The development of an in-house computer program for determining the motions and loads of advancing ships through sea waves in the frequency domain,is described in this paper.The code is based on the potential flow for...The development of an in-house computer program for determining the motions and loads of advancing ships through sea waves in the frequency domain,is described in this paper.The code is based on the potential flow formulation and originates from a double-body code enhanced with the regular part of the velocity potential computed using the pulsing source Green function.The code is fully developed in C++language with extensive use of the object-oriented paradigm.The code is capable of estimating the excitation and inertial radiation loads or arbitrary incoming wave frequencies and incidence angles.The hydrodynamic responses such as hydrodynamic coefficients,ship motions,the vertical shear force and the vertical bending moment are estimated.A benchmark container ship and an LNG carrier are selected for testing and validating the computer code.The obtained results are compared with the available experimental data which demonstrate the acceptable compliance for the zero speed whereas there are some discrepancies over the range of frequencies for the advancing ship in different heading angles.展开更多
The need to reduce the trends associated with climate change imposes measures to reduce the emissions of greenhouse gases to the atmosphere and increase the efficiency of the use of energy.The International Maritime O...The need to reduce the trends associated with climate change imposes measures to reduce the emissions of greenhouse gases to the atmosphere and increase the efficiency of the use of energy.The International Maritime Organization(IMO)has been active since 1997 in promoting the implementation of measures that lead to more efficient ship operation with less fuel consumption and less emissions(Tadros et al.,2023a).The measures include improved ship design and improved operational practices.Several indexes have been created to quantify different aspects of these improvements.The shipping industry has been very actively implementing several actions aiming at the decarbonization of ship operation and more need to continue being implemented.展开更多
The objective of this work is to analyze the fatigue reliability of complex welded structures composed of multiple web-frame joints, accounting for correlation effects. A three-dimensional finite element model using t...The objective of this work is to analyze the fatigue reliability of complex welded structures composed of multiple web-frame joints, accounting for correlation effects. A three-dimensional finite element model using the 20-node solid elements is generated. A linear elastic finite element analysis was performed, hotspot stresses in a web-frame joint were analyzed and fatigue damage was quantified employing the S-N approach. The statistical descriptors of the fatigue life of a non-correlated web-frame joint containing several critical hotspots were estimated. The fatigue reliability of a web-frame joint wasmodeled as a series system of correlated components using the Ditlevsen bounds. The fatigue reliability of the entire welded structure with multiple web-frame joints, modeled as a parallel system of non-correlated web-frame joints was also calculated.展开更多
几何上类似的可伸缩由制造了的 A 到照原尺寸的使硬的面板然后他们的倒塌行为的小规模的标本被调查。这被考虑使硬的面板压缩最终的力量测试根据几何可伸缩的法律被设计以便测试的输出能受到垂直弯曲的油轮壳的压缩地区的使硬的面板被...几何上类似的可伸缩由制造了的 A 到照原尺寸的使硬的面板然后他们的倒塌行为的小规模的标本被调查。这被考虑使硬的面板压缩最终的力量测试根据几何可伸缩的法律被设计以便测试的输出能受到垂直弯曲的油轮壳的压缩地区的使硬的面板被用作代表性时刻。油轮壳的最终的力量被 FE 分析用被横梁紧张测试和使硬的面板的压缩测试获得的试验性地发达的主人压力紧张曲线分析，并且当时与进步倒塌方法完成的结果相比。展开更多
The objective of this work is to analyse fatigue reliability of deck structures subjected to correlated crack growth.The stress intensity factors of the correlated cracks are obtained by finite element analysis and ba...The objective of this work is to analyse fatigue reliability of deck structures subjected to correlated crack growth.The stress intensity factors of the correlated cracks are obtained by finite element analysis and based on which the geometry correction functions are derived.The Monte Carlo simulations are applied to predict the statistical descriptors of correlated cracks based on the Paris-Erdogan equation.A probabilistic model of crack growth as a function of time is used to analyse the fatigue reliability of deck structures accounting for the crack propagation correlation.A deck structure is modelled as a series system of stiffened panels,where a stiffened panel is regarded as a parallel system composed of plates and are longitudinal.It has been proven that the method developed here can be conveniently applied to perform the fatigue reliability assessment of structures subjected to correlated crack growth.展开更多
The objective of this paper is to study the residual ultimate strength of box beams with impact-induced damage,as a model of what may occur in ship hulls.The bottom and side plates of ship hulls can suffer denting or ...The objective of this paper is to study the residual ultimate strength of box beams with impact-induced damage,as a model of what may occur in ship hulls.The bottom and side plates of ship hulls can suffer denting or fracture damage due to grounding,collision and other contacts during the ship’s service life and these impact-induced damages could result in considerable strength degradation.Box beams are firstly subjected to impact loading and then four-point bending loading is imposed on the damaged structures to assess the residual strength using ANSYS/LS_DYNA.The ultimate moment and collapse modes are discussed considering the effect of impact location.The impact-induced deformation is introduced in the four-point bending simulation,and the impact-induced stress is included or not to determine the effect of residual stress and distortion after impact.It is shown that impact location has significant influence on the residual ultimate bending moment of the damaged box beam providing that the impact energy is kept constant.The collapse modes also change when the impactor strikes on different locations.Damaged hard corner and inclined neutral axes might explain the reduction of ultimate strength and diverse collapse modes.The residual stress in the box beam after impact may increase or decrease the ultimate strength depending on impact location.展开更多
The assessment of the fatigue life of floating structures is an essential step in their design process,and thus it is included as one of the checks in the Rules of Classification Societies.Different methods have been ...The assessment of the fatigue life of floating structures is an essential step in their design process,and thus it is included as one of the checks in the Rules of Classification Societies.Different methods have been developed for that purpose,and new approaches are continuously being proposed,as simplified methods dully calibrated and validated or very heavy computational approaches.Integrity of these structures has to be ensured during their lifetime by checking their strength in light of existing cracks,eventually coexisting with other types of structural degradation.This special issue addresses this type of problems.展开更多
文摘The development of an in-house computer program for determining the motions and loads of advancing ships through sea waves in the frequency domain,is described in this paper.The code is based on the potential flow formulation and originates from a double-body code enhanced with the regular part of the velocity potential computed using the pulsing source Green function.The code is fully developed in C++language with extensive use of the object-oriented paradigm.The code is capable of estimating the excitation and inertial radiation loads or arbitrary incoming wave frequencies and incidence angles.The hydrodynamic responses such as hydrodynamic coefficients,ship motions,the vertical shear force and the vertical bending moment are estimated.A benchmark container ship and an LNG carrier are selected for testing and validating the computer code.The obtained results are compared with the available experimental data which demonstrate the acceptable compliance for the zero speed whereas there are some discrepancies over the range of frequencies for the advancing ship in different heading angles.
文摘The need to reduce the trends associated with climate change imposes measures to reduce the emissions of greenhouse gases to the atmosphere and increase the efficiency of the use of energy.The International Maritime Organization(IMO)has been active since 1997 in promoting the implementation of measures that lead to more efficient ship operation with less fuel consumption and less emissions(Tadros et al.,2023a).The measures include improved ship design and improved operational practices.Several indexes have been created to quantify different aspects of these improvements.The shipping industry has been very actively implementing several actions aiming at the decarbonization of ship operation and more need to continue being implemented.
文摘The objective of this work is to analyze the fatigue reliability of complex welded structures composed of multiple web-frame joints, accounting for correlation effects. A three-dimensional finite element model using the 20-node solid elements is generated. A linear elastic finite element analysis was performed, hotspot stresses in a web-frame joint were analyzed and fatigue damage was quantified employing the S-N approach. The statistical descriptors of the fatigue life of a non-correlated web-frame joint containing several critical hotspots were estimated. The fatigue reliability of a web-frame joint wasmodeled as a series system of correlated components using the Ditlevsen bounds. The fatigue reliability of the entire welded structure with multiple web-frame joints, modeled as a parallel system of non-correlated web-frame joints was also calculated.
基金financed by the Portuguese Foundation for Science and Technology (Fundao para a Ciência e Tecnologia), under contract SFRH/BD/65120/2009
文摘几何上类似的可伸缩由制造了的 A 到照原尺寸的使硬的面板然后他们的倒塌行为的小规模的标本被调查。这被考虑使硬的面板压缩最终的力量测试根据几何可伸缩的法律被设计以便测试的输出能受到垂直弯曲的油轮壳的压缩地区的使硬的面板被用作代表性时刻。油轮壳的最终的力量被 FE 分析用被横梁紧张测试和使硬的面板的压缩测试获得的试验性地发达的主人压力紧张曲线分析，并且当时与进步倒塌方法完成的结果相比。
基金Supported by China Scholarship Council under Grant No.2008110133
文摘The objective of this work is to analyse fatigue reliability of deck structures subjected to correlated crack growth.The stress intensity factors of the correlated cracks are obtained by finite element analysis and based on which the geometry correction functions are derived.The Monte Carlo simulations are applied to predict the statistical descriptors of correlated cracks based on the Paris-Erdogan equation.A probabilistic model of crack growth as a function of time is used to analyse the fatigue reliability of deck structures accounting for the crack propagation correlation.A deck structure is modelled as a series system of stiffened panels,where a stiffened panel is regarded as a parallel system composed of plates and are longitudinal.It has been proven that the method developed here can be conveniently applied to perform the fatigue reliability assessment of structures subjected to correlated crack growth.
基金This work contributes to the Strategic Research Plan of the Centre forMarine Technology and Ocean Engineering(CENTEC),which is financed by the Portuguese Foundation for Science and Technology(Fundação para a Ciência e Tecnologia-FCT)under contract UIDB/UIDP/00134/2020.
文摘The objective of this paper is to study the residual ultimate strength of box beams with impact-induced damage,as a model of what may occur in ship hulls.The bottom and side plates of ship hulls can suffer denting or fracture damage due to grounding,collision and other contacts during the ship’s service life and these impact-induced damages could result in considerable strength degradation.Box beams are firstly subjected to impact loading and then four-point bending loading is imposed on the damaged structures to assess the residual strength using ANSYS/LS_DYNA.The ultimate moment and collapse modes are discussed considering the effect of impact location.The impact-induced deformation is introduced in the four-point bending simulation,and the impact-induced stress is included or not to determine the effect of residual stress and distortion after impact.It is shown that impact location has significant influence on the residual ultimate bending moment of the damaged box beam providing that the impact energy is kept constant.The collapse modes also change when the impactor strikes on different locations.Damaged hard corner and inclined neutral axes might explain the reduction of ultimate strength and diverse collapse modes.The residual stress in the box beam after impact may increase or decrease the ultimate strength depending on impact location.
文摘The assessment of the fatigue life of floating structures is an essential step in their design process,and thus it is included as one of the checks in the Rules of Classification Societies.Different methods have been developed for that purpose,and new approaches are continuously being proposed,as simplified methods dully calibrated and validated or very heavy computational approaches.Integrity of these structures has to be ensured during their lifetime by checking their strength in light of existing cracks,eventually coexisting with other types of structural degradation.This special issue addresses this type of problems.
