“木兰”船体分段拖航过程中折断事故分析

以"木兰"船体分段拖航折断事故为工程案例,分别采用许用应力设计法、极限状态设计法两种分析方法对该船体梁强度进行校核,分析舱室进水对设计载荷的影响。结果表明:基于有限元的极限状态分析方法能够准确地得到结构极限承载能力,其损伤模式及过程与事故吻合较好,是可靠的事故分析方法。该船体分段在6级风浪载荷下的极限强度满足规范要求,但舱室进水严重恶化了中垂情况下船体梁的受力状态,最终导致了船体中垂折断事故的发生。     

浅析船体结构极限强度模型试验技术

船体结构极限强度是船体结构安全检验中的重要参考指标,因此船体结构极限强度模型试验技术在船舶工程行业中发挥着十分重要的作用,基于此,本文针对船体结构极限强度模型试验技术的应用进行详细的研究分析。在极限强度模型试验相关原理的基础上,从对甲板加筋板和箱型梁对不同模式下的船体结构极限强度模型试验技模型设计进行分析,最终采用实际的船体结构极限强度模型试验对极限强度模型进行验证。     

船体梁极限强度非线性有限元计算方法研究

文章针对Dow 1/3比例护卫舰模型,进行多种方案的船体梁极限强度非线性有限元计算,通过与Smith方法和模型试验结果的对比分析,研究船体梁极限强度非线性有限元建模技术,给出一种较为准确高效的船体梁极限强度非线性有限元计算方法。对于完善《船体梁极限强度的非线性有限元方法计算指南》具有一定的参考价值。     

船体梁在循环载荷下的极限强度研究

在船体极限强度的研究中,对船体到达极限强度后的剩余承载能力的研究非常重要,其关系到船体结构的生命力设计,用于判断船舶破损情况下是否还能保持一定的自存能力,制定救援方案以及作为船舶在极端情况下安全性的判断依据。目前此类研究多是针对单次加载,而在实际海洋环境中,船舶会受到交变载荷的作用,如果超过弹性范围,会留下塑性应变,这些残留应变会影响船舶最终承载能力的大小。本文以逐步崩溃法为基础,用Fortran语言开发了计算程序,该程序可以得到船体梁在极限强度后的承载能力,同时通过递增塑性法来模拟循环加载带来的影响,并采用非线性有限元法进行对比验证。     

复杂载荷作用下连接器基座加强区结构极限强度研究

文章基于混合相似理论进行了复杂载荷作用下的连接器基座加强区结构模型设计,完成了极限承载能力模型试验,并通过模型试验结果与数值仿真结果的对比,验证了数值仿真方法的正确性。通过文中的研究建立了超大型浮体连接器基座加强区结构模型试验技术、得到连接器基座加强区结构的极限压缩载荷,对多轴载荷作用下的结构物极限强度研究和推进具有重要意义。     

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。     

基于船体极限强度和碰撞剩余强度的HCSR对比分析

2013版HCSR对极限强度和船体梁载荷计算的诸多安全系数和公式做出了新的修正。第五章船体梁强度新增加针对船体梁剩余强度的计算和校核。本文基于Smith法,根据2013版HCSR中船体梁载荷计算公式和极限强度计算流程的规定,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76 000 t散货船为例,对完整船体的极限强度进行计算,对碰撞状态下破损船体的剩余强度进行计算并校核承载能力。通过对比ABS和DNV规范中的碰撞模型,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校核公式更严格。     

船舶碰撞和搁浅后剩余强度可靠性评估

在船舶发生碰和搁浅后,一方面是船体结构承载能力的削弱;另一方面是船舶浮态和外载荷分布的显著变化。基于这样的事实,本文给出了破缶船体外载荷和非对称弯曲极限强度分析方法,比较了基于横剖面模数和基于极限强度的剩余强度衡准,并给出了破损船体结构安全性评估的可行性方法。根据本文提出的方法,对６５０００ｔ散货船在完整状态以及碰撞和搁浅后的船体结构安全性进行了评估,并得了一些有意义的结论。     

油船实际装载操作中应校核极限强度

由于船体梁极限强度校核值不需要经船级社认可批准,不必纳入装载手册,仅需在设计阶段进行校核。实际设计工作中设计者会根据各自的需要和经验在结构吃水从出港到到港全程设计不同的中间状态,产生不同的实际操作最大静水弯矩值,供设计阶段校核船体梁极限强度的实际操作最大静水弯矩包络值值不且唯一性。文章以某实船为例进行计算分析,发现中间装载过程对弯矩包络值影响较大,不同的中间过程会产生不同的弯矩包络值,若以其中某组较小包络值作为设计阶段船体梁极限强度校核值,同时在船舶营运实际操作中又不对此船体梁极限强度进行校核,会给实际营运的的船舶带来安全隐患。为防止出现这一问题,建议将船体梁极限强度校核值作为强度衡准放入完工装载手册用以指导船长实际操作,确保所有实际操作状态的弯矩不得超过船体梁极限强度校核值。     

大型滚装船弯扭强度整船有限元分析

以大型滚装船为研究对象,采用现代的三维全船有限元分析技术及DNV船级社的SESAM软件系统,为全面研究整船弯扭强度,建立了全船有限元结构模型、质量模型、水动力计算模型;应用三维辐射—绕射理论和有限元程序进行波浪载荷的长期预报,在此基础上确定设计波参数;对全船结构有限元模型在设计波载荷作用下分析计算得到各种工况下船体结构的应力、变形响应,获得船体结构强度特点,对该类船舶的结构设计优化和强度分析有一定的参考价值,同时对其他类型船舶弯扭强度全船有限元分析有借鉴意义。     

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。     

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     

联合弯矩作用下含裂纹船体结构剩余极限强度评估方法研究

裂纹损伤对于船体结构来说难以避免,将削弱结构的极限强度,所以研究含裂纹损伤船体结构的剩余极限强度意义重大.对于含裂纹舱段结构,现有的研究主要针对垂向弯矩作用下的剩余极限强度,对于联合弯矩作用下的研究还很欠缺.本文采用非线性有限元分析方法,研究了垂向弯矩和水平弯矩联合作用下含裂纹舱段的剩余极限强度.提出了计算含裂纹船舯舱段在联合弯矩作用下剩余极限强度的计算公式,通过对含裂纹箱型梁的有限元计算结果进行拟合,得到公式中待定系数的表达式.研究结果表明,本文提出的方法可以快速预测船体结构在联合弯矩作用下的剩余极限强度.     

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.     

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.     

Research on the dynamic buckling of a typical deck grillage structure subjected to in-plane impact Load

The dynamic buckling of the main deck grillage would result in the total collapse of the ship hull subjected to a far-filed underwater explosion. This dynamic buckling is mainly due to the dynamic moment of the ship hull when the ship hull experiences a sudden movement under impact load from the explosion. In order to investigate the ultimate strength of a typical deck grillage under quasi-static and dynamic in-plane compressive load, a structure model, in which the real constrained condition of the deck grillage was taken into consideration, was designed and manufactured. The quasi-static ultimate strength and damage mode of the deck grillage under in-plane compressive load was experimentally investigated. The Finite Element Method (FEM) was employed to predict the ultimate strength of the deck grillage subjected to quasi-static in-plane compressive load, and was validated by comparing the results from experimental tests and numerical simulations. In addition, the numerical simulations of dynamic buckling of the same model under in-plane impact load was performed, in which the influences of the load amplitude and the frequency of dynamic impact load, as well as the initial stress and deflection induced by wave load on the ultimate strength and failure mode were investigated. The results show that the dynamic buckling mode is quite different from the failure mode of the structure subjected to quasi-static in-plane compressive load. The displacements of deck edge in the vertical direction and the axial displacements are getting larger with the decrease of impact frequency. Besides, it is found that the dynamic buckling strength roughly linearly decreased with the increase of initial proportion of the static ultimate strength P₀. The conclusions drawn from the researches of this paper would help better designing of the ship structure under impact loads.     

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.     

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.     

极限强度校核中的几个问题

极限强度检查是船级社规范中的重要部分。就当前船舶结构设计中一些有争议的问题,诸如极限弯矩定义、极限强度条件以及砰击振动弯矩计算等问题进行了讨论。     

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。