Ship collision risk assessment for the Singapore Strait

The Singapore Strait is considered as the bottleneck and chokepoint of the shipping routes connecting the Indian and the Pacific Ocean. Therefore, the ship collision risk assessment is of significant importance for ships passing through the narrow, shallow, and busy waterway. In this paper, three ship collision risk indices are initially proposed to quantitatively assess the ship collision risks in the Strait: index of speed dispersion, degree of acceleration and deceleration, and number of fuzzy ship domain overlaps. These three risk indices for the Singapore Strait are estimated by using the real-time ship locations and sailing speeds provide by Lloyd's MIU automatic identification system (AIS). Based on estimation of these three risk indices, it can be concluded that Legs 4W, 5W, 11E, and 12E are the most risky legs in the Strait. Therefore, the ship collision risk reduction solutions should be prioritized being implemented in these four legs. This study also finds that around 25% of the vessels sail with a speed in excess of the speed limit, which results in higher potentials of ship collision. Analysis indicates that the safety level would be significantly improved if all the vessels follow the passage guidelines.     

两类船-桥碰撞力差异及桥梁结构响应分析

 船桥碰撞是跨航道桥梁需考虑的重要问题。本文以美国AAHSTO规范推荐两类船舶为例,研究了驳船和散装货轮撞击桥梁后碰撞力、船艏刚度和碰撞能量的变化过程,讨论了导致两类船舶碰撞力、船艏刚度和碰撞能量变化差异的原因,分析了两类船桥碰撞桥梁结构的主要响应,并将本文动力模型计算响应与已有规范计算得到响应进行了对比。结果表明,两类船舶不同的船艏外形及内部构造会对碰撞力造成较大影响;同等吨位和碰撞速度下,驳船碰撞峰值荷载比散装货轮大,驳船碰撞的墩顶位移比散装货轮小,基底剪力和弯矩比散装货轮大,驳船与散装货轮作用下桥梁结构响应的动力反应系数存在较大差异;不同规范对于碰撞荷载规定差异较大,欧洲规范计算得到响应总体较大,中国公路规范荷载对于内河船舶撞击计算得到的响应最小,中国铁路规范计算得到的响应与其他规范海轮撞击响应进行对比最小。     

Optimal-control theory applied to ship maneuvering in restricted waters

Ship drivers have long understood that powerful interaction forces exist when ships operate in close proximity to rigid boundaries or other vessels. Controlling the effects of these forces has been traditionally handled by experienced helmsmen. The purpose of this study is to apply modern optimal-control theory to such maneuvering scenarios in order to show that helmsmen may some day be replaced by modern controllers. The maneuvering equations of motion are cast in a linear state-space framework, permitting the design of a linear quadratic (LQ) controller. The hydrodynamic effects are modeled using potential-flow theory in order to simulate the interaction forces and test the performance of the controller. This study demonstrates that the linear quadratic regulator effectively controls ship motions due to the presence of a boundary or other vessel over a broad range of speeds and separation distances. Viscous effects are modeled by equivalent linearization and, when compared to the effective damping introduced by the controller, are shown to be insignificant.     

船舶-自升式海洋平台碰撞相似率研究

海洋平台作为海洋能源勘探开发的主要组成部分,是海洋油气探井、钻井、开采的主要作业基地。船舶碰撞致使平台结构损伤破坏一直是威胁海洋平台安全的主要因素之一,开展海洋平台碰撞性能研究,揭示平台结构在碰撞过程中的损伤变形机理,对提升平台安全性具有重要意义。评估平台结构耐撞性能最可靠的方法是实船碰撞试验,然而因其耗资巨大而不易开展。按一定相似关系进行比例模型试验成为现实条件下的首选。本文基于相似第二定理,运用量纲分析法推导船舶-自升式海洋平台碰撞过程中各物理量的相似关系,为平台碰撞模型试验的开展及试验参数的确定提供重要依据。结合有限元仿真技术,以平台典型的T型和K型管节点为研究对象,建立不同缩尺比下的简化碰撞模型,比较验证相似理论的可靠性。研究结果表明,缩尺模型在碰撞冲击载荷下的结构损伤变形、碰撞力和能量吸收等动态响应与实尺度模型结果一致性较好。本文研究成果可以为大型平台结构碰撞模型试验设计提供技术支撑。     

Predicting the effect of various ISA penetration grades on pedestrian safety by simulation

Intelligent speed adaption (ISA) is one type of vehicle-based intelligent transportation systems (ITS), which warns and regulates driving speed according to the speed limits of the roads. Early field studies showed that ISA could reduce general mean speed levels and their variances in different road environments. This paper studies the effects of various ISA penetration grades on pedestrian safety in a single lane road. A microscopic traffic simulation tool, TPMA, was further developed and used to implement different ISA penetration grades. Momentary spot speed and traffic flow data are first logged in the traffic simulation for later prediction of pedestrian safety. Then a hypothetical vehicle–pedestrian collision model is extended from early researches in order to estimate two safety indicators: probability of collision, and risk of death. Finally, Monte Carlo method is applied iteratively to compute those safety indices. The computational result shows that raising ISA penetration in traffic flow will reduce both the probability of mid-block collision between vehicle and pedestrian and the risk of death in the collision accidents. Furthermore, the decrease of the risk of death will be more prominent than that of the collision probability according to this method.     

Traffic simulation based ship collision probability modeling

Maritime traffic poses various risks in terms of human, environmental and economic loss. In a risk analysis of ship collisions, it is important to get a reasonable estimate for the probability of such accidents and the consequences they lead to. In this paper, a method is proposed to assess the probability of vessels colliding with each other. The method is capable of determining the expected number of accidents, the locations where and the time when they are most likely to occur, while providing input for models concerned with the expected consequences. At the basis of the collision detection algorithm lays an extensive time domain micro-simulation of vessel traffic in the given area. The Monte Carlo simulation technique is applied to obtain a meaningful prediction of the relevant factors of the collision events. Data obtained through the Automatic Identification System is analyzed in detail to obtain realistic input data for the traffic simulation: traffic routes, the number of vessels on each route, the ship departure times, main dimensions and sailing speed. The results obtained by the proposed method for the studied case of the Gulf of Finland are presented, showing reasonable agreement with registered accident and near-miss data.     

碰撞条件下碳纤维增强复合材料（CFRP）加固自升式平台桩腿的性能分析

老龄化海洋平台在与船舶碰撞的碰撞事故作用下,会导致桩腿的变形,降低其承载性能。为了降低碰撞对桩腿受力性能的影响,提高桩腿的耐撞性能,提出了利用吸能能力较强的高强碳纤维增强复合材料（CFRP）加固平台桩腿局部损伤的方法。以某自升式海洋平台的桩腿为例,利用有限元法建立简化的碰撞模型,通过在局部损伤部位粘贴CFRP材料来提高桩腿的耐撞性能,验证CFRP加固方法提高其耐撞性能的有效性。研究表明,相同的碰撞条件下,在加固前碰撞力使桩腿产生了接近屈服强度的应力;在粘贴2层CFRP布后,桩腿吸收的能量下降56.8%,极值应力下降了8.66%。在粘贴CFRP板后,桩腿吸收的能量下降70.68%,桩腿的极值应力下降55.84%。随着CFRP厚度的增加其吸能的能力越强,桩腿的耐撞性能越好,提高了桩腿的受力性能。     

Integrated Virtual Assembly Environment and its application in ship piping layout

Complex pipe layout plays an important role in ship building. Pipes prefabricating and assembling often depends on testing and rebuilding in outfitting. This leads to more workload, high cost and longer manufacturing cycles. In this paper, a new virtual assembly system called Integrated Virtual Assembly Environment (IVAE) is introduced, in which the ship outfitting can be simulated and process planning can be completed. With the help of assembly constraints management, collision detection and response, assembly sequence and paths planning, users can assemble the parts interactively in a virtual outfitting environment, just as in an actual cabin. As well as for virtual ship outfitting, IVAE can also be used in general product development. As a typical case, the pipe layout in the engine room of a 5000?M³ hydraulic dredge from Hudong-Zhonghua Shipbuilding (Group) Co., Ltd is given to test virtual ship outfitting in IVAE.     

结构钢在船舶工业中的应用及发展

分析了当前船舶工业形势及船用结构钢现状,指出高技术船舶对船用钢材及其配套焊接技术提出了更高要求,相关开发、推广及应用工作必须及时跟进。     

Splashing a ship with collision-generated spray

The collision-generated spray flux was defined using formulas derived for the vertical distribution of the liquid water content and time of ship exposure to spray originating from the spray cloud induced by ship-wave collision. These formulas were derived using published data on a Russian field experiment in the Sea of Japan. The time-averaged water flux to an object (cylinder and vertical plate) can be computed for any given wind speed, fetch, ship speed and heading angle.The runoff of seawater from vertically oriented objects located on a ship has been investigated. The ratio between the duration of moving water film residence on the object's surface to the time interval between two successive splashings of a ship with spray has been computed for several values of wind speed, ship speed, and heading. This ratio has been used to correct the time-integrated ice growth rates on elevated objects. The results are applicable for calculating the ice loads on a ship.     

Evaluating marine traffic safety at channels

An approach for measuring effects of policy schemes for improving marine traffic safety at channels is presented. Operational models involving traffic, channel, and ship characteristics are provided, and both collision and channel deviation risks of actual channels are quantified using them. Moreover, traffic control, speed regulation, and center line indication are considered as channel safety policies, and their effects are also measured using the models. The results suggest that the speed regulation scheme is effective in reducing accident risk in channels. It is concluded that methodology demonstrated and knowledge obtained in this study are useful for planning and safe operation of channels.     

泰州大桥中塔墩防船撞研究

泰州大桥主墩位于航道边缘,可能遭受船舶的撞击。为保护大桥,综合考虑多种因素研究大桥中塔墩防船撞方案。针对泰州大桥三塔悬索桥型,结合通航船舶规划、桥梁参数、桥墩基础特点,开展防撞研究,提出针对性防撞方案,进行防撞特性计算分析,确定防撞方案的技术、经济特性。通过有限元数值仿真技术,研究泰州大桥在船舶撞击下的安全性和防撞方案的有效性。     

Mechanics of minor ship collisions

A structural method is presented by which the critical velocity for a minor collision of a ship striking another ship midships at right angles can be determined rather realistically with a minimum of computational effort. The velocity of the striking ship is defined as critical for a minor collision when the side wall of the struck ship just ruptures. This means the possibility of an oil spill in an oil tanker.The proposed method takes into account the deformability of both collision opponents. The energies absorbed in both ships, up to rupture of the struck ship hull, are computed using internal collision mechanics. The critical velocity can then be determined using external collision mechanics.The method is used for the collision of two equal oil tankers of 141,000 TDW with bulbous bows. The critical velocity was found to be 6.8 knots.     

预测船舶碰撞与搁浅结构动力响应的程序实现

该文介绍一个综合性解析计算程序,可用于预测船舶在碰撞和搁浅场景下的强非线性结构动力响应,包括结构变形阻力及能量耗散。解析计算方法具有使用方便,计算速度快,计算结果相对可靠的优点,易于工程应用。预测船舶碰撞与搁浅结构动力响应的程序包含两个模块,分别是船舶碰撞场景模块和船舶搁浅场景模块。船舶在碰撞和搁浅场景中,船体外板和内板等构件在外载荷作用下会出现弯曲、膜拉伸和撕裂的变形模式;船体桁材构件在外载荷作用下会出现弯曲和褶皱压溃变形模式。船体构件损伤失效所产生的结构变形阻力和能量耗散以解析的方式表达。此外,采用LS_DYNA程序开展数值仿真,验证解析计算程序的准确性和合理性。综合解析计算程序在结构设计阶段,对船体结构的耐撞性和船舶风险评估,都具有一定的工程应用价值。     

桥墩在船舶撞击作用下的损伤仿真研究

评述了考虑应变率效应和材料损伤的HJC混凝土模型,就材料参数的取值进行了讨论。通过刚性球撞击混凝土板的例子,讨论了HJC模型中损伤参数的敏感性,并据此确定了计算中采用的HJC模型参数。对一艘万吨级的散货船与桥墩的碰撞过程进行了仿真,给出了船舶与桥墩的碰撞力时程以及桥墩损伤形态。结果表明,由于混凝土的破损,船舶对桥墩的撞击力峰值显著降低。为获得真实的结果,在船舶与薄壁桥墩碰撞的仿真分析中应考虑混凝土的动态损伤特征。     

船-桥梁浮式钢套箱碰撞数值模拟中的流场处理方法对比研究

本文采用Ansys/Ls-dyna对1000吨级船舶与浮式桥梁钢套箱的碰撞过程进行了数值仿真,为了较精确地分析流场处理方法对于数值计算结果的影响,分别采用了流固耦合方法和附加质量系数法来模拟碰撞过程中流场的作用,并对比分析了两种方法下浮式钢套箱的碰撞力、撞深、竖向位移、内能变化等计算结果。研究结果表明,与采用附加质量系数法的结果相比,考虑流固耦合时防撞钢套箱的最大撞深较小而最大撞击力较大,且随着碰撞能量的增加,最大撞击力明显大于采用附加质量系数法的结果。因此对于桥梁的防撞钢套箱设计,常规附加质量系数法偏于危险,有必要用流固耦合方法来考虑流场的作用。另外,船体的撞击能量越大时,浮式钢套箱的竖向位移约束也越重要,可以通过设计浮式钢套箱的压载水,减小钢套箱在碰撞过程中的竖向位移,以提高其吸能效果。     

A proposed method of predicting ship collision damage

In the past, research on ship collision strength has centered on nuclear ship structures, but now emphasis is shifting to low-energy collisions of ordinary ships carrying hazardous cargoes including crude oil.A ship collision is too complex to study using theoretical methods alone, yet tests with small-scale models of thin steel plate fail to duplicate actual ship collision damage for the following reasons:

1. (1) The fracture of actual ship shell plate and model shell plate defies the law of similarity;

2. (2) Some structural members are usually omitted for ease of fabrication in relatively small models.

Accordingly, the authors propose a method for predicting ship collision damage that resorts to three combined experiments:

1. (1) A fundamental test determining the initiation of plate fracture;

2. (2) A local structure model test evaluating the effects of structural details;

3. (3) A structural model test investigating the deformation of a ship hull.

This paper reviews, by way of example, some results of the experimental studies which the authors have performed.The laws of similarity proved very important in the study of plate fracture.The authors believe that the proposed method will prove useful especially in dealing with low-energy ship collisions.     

船舶碰撞搁浅中强肋框承受面内载荷时变形机理研究

以船舶碰撞与搁浅中强肋框构件为研究对象,用塑性力学解析理论研究强肋框构件承受面内载荷时的结构变形机理,并据板材面内受压变形时的新特点,提出新的强肋框板面内受压变形模式。在此基础上运用塑性力学理论推导出结构变形能、瞬时结构变形阻力及平均结构变形阻力的解析计算公式。利用已有试验结果对该解析计算方法进行验证。结果表明,该方法准确度高、解析计算方便,适用于船体抗撞性结构设计及船舶碰撞与搁浅事故风险快速评估。     

Thin-ship theory and influence of rake and flare

The basic computational task of the thin-ship theory of free-surface potential flow about a ship that advances at constant speed along a straight path in calm water, of large depth and lateral extent, is considered. Specifically, a straightforward method for evaluating the pressure and the wave profile at a ship hull (the wave drag, hydrodynamic lift and pitch moment, and sinkage and trim are also considered) in accordance with Michell’s thin-ship theory is given. A main ingredient of this method is a simple analytical approximation to the local-flow component in the expression for the Green function (associated with the classical Michell–Kelvin linearized free-surface boundary condition) of thin-ship theory. This practical Green function is used to evaluate and analyze steady flow about a four-parameter family of ship bows with rake and flare. In particular, the variations of the bow-wave height and location with respect to the draft-based Froude number, the entrance angles at the top and bottom waterlines, and the rake angle are explored via a systematic parametric study. This parametric study provides estimates—immediately useful for design—of the influence of rake and flare on the height and the location of a ship bow wave, and shows that rake and flare effects can be significant, especially at low Froude numbers.