考虑非对称剖面中和轴偏转的改进Smith法研究
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摘要
简化逐步破坏法(Smith法)是目前相关船级社规范推荐的船体极限弯矩计算方法之一,其计算精度取决于中和轴位置和单元应力-应变关系的计算精度。针对目前规范中单一的"力平衡准则"无法有效考虑非对称剖面(含破损状态)中和轴偏转的问题,文章在力平衡准则的基础上,进一步考虑剖面的力矢量平衡准则,结合多目标粒子群优化算法(MOPSO)研究建立了一种非对称剖面中和轴确定方法,在此基础上改进了现有的Smith法,以实现非对称剖面的极限承载能力分析。以Dow1/3护卫舰模型为例,开展了完整正浮工况和多个破损横倾工况的极限弯矩计算。结果对比分析表明:对于受损船舶,中和轴偏转对剖面弯矩有显著影响,基于PSO的中和轴确定方法具有较好的自适应和计算精度。
The Smith's method is stipulated by many classification societies as one of the methods for estimating ultimate/residual strength of hull girder, its calculation accuracy depends on the accuracy of the neutral axis position and stress-strain relationship of elements. However, for the asymmetric hull cross-sections(including damaged conditions), the single ‘force equilibrium criterion' in the current rules cannot effectively consider the rotation of neutral axis, the additional force vector equilibrium also needs to be applied so as to determine the neutral axis plane. This paper proposes a multi-objective particle swarm optimization(MOPSO) based iteration method to trace the motion of the neutral axis plane of asymmetric cross sections,based on which, the improved Smith's method is given for estimating the ultimate bearing capacity of the asymmetric hull cross-sections. Taking the Dow's 1/3 frigate model as an example, the ultimate bending moments under intact condition and damaged conditions with different heeling angles were calculated. The results show that the rotation of the neutral axis has a significant effect on the bending moment of the damaged ship. In addition, the PSO based Smith's method has good self-adaptivity and calculation accuracy.
The Smith's method is stipulated by many classification societies as one of the methods for estimating ultimate/residual strength of hull girder, its calculation accuracy depends on the accuracy of the neutral axis position and stress-strain relationship of elements. However, for the asymmetric hull cross-sections(including damaged conditions), the single ‘force equilibrium criterion' in the current rules cannot effectively consider the rotation of neutral axis, the additional force vector equilibrium also needs to be applied so as to determine the neutral axis plane. This paper proposes a multi-objective particle swarm optimization(MOPSO) based iteration method to trace the motion of the neutral axis plane of asymmetric cross sections,based on which, the improved Smith's method is given for estimating the ultimate bearing capacity of the asymmetric hull cross-sections. Taking the Dow's 1/3 frigate model as an example, the ultimate bending moments under intact condition and damaged conditions with different heeling angles were calculated. The results show that the rotation of the neutral axis has a significant effect on the bending moment of the damaged ship. In addition, the PSO based Smith's method has good self-adaptivity and calculation accuracy.
引文
[1]Smith C S.Influence of local compressive failure on ultimate longitudinal strength of a ship’s hull[C]//Proceedings of the International Symposium on Practical Design in Shipbuilding(PRADS).Tokyo,Japan,1977:73-79.
[2]Chen K Y,Kutt L M,Piaszczyk C M,Bieniek M P.Ultimate strength of ship structures[J].Transactions of the Society of Naval Architects and Marine Engineers,1983,91:149-168.
[3]Ueda Y,Rashed S M H.The idealized structural unit method and its application to deep girder structures[J].Computers and Structures,1984,18(2):227-293.
[4]International Association of Classification Societies(IACS).Common structural rules for bulk carriers and oil tankers[S].2014.
[5]Choung J,Nam J M,Ha T B.Assessment of residual ultimate strength of an asymmetrically damaged tanker considering rotational and translational shifts of neutral axis plane[J].Marine Structures,2012,25(1):71-84.
[6]Li C F,Fu P,Ren H L,Xu W J,Guedes Soares C.Ultimate bearing capacity assessment of hull girder with asymmetric cross-section[C]//Proceedings of the 36th International Conference on Offshore Mechanics and Arctic Engineering(OMAE),2017,June,25-30.Trondheim,Norway,2017.
[7]Kennedy J,Eberhart R C.A discrete binary version of the particle swarm algorithm[C].Proceedings of IEEE International Conference on Systems Man and Cybernetics,1997,5:4104-4108.
[8]Dow R S.Testing and analysis of 1/3-scale welded steel frigate model[C]//Proceedings of the International Conference on Advances in Marine Structures.ARE,Dunfermline,Scotland,1991:749-773.
[9]Yao T,Asrup O C,Caridis P,Chen Y N,Cho S R,Dow R S,Niho O,Rigo P.Special task committee VI.2:Ultimate hull girder strength[C]//Proceedings of the 14th International Ship and Offshore Structures Congress,2000,October 2-6.Nagasaki,Japan,2000.
[10]Paik J M,Amlashi H,Boon B,Branner K,Caridis P,Das P,et al.Committee III.1:Ultimate strength[C]//Proceedings of the 18th International Ship and Offshore Structures Congress,2012,September 9-13.Rostock,Germany,2012.
[2]Chen K Y,Kutt L M,Piaszczyk C M,Bieniek M P.Ultimate strength of ship structures[J].Transactions of the Society of Naval Architects and Marine Engineers,1983,91:149-168.
[3]Ueda Y,Rashed S M H.The idealized structural unit method and its application to deep girder structures[J].Computers and Structures,1984,18(2):227-293.
[4]International Association of Classification Societies(IACS).Common structural rules for bulk carriers and oil tankers[S].2014.
[5]Choung J,Nam J M,Ha T B.Assessment of residual ultimate strength of an asymmetrically damaged tanker considering rotational and translational shifts of neutral axis plane[J].Marine Structures,2012,25(1):71-84.
[6]Li C F,Fu P,Ren H L,Xu W J,Guedes Soares C.Ultimate bearing capacity assessment of hull girder with asymmetric cross-section[C]//Proceedings of the 36th International Conference on Offshore Mechanics and Arctic Engineering(OMAE),2017,June,25-30.Trondheim,Norway,2017.
[7]Kennedy J,Eberhart R C.A discrete binary version of the particle swarm algorithm[C].Proceedings of IEEE International Conference on Systems Man and Cybernetics,1997,5:4104-4108.
[8]Dow R S.Testing and analysis of 1/3-scale welded steel frigate model[C]//Proceedings of the International Conference on Advances in Marine Structures.ARE,Dunfermline,Scotland,1991:749-773.
[9]Yao T,Asrup O C,Caridis P,Chen Y N,Cho S R,Dow R S,Niho O,Rigo P.Special task committee VI.2:Ultimate hull girder strength[C]//Proceedings of the 14th International Ship and Offshore Structures Congress,2000,October 2-6.Nagasaki,Japan,2000.
[10]Paik J M,Amlashi H,Boon B,Branner K,Caridis P,Das P,et al.Committee III.1:Ultimate strength[C]//Proceedings of the 18th International Ship and Offshore Structures Congress,2012,September 9-13.Rostock,Germany,2012.