船舶结构的搁浅数值仿真研究

文章用数值仿真法研究了船舶结构搁浅中的内部力学问题,分析了典型双层底结构的损伤变形、受力和能量耗散结果。研究表明,损伤变形集中于搁浅的区域,搁浅力学问题主要考虑局部的船体结构;肋板的存在显著地增加船底结构的抗搁浅能力,使礁石的垂向贯入量会略有减小;当纵桁远离搁浅区域时,它的吸能能力无法发挥,抗搁浅作用明显削弱。     

一种新型抗搁浅双层底结构

油轮双层底结构的抗搁浅设计对于防止石油泄漏、保护海洋环境具有十分重要的意义.本文提出了一种新式的抗搁浅YF双层底结构,利用数值仿真方法分析了该新式结构的损伤变形、搁浅力和能量耗散,并与原结构进行了比较.研究表明,YF双层底结构比原结构具有更大的吸能能力和抗搁浅能力.     

船舶搁浅于台型礁石场景极限强度解析预报方法

针对双层底油轮搁浅于台型礁石的事故场景,通过对船底构件结构损伤机理的分析,提出一套结合船底结构损伤程度推算方法和Smith方法,评估损伤后船体剩余极限强度的解析计算预报方法。研究中应用数值仿真技术,模拟了船舶搁浅过程中的结构损伤及搁浅后船体极限承载过程,并与解析预报方法的结果进行了对比。结果表明,文中提出的对搁浅损伤后船舶剩余强度的解析预报方法准确性较好,对船舶双层底耐撞性结构设计和安全性评估都有一定的指导意义。     

船舶双层底结构与台形礁石碰撞能量及搁浅阻力分析

提出一套基于双层底油轮搁浅于台型礁石场景下的结构损伤变形非线性机理模型和解析计算方法,并通过数值仿真计算验证该机理模型和解析方法的准确性。在整合双层底板材变形解析计算模型和加强筋变形解析计算模型的基础上,提出的结构变形机理模型能够同时考虑船底板材和加强筋的变形模态。以双层底油轮的一个舱段作为研究对象,使用数值仿真软件LS_DYNA在较大的撞深和礁石倾角变化范围内进行仿真计算,并进行比较。研究结果表明该解析计算模型的总变形能和平均水平搁浅阻力与数值结果吻合得较好,从而验证了机理模型和解析计算方法的可靠性。研究成果可以方便地应用到双层底船舶搁浅场景的结构性能快速预报,以及船舶耐撞性能结构设计中。     

船舶搁浅研究综述

船舶搁浅事故会引起船体破损、环境污染和人员伤亡等严重后果.本文从船舶搁浅力学、搁浅频率评估和破损船体剩余强度等方面阐述了船舶搁浅领域的研究现状,分析和总结了实船事故调查、试验、数值模拟和简化解析等方法;并对今后的研究提出了建议.     

礁石切割加筋板的数值仿真研究

板的切割是船舶高能搁浅过程中的主要能量吸收机制之一，船壳板的破裂会导致货物泄露、船舱进水等严重后果。本文对船舶搁浅过程中的礁石切割加筋板问题进行了数值仿真研究，比较分析了全纵向加强的板、全横向加筋板以及纵横向加强的板在切割过程中的损伤变形、切割力、能量耗散等特性。     

船舶搁浅研究综述

船舶搁浅事故会引起船体破损、环境污染和人员伤亡等严重后果。本文从船舶搁浅力学、搁浅频率评估和破损船体剩余强度等方面阐述了船舶搁浅领域的研究现状，分析和总结了实船事故调查、试验、数值模拟和简化解析等方法；并对今后的研究提出了建议。     

考虑弹塑性土体作用的船舶搁浅损伤特性研究

船舶软搁浅是指船舶搁置在由较软粘土构成的海床或者在柔软的浅滩上的事故。航运业的发展与船舶的大型化趋势使船舶发生软搁浅的风险大大增加,研究船舶的软搁浅性能对船舶设计与制造具有重要意义。本文基于有限元分析软件ABAQUS,选取典型的软搁浅场景,以12,000DWT油船舱段结构为分析对象,研究舱段结构在搁浅过程中的变形、吸能、加速度响应等性能参数。通过系统分析不同速度对船体结构的搁浅性能的影响,全面分析其搁浅性能。本文的相关结论可以为分析船舶软搁浅事故及设计抗冲击舱段结构有一定指导作用。     

船舶搁浅研究的现状与趋势

船舶搁浅会引发船体破损、环境污染和人员伤亡等灾难。本文从船舶搁浅力学、搁浅频率评估和破损船体剩余强度等方面阐述了船舶搁浅领域的研究现状，分析和总结了试验、数值模拟和实船事故调查等方法，并对今后的研究提出了建议和展望。     

小水线面船搁浅模式及单点搁浅强度计算

小水线面双体船（SWATH）的搁浅强度、潜体碰撞性能与防撞设计是SWATH有别于常规船舶的关键技术。通过对SWATH的吃水特性进行研究，指出SWATH深置于水中的潜体极易与海底擦碰或搁浅，引起搁浅强度问题。分析SWATH的自身结构特点、航行与锚泊过程，提出SWATH可能的两个潜体整体搁浅、两个潜体多点搁浅、两个潜体两点搁浅、单个潜体整体搁浅、单点搁浅。对进入每一种搁浅模式的过程进行力学行为分析，将船舶的搁浅过程划分为接触阶段和搁浅阶段。接触阶段一般会使SWATH潜体局部凹陷或破口，亦有可能出现整船性的损伤：支柱断裂或显著塑性变形、连接桥断裂或连接桥显著塑性变形等。在搁浅阶段，搁浅处船体被抬升可能造成SWATH整船的结构破坏、局部受损结构的“继续破坏”。研究了SWATH搁浅后保证整船结构完整性和结构不变性的能力、抵抗局部受损结构“继续破坏”的能力。提出应采用的搁浅强度研究方法和思路并对某SWATH实船进行计算。     

A simplified method to predict grounding damage of double bottom tankers

This paper presents a set of analytical expressions for the calculation of damage opening sizes in tanker groundings. The simplified formulas were given for the grounding force, longitudinal structural damage and the opening width in the inner and outer plating of a tanker's double bottom. The simplified formulas derived are based on a set of numerical simulations conducted with tankers of different dimensions- 120, 190 and 260 m in length. The simulations were performed for five penetration depths and for several rock/ground topologies.The formula for the horizontal grounding force was derived provided the grounding force is proportional to the contact area and the contact pressure. By use of regression analysis it was shown that the contact pressure for any combination of ship and rock size can be expressed with a single normalized polynomial. The actual contact pressure was found by scaling the normalized pressure with the structural resistance coefficient. Given the formulation for the normalized contact pressure, the actual contact force for a ship can be found as a product of average contact pressure and the contact area.The longitudinal length of the damage was evaluated based on the average contact force and the kinetic energy of the ship. The damage opening widths in the outer and inner bottom of the ship were derived separately for two ranges of relative rock sizes as they have strong influence on the deformation mode. The damage widths were given as a function of rock size, penetration depth and double bottom height. To improve the prediction of the onset of the inner bottom failure, a critical relative penetration depth as a function of the ratio of the rock size and the ship breadth was established.Comparison to the numerical simulations showed that the derived simplified approach describes the horizontal grounding force and the damage length well for the penetration depths above 0.5 m. For the range of specified relative rock sizes, the damage width in the inner and outer bottom deviates from numerical simulations approximately up to 25%, which was considered sufficient for the analyses where rapid damage assessment is needed. Comparison was also made to real accidental damage data and to the results of several simplified formulas.     

基于ABAQUS的船舶搁浅数值仿真研究

船舶搁浅性能研究是船底结构设计的一个重要环节。应用国际上通用的动力有限元程序ABAQUS／EXPLICIT对船舶搁浅动力学过程进行仿真研究。通过系列仿真试验,对不同搁浅位置及摩擦系数的情形下船底结构的搁浅性能,包括结构的损伤变形、搁浅力和能量的吸收分别进行对比和分析,得到一部分重要的结论,为船舶搁浅性能的评估及结构优化设计提供重要依据。     

Understanding ship-grounding events

The paper presents a simple procedure to estimate the damage to a ship bottom and the associated seabed topology that results from a dynamic grounding event. The seabed is modeled as a rigid body and parameterized by a quadratic surface, i.e., a paraboloid, which can in principle model a wide range of seabed topologies. A nonlinear finite element program (LS-DYNA) is used to simulate the contact force versus the lateral penetration, from which the horizontal force component of powered grounding is estimated. The simplified procedure for analyzing dynamic and static grounding events is outlined. Simulations are performed for different ship speeds and for different initial levels of obstruction over the keel. It is shown that a static approach may replace the dynamic grounding simulation, thereby considerably reducing the computational work. The static approach allows for the quick estimation of the energy absorption during powered grounding, which is imperative for decision making during critical situations. The ultimate goal of the study is to provide a near real-time prediction of the risk of rupture of the cargo tanks and hull girder failure. Moreover, the residual strength of damaged ships is an important issue that is related to operations involved in the salvage of wrecked vessels, such as re-floatation and towing.     

Analysis of structural crashworthiness of double-hull ships in collision and grounding

A conceptual design framework for collision and grounding analysis is proposed to evaluate the crashworthiness of double-hull structures. This work attempts to simplify the input parameters needed for the analysis, which can be considered as a step towards a design-oriented procedure against collision and grounding. Four typical collision and grounding scenarios are considered: (1) side structure struck by a bulbous bow, (2) side structure struck by a straight bow, (3) bottom raking, (4) bottom stranding. The analyses of these scenarios are based on statistical data of striking ship dimensions, velocities, collision angles and locations, as well as seabed shapes and sizes, grounding depth and location. The evaluation of the damage extent considers the 50- and 90-percentile values from the statistics of collision and grounding accidents. The external dynamics and internal mechanics are combined to analyse systematically the ship structural damage and energy absorption under accidental loadings.     

船舶搁浅于刚性斜坡数值仿真的模型化技术

显式非线性有限元分析已逐渐成为研究船舶搁浅问题的重要方法,但其模型化技术是实现数值仿真的关键。本文将搁浅船处理为可变形结构,用弹塑性材料模拟并进行整船建模,斜坡处理为刚体,用刚性材料模拟,船舶与斜坡之间定义为主从接触,船艏定义为自接触。通过仿真计算,获得并讨论了搁浅过程中的船体运动情况、搁浅接触力曲线、能量转化及船舶损伤变形情况。算例表明本文的模型化技术可以用于船舶搁浅的仿真计算。     

Analytical modelling of ship bottom grounding considering combined surge and heave motions

This paper provides a new contribution to the analytical treatment of ship grounding accidents. New formulations are proposed to assess the resisting force of outer/inner bottom plating and transverse floors when the vessel undergoes combined surge and heave motions during the grounding event. Considering shallow and sharp rocks described by parabolic functions, analytical solutions are derived from plastic limit analysis and validated by comparison to non-linear finite element simulations. A failure criterion is also proposed to trigger the rupture of the bottom plating and all the derived closed-form expressions are implemented into an in-house solver. The solver is then coupled to a 6-DOFs external dynamics program, which allows to account for the action of the surrounding water. Resulting tool is first validated on a full scale cruise ship by comparison to finite element results. It appears than although some discrepancies arise, especially in the response of transverse floors after rupture, the bottom damage distribution seems to be well predicted. Finally, the developed tool is used to quickly predict the grounding response of different types of ships and the influence of their mass and hydrodynamic properties on the damage extent is investigated.     

船底座礁实验数值模拟中选择参数影响研究

非线性有限元方法是分析船舶碰撞和搁浅问题的一个强有力工具,但是数值模拟结果的可靠性很大程度上依赖于对工程问题的恰当处理和有限元软件中主要参数的准确控制.本文以某单壳船底结构准静态座礁实验结果为例,用非线性有限元软件LS-DYNA进行数值模拟,研究了下列选择参数对单壳船底结构抗撞性的影响:边界条件;船底结构的材料模型;壳单元类型;船底结构与礁石模型之间的摩擦系数;船底结构的残余应力.通过比较计算结果的碰撞力曲线,能量吸收曲线来评价这些参数对数值模拟的影响并给出了一些建议.