桥梁上部结构防船撞研究

船舶撞击桥梁上部结构是船撞桥事故模式之一,其撞击特性与撞击桥墩特性相比有所不同。现着重研究了船舶撞击桥梁上部结构的风险分析、撞击力、防撞保护等技术问题,并提出设置警示设施、AIS系统建设、拦截、红外线监测、警戒等防护措施,供通航安全部门参考。     

Fast evaluation of ship-bridge collision force based on nonlinear numerical simulation

The max collision force of ship-bridge collision is one of the most important references for bridge design. By means of nonlinear digital simulation method, the collision forces of the collisions between rigid bridge pier and ship bow were calculated out for four different ships, whose tonnages are 5 000, l0 000,50 000 and 60 000 DWT respectively. Curves of collision force-penetration and absorbed energy-penetration are obtained, and the data of the max loads are then summarized. On the basis of these curves and data, a set of curves describing the relationships between max collision forces and tonnages of the ships are successfully presented, by which the max collision forces of the ships-bridge with different tonnages and in different velocities can be estimated easily and reliably.     

An analytical method for predicting the ship side structure response in raked bow collisions

As an increasing number of ships continue to sail in heavy traffic lanes, the possibility of collision between ships has become progressively higher. Therefore, it is of great importance to rapidly and accurately analyse the response and consequences of a ship's side structure subjected to large impact loads, such as collisions from supply vessels or merchant vessels. As the raked bow is a common design that has a high possibility of impacting a ship side structure, this study proposes an analytical method based on plastic mechanism equations for the rapid prediction of the response of a ship's side structure subjected to raked bow collisions. The new method includes deformation mechanisms of the side shell plating and the stiffeners attached. The deformation mechanisms of deck plating, longitudinal girders and transverse frames are also analysed. The resistance and energy dissipation of the side structure are obtained from individual components and then integrated to assess the complete crashworthiness of the side structure of the struck ship. The analytical prediction method is verified by numerical simulation. Three typical collision scenarios are defined in the numerical simulation using the code LS_DYNA, and the results obtained by the proposed analytical method and those of the numerical simulation are compared. The results correspond well, suggesting that the proposed analytical method can improve ship crashworthiness during the design phase.     

Design of offshore structures against accidental ship collisions

In this paper, we investigate the damage to offshore platforms subjected to ship collisions. The considered scenarios are bow and stern impacts against the column of a floating platform and against the jacket legs and braces. The effect of the ship–platform interaction on the distribution of damage is studied by modeling both structures using nonlinear shell finite elements. A supply vessel of 7500-ton displacement with bulbous bow is modeled. A comprehensive numerical analysis program is conducted, and the primary findings are described herein. The collision forces from the vessel are compared with the suggested force–deformation curves in the NORSOK code. For collisions with floating platforms we particularly focus on the crushing behavior and potential penetration of the bulbous bow and stern sections into the cargo tanks or void spaces of semi-submersible platforms. For fixed jacket platforms we investigate whether jacket braces can penetrate into the ship without being subjected to significant plastic bending or local denting.Adequate treatment of the relative strength between the interacting bodies is especially relevant for impacts with high levels of available kinetic energy, for which shared energy or strength design is aimed at. Simplifying one body as rigid quickly leads to overly conservative and/or costly solutions, and is in some cases non-conservative.The numerical analysis is used to develop a novel pressure–area relation for the deformation of the bulbous bow and stern corners of the supply vessel. Procedures for strength design of the stiffened panels are discussed. Refined methods and criteria are proposed for strength design of platforms, including both floating and jacket structures. The adequacy of the NORSOK design guidance for collisions against jacket legs is evaluated. The characteristic strength of a cylindrical column is used to develop a novel criterion for the resistance to local denting from stern corners and bulbous bows.     

Drift-wood collision load on bow structure of high-speed vessels

Impact load estimation of drift-wood hitting against the bow structure of high-speed vessels has been investigated. It may be difficult for the craft operator to detect in advance a drift-wood floating just below the ocean surface and to avoid the collision with it. It is particularly difficult for operators of the high-speed vessels in night cruising mode. The probability of the accident may be higher than that of the collision with rocks or other ships because of the difficulties of early detection of the floating object. Impact loads are estimated for drift-wood of different sizes and craft speed considering whipping motion and local crushing of the wood at the hitting region. A simplified formula for the load estimation is proposed based on the modal approach and the energy balance. Predicted impact loads can be applied to the initial design of the bow structure and collision bulkhead of the craft to secure the structural safety against a possible accident.     

基于MD Nastran的船-冰碰撞数值仿真研究

船舶与海冰的碰撞过程十分复杂,涉及多种非线性问题。文章运用 MD Nastran对船舶艏部与冰的碰撞进行数值仿真计算,来模拟这一过程。得到了碰撞结束后,船首和海冰的损伤变形情况,船体结构的应力应变情况,以及在船—冰相互作用过程中的能量变化,应力应变变化。研究结果描述了船舶与冰碰撞的详细过程,揭示了冰载荷作用下船体结构的响应规律,可为船舶抗冰载荷设计提供参考。     

船-桥碰撞力学问题研究现状及非线性有限元仿真

归纳研究了船舶与桥梁碰撞力学的几种典型计算方法，并对各自的特点进行了分析。文中借助DYTRAN非线性有限元程序，以一艘4万吨级的油船与长江上某一斜拉索桥发生正向碰撞为例，演示了有限元法仿真计算船-桥碰撞问题的一般过程。反映了船-桥碰撞过程中船艏、桥梁承合、桥面和拉索的力与变形的时间历程，得到了具有指导意义的结论。     

船艏横向加强框架对船艏耐撞性能的影响

在撞击过程中船艏结构的典型损伤是外壳板和内加筋的褶皱，撕裂和弯曲。在以前的船舶结构的碰撞分析的简化方法或数值模拟中往往略去横向肋骨框架对船艏碰撞性能的影响。本文利用有限元数值仿真方法研究了横向肋骨框架在碰撞损坏过程中的作用，发现其对船艏结构的损伤形态、碰撞力及能量耗散有重要影响。因而是碰撞计算中不可忽略的因素。     

基于整船整桥模型的船桥碰撞数值仿真

桥梁在船舶碰撞时受到的动力载荷和响应是复杂的动力非线性问题。近代非线性有限元技术为该问题的求解提供了有效的工具。本文简述了该技术的基本原理，并基于整船整桥模型，对一艘4万吨实船与桥梁的碰撞过程进行了计算。仿真结果显示了船艏结构损坏、碰撞力演变、能量传递和桥墩内部应力变化的详细情景，讨论了船—桥碰撞的力学特征。本文演示的方法比传统的经验公式和简化解析法提供了更为精确的结果。所提供的桥墩应力状态对桥梁的设计与碰撞后的损伤评估有重要参数价值。     

Energy dissipation in high-energy ship-offshore jacket platform collisions

Ship collisions with offshore structures may be characterized by large amounts of kinetic energy that can be dissipated as strain energy in either the ship, or the installation, or shared by both. In this paper a series of FE numerical simulations are performed with the aim of providing a clearer understanding on the strain energy dissipation phenomenon, particularly upon the ship-structure interaction. Ships of different dimensions and layouts are modelled for impact simulations. Likewise, three platform jacket models of different sizes and configurations are considered. The collision cases involve joints, legs, and braces and are simulated for several kinetic energy amounts of the vessels and different impact orientations. An overview of the plastic deformation mechanisms that can occur in both ship and jacket structure is also given. The results from the various models with different collision scenarios are compared in terms of the strain energy dissipation with respect to the different ship/installation strength ratios. From the FEA simplified approaches are also derived in terms of the relative stiffness of the two structures for assessing the responses and energy absorptions of the two structures. The conclusions drawn from this study can be applied to a broader range of collision assessment of offshore steel jacket platforms subjected to high-energy ship impacts.     

Statistical Analysis of Ship Collisions with Bridges in China Waterway

Having carried out investigations on ship collision accidents with bridges in waterway in China, a database of ship collision with bridge (SCB) is developed in this paper. It includes detailed information about more than 200 accidents near ship' s waterways in the last four decades, in which ships collided with the bridges. Based on the information a statistical analysis is presented tentatively. The increase in frequency of ship collision with bridges appears, and the accident quantity of the barge system is more than that of single ship. The main reason of all the factors for ship collision with bridge is the human errors, which takes up 70%. The quantity of the accidents happened during flooding period shows over 3 - 6 times compared with the period from March to June in a year. The probability follows the normal distribution according to statistical analysis. Visibility, span between piers also have an effect on the frequency of the accidents.     

On the global ship hull bending energy in ship collisions

During ship collisions part of the kinetic energy of the involved vessels immediately prior to contact is absorbed as energy dissipated by crushing of the hull structures, by friction and by elastic energy. The purpose of this report is to present an estimate of the elastic energy that can be stored in elastic hull vibrations during a ship collision.When a ship side is strengthened in order to improve the crashworthiness it has been argued in the scientific literature that a non-trivial part of the energy released for structural deformation during the collision can be absorbed as elastic energy in global ship hull vibrations, such that with strong ship sides less energy has to be spent in crushing of the striking ship bow and/or the struck ship side.In normal ship–ship collision analyses both the striking and struck ship are usually considered as rigid bodies where structural crushing is confined to the impact location and where local and global bending vibration modes are neglected. That is, the structural deformation problem is considered quasi-static. In this paper a simple uniform free–free beam model is presented for estimating the energy transported into the global bending vibrations of the struck ship hull during ship–ship collisions. The striking ship is still considered as a rigid body. The local interaction between the two ships is modeled by a linear load–deflection relation.The analysis results for a simplified model of a struck coaster and of a large tanker show that the elastic energy absorbed by the struck ship normally is small and varies from 1 to 6% of the energy released for crushing. The energy stored as elastic global hull girder vibrations depends on the ship mass, the local stiffness of the side structure, and of the position of contact. The results also show that in case of highly strengthened ship sides the maximum global bending strains during collisions can lead to hull failure.     

通航河流桥梁主动防船撞措施探讨

文章从影响通航条件的主要因素,即建桥对通航条件的影响入手,从桥梁选址、桥跨及墩位布设以及通航净空尺度等角度,全面分析了预防船撞桥事故发生的相关措施和技术要求,提出了从桥梁设计角度如何实现桥梁主动防船撞的方法,其成果可为桥梁设计借鉴参考。     

水介质对船冰碰撞结构响应的影响

以极地运输船舶艏部作为研究对象,建立基于流固耦合算法的船-水-冰耦合技术对三维船艏与冰体碰撞的结构响应问题进行了研究,结合非线性有限元软件LS-DYNA对比分析了考虑流固耦合(即有水介质)的船-水-冰碰撞模型和不考虑流固耦合(即无水介质)的船-冰碰撞模型与同质量不同速度的冰体发生碰撞下的结构响应问题,揭示了不同碰撞工况下船舶在损伤变形、碰撞力、速度等方面的变化特征及差异,同时阐述了水介质在船冰碰撞中的作用,可以为极地运输船舶的抗冲击结构设计提供参考。     

长江干线船撞桥事故分析

对发生在长江干线上的船撞桥事故进行了分析研究。通过调研掌握了一百余份有关资料 ,包括四十年来发生在十余座长江大桥的 172起船撞桥事故 ,在对事故进行统计分析与研究的基础上 ,得出了一些重要的结论。长江船撞桥事故在数量上略呈增长态势 ,船队撞桥事故远多于单船 ,约占 86 %。船撞桥的概率与桥梁跨距、洪水、能见度等因素有关 ,尤其是洪水对船撞桥概率影响较大 ,近似呈正态分布。发生船撞桥事故的第一位原因是人员失误 ,占 78%以上。     

俄罗斯规范下船舶撞击能量计算和护舷选型

护舷是船舶与陆域建筑物接触的装置,它能够有效地防止船体免于在靠泊、停泊中产生损坏,也能够起到保护陆域结构物的作用。一个完整的护舷设计应包含几种护舷布置的替代方案,护舷选型的确定对泊位设计有着至关重要的作用,直接影响着码头的设计荷载。依据俄罗斯规范对码头护舷选型进行案例分析,并与国标进行比较,为港口工程工作者提供设计参考。     

桥梁墩身避碰承台轮廓设计研究

墩身抗撞能力远不及承台，没有必要使墩身像承台一样抗撞，只要结构尺寸合理就能达到墩身避碰目的。本文根据船首形状，吃水，碰撞变形，桥墩形状和水文条件等，建立墩身避碰数学模型，以例验证。     

船舶与桥墩碰撞的数值模拟

利用有限元软件,模拟4种不同载重吨位的船舶以不同的速度与某桥墩发生碰撞的过程,演示有限元法仿真计算船桥碰撞问题的一般过程,着重分析船舶和桥墩的损伤程度.在此基础上,归纳出撞深速度、撞击时间-速度和桥墩的应力分布.     

On Impact mechanics in ship collisions

The purpose of this paper is to present analytical, closed-form expressions for the energy released for crushing and the impact impulse during ship collisions. Ship–ship collisions, ship collisions with rigid walls and ship collisions with flexible offshore structures are considered. The derived mathematical models include friction at the contact point so that situation where the collision results in a sliding motion is included. Results obtained by application of the present procedure are compared with results obtained by time simulations and good agreement has been achieved. In addition, a number of illustrative examples are presented. The procedure presented in the paper is well suited for inclusion in a probabilistic calculation model for damage of ship structures due to collisions.     

船舶舷侧结构耐撞性分析

为研究船舶舷侧结构的碰撞损伤过程,采用非线性动态响应分析方法,使用ANASYS/LS-DYNA显式动力分析软件,对船艏和船舷垂直碰撞过程进行数值仿真,获得了碰撞力、能量吸收和结构损伤变形的时序结果。为了分析船舶舷侧结构耐撞性能,本文对比了常见油船、新型Y型和X型舷侧结构的仿真过程,结果表明新型舷侧结构在整体的耐撞性能上优于传统的舷侧结构,承载构件的不同也会对结构的耐撞性产生很大的差异。