大型油船和集装箱船静水弯矩的统计特性研究

本文介绍了国内外静水弯矩的研究现状，对Soares和Moan的经验回归公式进行了详细讨论，发现不同的研究人员对静水弯矩统计特征的认识存在相当大的差异。文中对静水弯矩均值和变异系数对船舶总纵强度安全指数的敏感度进行了分析，发现均值比变异系数更加重要。在分析和比较的基础上，根据简单可靠的原则，对集装箱船和油船的静水弯矩统计特征计算提出了如下建议：集装箱船，Cov=0．30；油船，满载（中垂）时，Cov＝0．4，压载（中拱）时，Cov=0．70。     

船体梁静水载荷效应统计预报

船体梁静水剪力、弯矩等是由装载状态决定的载荷效应。营运船舶装载记录表明，实际装载状态具有不确定性，由此导致载荷效应发生变异，其统计特性可利用回归公式或随机模拟原理进行估算或预报。通过对油船、散货船、滚装船及集装箱船约2000种随机工况所作的统计分析，表明其静水弯矩等随装载偏差的变化近似于正态分布律，并具有比船体中剖面模数或钢材屈服极限更为显著的变异性。在船舶结构可靠性分析或理性设计中，合理估算并预报这种及异性是必要的。     

Mooring load of a ship single-point moored in a steady current

The Technical Committee I.2 of the 14th International Ship and Offshore Structures Congress 2000 identified the occurrence of highly peaked loads in the mooring hawser of single-point moored (SPM) ships as an important issue. Industry, research laboratories and universities were requested to contribute to a systematic study investigating the mooring load of two single-point moored tankers subject to a steady current. Contributions were received from three industrial participants, one research laboratory, and three universities. Comparative simulated time histories of the mooring load as well as the corresponding horizontal motion response of the SPM tankers were analyzed. A relatively large spread characterized the predicted results.     

Hull-girder reliability of new generation oil tankers

A series of new generation oil tankers is presently under construction. These ships differ from traditional oil tankers by their unusual form and therefore direct hydrodynamic analysis is used to determine design vertical wave bending moments instead of adopting IACS rule values. The purpose of the paper is to quantify changes in hull-girder reliability resulting from the new design features. To achieve this, first-order reliability analysis is carried out with respect to ultimate collapse bending moment of the midship cross section of a new generation oil tanker and of a conventional “rule” designed oil tanker. The stochastic model of wave-induced bending moment is derived from direct hydrodynamic analysis performed according to IACS Recommendation No. 34 Standard Wave Data, Rev 1, 2000. The probability distribution of the still water bending moment is assumed based on the data from loading manuals. The model uncertainties of linear wave loads, non-linearity of the response as well as load combination factors are included in the reliability formulation. The reliability analysis is performed for three relevant loading conditions: full load, ballast and partial load and for two states of the hull: the “as-built” hull and “corroded” hull according to anticipated 20-year corrosion. One of the most interesting conclusions from the study is that the annual hull-girder reliability of new generation oil tanker is increased considerably compared to the conventional oil tanker. Sensitivity and parametric studies are performed with respect to random variables representing modelling uncertainties. The results of a sensitivity study enable sorting of pertinent variables according to their relative importance, while parametric study is used to quantify changes in the reliability indices for moderate variation of input parameters. Furthermore, some other results and discussions are presented pointing out the benefits of introducing the ship reliability methods in design practice, especially if this refers to new designs.     

Structural reliability of two bulk carrier designs

The paper aims at quantifying the changes in notional reliability levels that result from redesigning a traditional single-hull bulk carrier to become a double-hull structure. The probability of failure is calculated using a first-order reliability method. The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out. The still water loads are defined on the basis of a statistical analysis that accounts for the ship type. The ultimate collapse bending moment of the midship cross section is used as the basis for the reliability formulation. It is shown that by introducing the double-hull in the bulk carriers their level of structural safety can be increased up to values typical of tankers. Additionally, the time-dependent degrading effect of corrosion on the ultimate moment is also taken into account in the reliability assessment of bulk carriers.     

Replacement of very large and ultra large crude carriers

The technical and economic conditions of World War II that led to the building of Liberty vessels and compared with those that led to the building of the present very large and ultralarge crude carries (VLCCs and ULCCs) for the purpose of revealing similarities that could indicate when a massive replacement of the existing large tankers is to be expected. The Liberties were replaced within a relatively short time by ships of twice their efficiency and in a situation where transport demand was growing and insurance premiums for old vessels greatly increased. International rules and regulations played on great role. The development of tankers has not produced ships that from an economical point of view are markedly better than previously existing vessels; the demand for tankers has not increased during the last 15 years; the insurance coasts of existing tankers have increased only moderately; and the introduction of new international and national rules for tanker design have made it worthwhile to conserve existing vessels. Although there is a similarity in age distribution between the Liberties and the VLCCs and ULCCs, the situation of the two categories of vessel is otherwise so different that a demand for a VLCC and ULCC replacement of the same magnitude as was experienced for the Liberties cannot be expected.     

Scheduling short-term marine transport of bulk products

A multinational company uses a personal computer to schedule a fleet of coastal tankers and barges transporting liquid bulk products among plants, distribution centres (tank farms), and industrial customers. A simple spreadsheet interface cloaks a sophisticated optimization-based decision support system and makes this system useable via a varity of natural languages. The dispatchers, whose native language is not English, and some of whom presumably speak no English at all, communicate via the spreadsheet, and view recommended schedules displayed in Gantt charts both internationally familiar tools. Inside the spreadsheet, a highly detailed simulation can generate every feasible alternate vessel employment schedule, and an integer linear set partitioning model selects one schedule for each vessel so that all loads and deliveries are completed at minimal cost while satisfying all operational requirements. The optimized fleet employment schedule is displyed graphically with hourly time resolution over a planning horizon of 2-3 weeks. Each vessel will customarily make several voyages and many port calls to load and unload products during this time.     

Fatigue damage calculation for oil tanker and container ship structures

The fatigue behaviour of longitudinal stiffeners of oil tankers and container ships, subjected to dynamic loads, is analysed. The following dynamic load components are considered: hull girder vertical wave bending moment, alone and combined with the horizontal wave bending moment, hydrodynamic pressure and inertial forces caused by cargo acceleration.

The spectral method was selected to calculate the fatigue damage, based on S—N curves and Miner's rule. Following this approach, the fatigue damage may be calculated as a function of a stress parameter Ω_p, which represents the cumulative effect of wave induced loads in the unit of time and incorporates the combined effects of stress level and its occurring frequency.

Simple formulas for Ω_p of oil tankers and container ships are given, obtained from the results of hydrodynamic analyses performed on several ships, in different wave environments.

Several examples show the applicability of the methods to real ship structures. The method, however, still needs to be calibrated because of the simplifying hypotheses introduced in the loading conditions.     

基于MSC.Dytran的液舱晃荡分析

液货船发展的关键技术之一是解决液舱内流体的晃荡问题。MSC.Dytran有限元程序能较好的模拟贮液容器的液面晃荡问题。以载液船舶液舱为研究对象,利用MSC.Dytran程序对矩形液舱在一确定装载水平下的液面晃动进行仿真分析,得到了不同时刻舱内液体的液面形状。     

Marine accident analysis for collision and grounding in oil tanker using FTA method

In this study, collision and grounding data registered in GISIS (Global Integrated Shipping Information System) were investigated for oil tankers. The database includes the information of the collision and grounding accidents during the period between 1998 and 2010 in oil tankers. The risk assessments were carried out using fault tree analysis (FTA) programme for the incidents as collision and grounding occurred in oil tankers. In this study, we were able to investigate first the potential problems which cause the collision and grounding accidents have been determined, second, the occurrence of accidents has been shown with causal factors by the FTA method, and, finally, the significance degree of the initial events causing occurrence of accidents have been put forth. Collision in oil tanker resulted in economical loss (81%), pollution (6%) and death or injury (13%). Grounding in oil tanker resulted in economical loss (91%) and pollution (9%). According to the FTA results, the main reason for the accidents originating from human error is as follows: for collision accidents, Convention on the International Regulations for Preventing Collisions at Sea (COLREG) violation and the lack of communication between vessels; and for grounding accidents, the interpretation failure of the officer on watch and lack of communication in the bridge resource management.     

关于码头通航仿真模拟的若干思考

应用模拟器对港航工程进行仿真,得到在模拟环境下船舶航行及靠离泊相关数据.分析国内进行通航安全评估模拟试验的现状和不足.探讨制作精确的水域电子海图,设计船舶模型和仿真水流、潮汐、海浪,建立模拟地区三维视景模型,优化模拟试验方案,提高仿真模拟精度.     

基于HCSR与CSR—OT的油船屈服强度直接计算评估对比分析

针对屈服强度直接计算的载荷、计算工况、建模原则、边界条件及屈服强度衡准,对比HCSR和CSR—OT,分别应用这两规范对多条油船样船进行屈服强度直接计算,提出一种可行的数据对比方法对油船典型构件的计算结果进行统计分析,给出关于HCSR屈服强度直接计算的具体处理方法。     

晃荡对CSR油船设计的影响

为明确船舶营运过程中晃荡载荷对不同船型液货舱构件的影响,基于《散货船和油船结构共同规范》,分析晃荡载荷的形成及决定晃荡载荷的因素,结合纵向和横向晃荡在油船中的具体载荷水平,分析晃荡运动对CSR油船液货舱结构的影响,以VLCC制荡舱壁为优化目标,提出新的设计方案,采用MSC.Patran&Nastran有限元分析软件,论...     

波激振动和砰击颤振对大型油船疲劳强度影响研究

文章给出线性波激振动和砰击颤振引起的大型油船结构疲劳贡献度的计算方法。基于三维线性水弹性理论可计算得到包括刚体和2节点的振动模态下的垂向弯矩的传递函数,采用谱分析法对某30万吨油船进行结构疲劳强度计算,分析波激振动对船体结构疲劳损伤影响;基于二维非线性波浪载荷程序（含砰击颤振的波浪载荷）,采用时域方法对该油船进行船体梁弯矩计算,分析砰击颤振对船体梁弯矩及疲劳载荷的影响;结果表明对于该类大型油船波激振动和砰击颤振对船体的结构疲劳损伤的影响不可忽略。     

A statistical investigation of time-variant hull girder strength of aging ships and coating life

Risk- and reliability-based approaches are increasingly being applied in assisting inspection and maintenance planning. One of the keys to such approaches is properly predicting the hull girder strength (HG) of gradually degradated hull structures. The development has been limited by the lack of data on aging ships—validation of the developed methods has not been possible. To fill the gap of knowledge on hull strength of ships in service, this paper presents a database of as-gauged hull structures and a statistical study of the time-variant HG of tankers. The expanded data set was collected from 2195 as-gauged girth belts (transverse sections) of 211 single-hull tankers that were 12–32 years old. It was intended to (1) provide actual data on hull girder section modulus (HGSM) of tankers, (2) investigate the general trends of the change in the HG over ships’ service life, and (3) propose formulations for presenting time-variant HGSM and coating life.

The data set demonstrated a high variation of HGSM that changed over time. The mean value and standard deviation of HGSM loss were derived as functions of time. The probability density function (pdf) of coating life was also derived. Comparisons were made between previous studies on HG and the current data set. It was found that almost all previous studies showed much greater HG loss than what this database revealed. The refinement of existing calculations appears to be needed. The data set and statistical study were expected to form the basis for validating formulations of HG that are key components in risk- and reliability-based approaches.     

AMP系统在集装箱船上的应用研究

主要阐述了可替换船用电力系统（以下简称AMP系统）构成和原理,并以实船应用为例,分析了适用于集装箱船的全集成固定式和半固定式AMP系统基本设备配置;船舶到港、离港时半固定式AMP系统的操作流程及AMP系统的应用前景。     

Investigation on structural performance predictions of double-bottom tankers during shoal grounding accidents

An investigation is carried out in this paper for the predictions of structural performance of double-bottom tankers during ship grounding over the “shoal” type seabed obstacles. Hong and Amdahl developed a simplified analytical model for the unstiffened double bottom. This method is carefully studied, verified and then used as the first stage of our prediction. The second stage is concerned with stiffeners since stiffeners are indispensable components for double-bottom tankers. A prevailing way to handle is to smear stiffeners onto their attached plating known as the smeared thickness method. However, the effective ratio in this method is dubious in such shoal grounding accidents. Proper values of this parameter are determined in stage two, and then together with the method in stage one, constitute a reliable and efficient tool for structural performance predictions of double-bottom structures in shoal grounding accidents.A double-bottom tanker is chosen as object for the case study. Finite element models of the hold both stiffened and unstiffened are created for numerical simulations using the LS_DYNA software. Simulation cases cover a wide range of slope angles of the indenter and indentations. Numerical results show that Hong and Amdahl's model in stage one is capable of predicting energy dissipation with high precision but poor accuracy for grounding resistances, and a possible reason may be the neglect of vertical resistance. The updated smeared method proposed in stage two is also proved to be capable of grasping major characteristics of stiffeners. Results and conclusions drawn from this paper can be conveniently applied for assessments of the performance of ship double-bottom structures during shoal sliding grounding scenarios, and will benefit the application of accidental limit state design concept in the ship design stage.     

Time-domain strip method with memory-effect function considering the body nonlinearity of ships in large waves (second report)

In the previous paper, one of the authors proposed a new time-domain nonlinear strip method for a rigid body, in which hydrodynamic forces are evaluated by a convolution integral with the memory function computed for the instantaneous submerged part of the transverse sections, and the Froude–Krylov and hydrostatic forces are evaluated on the instantaneous wetted hull surface. In this paper, first, that nonlinear strip method is extended for an elastic body using a method of superposition of elastic mode functions, which enabled us to investigate whipping phenomena due to impulsive large waves. Second, the influence of different approximations of the pressure above the still-water surface is investigated, and then the results calculated by the proposed nonlinear strip method are compared with the experimental ones. Third, whipping phenomena observed for an elastic body at higher Froude numbers are studied through a comparison between computed and measured results. Higher-frequency vibrations in the vertical bending moment due to slamming are discussed. Furthermore, the wave load due to green water on deck is calculated by introducing a practical model, and the effects of the green water on responses of both rigid and elastic bodies are investigated.     

A case study related to the improvement of working and rest hours of oil tanker deck officers

Navigation safety on coastal waters is an extremely important issue. Fatigue is an important factor threatening navigation safety. Considering that the vessel type is an oil tanker, such a threat is not posed only to the crew but also to the environment. Most of the tankers navigating coastal waters are in the small tanker category. Therefore, this study examined the working and resting hours of the deck officers in the oil tankers navigating coastal waters. The study utilized the ISF Watchkeeper 3 program for assessing and interpreting the working periods. The study reached the conclusion that the first and second officers in particular are working under unsuitable conditions. To improve the working conditions of the deck officers, effects of additional cargo officer on board was investigated. This study is in quality of recommendation. The study elucidated that the cargo officer practice determines the working and resting hours of deck officers, in the work on the oil tankers, and compliance with the related conventions.     

镇海算山码头#7泊位改造工程的论证复核

介绍镇海算山码头#7泊位5万吨级成品油码头兼靠10万吨级油轮的改造设计。对泊位长度、靠泊设施间距、泊位作业标准和平面水域等进行全面论证,对码头水工建筑物的设计荷载、结构内力进行复核计算。本着投资少、工期短、施工简单和对生产影响小的原则,提出对码头上的登船梯、系船设施等进行必要的改造,以满足兼靠10万吨级油轮的需要。