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.     

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.     

UR-S11A对大型集装箱船结构设计的影响研究

国际船级社协会针对集装箱船的新标准UR-S11A已于2016年7月1日正式生效,其对大型集装箱船结构设计的具体影响值得研究。以一艘13 500 TEU集装箱船为例,首先分析了UR-S11A相比UR-S11和劳氏船级社(LR)规范在强度校核上的差异,然后通过对总纵屈服强度、屈曲强度和极限强度的研究分析了新标准对船体结构的影响。结果表明,UR-S11A对在0.3~0.4船长处船体梁的总纵弯曲和极限强度的要求更高,部分纵舱壁板与外板的剪切和屈曲强度以及双层底桁材纵骨的屈曲强度受新规范影响较大。     

桁材开孔腹板的线性屈曲强度分析

船体在总纵弯曲时甲板纵桁和船底纵桁承受较大的轴向压力,而在桁材腹板上开孔会影响其腹板的屈曲强度.针对这一问题,应用有限元屈曲特征值分析方法对受轴向压力开孔腹板的屈曲载荷进行计算.通过对计算结果的分析,对开孔尺寸和开孔位置对腹板屈曲强度影响的规律进行了归纳,并对腰圆孔和圆孔对腹板屈曲的影响程度做出了比较,对船体结构中腹板开孔尺寸及位置提出了一些建议.     

Progressive collapse analysis of ship hull girders subjected to extreme cyclic bending

This paper introduces a novel analytical method to predict the buckling collapse behaviour of a ship hull girder subjected to several cycles of extreme load. This follows the general principles of the established simplified progressive collapse method with an extended capability to re-formulate the load-shortening curve of structural components to account for cyclic degradation. The method provides a framework for assessing residual hull girder strength following a complex series of unusually extreme load events where the wave induced bending moment rises close to, or even surpasses, the monotonic ultimate strength. These load events may be sequential, such as might be caused by a series of storm waves, or they may occur as a collection of discrete events occurring over a longer period. The extreme cyclic bending amplifies the distortion and residual stress initially induced by fabrication in the flanges of the girder, which results in a deterioration of the residual ultimate strength. Validation is firstly completed through a comparison with previously published experimental work and secondly via comparison with numerical simulation on four ship-type box girders using the nonlinear finite element method.     

不对称船体结构总纵强度计算方法及影响分析

传统的船体结构总纵强度梁理论计算一般是基于对称的船体横剖面,文中提出了不对称船体结构梁理论弯曲正应力的计算方法,并选取样船作为算例,结合有限元计算进行弯曲正应力对比分析,验证梁理论计算的准确性。同时对比将不对称结构视为对称结构时的梁理论计算总纵弯曲正应力,提出不对称结构对总纵强度的影响。     

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.     

双体船大开口角隅节点疲劳强度优化方法研究

与同样吨位的单体船相比,双体船具有更大的甲板面积、更大的舱容。在双体船大开口角隅位置,由于应力集中,更容易引起疲劳损伤的迅速积累。因此,在结构设计中,角隅位置的疲劳强度一直是工程界关心的部分。本文使用谱分析方法研究双体船角隅节点的疲劳强度。在疲劳校核基础上对角隅位置进行优化设计,研究增加板厚和增设肘板对角隅处疲劳强度的影响。在此基础上分析不同优化方法的适用性,为船舶设计与安全性能提供适当的建议。     

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.     

两种强力甲板结构形式在大变形损伤状态下的极限强度分析

针对2种不同强力甲板结构形式的舰船,应用ABAQUS非线性有限元分析工具,计算舰体在强力甲板大变形损伤状态下的总纵极限承载能力.采用冲击动载荷来模拟得到结构的大变形损伤状态,并将其作为初始状态进行极限承载能力分析.分析结果表明,纵向箱形梁这种新型强力甲板结构形式相比常规强力甲板结构形式,在大变形损伤下舰体总纵极限承载能力等方面具有显著的优越性.     

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     

某平底浅吃水船上层建筑应力集中分析及改善措施

对某平底浅吃水船上层建筑应力集中的成因进行了理论分析,并应用有限元数值计算方法对船体结构强度进行了三维有限元分析．根据计算结果对上层建筑前端壁与主船体的连接方式进行了优化．经实船检验,该优化设计提高了这类船舶结构的安全性,实用可行．     

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。     

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。     

用整船有限元模型分析方法计算舰船的总纵强度

当舰船设有长度较长但开口较多的上层建筑时,其船体结构的复杂性使船体总强度很难用常规的梁理论方法确定.本文采用整船三维有限元分析方法,通过整船加载和惯性平衡处理,计算出设计目标船的总纵弯曲变形和应力分布,以及上层建筑参与船体总纵强度的有效度,为船体总强度校核提供依据.     

A theory of coupled beams for strength assessment of passenger ships

This paper describes a coupled beam method, which estimates elastic response in the longitudinal bending of a passenger ship with a large multi-deck superstructure. The method can be applied during an early project stage, when detailed three-dimensional finite element modelling is not yet possible. The theory is based on the assumption that each deck in the superstructure and also the main hull can be considered as a thin-walled beam. These beams are coupled to adjacent beams with springs modelling vertical and shear stiffness. The shear effect in the side and deck structures is included with options for large openings. As a result, the method allows for the calculation of the normal stresses and vertical deflections in the arbitrary location of the hull girder. Average longitudinal displacements of deck structures and shear stresses in the side structures can be estimated as well. Simplified structures were analysed in order to validate the coupled beam method against the three-dimensional finite element method.     

On board measurement of stresses and deflections of a Post-Panamax containership and its feedback to rational design

One of the most important points in structural design of containerships is the strength of hatch corners. Formerly, hatch corners used to be assessed by combining the component induced by hull girder vertical bending and the component induced by hull girder torsion. In the design of new generation containerships without deck girders, the effect of cross deck fore-aft deflection has also become prominent.Another point is the impact of structural displacement on the deck fittings. About new generation ships, large fore-aft deflection of cross decks raised the new problem of interference of hatch covers, lashing bridges and other deck fittings.To cope with such problems, comprehensive analysis has been carried out during the design stage of a Post-Panamax containership. In parallel with this analysis, on-board measurement had been conducted for 3 years after delivery, in order to confirm wide varieties of structural reaction of a large container ship in seaways. Procedure to derive components of stress and deformations from selected measurement points was developed, and actual values were calculated based on actual measurement.From long-term prediction of each component, it was found that design assumption was in general appropriate. However, regarding the fore-aft deflection of cross deck strip, actual stack load is generally much smaller than the design value, and the resulting predicted extreme value was much smaller than design assumption. This factor should be taken into account in the design stage.Regarding the correlation between hull girder vertical bending and fore-aft deflection of cross deck strip, design assumption of full combination is too conservative. From the measurement, no explicit correlation was observed. Regarding the correlation between hull girder vertical bending and wave induced torsion, design assumption of no correlation was appropriate. From these results, new formulae to combine these three deflection modes were proposed.Whipping was observed in the measured data, indicating that more careful attention should be paid to avoid large stress concentration in deck area to enhance fatigue strength.     

船体结构极限强度模型试验技术研究

船舶结构的极限承载能力是反映船舶结构安全可靠的重要指标,历来受到船舶工程界的广泛关注;而模型试验技术对船体梁极限承载能力研究拥有重要的意义.本文首先对船体极限强度相似模型设计进行研究,提出了稳定性相似模型补偿的设计方法;接着结合多例经典船体梁缩比模型试验与非线性有限元数值仿真计算结果相结合的对船体梁极限承载能力进行预报的案例,分别从相似准则、弯扭组合极限强度、弯剪极限强度等几个不同的侧重点分别对各个案例进行了详细的总结分析;最后列举了本研究组曾开展的其他若干经典极限强度模型试验.为今后船体梁极限承载能力模型试验研究提供了参考.     

砰击载荷作用下双体船强度计算方法研究

舰船的砰击载荷与结构响应的研究一直备受关注.对于双体船来说,砰击按部位可分为底部砰击、外飘砰击和甲板上浪,和连接相邻船体的甲板下侧,即湿甲板砰击.目前对于双体船的砰击计算还不完善,因此对于该船型的砰击研究十分必要.本文分别利用规范计算和直接计算的方式,对砰击载荷作用下双体船强度影响进行研究.规范计算主要基于中国船级社规范计算砰击载荷,直接计算则是通过线性势流理论预报船波相对速度,借助相关规范确定砰击压力系数,实现砰击载荷的直接计算.通过有限元软件加载计算,分析比较2种载荷计算方法对双体船强度的影响,以指导砰击载荷作用下双体船局部结构的设计实践.     

10300DWT(纸/拖车)滚装船船体设计中的若干问题

本文以10300 DWT(纸/拖车)滚装船为依托,探讨该类船舶的船型特点及设计建造过程中应注意的相关问题。如：总纵强度、横向强度、有限元分析、车辆甲板负荷及大舱通风问题等。