外文翻译-单双舷侧散货船结构可靠性分析.doc

外文原文Structural Reliability Analysis of a Single Hull Bulk Carrier and a Double Hull Bulk CarrierProfessional paperAbstract：The ultimate bending moment and the maximal shear stress of two structural forms (sin -gle-hu11 and doublehul1) are calculated by using the combined moment which determined by stochastic process, and then the assessment of reliability is carried outThe results indicate that by introducing the double hull structure，the shear stress decreases a lot，while the capability resistance to bending can be enhanced to some extent alsoFinally，the effects on ultimate bending moment and the maximum shear stress with different width of double side skin are investigated， after the analysisthe proposal of selecting the width of double side skin is put forwardKey words：bulk carriers；single hull；double hull；reliability1 IntroductionThe LMIS casualty database shows that structural failure contributes with 19 of the e- conomic losses and 74 of the fatalities on bulk carriers，so the focus on the structural failure events in present structural reliability study seems justifiedThe statistical data also shows that app70 of the casualties on the bulk carriers are resulted from water ingress due to broadside failure；water ingress due to failure of hatch covers and coamings；water ingress in the fore endIt indicates that the assessment of reliability to ultimate bending strength and broadside on bulk carriers is useful to the safety of shipsA single hull bulk carrier is remoulded to a double hull structure in this paperThe reliability of the two structural forms is compared；the results indicate that the shear stress of broadside has been decreased a lot on the double hull bulk carrier，the probability of structural failure is decreased；the double hull structure come into being box，which strengthens the torsion rigidity at the same time the corruptness on outer side shell can be turned awayUsing double hull structure is a useful method to increase the strength of side shell and ensure the safety of the ship，while the effect on longitudinal strength is obsolete2 The combined bending momentStill water and wave bending moments are to be calculated when assessing the total lon- gitudinal strength，and the combined bending moment is used as the total longitudinal bending moment of the hullThe still water bending moment is varied with different loading condi- tionEven though at the same loading condition，the value and operating time of the load is modified due to the difference of the load collocations and the sail time，so it should be regarded as stochastic processesWave bending moment is the load operating on the hull by the wave，it should be regarded as stochastic process in the design life cycle because of the randomicity of the waveIn actual ship rule such as China CCS，Norway DNV，and SII of IACS，the method of managing the still water and wave bending moments is adding the maximums of the two loads viztwo maximums appear at the same time in the design life cycleThe still water and wave bending moments are not regarded as stochastic processes but stochastic variable by SodingIt shows that the combined method in actual ship criterion is conservativeThe Moan Jiao combination factor is adopted in this paper，the still water and wave bending moments are regarded as stochastic processes and then combinedThe load combination factor is introduced to decrease the conservation arose by adding the maximum directlyThe combined bending moment can be defined as an envelope process of the sum of the still water bending moment and the largest wave bending moment in a given load condition，that is， （1）whereis the duration of a given loading condition andare the combined bend- ing moment and still water bending moment in a given loading condition，respectivelyIt is further assumed that the local maxima of (the wave bending moment) can be modeled as a spike process with a mean arrival rate of The combined bending moment，i，e，the envelope process，is thus a Poisson rectangular pulse process as shown in Fig1Using a solution by Larrabeethe probability function of the combined bending moment is expressed as follows， （2）where is the mean arrival rate of a wave cycle，and is the mean arrival rate of still waterloading conditionFig1 Envelope process for sum of rectangular pulse process and spike processThe combined bending moment，is so determined that it corresponds to a probability of exceedance equal to For practical design considerations，load combination factors for still water and wave bending moments，denoted as and ，respectively，are introduced to the following design equation： （3）in which ， and refer to， and in the design lifetime respectively，the design lifetime =20 yearsis determined by Ferry Borges method （4）for a large value of ，we have （5）Substituting equation (5) into equation (4)，the following solution is obtained， （6）where is then determined，adding the following function， （7）the load combination factors can be determinedThe limit state equation for hull girder collapse is given， （8）where is the ultimate vertical bending moment ， and is the uncertainty variable which denotes the ultimate bending moment，wave bending moment and the effect of non-linearity，respectivelyis fitted by a normal distribution with a mean value to l，and the coefficient of variation is equal to 01 5 by estimationThe effect of the nonlinear wave is taken into account in a normally distributed random variable with a covof 015the mean value of sagging and hogging are determined by following function， (sagging) （9） (hogging) （10）where ， is the linear vertical wave bending moment，sagging and hogging vertical wave bending moment respectively A random variable is used to introduce the uncertainty of sea conditionIn this paper，a normal distribution function is assumed with a mean value to 0.70 and a coefficient of variation equal to 0.15The reliability index is obtained with genetic algorithm3 The example of an actual shipThe“Manhai”bulk carrier is used for an examplethe ultimate bending moment and themaximal shear stress in two structural forms （singlehull and doublehull） are calculatedThereliability assessment of total longitudinal strength is carried through with ultimate strengthAt the same time，the certain analysis of the maximal shear stress is calculatedThe main scale of the bulk carrier is shown in Tab.1. Here the “Manhai” bulk carrier will be remoulded to double hull structureThe width between the outer and inner side (width of double hull) is defined as 1.2m according to the data of mother ship and the construction requirementThe portion between the double hull is remoulded to platform according to requirement of the criterion CCSThe oblique top longitudinal set in primary top side tank and bottom side tank between double sides will be cutAt the strong frame number，setting transverse frame between platforms，at the common frame number，ribs is setTab1 The principle dimension of“Manhai”bulk carrierThe computation graphs of two structures are shown in Fig2，the parameters of the calcu- lation process are shown in Tab2single hull bulk carrier double hull bulk carrierFig2 The computation graphs of the midship sectionTab.2 The selection of parameterAccording to DNV rule，the maximal still water bending moment in design lifecycle is, （11）where L，B， is ship length，beam of ship，block coefficient； is the wave coefficient. (12)The maximal wave bending moment in design lifecycle is （13）so and of single hull structure can be obtained(shown as Tab3).The combination factor at sagging and hogging can be calculated by Matlib program =0.7214(sagging): =0.6697(hogging).Tab.3 The maximal still water bending moment and the wave bending moment (unit kNm)The calculation in this paper is carried out in the base of double hull remould，so the principle dimension of two structures have no difference，but the design draft of double hull structure has appropriate increaseAccording to formula(11)to(13),the Principle dimensions that affect the combination factor are ship length，beam of ship and block coefficient whi1e the design draft is no effect to it，so the combination factor of two structures is equalThe method in Ref, chapter 2，section 7 is used in this paper，the ultimate bending moments of two structure are then calculated，the obtained is defined as expected value of ultimate bending moment，the uncertainty of estimation to and uncertainty of model are em-bodied in random variable .The maximal shear stress of broadside is calculated according to the prescript about the shear stress of broadside inclassification and building rule of steel ship(2001)，the fascicule of ship structure，part 2，chapter 2According to correlative data of“Manhai”，maximal shear stress appears at the condition of fetching the harbour when loading in alternate hold，the flame number is 75，the maximal shear force .The verification shows that the sum of still water shear and wave shear is maximal at this location when sagging，the value isThe details of result are shown in Tab4：Tab4 Ultimate bending moment and maximal shear stressThe reliability index of the single hull bulk carrier with the total longitudinal bending moment at the condition of hogging is calculated using genetic algorithm，=5.356；here，=0.048；,=0.764；=0.978；=97282.9kNm；.The reliability index of sagging is：=4.680；here，=0.101；=0.762；=1.052 =2.700xkNm；.The reliability index of the double hull bulk carrier with the total longitudinal bending moment at the condition of hogging is：=5.37l；here，=0.048；=0.764；=0.978; =97303.01kNm；.The reliability index of sagging is：=4.847；here，=0.0.098；=0.763；=1.053 =2.705xkNm；.The results above show that the resistance to bending can be enhanced by remoulding the ship to double hull structure，but obsoleteWhile the shear stress of side can be decreased to half of primary structures (50.7) by leading in double hull structure，so the result of enhancing the shear strength is very obvious4 The width of double side skinThe selection of the width of double side skin refers to many aspects，such as structure，cost and constructionetcHere the effects to result arose by the width are to be discussedIn this paper，1.20m，1.35m，1.50m，1.65m，and 1.80m are used as the width of double side skin， ultimate bending moment and maximal shear stress are calculated respectively while the other conditions are changeless the calculation process is the same to the condition of 1.20mUltimate bending m0ment and maximal shear stress are shown in Tab5Relevant curves of ultimate bending moment and maximal shear stress are shown in Fig.3Tab5 The effect of the width of double side skinFig3 The effect of the width of double side skin to ultimatebending moment and maximal shear stressIt can be seen from Tab.5 and Fig.3，when the width of double side skin increases，the location of neutral axis reduces，the ultimate bending moment increases appreciably at the beginning and then reduces，while the maximal shear stress reduces appreciably at the beginning and then increasesSo the width of double side skin is not the bigger，the better，but exists an optimum value，here，the ultimate bending moment and maximal shear stress can both reach the optimum valuesFor the bulk carrier of this paper，the optimum value is about 1.50m5 Conclusions and suggestionThe following conclusions can be obtained by comparing the difference of two structures center on reliability：(1)For the bulk carriers，the broadside is one of the most slender structuresIt endures multiple actions such as shear force，torsion moment and local stress etcThe shear strength of side can be enhanced greatly by remoulding the bulk carrier to double hull structureIt can be made out from this paper，the shear stress of side can be decreased to half of primary structures (decreased from 76.987N/ to 39.036N/ )by leading in double hull structure，the shear strength of side is to be enhanced；(2)Capability resistance to bending can be enhanced to some extent by the double hull structureThe increased extent of reliability index of sagging and hogging is equal on the whole，it is increased 0.021 at hogging，and increased0.024at saggingAccording to the example，the ultimate bending moment increased 2.8（increased from 3.662xkNm to 3.765x kN，m)； 。(3) When the width of double side skin increased from 120m to 180m the ultimate bending moment increased at the beginning and then reduced，while the maximal shear stress reduced at the beginning and then increased，so there is an optimum valueIt should be noticed，from 1.20m to 1.50m，the width of double side skin increased 2 ，but the change extend of shear stress and ultimate bending moment is less than 1/10 of the change of widthAt the same time，the cost of ship is increased if the double hull structure is introducedfor this paper，when the width of double side skin is 1.20m，1.50m，1.80m，the cost increased respectively 6 ，6.5 and 6.4.Otherwise，the storage capacity will decrease by introducing double hull structure，the storage capacity decrease about 3 when the width of double side skin is 120mdecrease about 4.5 when the width of double side skin is 1.50m and 5.8 when 1.80mso the width of double side skin need not select the optimum value from the point of economical efficiencyFor this paper ,the optimum value calculated is 1.50m，compare to 1.20m，the change extent of ultimate bending moment and maximal shear stress is only 0.2while the cost increased 0.5，at the same time，the storage capacity decreased 1.5So the selection of the width is an integrated problem，structure strength，economical efficiency，construction requirement and many other aspects should be considered，the width of double side skin should be tried to dwindle after meeting the requirement of structure strength and construction conditionNo need to select the optimum value外文译文单双舷侧散货船结构可靠性分析 专业论文摘要：采用按随机过程确定的载荷组合弯矩和双舷侧两种结构分别计算船舶的极限弯矩和最大剪应力，进行可靠性评估，结果表明双舷侧结构可以大幅减小舷侧的剪应力，并在一定程度上提高了总纵强度；最后分析了双舷侧宽度对极限弯矩和最大剪应力的影响，提出了选取双舷侧宽度值的建议。关键词：散货船；单舷侧；双舷侧；可靠性1介绍由物流管理信息系统的伤亡数据库显示,结构破坏导致了19%的经济损失和74%的散货船事故,所以在目前的结构可靠性研究中关注结构破坏事件显得合情合理。统计数据还显示,散货船伤亡人数中的70%都是由于舷侧破坏导致进水;舱口盖和舱口围板的破坏导致进水;前端部分进水。它表明对前端和舷侧的抗弯强度的可靠性评估对散货船安全有很大帮助。在本文介绍单体散货船改造为双体船的船舶结构。比较两个结构形式的可靠性,结果表明,在双壳散货船中舷侧的剪切应力已经减少了很多,结构破坏的概率却降低了;双壳结构形成箱,增强了扭转刚度同时避免舷侧外板的改变。使用双壳结构对提高舷侧外板的强度和确保船只的安全是一个有用的方法,而对纵向强度的影响很小。2组合弯矩静水和波浪弯矩的计算是用来评估总纵强度,并结合弯矩用作总纵向弯矩的船体。在静水弯矩是随不同的加载条件改变。即使在同一加载条件，负载的价格和工作时间由于不同的负载配置和航行时间而被修改,所以它应当被视为随机过程。波浪弯矩是指负载加载在有波浪的船体,它可以被视为设计生命周期中的随机过程,因为波浪的随机性。对于实际的船规如中国CCS、挪威DNV、和国际船级社的SII,其方法是管理静水和波浪弯矩的最大值是添加两个加载,即在设计生命周期中出现的两个最大值。同时静水和波浪弯矩不能被视为随机过程但可以是随机变量.其表明该组合方法在实际船舶标准中是比较保守的。本文采用的是Moan Jiao组合因素,静水和波浪弯矩被视为随机过程然后组合,引入负载的组合因素可以直接通过增加最大值来减少保护的出现。合并后的弯矩可以被定义为一个在给定的负载情况下的静水弯矩和最大波浪弯之和的信封过程,即, （1）其中，是一个给定的时间加载条件。和分别是合并后的弯矩及静水弯矩在给定加载条件, 并进一步假设当地最大(波浪弯矩)可以建模为一个平均到达率的峰值过程。合并后的弯矩,像 的信封的过程,因此是一个泊松矩形脉冲过程，如图1所示。使用Larrabee解决方案。概率函数的组合弯矩表达如下, （2）其中，是一波周期的平均到达率, 是静水加载条件的平均到达率。图1 包络过程为总结矩形脉冲过程和飙升过程合并后的弯矩, 是确定的,它相当于一个超过数等于的概率。对于实际的设计考虑, 分别指示为和荷载组合因素对静水和波浪弯矩,被介绍给下列设计方程: （3）其中, ，和分别参考在设计寿命中的，和，设计寿命=20年。由Ferry Borges方法计算 （4）对于的数值,我们有 （5）取代方程(5)到方程(4),下面的解, （6）然后确定值,添加到下面的函数, （7）负载组合因素可以决定。这个极限状态方程对倒塌船体梁有如下, （8）是最终的纵向弯矩。，和是表示极限弯矩不确定性变量，分别为波浪弯矩和非线性的影响,拟合了正态分布平均值l,而变异系数估计等于0.15。这个非线性波的作用是考虑一个通常分布包含0.15的协方差矩阵的随机变量，而垂和中拱的平均值取决于以下函数, (sagging) （9） (hogging) （10），分别是线性垂直波浪弯矩,下垂和中拱垂直波浪弯矩。一个随机变量是用来介绍海洋条件的不确定性。在本文，一个正常的分布函数是假定平均值为0.70,变异系数等于0.15。可靠性指标是由遗传算法获得。3 实船范例以“Manhai”散货船为例，计算最终的弯矩和最大剪切应力在两个结构形式(单壳和双壳)，总纵强度可的靠性评估是通过极限强度确定。同时，分析某些最大剪切应力的计算。散货船的主尺度显示在表.1中。这里的“Manhai”散装货船将改造为双壳结构，宽度介于内部和外部一侧(双壳的宽度)根据母型船的数据和施工需求被定义为1.2 m，根据CCS的标准要求,平台部分用双壳结构。斜顶纵向设置在主要的顶边舱和底部边舱两面之间的将被削减。在强帧数,设置平台之间的横向框架, 设置共同的帧数,肋骨。表.1“Manhai”散货船的尺寸要求两种结构的计算图形显示在图.2, 计算过程的参数显示在表.2。单壳散货船 双壳散货船图.2 船中剖面的计算图表表.2 参数的选择根据DNV规则,最大静水弯矩在设计生命周期是, （11）在L,B, 是船长,船宽,方形系数; 是波浪系数。 (12)最大波浪弯矩在设计生命周期是 （13）所以和的单壳船体结构可以得到（如表.3显示）。结合在下垂和中拱的因素可以由Matlib程序计算,=0.7214(sagging): =0.6697(hogging).表.3 最大静水弯矩和波浪弯矩 (单位 kNm)在本文的计算是进行基础的双壳改造,所以两种结构的主尺度没有多大区别,但双壳结构的设计草案有适当的相