-dimensional boundary element method. Methods for calculating the forward-speed free-surface Green function are discussed and a computer program with this Green function is developed. According to the special rules, the wave loads under several typical design conditions of the platform are calculated. The maximum vertical bending moment, torsion moment and horizontal split force are determined from a series of contour maps of wave loads for the wave period of 5 to 18 seconds at a certain interval and the wave phase of 0degrees to 360degrees at a certain interval. The wave height is determined by the function of wave period with a given exceedance probability. The maximum wave loads under the combination of wave parameters are used as the input of hydrodynamic pressure in the three-dimensional finite element analysis process. The transfer functions of wave loads on the platform are used for the fatigue strength analysis of the K-tubular joint and the sub-model of the structure.展开更多
文摘In this paper, reliability analysis for the offshore jacket platform with the interaction of structure- pile- soil under extreme environmental loads is carried out. The inherent uncertainties of the environmental load, foundation soil, platform itself, and calculating models are evaluated. The action of extreme loads on the offshore platform is modeled as a function of extreme wave height. The system capacity of the whole platform is determined by nonlinear pushover analysis, and the relevant probability property is obtained by the simulation method. The reliability model for the whole jacket platform is described as the relationship between the load and resistance based on the offshore design codes. The reliability of whole platform is calculated by the analytical method and the importance sampling method on the basis of a case study for a tripod jacket platform.
基金supported by the National Natural Science Foundation of China(Grant No.51405468)
文摘Innovative features of wind turbine blades with flatback at inboard region,thick airfoils at inboard as well as mid-span region and transversely stepped thickness in spar caps have been proposed by Institute of Engineering Thermophysics,Chinese Academy of Sciences(IET-Wind)in order to improve both aerodynamic and structural efficiency of rotor blades.To verify the proposed design concepts,this study first presented numerical analysis using finite element method to clarify the effect of flatback on local buckling strength of the inboard region.Blade models with various loading cases,inboard configurations,and core materials were comparatively studied.Furthermore,a prototype blade incorporated with innovative features was manufactured and tested under static bending loads to investigate its structural response and characteristics.It was found that rotor blades with flatback exhibited favorable local buckling strength at the inboard region compared with those with conventional sharp trailing edge when low-density PVC foam was used.The prototype blade showed linear behavior under extreme loads in spar caps,aft panels,shear web and flatback near the maximum chord which is usually susceptible to buckling in the blades according to traditional designs.The inboard region of the blade showed exceptional load-carrying capacity as it survived420%extreme loads in the experiment.Through this study,potential structural advantages by applying proposed structural features to large composite blades of multi-megawatt wind turbines were addressed.
文摘This paper studies the effect of non-symmetric flood and rigidity loss of damaged ship hulls to external loads. Based on the calculation method of ultimate strength of damaged ship hulls under non-symmetric bending, the effect of collision, grounding and explosion damage on the ultimate strength of ship hull is also analyzed. Then, residual strength index of damaged ship hulls is given based on extreme loads and ultimate strength calculations. The critical sea state of damaged shin hulls is also predicted.
文摘With the development of cutting-edge sciences and new technologies,we have to consider the size,the density,the hardness,the stiffness and other properties of engineering materials and structures beyond the conventional ranges,as well as their mechanical behavior in extreme environments,such as ultra-conventional temperature,speed,physical and chemical fields,and severe weather,and more effective theories and methods of mechanics are required.This paper first gives the fundamental definition and the scientific connotation of extreme mechanics,then reviews the studies of extreme mechanics from three aspects:the extreme properties,the extreme loads,and the discipline development,as well as major engineering and scientific challenges.The characteristics of extreme mechanics and major challenges in the aspects of mechanical theory,computational methods and experimental techniques are discussed.Prospectivei developments of extreme mechanics are suggested.
基金This work was supported by Korea Research Fellowship Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT。
文摘In this study, the aerodynamic characteristics of tall buildings with corner modifications (e.g., local wind force coefficients, mean pressure distributions, normalized power spectrum density, and extreme local pressure) were examined. Wind tunnel experiments were conducted to measure the wind pressures on building models with different heights and recessed corners of different ratios. At a wind direction of a = 0° (i.e., wind blowing on the front of a building), corner modifications effectively reduced wind forces in all cases. Specifically, small corner modification ratios reduced wind forces more effectively than their larger counterparts. However, corner modifications resulted in extreme local pressure on building surfaces. In addition, for small corner modification ratios, the probability of extreme local pressure occurring at a = 0° was high. This probability was also high for large corner modification ratios at a = 15° (i.e., wind blowing slightly obliquely on the front of a building) because wind blowing obliquely creates substantial vortex shedding on one side surface and extreme negative pressure over one building side surface. Results of computational fluid dynamic modeling were adopted to determine details of the aerodynamic characteristics of tall buildings with corner modifications.
文摘应用有限元仿真技术,以我国南海使用的深水半潜式海洋钻井平台为原型建立模型,进行极限工况下波浪参数搜索工作.依据ABS(American Bureau of Shipping)和DNV(Det Norske Veritas)规范,应用随机性设计波法搜索并确定深水半潜式平台两浮体之间分离力最大工况、纵向剪切力最大工况、绕横轴扭矩最大工况以及总纵垂向弯矩最大工况共四种极限工况下的波浪参数,并通过所得波浪参数计算平台表面载荷分布.
基金National Science and Technology Support Program of China ( No. 2009BAG15B02)Key Pro-grams for Science and Technology Development of Chinese Transportation Industry( No. 2008-353-332-180)
文摘The traffic condition of Taizhou Yangtze River Bridge is obtained to a certain extent, according to the traffic investigation nearby Taizhou Bridge. The statistical characteristics of the traffic conditions are acquired by statistical analysis. Simulation of the extreme vehicle loads and the sensitive analysis of load parameters are carried out based on these data complemented, which would guide the determination of the frictional coefficient between the main cables and the saddle.
文摘For the global and structural fatigue strength analysis of a semi-submersible platform, wave loads under design conditions are calculated by use of the three-dimensional boundary element method. Methods for calculating the forward-speed free-surface Green function are discussed and a computer program with this Green function is developed. According to the special rules, the wave loads under several typical design conditions of the platform are calculated. The maximum vertical bending moment, torsion moment and horizontal split force are determined from a series of contour maps of wave loads for the wave period of 5 to 18 seconds at a certain interval and the wave phase of 0degrees to 360degrees at a certain interval. The wave height is determined by the function of wave period with a given exceedance probability. The maximum wave loads under the combination of wave parameters are used as the input of hydrodynamic pressure in the three-dimensional finite element analysis process. The transfer functions of wave loads on the platform are used for the fatigue strength analysis of the K-tubular joint and the sub-model of the structure.
