Influence of initial distortion of 3 mm thin superstructure decks on hull girder response for fatigue assessment

This paper investigates the influence of initial distortion of 3 mm thin superstructure decks on hull girder response and fatigue assessment. Part of the traditional superstructure of a prismatic passenger ship is replaced by thin decks with initial distortion amplitude of 0, 1 and 2 times the IACS limit value for thicker plates, i.e. 0, 6 and 12 mm. Both geometrically linear and nonlinear finite element (FE) analysis is used. For reference also traditional superstructure with 5 mm plate thickness is analyzed. Thin straight superstructure decks give 43% of weight reduction and carry approximately 30% less load than corresponding thick straight decks in traditional model. The load that is not carried by thin decks is divided between other traditional decks. The redistribution of forces also happens at the deck level between plates, stiffeners, girders and longitudinal bulkheads. The presence of initial distortion with the shape of one half wave between web frames and stiffeners causes an additional few percent-decrease in forces carried. The results and conclusions are similar for hogging and sagging loading conditions and differences between geometrically linear and nonlinear FE analysis are very small. This means time saving since the panel loading for fatigue assessment can be defined from geometrically linear hull girder response analysis without considering the initial distortions.     

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.     

40000dwt散货船设计阶段船体振动分析控制

在40 000 dwt灵便型散货船设计建造过程中,为了控制船体出现的有害振动,对船体总体振动、上层建筑总体振动及船体艉部局部结构进行了振动预报分析.对船体总体振动和上层建筑总体振动进行分析,避免与主机和螺旋桨激励发生共振;对于船舶艉部结构,重点关注上层建筑各层甲板工作和生活等重要区域的振动情况,采用结构有限元法分析各层甲板的振动特性,设计时通过调整局部结构刚度并保证一定频率储备来避免共振,为船体结构减振设计提供依据.本文给出了设计阶段船舶总体、上层建筑总体及局部结构振动计算分析方法和过程,可对船舶设计者提供有益的参考.     

A comparative study on the hull strength of a ship with thin-walled box girders

1 Introduction1 The permanent aim is that the ship designers try to optimize the ship structure to improve the strength of hull. The traditional design of ship structure avoiding damage is involved with many transverse bulkheads set up in the ship in orde…     

船体振动响应预报

利用有限元技术对船体总振动、上层建筑整体和各层甲板局部自由振动频率及上层建筑振动响应进行了预报。介绍了用于振动计算的单层甲板模型、尾部上层建筑模型、全船模型和简化全船模型及应用实例。研究了上层建筑和船体之间的耦合影响，并根据具体算例对各种模型化方法的效果进行了评价。     

汽车滚装船艉部布置特征

与普通运输船相比,汽车滚装船船型特征明显,船身高大,有多层甲板。船体采用中段肥胖,艏、艉部线型瘦削,特别是艉部机舱等的布置,外形采用方艉,设有宽大的艉门兼作跳板,方便车辆进出。     

5000 t自航甲板驳船波浪载荷与总纵强度研究

针对5 000 t自航甲板驳船,研究甲板宽大型驳船的波浪载荷及结构强度问题。根据船舶作业海域的海况条件,通过对波浪诱导载荷响应函数的计算,得出并预报船体所承受的波浪载荷。确定结构强度计算工况,分析甲板驳船结构强度问题。     

船舶在波浪中的水平弯曲——扭转耦合响应水弹性分析

本文以二维反对称水弹性理论分析了大开口船体结构的弯扭耦合响应。分析中船体结构简化为Ｔｉｍｏｓｈｅｎｋｏ梁,流体的作用以切片理论来考虑。计算结果和模型试验结果吻合良好,这为大开口船舶的弯扭耦合分析提供了有效简便的计算方法。     

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．     

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.     

基于NURBS表达的主船体虚拟分舱及舱容计算

在船体曲面、甲板面NURBS表达和内底内壳多面体表达,有效的平面与曲面求交算法和几何特性计算方法基础上,给出了任意形状舱室的舱容计算方法.根据围闭舱室的几何元素(舱壁、甲板、船体曲面或内底和内壳)不同,将舱室分为12种基本形状,只需要船体曲面的型值信息、舱壁位置或折点信息以及内底和内壳的折点位置信息,即可进行参数化虚拟分舱和舱容计算,避免繁琐的舱室型值信息的人工输入,减少人工工作量,提高工作效率.该方法可以计算任意液面包括任意倾斜液面下的舱容,计算结果精确,方法简洁,为船舶3D参数化设计奠定基础.     

全球FPSO船型开发领域核心技术的演化分析

以国内外专利数据为分析对象,采用专利计量分析的技术方法深入研究浮式生产储油卸油装置(FPSO)开发技术的演化态势,对FPSO船型开发领域的核心专利进行分析,总结出FPSO船型开发的发展路线.结果表明:当前FPSO船型开发领域的主要研究方向是旧船改造、新概念FPSO和通用FPSO.旧船改造的技术点主要聚焦于超大型船舶设计;新概念FPSO的技术点主要集中于浮体形状设计、上部甲板大型化和刚性立管作业问题;通用FPSO的技术点主要侧重于标准化船壳设计、模块化FPSO设计和FPSO一体化建造,未来企业可考虑在模块化FPSO的上甲板承载与布局、管线布置、生活区布置、减摇和抑制垂荡问题上进行专利布局研究.     

船体结构对水下冲击波动态响应的数值研究

船舶的水下爆炸响应是一个重要而复杂的问题,对船舶抗爆能力的提高有着重要的意义.本文使用商业有限元程序ABAQUS对某船体在水下爆炸冲击波作用下的动态响应进行了数值模拟.该问题解决中包括流固耦合问题,边界条件的处理.详细给出了某船舶在水下爆炸的响应结果,揭示了船体的加速度响应、船体的应力响应、船体的速度响应3个方面的响应规律.通过和相关试验数据进行比较,表明数值结果与试验结果两者吻合良好.最后考察并给出了各层甲板在关键肋位上的点的应力和速度响应峰值.所得到船舶在水下爆炸下的响应规律,为船舶设计提供有力的依据.     

深V形船型对小型军舰快速性能的影响

本文根据５００吨级圆舭形快速攻击艇的船长、船宽、排水量、甲板面积和舱内平台面积设计深Ｖ形线型。通过各种不同线型特征的Ｖ形船型的模型试验，分析船舯底升角、后体形状和浮心纵一位置对深Ｖ形性能的影响，可要深Ｖ形线型设计依据。     

甲板船总纵强度计算的两种方法对比

分别运用水动力计算结合全船有限元方法以及薄壁梁理论计算89 m甲板船的总纵强度.结果的比较分析表明,两种方法都能适用该类船型.     

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.     

Investigations of vehicle securing without lashings for Ro-Ro ships

To reduce the area on deck occupied by each car and the labour and time required for lashing and unlashing cars, it has been proposed by the author that in some conditions, cars on decks could be transported without lashing. To evaluate cargo securing based on this “lashing-free” concept, computational code was developed to calculate the vehicle–deck interactions for various ship motions. The code was structured by incorporating a vehicle model into a piece of ship motion calculation code. A series of time-domain simulations were conducted to evaluate vehicle securing. It was found that for a target ship consisting of a 6000-unit Ro-Ro vessel, vehicle securing is mainly influenced by the ship's rolling motions and is highly dependent on the wave height and loading conditions. It was suggested from the analysis that vehicles could be secured without being lashed in a large area of the ship in specific weather conditions and on some routes with less adverse sea states. However, it is still suggested that conventional lashing holes should be constructed on the deck because in severe sea states the cars will still need to be lashed. The limitations of the current investigations are also presented. The relevant research work was carried out at the Division of Ship Design and Engineering, Department of Shipping and Marine Technology, Chalmers University of Technology.     

飞机轮载作用下的甲板动响应

本文从工程应用的角度出发，提出了一个逆求飞机起落架系统非线性动力特性的方法，并将飞机起落架系统以及在波浪运动的船体国反结构看作一个耦合的动力学系统，建立了一套着舰飞机与甲板瞬态相互作用的动力学分析方法，用该方法可以预报在各种海况，航速及机降工况下舰船甲板的动应及飞机承受的冲击过截，本文给出了计算例子。     

Longitudinal strength of ships with accidental damages

This paper presents an investigation of the longitudinal strength of ships with damages due to grounding or collision accidents. Analytical equations are derived for the residual hull girder strength and verified with direct calculations of sample commercial ships for a broad spectrum of accidents. Hull girder ultimate strengths of these sample vessels under sagging and hogging conditions are also calculated, based on which correlation equations are proposed. To evaluate a grounded ship, using the section modulus to the deck would be optimistic, while using the section modulus to the bottom would be conservative. On the contrary, to evaluate a collided ship, using the section modulus to the deck would be conservative, while using the section modulus to the bottom would be optimistic. The derived analytical formulae are then applied to a fleet of 67 commercial ships, including 21 double hull tankers, 18 bulk carriers, 22 single hull tankers and six container carriers. The mean values, standard deviations and coefficients of variation for the coefficients in these new analytical formulae are obtained. The ship length exhibits little influence on these coefficients because they are close to the mean values although ship length spans from 150 to 400 m. The ship type shows some influence on the residual strength. Uniform equations are proposed for commercial ships which do not depend on a ship's principal dimensions. These formulae provide very handy tools for predicting the residual strength in seconds, without performing step-by-step detailed calculations, an obvious advantage in cases of emergency or salvage operation.     

横向围壁设置对大跨度双层甲板弯曲特性的影响分析

针对大跨度单层甲板横向弯曲刚度偏弱的特点,探讨在2层大跨度单层甲板之间设置若干横向围壁,使其形成大跨度双层箱型甲板,并采用结构有限元数值分析方法对其进行计算,讨论设置横向围壁对大跨度双层甲板弯曲特性的影响.文中给出横向围壁间距与大跨度双层甲板变形和应力的关系曲线,引入了用于横向围壁结构初步设计的横向围壁载荷与其间距关系的有效承载系数.研究结果表明:设置横向围壁的大跨度双层甲板,可解决大跨度单层甲板横向弯曲刚度偏弱的问题.