大型全回转浮吊滚轮轨道公差的分析和设计

全周滚轮回转支撑是大型全回转浮吊的重要组成部分,分析了此类回转支撑中滚轮和轨道的制造误差对实际轮压产生的影响,并为此提出了一种可行的设计思路,为合理确定滚轮直径公差和轨道平面度公差提供了计算方法和理论依据.     

基于ADAMS的滚子夹套式回转支承的动态仿真

采用ADAMS软件,对滚子夹套式回转支承进行刚柔耦合动态仿真分析,得到滚子轮压值和分布规律,为滚子夹套式回转支承轮压计算提供了一种可行的方法。     

大型全回转浮吊回转支撑技术研究

随着陆地资源的渐渐枯竭,人类已把眼光投向广袤的海洋,可以远洋作业的大型浮吊已成为海洋工程不可或缺的设备.近年来,浮吊呈现出蓬勃发展的态势,目前世界上最大的浮吊(在建)起重量已达到12 000 t. 1 大型浮吊回转支撑的类型 1.1 台车式回转支撑 台车式回转支撑沿用了门机的大车行走机构类似的设计(见图1),采用平衡梁形式,不同点在于:门机的大车行走机构做直线运动,而浮吊作回转运动;门机的行走机构主要受垂直力,浮吊主要考虑倾覆力矩的影响.     

7500吨全回转浮吊“蓝鲸”号创下世界纪录

2008年5月7日，起重量世界第一的海上浮吊——“蓝鲸”号7500吨全回转浮吊在上海振华港机公司研制成功。“蓝鲸”号浮吊船体长239米，宽50米，它既可将吊具深入水下150米，又可将重物提升到水上125米。其起重臂可以放倒或旋转，十分灵活。7500吨全回转浮吊能自如应对恶劣环境，大大扩展了我国海事工程和求助打捞事业可涉猎的海域。     

大型浮吊船体全回转起吊作业的稳性研究

基于对某超大型海上起重浮吊船体在静水和波浪中的完整稳性的计算分析,研究了在不同浪向角下全回转起吊作业的完整稳性,探讨了波浪对静稳性力臂GZ曲线、横摇纵倾及初稳性高度等稳性要素的影响,并提出衡量大型浮吊船体在波浪中稳性的几点建议.     

7500吨全回转浮吊“蓝鲸”号完工交船

5月7日上午，长兴岛岸边水面，7500吨全回转自航浮吊“蓝鲸”号，从容不迫地将7500吨的重物稳稳吊起．并作360度旋转……这标志着目前世界最大的全回转自航浮吊建成。     

“夏长”轮打捞起浮过程的数值模拟与分析

以整体打捞"夏长"轮沉船为例,给出大吨位沉船起浮过程的控制条件,提出应用GHS软件建立沉船计算模型进行数值模拟的方法,计算出沉船打捞起浮过程中货舱及压载舱不同排压水方案、艉部起浮吊力增减等不同工况下,沉船总纵强度、剪切强度及浮态的变化情况,据此得到最优起浮排压水及起浮吊力设计方案。沉船起浮过程的数值模拟结果与工程数据高度吻合,证明数值模拟方法正确。     

全回转浮吊建造的质量控制

介绍了7500t全回转浮吊项目建造的难点;详尽述及了设计阶段的质量控制、采办阶段的质量控制、施工阶段的质量控制、设备调试与船舶交接阶段的质量控制以及质量控制措施。由于抓住了质量控制要点,采取了有效的质量控制措施,从而有效地保证了7500t全回转浮吊项目的建造质量。     

全回转浮吊主机吊装方案研究

国内早期建造的全回转浮吊基本没有DP定位功能,近年来随着远洋作业增多,全回转浮吊改装增加DP定位功能的市场相应出现,DP系统耗电量巨大,必然要求增加主机数量。由于浮吊自身的特殊性,常规吊装作业方法无法应用,本文结合生产实际问题,通过三维建模和有限元分析软件设计了一套主机吊装起重装置,具有安全易操作、安装精度高和使用成本低等优点,特别适合大型船舶在漂浮状态下进行主机等设备吊装作业时使用。     

某NGW型减速器行星轮支撑轴承承载能力扩容设计

针对某NGW型减速器行星轮支撑轴承在传递功率扩容后比压偏大的问题,通过调整该支撑轴承的结构尺寸,有效降低了该轴承比压。同时借助轴承分析软件以及有限元分析软件,对该轴承的油膜压力及厚度分布的合理性进行了复核计算。最后通过实物运行试验,验证了该行星轮支撑轴承功率扩容设计的合理性,为该类行星轮支撑结构的设计提供一定的参考。     

Cyclic plastic deformation of overbend pipe during deepwater S-lay operation

In deepwater S-lay operations, the combined influences of stinger curvature, axial tension and roller support force can induce very large plastic deformation in the pipe. Dynamic loads from vessel motion and pipe sliding down the stinger lead the cyclic plastic deformation. This paper investigates the cyclic plastic stress history of the overbend pipe subjected to the dynamic pipelaying loading. The dynamic roller support forces are obtained through an innovative large scale hybrid substructure experiment constructed to simulate the pipe-stinger impact behavior. The measured roller forces are used to verify a 3D finite element analysis results developed with ABAQUS/Standard to observe the dynamic pipe stress history. The results confirm that the roller support can induce stress concentration in the pipe and the combined dynamic pipelaying loadings can cause extensive cyclic plastic deformation.     

Uncertainty analysis of extreme mooring loads associated with environmental contours and peak tension distributions

This paper aims to assess the uncertainty on the extreme mooring loads of floating system considering short-term variability. Two environmental contour approaches based on the inverse First and Second Order Reliability Methods are employed to identify critical sea states that may give rise to extreme loads. The uncertainty related to the construction of environmental contours is addressed including significant differences due to marginal distribution fitting, parameter estimation methods and joint models. Three measured datasets are analysed using a known conditional joint distribution and proposed mixed copula model. 3-h time domain numerical simulation for each sea state is conducted and the characteristic extreme responses of mooring lines subjected to design loads are assessed. The uncertainties due to various statistical models including the average conditional exceedance rate method as well as global maxima, peak-over-threshold method combined with Gumbel distribution, Generalized Extreme Value distribution, Generalized Pareto distribution and 3-parameter Weibull distribution are investigated and quantified. It is observed that marginal distributions, joint models and parameters estimation methods have apparent effect on design loads estimation, and the extreme tensions of the semi-submersible platform shows significant difference using various probabilistic models. The results indicate that those epistemic uncertainties should be account for in the reliability analysis or safety factor calibration for mooring systems.     

Required test durations for converged short-term wave and impact extreme value statistics–Part 2: Deck box dataset

In the assessment of wave-in-deck loads for new and existing maritime structures typically model tests are carried out. To determine the most critical conditions and measure sufficient impact loads, a range of sea states and various seeds (realisations) for each sea state are tested. Based on these measurements, probability distributions can be derived and design loads determined. In air gap model testing usually only few, if any, impact loads occur per 3-hour seed. This can make it challenging to derive reliable probability distributions of the measured loads, especially when only a few seeds are generated. In addition wave impact forces, such as greenwater loading, slamming, or air gap impacts are typically strongly non-linear, resulting in a large variability of the measured loads. This results in the following questions: How many impacts are needed to derive a reliable distribution? How is the repeatability of individual events affecting the overall distribution? To answer these questions wave-in-deck model tests were carried out in 100 x 3-hour realisations of a 10,000 year North Sea sea state. The resulting probability distributions of the undisturbed wave measurements as well as the measured wave-in-deck loads are presented in this paper with focus on deriving the number of seeds and exposure durations required for a reliable estimate of design loads.The presented study is Part 2 of a combined study on guidance for the convergence and variability of wave crests and impact loading extreme values. The data set of Part 1 ([1]) is based on greenwater loads on a sailing ferry and the data set of Part 2 on wave-in-deck loads on a stationary deck box.     

Characteristics of gas explosion loads and structural responses of blast wall on FPSO

Gas explosions generally cause catastrophic damage to surrounding structures and humans. The application of blast wall can effectively prevent the damage. The uniform explosion load is widely used in assessing structural response, but it cannot represent the non-uniform characteristic of actual explosion pressures. The main contents of this paper are to study the effect of gas cloud characteristics on explosion pressure distribution, and analyze the effect of non-uniform loads on structural responses. The results reveal that the explosion loads have strongly spatial inhomogeneous when explosion scenarios have large sized cloud or long combustion distance. By establishing the overpressure-probability exceedance curves for uniform loading method and distributed loading method, based on the given accident frequency several design loads are determined. The structural responses of blast wall under design loads are assessed based on explosion evaluation acceptance criteria. It can be seen that the use of uniform loading method underestimates the structural response and misjudges the deformation pattern compared to actual explosion loads. Global and local explosion pressures should be considered simultaneously in the design specification. The overpressure-probability exceedance curves for non-uniform explosion pressures are recommended to establish the design load for blast wall.     

Structural design considerations for ships operating in arctic regions北大核心CSCD

冰脊和冰山与极地船体发生碰撞将影响船体结构安全,并决定船体结构设计载荷。船体结构设计应遵循基于风险的设计原则,通常涉及以下极限状态设计准则:1)服务极限状态(SLS);2)最终极限状态(ULS);3)疲劳极限状态(FLS);4)事故极限状态(ALS)。最终极限状态和事故极限状态对应于发生概率极低的船与冰脊作用以及冰山撞击事件,旨在确保船体结构不会完全损毁。然而,对于较低概率水平的冰载荷分析,需进行较大数据量的工况分析,计算耗时无法承受。为此,引入环境等值轮廓方法,来大幅减少冰载荷分析所需工况数量,并给出设计工况最有可能的冰体参数组合方式。结合最终极限状态和事故极限状态,举例说明这一方法的运用方式。环境等值轮廓方法可为现有极地船舶船体结构设计方法提供有效补充。     

基于模糊可靠性理论的高速线材轧辊优化设计研究

工作时受交变应力的作用,高速线材轧辊断裂问题时有发生.文章利用模糊可靠性理论,探讨在随机变量和模糊变量组合时轧辊的模糊可靠性设计方法.设计实例和生产实践证实了该方法具有优化设计的效果,使轧辊使用寿命显著提高.     

船型结构物的总纵强度直接简化计算技术研究

从简化载荷施加和力学三维有限元模型的建立上进行了船型结构物的总纵强度直接简化计算技术的研究。直接简化计算技术绕开现代流行却复杂较难实现的设计波方法,借助规范波浪载荷的分布,结合现代数值计算技术,利用数值积分实现波浪载荷的模拟,同时寻求船体静水载荷分布数值化和解决三维粗网格模型的快速模拟,最终实现船型结构物设计载荷的数值模拟和总纵强度的三维设计。文章旨在寻求适合于前期设计阶段的船体结构总纵强度三维设计技术,并有效解决质量分布模拟而引起的一些客观问题,同时突破传统的二维剖面设计中非连续结构参与总纵强度的主观性判断,从工程应用角度快速有效地完成船体结构刚度和强度设计。     

半潜式钻井平台风载荷CFD预报

在平台设计过程中,海洋平台受到的风载荷是稳性分析与结构设计需要考虑的重要因素。本文采用CFD技术,对某型半潜式钻井平台在作业工况下受到的风载荷进行了预报,分析了湍流模型、风速剖面形式、湍流强度分布等因素对半潜式钻井平台风载荷的影响。结果表明：不同湍流模型对海洋平台风载荷的预报偏差在2%以内,可以忽略湍流模型的影响；风速剖面对风载荷有较大影响,随着风速梯度的增加而增大；湍流强度分布对海洋平台风载荷的影响在6%以内。研究结论可为建立高精度的海洋平台风载荷数值预报方法提供技术支持。     

悬臂板在集中荷载作用下的弯矩计算方法

推导了悬臂板结构在矩形荷载、三角形荷载、圆形荷载、多边形荷载等集中荷载作用下,在规范建议的荷载有效分布宽度内的弯矩计算公式。     

矮塔斜拉桥索鞍静力分析

结合一座矮塔斜拉桥设计、整体计算情况,为研究骑跨式索鞍局部受力状况,采用三维有限元软件建立矮塔斜拉桥索鞍区有限元模型,选取整体计算中最不利荷载进行静力分析,得到了桥塔索鞍区混凝土和索导管应力分布状况,分析索鞍处混凝土应力规律,对索鞍锚固区设计方案进行综合评价,并提出改进建议。