特定航线江海通航船波浪载荷研究

为了能对江海通航船型的结构强度进行合理评估,根据载荷第一原则,按特定航线所在的E1海区的波浪统计资料,对该海区船舶的波浪载荷进行了系统研究,并给出了航行于该海区江海通航船的波浪附加弯矩、波浪附加剪力、波浪水平弯矩及波浪扭矩的长期预报值.本文的研究结果已纳入中国船级社《特定航线江海通航船检验指南》中,对特定航线江海通航船的发展起到了积极的推进作用.     

薄膜型LNG船全船结构屈服和疲劳强度分析

以某薄膜型液化天然气（Liquefied Natural Gas，LNG）船的结构设计为例，开展全船屈服强度校核和基于精细网格的有限元疲劳强度分析。针对5种典型装载状态，基于美国船级社（American Bureau of Shipping，ABS）全船强度直接计算指南，采用ABS-DLA/SFA系列软件，用三维波浪载荷预报程序对波浪随机载荷进行长期预报。基于预报结果，针对每种装载状态计算15个设计波参数组，求解全船结构在各载荷组合工况下的应力分布，继而完成屈服强度校核。以甲板机械室与穹顶甲板相交处的关键节点区域的节点设计为例开展细网格局部强度分析，并通过各种改进设计解决应力集中问题。针对2种常用典型操作装载状态及营运于北大西洋海区疲劳寿命满足40a的要求，基于ABS全船疲劳强度直接计算指南计算2个典型细化位置热点应力传递函数，通过谱分析得到疲劳累积损伤和疲劳寿命，完成疲劳强度校核。采用的全船强度和疲劳分析方法和思路适用于其他超大型船舶的结构分析。     

海洋核动力平台疲劳寿命评估

针对海洋核电平台,提出一种疲劳评估方法。考虑海洋核电平台的工作特性,工作状态时选取首向浪向不等概率分布的波浪载荷,拖航状态时选取全浪向等概率分布的波浪载荷,分别计算出两种波浪载荷下的疲劳损伤度,再根据两种状态下的时间分配系数得到总的损伤度。根据提出的疲劳评估方法,建立核电平台的有限元模型,选取危险疲劳节点进行细化处理,通过有限元分析得到应力传递函数以及疲劳损伤度,验证了评估方法的可靠性,确定了危险疲劳节点的位置,并为类似平台的疲劳问题提供参考。     

3800箱集装箱船总纵强度计算两种方法对比研究

本文对3800箱集装箱船进行了整船有限元分析，计算了在设计静水弯矩、波浪弯矩、水平弯矩和扭矩作用下的船体总纵强度，并与基于薄壁梁扭转理论的总纵强度计算结果进行了比较，对两种方法的应用前景作出评论。     

圆筒型FPSO上部模块支撑结构疲劳分析

与船型FPSO相比,圆筒型FPSO没有明显的总纵弯曲,上部模块与船体结构之间通常采用刚性支墩来连接,水平运动所产生的弯矩和装/卸载引起的船体垂向变形对模块支撑结构的影响较为显著。因此,以“希望6号”圆筒型FPSO上部模块支撑结构为研究对象,基于DNVGL船级社规范,介绍一种简化疲劳分析方法。以FPSO运动加速度和船体变形载荷作为载荷输入条件,利用SESAM/GeniE软件进行有限元分析,得到结构在所有组合工况下应力的扫描计算结果。根据作业海域各个方向波浪发生的概率,运用简化疲劳分析方法计算得到所关注节点的疲劳损伤和各个工况对结构节点疲劳损伤度的贡献。结果表明,所关注节点的疲劳强度均满足设计疲劳强度要求;同一节点的疲劳损伤对不同浪向的敏感度不一样。该简化疲劳分析方法同样适用于承受周期性载荷的FPSO上部模块主结构和其他型式海洋结构物的疲劳分析。     

Reliability analysis of a bulk carrier in ultimate limit state under combined global and local loads in the hogging and alternate hold loading condition

The alternate hold still-water loading in hogging combined with wave loading is critical for the safe design of bulk carriers. The ultimate longitudinal strength of the hull girder of bulk carriers in this condition has been found to be considerably reduced by the action of local lateral pressure loads. In the present paper, an interaction equation based on the ultimate hull girder strength assessment obtained by nonlinear finite element analyses is adopted to consider the relationship between ultimate longitudinal bending capacity and average external sea pressure over the bottom. This interaction equation is used as the basis for the failure function. The annual probability of failure is obtained by FORM analysis considering two typical load cases, namely, pure longitudinal hogging bending moment and combined global hogging bending moment and local lateral pressure loads. The effect of heavy weather avoidance on the failure probability is evaluated. The results show that the local lateral pressure has a significant influence on the annual probability of failure of bulk carriers in the hogging and alternate hold loading condition.     

Finite Element Simplified Fatigue Analysis Method for a Non-tubular Joint of an Offshore Jacket Platform

This paper proposes the finite element simplified fatigue analysis method for fatigue evaluation of the composite non-tubular joint structure of an offshore jacket subjected to wave loads. The skirt pile sleeve of the offshore jacket, which had been in service, was taken as an example of the non-tubular joint structure. SACS software was used for global analysis of multi-directional wave loads for the jacket platform, and ALGOR software was used to build a finite element model, perform finite element analys...     

双壳型船体结构稳态温度场和温度应力

用简化解析方法和有限元数值方法,分析了双壳型船体货舱区域在运载高温液货时的稳态温度场;根据船体结构的温度分布,用有限元法计算了其温度应力,同时与货物压力、海水静动压力、总纵弯矩等载荷作用下的结构应力做了比较。研究结果表明：在货舱结构温度场分析中用简化分析方法和有限元数值方法所得的计算结果相当一致;高温液货大幅度增加船体结构的纵向应力和横向应力,同时加剧结构不连续处的应力集中;槽型舱壁可以有效地释放     

基于桩-土相互作用的内河架空直立式码头地震响应分析

采用有限元法,分别建立桩-土-码头结构模型、地基刚性假定的码头模型和工程计算简化的码头模型。通过模态分析和动力时程分析,得出3种码头模型的基频和水平位移最大值,以及码头立柱内力的最大响应值。研究表明:与地基刚性假定模型相比,由桩-土-码头结构模型所得的结构基频、水平位移最大值、立柱的剪力和弯矩值将会减小,轴力值基本不受影响;与工程计算简化模型相比,结构的基频、立柱的剪力和弯矩值将增大,但是水平位移最大值将减小,轴力值基本不变。     

Time domain analysis procedures for fatigue assessment of a semi-submersible wind turbine

Long term time domain analysis of the nominal stress for fatigue assessment of the tower and platform members of a three-column semi-submersible was performed by fully coupled time domain analyses in Simo-Riflex-AeroDyn. By combining the nominal stress ranges with stress concentration factors, hot spot stresses for fatigue damage calculation can be obtained. The aim of the study was to investigate the necessary simulation duration, number of random realisations and bin sizes for the discretisation of the joint wind and wave distribution. A total of 2316 3-h time domain simulations, were performed.In mild sea states with wind speeds between 7 and 9 m/s, the tower and pontoon experienced high fatigue damage due to resonance in the first bending frequency of the tower from the tower wake blade passing frequency (3P).Important fatigue effects seemed to be captured by 1 h simulations, and the sensitivity to number of random realisations was low when running simulations of more than 1 h. Fatigue damage for the tower base converged faster with simulation duration and number of random realisations than it did for the platform members.Bin sizes of 2 m/s for wind, 1 s for wave periods and 1 m for wave heights seemed to give acceptable estimates of total fatigue damage. It is, however, important that wind speeds that give coinciding 3P and tower resonance are included and that wave periods that give the largest pitch motion are included in the analysis.     

Local structural response to seakeeping and slamming loads

A common approach to investigate the response of a structural detail such as a hatch corner is to compute the seakeeping loads using a linear 3D Boundary Element Method (BEM) and transfer the seakeeping loads to a Finite Element (FE) model of the ship structure. This approach is suitable for computations of the fatigue loading of structural details near amidships because a majority of the fatigue loading will occur in mild sea-states where the loading may be assumed linear. However, the linear seakeeping model may not hold when one investigates the ultimate response of the local bow structure of a ship which is designed to remain operational in severe conditions, for example, a frigate. A linear seakeeping analysis will significantly underpredict the loading at the bow because both the impulsive slamming loads and the non-linearities in the non-impulsive wave loads will contribute significant to the structural loading.The non-linear loads require one to first derive a short-term distribution of the local structural response before the ultimate value of the response can be derived. A method to compute the short-term distribution of a structural detail is presented in this paper. The first step is to perform seakeeping analyses which includes slamming, non-linear Froude-Kryloff and hydrostatic loads. The short-term distribution of the total hydrodynamic loading at the structural detail is obtained by simulating the seakeeping response for several hours. The response of the local structure is computed for the most severe impacts found in the seakeeping simulation. The hydrodynamic loading, including the non-linear contributions, is transfer to the structural model and the structural response is computed using the FE-method. The results of the structural analyses allow one to transform the short-term distribution of the structural loading to a short-term distribution of the response of the structural detail. A designer can obtain the ultimate structural response by entering the probability at which one accepts overloading of the structure in the short-term distribution of the response of the structural detail.     

Finite element simplified fatigue analysis method for a non-tubular joint of an offshore jacket platform

This paper proposes the finite element simplified fatigue analysis method for fatigue evaluation of the composite non-tubular joint structure of an offshore jacket subjected to wave loads. The skirt pile sleeve of the offshore jacket, which had been in service, was taken as an example of the non-tubular joint structure. SACS software was used for global analysis of multi-directional wave loads for the jacket platform, and ALGOR software was used to build a finite element model, perform finite element analysis, post-process stress results for acquiring the stress range, and perform fatigue evaluation. The analysis results indicate that the extreme stress range is within the allowable stress range and meets the requirements of DNV code. That means the simplified fatigue analysis method is effective and can be used in fatigue design for the non-tubular joint structure of an offshore jacket.     

半潜式平台结构屈曲强度评估

半潜式平台是海洋工程领域重要的浮式装置,采用直接计算法对某半潜式平台结构的屈曲强度进行了评估.首先,对半潜式平台结构进行有限元模型化,然后根据海况不同将静水、正常工作和风暴自存三种状态划分为48种计算工况,利用频域内的三维线性水动力理论和设计波法计算半潜式平台在各工况下的波浪载荷,同时考虑各工况下的莫里森力、风载荷、锚链预张力、吊车载荷和钻井载荷等载荷,进而计算平台在48种工况下的应力响应.最后根据ABS规范对平台结构进行屈曲强度校核.结果表明,屈曲强度是平台结构强度的重要指标之一,应在设计时给予合理评价,评估结果可为半潜式平台设计开发提供参考.     

万箱级超大型集装箱船结构设计

以708研究所开发的万箱级超大型集装箱船为依托平台,简要介绍了超大型集装箱船的结构关键技术设计,如典型中剖面的设计和优化、波浪载荷预报、全船有限元扭转强度分析、振动和噪声分析等,希冀为超大型集装箱船的实船设计提供参考。     

水下波能装置的波致弹性变形研究（英文）

Structural integrity has remained a challenge for design and analysis of wave energy devices. A difficulty in assessment of the structural integrity is often laid in the accurate determination of the wave-induced loads on the wave energy devices and the repones of the structure. Decoupled hydroelastic response of a submerged, oscillating wave energy device to extreme nonlinear wave loads is studied here. The submerged wave energy device consists of an oscillating horizontal disc attached to a direct-drive power take-off system. The structural frame of the wave energy device is fixed on the seafloor in shallow water. Several extreme wave conditions are considered in this study. The nonlinear wave loads on members of the submerged structure are obtained by use of the level I Green-Naghdi equations and Morison's equation for cylindrical members.Distribution of Von Mises stresses and the elastic response of the structure to the extreme wave loads are determined by use of a finite element method. The decoupled hydroelastic analysis of the structure is carried out for devices built by four different materials, namely stainless steel, concrete, aluminium alloy, and titanium alloy. The elastic response of these devices is studied and results are compared with each other. Points of maximum stress and deformations are determined and the structural integrity under the extreme conditions is assessed. It is shown that the proposed approaches provide invaluable information about the structural integrity of wave energy devices.     

On board measurement of stresses and deflections of a Post-Panamax containership and its feedback to rational design

One of the most important points in structural design of containerships is the strength of hatch corners. Formerly, hatch corners used to be assessed by combining the component induced by hull girder vertical bending and the component induced by hull girder torsion. In the design of new generation containerships without deck girders, the effect of cross deck fore-aft deflection has also become prominent.Another point is the impact of structural displacement on the deck fittings. About new generation ships, large fore-aft deflection of cross decks raised the new problem of interference of hatch covers, lashing bridges and other deck fittings.To cope with such problems, comprehensive analysis has been carried out during the design stage of a Post-Panamax containership. In parallel with this analysis, on-board measurement had been conducted for 3 years after delivery, in order to confirm wide varieties of structural reaction of a large container ship in seaways. Procedure to derive components of stress and deformations from selected measurement points was developed, and actual values were calculated based on actual measurement.From long-term prediction of each component, it was found that design assumption was in general appropriate. However, regarding the fore-aft deflection of cross deck strip, actual stack load is generally much smaller than the design value, and the resulting predicted extreme value was much smaller than design assumption. This factor should be taken into account in the design stage.Regarding the correlation between hull girder vertical bending and fore-aft deflection of cross deck strip, design assumption of full combination is too conservative. From the measurement, no explicit correlation was observed. Regarding the correlation between hull girder vertical bending and wave induced torsion, design assumption of no correlation was appropriate. From these results, new formulae to combine these three deflection modes were proposed.Whipping was observed in the measured data, indicating that more careful attention should be paid to avoid large stress concentration in deck area to enhance fatigue strength.     

万箱集装箱船典型货舱结构极限承载能力计算

随着世界货运量的需求增加,集装箱船的大型化发展从未停止。近十年内,有2艘大型集装箱船先后在海上遭到极端载荷而丧失结构承载能力以致发生灾难性毁坏,给航运界敲响了警钟。为了避免今后大型集装箱船再次遭遇上述严重事故,保证营运中使用的安全性和航行时结构的可靠性,国际船级社协会专门针对集装箱船的规范要求进行修改,提高了载荷设计值,并且要求评估典型货舱结构的极限承载能力。本文针对万箱集装箱船典型货舱结构,基于逐步破坏法和有限元法,计算了垂向和水平方向的极限弯矩。结果表明,在初步设计阶段逐步破坏法有着快速高效的优势,但是考虑到载荷变化的多样性和船体结构的复杂性,还是需要应用非线性有限元法进行建模计算,给出最终评估结果。     

Efficient estimation of extreme long-term stresses by considering a combination of longitudinal bending stresses

Longitudinal stresses due to combined horizontal and vertical bending moments in ships, corresponding to a return period of 20 years, are estimated by linear response analysis. In principle, the stress should be obtained by combining the stress in all sea states that can occur over a long-term period. A method to determine the desired long-term extreme stress by considering only a few short-term sea states is presented. The sea states have a certain probability of occurrence, and are each identified by a contour line in the (H _s, T _p)-plane. This approach makes it possible to estimate the extreme loads on the vessel in a practical and accurate manner. Moreover, it is shown that the long-term stress can be estimated by combining the individual long-term extreme stresses due to vertical and horizontal bending moments by using the sum-of-squares approach and accounting for the correlation between stresses. It was found that the correlation coefficient can be taken as the largest of the ones calculated along the contour line. It is shown that this correlation coefficient can even be approximated by the normalized phase angle at the wave length where the dominant response has its peak value. A comparison with the results obtained using well-known combination rules is presented. While linear analysis has been used here, it is believed that the approach can be generalized to stresses with nonlinear behavior, and hence represent a significant improvement in calculation efficiency. Received: September 18, 2001 / Accepted: December 18, 2001     

挖泥船破损强度分析研究

对单长泥舱布置的挖泥船进行舱段破损强度分析。应用传统理论方法对船舶破损后的载荷进行计算,根据CCS的《钢质海船入级与建造规范》(2004)计算船舶两种工况的弯矩剪力,通过建立船舶舱段非线性有限元模型,计算舱段的极限强度。对以上三种计算结果进行比较分析,得出相关结论。     

深水悬链复合锚泊线疲劳损伤计算

以某座Spar平台的锚泊系统为研究对象,首先利用三维绕射理论计算Spar平台主体波浪力,得到平台的总体运动响应时程。再建立复合锚泊线的二维非线性有限元动力分析模型,基于DelVecchio(1992)提出的经验公式,采用迭代的方法计算复合锚泊线的刚度。锚泊线和海床之间的接触作用基于刚性海床假定,基于Morrison公式计算锚泊线的惯性力和拖曳力荷载,根据计算得到的平台主体运动响应时程作为锚泊线顶端输入条件,在时域范围内进行复合锚泊线的动力分析。计算得到中国南海某海域各短期海况条件下复合锚泊线应力的时间历程曲线,采用雨流法对其计数得到对应于各短期海况条件下的疲劳载荷谱。最后根据Miner线性累积损伤模型,对复合锚泊线在长期海况条件下的疲劳损伤进行比较计算。