循环弯曲载荷下船体梁的极限纵强度

根据生破坏的强度准则，详细讨论了循环弯曲载荷下船体梁的非弹性变形性能。给出了循环弯曲载荷下船体梁极限强度的简化分析方法。进行了纵筋加强箱形薄壁梁模型的循环弯曲试验。理论计算与试验结果作了比较，两者吻合较好。     

基于完整船体极限强度和搁浅剩余强度的协调共同结构规范对比分析

文章基于Smith法,根据国际船级社协会发布的2013版协调共同结构规范(HCSR)中破损模型、失效模式和载荷模型,考虑材料屈服、结构单元屈曲及后屈曲的特性,应用FORTRAN程序设计语言编写船体极限强度计算程序,以某76000吨散货船为算例,对完整船体的极限强度进行计算,对搁浅状态下破损船体的剩余强度进行计算并校核承载能力。通过在中拱和中垂工况下与其他规范的对比验证,2013版HCSR指定的剩余强度校核公式及船体梁载荷计算公式中选取的安全系数要求更高,校核更严格。     

波浪中船体梁后极限强度特性的实验评估(英文)

Experimental investigations into the collapse behavior of a box-shape hull girder subjected to extreme wave-induced loads are presented.The experiment was performed using a scaled model in a tank.In the middle of the scaled model,sacrificial specimens with circular pillar and trough shapes which respectively show different bending moment-displacement characteristics were mounted to compare the dynamic collapse characteristics of the hull girder in waves.The specimens were designed by using finite element(FE)-analysis.Prior to the tank tests,static four-point-bending tests were conducted to detect the load-carrying capacity of the hull girder.It was shown that the load-carrying capacity of a ship including reduction of the capacity after the ultimate strength can be reproduced experimentally by employing the trough type specimens.Tank tests using these specimens were performed under a focused wave in which the hull girder collapses under once and repetitive focused waves.It was shown from the multiple collapse tests that the increase rate of collapse becomes higher once the load-carrying capacity enters the reduction path while the increase rate is lower before reaching the ultimate strength.     

Ultimate strength of container ships subjected to combined hogging moment and bottom local loads,Part 2: An extension of Smith's method

This paper is the second of two companion papers concerning the ultimate hull girder strength of container ships subjected to combined hogging moment and bottom local loads. The nonlinear finite element analysis in Part 1 has shown that local bending deformation of a double bottom due to bottom lateral loads significantly decreases the ultimate hogging strength of container ships. In this Part 2, extending Smith's method for pure bending collapse analysis of a ship's hull girder, a simplified method of progressive collapse analysis of ultimate hogging strength of container ships considering bottom local loads is developed. The double bottom is idealized as a plane grillage and the rest part of the cross section as a prismatic beam. An average stress-average strain relationship of plate/stiffened plate elements employed in Smith's method is transformed into an average stress-average plastic strain relationship, and implemented in the conventional beam finite element as a pseudo strain hardening/softening behaviors. The extended Smith's method is validated through a comparison with nonlinear finite element analysis.     

破损船体非对称弯曲极限强度分析及可靠性评估

在船体发生破损后,其剩余有效剖面是非对称的,船体还可能倾斜。本文首先对破损船体非对称弯曲进行了弹性和塑性分析,在此基础上假设了破损船体发生整体破坏时的剖面应力分布,给出了破损船体非对称弯曲极限强度分析方法,并采用了比较精细的方法计算加筋板格的屈曲极限强度。以箱型梁模型和超大型油船为例,将本文的计算结果与试验、ＩＳＵＭ法及解析公式的结果进行了比较。基于破损船体极限强度,结合重要性样本法,对６５,００     

Ultimate strength of container ships subjected to combined hogging moment and bottom local loads part 1: Nonlinear finite element analysis

This paper is the first of two companion papers concerning the ultimate hull girder strength of container ships subjected to combined hogging moment and bottom local loads. In the midship part of container ships, upward bottom local loads are usually larger than the downward ones. This leads to the increase of biaxial compression in the outer bottom plating and the reduction of the ultimate hull girder strength in the hogging condition. In this Part 1, the collapse behavior and ultimate strength of container ships under combined hogging moment and bottom local loads are analyzed using nonlinear finite element method. Buckling collapse behavior of bottom stiffened panels during the progressive collapse of a hull girder is closely investigated. It has been found that major factors of the reduction of ultimate hogging strength due to bottom local loads are (1) the increase of the longitudinal compression in the outer bottom and (2) the reduction of the effectiveness of the inner bottom, which is on the tension side of local bending of the double bottom. The obtained results will be utilized in the Part 2 paper to develop a simplified method of progressive collapse analysis of container ships under combined hogging moment and bottom local loads.     

船体梁极限强度的近似计算

船体梁的总纵强度是反映船舶结构安全可靠的最基本的强度指标。船体结构极限强度评估对于船舶结构初步设计、使用、维护和维修都非常重要，因此船体梁极限强度研究成为近几十年来船舶工程界的热点研究课题之一。到目前为止有两种典型的加筋板和船体梁的极限强度分析方法，它们是直接计算法和逐步破坏分析法。本文基于加筋板单元的平均应力应变曲线和逐步破坏分拆方法，提出了加筋板和船体梁极限强度的简化分析方法，考虑了初始挠度和残余应力对加筋板单元极限强度的影响。数值结果表明，采用本文简化方法得到的结果与有限元计算结果或其它逐步破坏分析结果比较符合。     

船体总纵极限强度可靠性分析的拉丁超立方抽样法

本文将拉丁超立方抽样法与条件期望和对偶变数方差减缩技术组合用于分析船体总纵极限强度可靠性。在一系列不同的极限状态函数条件下，对随机抽样法和拉丁超立方抽样法以及是否使用方差减缩技术进行了比较研究，使用组合方法获得了稳定的结果和较大的方差减缩，最后，基于极限强度，将该组合方法用于评估散货船在极值弯矩作用下的船体梁安全性。     

Parametric dependencies of the post-ultimate strength behavior of a ship’s hull girder in waves

To rationally assess the consequence of a ship’s hull girder collapse, it is necessary to know the post-ultimate strength behavior of the hull girder including the global deformation and motions under extreme wave-induced loads. In the foregoing research, the authors proposed a numerical analysis system to predict the collapse behavior in waves including the post-ultimate strength behavior. The primary objective of the present paper is to clarify the parametric dependencies of the severity of the collapse in a rational manner. The parameters may include those related to load-carrying capacity and the extreme loads. To this end, an analytical solution to describe the post-ultimate strength behavior is derived. Assuming that a plastic hinge is formed at the midship during the collapse procedure, the whole ship is modeled as a two-rigid-bodies system connected to each other amidship via a nonlinear rotational spring, which represents the nonlinear relationship between the bending moment and the rotational angle. The relationship may be modeled as piece-wise linear curves. It is further assumed that large motions and elastic/plastic deformations of the hull girder may not affect the load evaluations, and that the hull girder is subjected to a large single wave. Some important parameters to predict the severity of the collapse are specified based on the analytical solution.     

核发电船堆舱破损状态极限强度分析

对于核发电船而言,考虑到核反应堆的安全性问题,船体结构即使发生破坏,也要保证整体的强度,所以有必要针对破损后的船体梁进行极限强度分析。在船体剩余极限强度分析中,核反应堆舱所处舱段的极限承载能力是整个核发电船极限强度分析的关键。文章研究的重点集中在核反应堆舱段,在该舱段选取危险剖面进行剩余极限强度分析。同时,采用中和轴偏转的Smith方法对反应堆舱段进行破损船体极限强度计算,并结合HCSR规范对其进行评估。根据该核电船作业海域的海况资料,对其遭遇的波浪载荷进行长期极值预报,进而得出该船破损情况下的设计极限弯矩。结果表明,该船的设计极限弯矩满足规范中的要求,为基于规范的特定海域中的特定船型剩余强度评估提供参考。     

散货船碰撞损伤后的剪切极限强度

船体梁受到碰撞损伤后,必须有足够的剩余强度用以抵抗最大外弯矩,同时还需能够承受最大剪力.在众多类型的船舶中,散货船是一种抗剪能力较差的船型.对于其碰撞损伤后纵向剩余极限弯矩的研究已有较多的文献[2-7],而对于碰撞损伤后的剪切极限强度的研究目前还比较少.针对这一现状,本文的主要目的在于分析讨论散货船受到碰撞损伤后的极限承剪能力;分析结构几何尺寸,碰撞损伤形状以及边界条件等各种因素对碰撞破损船体抗剪能力的影响.为了方便起见,文中也给出了相应的回归经验公式.本文同时还推导了一个船体梁碰撞损伤后的初始屈服剪力计算公式.最后,本文以一艘散货船为例,计算分析其碰撞损伤后的抗剪能力,从中得出一些有益的结论.     

CFRP修复的FPSO点蚀船体梁极限强度分析

采用非线性有限元法对中拱和中垂工况条件下碳纤维增强聚合物(Carbon Fiber Reinforced Polymer, CFRP)修复的浮式生产储卸油装置(Floating Production Storage and Offloading, FPSO)点蚀船体梁极限强度进行仿真分析。对比FPSO的完整船体梁、点蚀船体梁和CFRP修复的点蚀船体梁的中拱极限弯矩和中垂极限弯矩，分析CFRP对FPSO点蚀船体梁的修复效果，并分析胶层失效规律。结果表明，CFRP可为船舶的高效修复提供一种新的方式。     

破损散货船剩余极限强度的评估与分析

船体发生破损后.其剩余有效剖面是非对称的,船体还可能倾斜.根据IACS共同规范(CSR),采用逐步破坏分析法计算船体梁在不同破损情况下的剩余极限强度,同时编制了计算程序.对1艘散货船在完整和不同破损状态下的船体结构安全性进行了系统评估,并得到了一些有意义的结论.     

破损船体剩余强度衡准研究

本文研究了船体破损非对称淹水和刚度损失引起的船体外载荷变化,并利用破损船体非对称弯曲极限强度计算方法详细分析碰撞、搁浅和爆炸破损对船体极限强度的影响.然后基于破损船体极值载荷和极限强度,给出破损船体剩余强度衡准,并对破损船体临界海况进行预报.     

循环载荷下箱型梁极限强度性能实验研究

通过系列箱型梁模型实验,研究了箱型梁在极值循环弯曲载荷下的极限承载性能。分别对四个加筋箱型梁模型进行了循环载荷下的四点纯弯实验,实验分别采取单向及双向循环载荷两种施加方式。在单向循环弯曲实验中,模型的后续循环的极限强度与前一循环的后极限强度阶段的卸载点接近,但塑性变形有明显增加,极限承载能力下降显著;双向循环弯曲中,反向弯矩虽然抵消了部分塑性变形,但箱型梁的极限承载能力仍有明显下降。实验表明,实验加载过程中,箱型梁在承受极值循环载荷初期,其构件崩溃速率较缓,而一旦进入后极限阶段,崩溃速率显著加快;箱型梁在极值循环弯曲载荷下的极限承载性能,即后极限强度性能,相比一次性极限强度值逐步下降。     

Experimental and numerical investigations of the ultimate torsional strength of an ultra large container ship

Structures of ultra large container ships (ULCS) are characterized by large deck openings and low torsional rigidity. It is essential to comprehensively figure out their collapse behaviors under pure torsion with both model experiments and numerical simulations, making an evaluation of their ultimate torsional strength. In this paper, a similar scale model of a 10,000TEU container ship has been designed and manufactured first, in which both geometric similarity and strength similarity are taken into account. Next the collapse behaviors of the test model are detailedly illustrated with both experimentally and numerically obtained results. Then discussions on warping or shear buckling deformations involved in the collapse process of the structure are conducted with extended numerical simulations. Finally, the ultimate torsional strength of the true ship is evaluated according to the similarity theory. Results show that it is the yielding and shear buckling of the side shells that causes the failure of the hull girder under pure torsion. Further nonlinear finite element analysis demonstrates that it may either have warping or shear buckling deformations in the torsional collapse process of the hull girder with a large deck opening, depending on the local rigidity distribution of side shells, which has a significant effect on the ultimate torsional strength of the hull girder.     

Design safety margin of a 10,000 TEU container ship through ultimate hull girder load combination analysis

Assessment of the ultimate longitudinal strength of hull girders under combined waveloads can be of particular importance especially for ships with large deck openings and low torsional rigidity. In such cases the horizontal and torsional moments may approach or exceed the vertical bending moment when a vessel progresses in oblique seas. This paper presents a direct calculation methodology for the evaluation of the ultimate strength of a 10,000 TEU container ship by considering the combined effects of structural non-linearities and steady state wave induced dynamic loads on a mid ship section cargo hold. The strength is evaluated deterministically using non-linear nite element analysis. The design extreme values of principal global wave-induced load components and their combinations in irregular seaways are predicted using a cross-spectral method together with short-term and long-term statistical formulations. Consequently, the margin of safety between the ultimate capacity and the maximum expected moment is established.     

Hull girder strength

Hull girder strength is the most fundamental strength of a ship structure. To assess the hull girder strength, estimations of both extreme load which may act on the hull girder and the capacity of the hull girder are necessary, and many research works have been performed from this aspect. In the present review article, attention is focussed on the capacity of a ship hull girder. At the beginning, a short historical review is given in relation to the research works on hull girder strength, and some consideration is introduced on the ultimate hull girder strength from the design aspect. Then, state of the art and the future direction of the research works on hull girder strength are described.     

复合材料船体纵向极限强度可靠性分析

把船体甲板或船底板结构视为是一系列加筋板单元的组合，然后利用复合材料梁柱理论计算船体加筋板单元构件的极限承载能力，最后用Smith法计算复合材料船体的极限承载能力。由于复合材料船体纵向极限强度的极限状态方程不能简单地用船体各参数显式表达，故将近年发展起来的响应面法与JC法相结合，对复合材料船体纵向极限强度进行了可靠性分析。并讨论了影响船体纵向极限强度可靠性各变量的敏感性。     

Ultimate strength analysis of a bulk carrier hull girder under alternate hold loading condition,Part 2: Stress distribution in the double bottom and simplified approaches

This is the second of two companion papers dealing with nonlinear finite element modelling and ultimate strength analysis of the hull girder of a bulk carrier under Alternate Hold Loading (AHL) condition. The methodology for nonlinear finite element modelling as well as the ultimate strength results from the nonlinear FE analyses was discussed in the companion paper (Part 1). The purpose of the present paper is to use the FE results to contribute towards developing simplified methods applicable to practical design of ship hulls under combined global and local loads. An important issue is the significant double bottom bending in the empty hold in AHL due to combined global hull girder bending moment and local loads. Therefore, the stress distributions in the double bottom area at different load levels i.e. rule load level and ultimate failure load level are presented in detail. The implication of different design pressures obtained by different rules (CSR-BC rules and DNV rules) on the stress distribution is investigated. Both (partially) heavy cargo AHL and fully loaded cargo AHL are considered. Factors of influence of double bottom bending such as initial imperfections, local loads, stress distribution and failure modes on the hull girder strength are discussed. Simplified procedures for determination of the hull girder strength for bulk carriers under AHL conditions are also discussed in light of the FE analyses.