自升式钻井平台的抗冰性能评价

自升式钻井平台属于典型的柔性结构。由于冰与柔性抗冰结构相互作用的复杂性,长期以来尚未形成基于动冰力响应分析的结构设计。结构抗冰设计中大都是从极端荷载出发,只考虑最大静冰力或最大倾覆力矩是否能推倒平台。基于对渤海辽东湾柔性抗冰平台的多年监测,发现强烈的冰激振动引起平台管节点疲劳失效、上部设施的非正常运行、作业人员不舒适等问题的风险性要远大于极端静冰荷载下结构的整体安全问题。文中基于多年现场冰与结构作用观测及冰荷载的研究成果,提出了柔性抗冰结构设计中应考虑的主要失效模式及评价方法。最后,以渤海某典型自升式钻井平台为例,对其抗冰性能进行评价。该文的研究可为寒区自升式平台的抗冰概念设计提供合理依据。     

冰激自升式钻井平台的动力响应分析

由于冰荷载研究的限制,冰区自升式钻井平台尚未形成基于动冰力响应分析的结构设计。为了合理地开展自升式平台结构的抗冰概念设计与安全评价研究,冰荷载下自升式钻井平台的动力响应分析是十分必要的。该文首先分析该类柔性结构在动冰荷载下的动力特性;其次,结合开展的自升式平台冰荷载模型实验研究,明确带齿条桩腿的自升式平台冰荷载作用形式;最后,对渤海某自升式钻井平台在典型冰况下进行冰振动力响应分析。文中的研究对冰区自升式钻井平台抗冰设计及冰振安全评估提供了合理的参考。     

渤海单立柱桶型基础平台冰振分析

桶形基础平台是一种新型的海洋结构,由于目前对该结构的研究集中在桶基失效及承载力方面,其抗冰振性能还很模糊。文章基于对渤海单立柱式桶基平台的多年现场监测,发现其冰振加速度响应显著,明显高于导管架平台结构。利用谱分析方法对一实际桶基平台进行了冰振疲劳寿命分析,计算结果表明,关键点疲劳寿命符合规范要求。最后,提出此类结构冰振抑制策略,为其结构抗冰设计提供依据。     

冰区海上风电基础的抗冰性能分析

海上风电基础属于典型的柔性结构。由于冰与柔性抗冰结构相互作用的复杂性,长期以来尚未形成基于动冰力响应分析的结构设计。结构抗冰设计中大都是从极端荷载出发,只考虑最大静冰力或最大倾覆力矩。基于对渤海辽东湾柔性抗冰结构的多年监测,发现强烈的冰激振动引起柔性结构的风险性要远大于极端静冰荷载下结构的整体安全问题。为了明确冰区风电基础结构的抗冰性能及抗冰设计的合理性,文章结合基于多年现场冰与结构作用观测及冰荷载的研究成果,明确该类柔性结构与海冰作用形式及其动力特性;提出了柔性抗冰结构设计中应考虑的主要失效模式及评价方法。最后,以渤海某典型风电基础为例,对其抗冰性能进行评价。该文的研究可为寒区风电基础的抗冰设计及安全保障提供合理依据。     

波斯湾中受随机波作用的某新建离岸导管架平台时域动力分析研究（英文）

API RP2 A WSD is a design code in practice for design of jacket platforms in the Persian Gulf but is based on the Gulf of Mexico environmental condition. So for the sake of using this code for the Persian Gulf, it is better to perform a calibration based on this specific region. Analysis and design of jacket platforms based on API code are performed in a static manner and dynamic analysis is not recommended for such structures. Regarding the fact that the real behavior of the offshore jacket platforms is a dynamic behavior, so in this research, dynamic analysis for an offshore jacket platform in the Persian Gulf under extreme environmental condition is performed using random time domain method. Therefore, a new constructed offshore jacket platform in the Persian Gulf is selected and analyzed. Fifteen, 1-h storm, simulations for the water surface elevation is produced to capture the statistical properties of extreme sea condition. Time series of base shear and overturning moment are derived from both dynamic and static responses. By calculating the maximum dynamic amplification factor(DAF) from each simulation and fitting the collected data to Weibull distribution, the most probable maximum extreme(MPME) value for the DAF is achieved. Results show that a realistic value for DAF for this specific platform is 1.06, which is a notable value and is recommended to take into practice in design of fixed jacket platform in the Persian Gulf.     

我国海上导管架平台抗冰锥体的设计实践

冰激振动是渤海重冰区导管架平台的主要危害.渤海重冰区导管架平台在腿柱上安装了抗冰锥体,基本解决了平台冰激振动问题.主要阐述了抗冰锥体的基本抗冰原理和设计方法,分析了渤海典型导管架平台抗冰锥体的设计实践,对渤海重冰区导管架平台和抗冰锥体的设计提出了建议.     

渤海导管架平台的破冰锥体设计

主要阐述了渤海辽东湾重冰区海域锦州21-1 BOP和锦州9-3E WHPA平台导管架破冰锥体的设计实践,并对渤海重冰区平台导管架破冰锥体的设计提出了建议.     

基于监测的宽窄抗冰锥体结构判据分析（英文）

Ice-induced structural vibration generally decreases with an increase in structural width at the waterline. Definitions of wide/narrow ice-resistant conical structures, according to ice-induced vibration, are directly related to structure width, sea ice parameters, and clearing modes of broken ice. This paper proposes three clearing modes for broken ice acting on conical structures: complete clearing, temporary ice pile up, and ice pile up. In this paper, sea ice clearing modes and the formation requirements of dynamic ice force are analyzed to explore criteria determining wide/narrow ice-resistant conical structures. According to the direct measurement data of typical prototype structures, quantitative criteria of the ratio of a cone width at waterline(D) to sea ice thickness(h) is proposed. If the ratio is less than 30(narrow conical structure), broken ice is completely cleared and a dynamic ice force is produced; however, if the ratio is larger than 50(wide conical structure), the front stacking of broken ice or dynamic ice force will not occur.     

Classification criterion of narrow/wide ice-resistant conical structures based on direct measurements

Ice-induced structural vibration generally decreases with an increase in structural width at the waterline. Definitions of wide/narrow ice-resistant conical structures, according to ice-induced vibration, are directly related to structure width, sea ice parameters, and clearing modes of broken ice. This paper proposes three clearing modes for broken ice against conical structures: complete clearing, temporary ice pile up, and ice pile up. In this paper, sea ice clearing modes and the formation requirements of dynamic ice force are analyzed to explore criteria determining wide/narrow ice-resistant conical structures. According to the direct measurement data of typical prototype structures, primary quantitative criterion of the ratio of a cone width at waterline (D) to sea ice thickness (h) is proposed. If the ratio is less than 30 (narrow conical structure), broken ice is completely cleared and a dynamic ice force is produced; however, if the ratio is larger than 50 (wide conical structure), the front stacking of broken ice or dynamic ice force will not occur.     

Assessment of offshore structures under extreme wave conditions by Modified Endurance Wave Analysis

Recently, various approaches have been introduced to estimate the response of offshore structures in different sea states by stepwisely intensifying records. In this article, a more practical approach entitled Modified Endurance Wave Analysis (MEWA) considering the random and probabilistic nature of wave loading and utilizing optimal time duration is introduced. Generation procedure of this approach is described based on two practical wave theories: random and constrained new-wave. In addition, assessment of a simplified model representing a typical fixed offshore platform under extreme wave conditions in the Persian Gulf is performed making use of MEWA. A comparative analysis has been also carried out to investigate the accuracy and computational costs of MEWA. The results indicate that MEWA can be a time-saving and also reliable method both in design and assessment of offshore platforms.     

Dynamic ice loads for offshore wind support structure design

For offshore wind farms which are planned in sub-arctic regions like the Baltic Sea and Bohai Bay, support structure design has to account for load effects from dynamic ice-structure interaction. There is relatively high uncertainty related to dynamic ice loads as little to no load- and response data of offshore wind turbines exposed to drifting ice exists. In the present study the potential for the development of ice-induced vibrations for an offshore wind turbine on monopile foundation is experimentally investigated. The experiments aimed to reproduce at scale the interaction of an idling and operational 14 MW turbine with ice representative of 50-year return period Southern Baltic Sea conditions. A real-time hybrid test setup was used to allow the incorporation of the specific modal properties of an offshore wind turbine at the ice action point, as well as virtual wind loading. The experiments showed that all known regimes of ice-induced vibrations develop depending on the magnitude of the ice drift speed. At low speed this is intermittent crushing and at intermediate speeds is ‘frequency lock-in’ in the second global bending mode of the turbine. For high ice speeds continuous brittle crushing was found. A new finding is the development of an interaction regime with a strongly amplified non-harmonic first-mode response of the structure, combined with higher modes after moments of global ice failure. The regime develops between speeds where intermittent crushing and frequency lock-in in the second global bending mode develop. The development of this regime can be related to the specific modal properties of the wind turbine, for which the second and third global bending mode can be easily excited at the ice action point. Preliminary numerical simulations with a phenomenological ice model coupled to a full wind turbine model show that intermittent crushing and the new regime result in the largest bending moments for a large part of the support structure. Frequency lock-in and continuous brittle crushing result in significantly smaller bending moments throughout the structure.     

浮式抗冰平台设计理念及水动力特性研究

钻探极地地区近海石油和天然气资源对移动式离岸钻井平台的水动力性能、抗冰性能和作业性能有着极大的要求。本文主要介绍了浮式抗冰平台的设计方案,并结合当今最新一款半潜式抗冰平台的设计理念,分别从频域和时域分析的角度与传统的半潜式平台作对比,分析得出其具有优越的水动力性能,垂荡、横摇、纵摇运动响应都优于传统的半潜平台,为下一步抗冰性能分析及其关键技术的研究做基础,同时也给半潜式平台带来新的设计理念,为浮式抗冰平台的设计建造提供合理思路。     

抗冰海洋平台的全寿命优化设计I-理论与模型

文章基于投资—效益准则,建立了抗冰平台全寿命总费用最小的优化设计模型;考虑了多种类型的性能要求(结构、设备、人员),并建立了相关判据;提出了包括结构的初始费用、维修费用和期望损失费用的冰区海洋平台全寿命总费用评估模型;提出了平台结构主要功能的确定及描述方法、相应的功能失效损失值估计模型。     

导管架式海洋平台自适应预测逆控制研究

文章提出了一种新的基于动态刚度阵法的导管架式海洋平台模糊神经网络自适应预测逆控制模型。该模型是通过安放在海洋平台桩腿上的压力传感器实时采集海洋平台所受波浪力,然后应用动态刚度阵法快速而准确地计算出平台顶部的响应,再将此响应作为模糊神经网络预测逆控制器的输入信号,预测出下一时刻平台顶部的控制力来对海洋平台振动响应进行控制;同时,通过反馈的自适应预测逆控制器来减小扰动和前馈控制的误差。为了验证该模型的抗干扰能力,文中还对有随机风载荷扰动情况下的导管架式海洋平台主动控制进行了研究。最后的数值算例结果表明,文中所提出的导管架式海洋平台主动控制模型具有较强的抗干扰能力,能很好地解决控制系统中存在的时滞问题,可有效地控制导管架式海洋平台的振动响应。     

锥体海洋平台结构冰荷载的离散单元分析

在冰区油气开发中,锥体结构可以有效降低冰力,避免强烈的冰激振动,是目前渤海油气平台的主要结构形式。为研究海冰与锥体结构的相互作用过程,文章建立了适用于模拟海冰破碎特性的离散单元模型。该模型将海冰离散为若干个具有粘接-破碎功能的颗粒单元,并通过海冰弯曲试验确定了单元间的粘接强度;然后对海冰与锥体结构的作用过程进行了数值计算,获得了相应的动冰荷载及冰振响应;在此基础上讨论了不同锥角影响下冰荷载及结构振动响应的变化规律。结果表明,水平方向冰荷载及结构冰振响应随锥角的增加明显增加,而竖直方向冰荷载则显著降低。该离散单元模型还可进一步应用于不同类型抗冰结构的冰荷载分析,有助于解决冰区结构物的抗冰结构设计和冰致疲劳分析。     

抗冰海洋平台的全寿命优化设计Ⅱ—算法与应用

针对抗冰海洋平台全寿命优化设计模型中的不同类型可靠度分析问题,提出了相应的计算方法,包括冰区导管架平台整体抗力和极值冰力响应的概率统计特性及整体可靠度的高效近似算法,基于首次超越破坏机制的海洋平台冰振动力可靠性分析,基于等效应力幅值近似计算的疲劳寿命分析等。最后,以渤海某抗冰平台为例,实现了全寿命总费用最小的抗冰海洋平台优化设计。结果表明,基于风险的全寿命优化模型比基于规范的静力设计和仅考虑动力的最优设计相比更加合理。     

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.     

一种基于冰载荷引起的船体结构疲劳损伤分析方法

目前对基于冰载荷引起的船体结构强度问题已经发展的较为成熟,但是基于冰载荷引起的结构疲劳强度的研究比较少。针对该问题,如果有一种简化方法来指导早期的结构设计,对船舶设计者来说是很有现实意义的。本文对英国劳氏船级社发布的ShipRight FDA ICE_^[1]作概括性的介绍,旨在向读者介绍这一简单而高效的评估方法以及技术背景和注意要点等。最后文章根据这一方法给出数条油船和LNG船的算例,并验证通过该方法改善疲劳节点的可行性。     

近海结构疲劳计算中波浪与结构建模探讨

文章根据作者已提出的基于海况频度分布的统计分类及非线性动力学计算的疲劳评估方法,通过进一步改进波浪能的输入,提出了一种更为有效的计算方法。通过将这一方法运用到一典型导管架结构的疲劳计算,文中首先研究了波浪方向对疲劳破坏的影响,进而分析了波浪谱中若干重要参数及HHT-α时间积分中步长对疲劳计算结果的影响。通过对结构反应的统计研究,发现海况的恶劣程度并不直接影响结构响应非高斯趋势的显著程度。文中提出的方法在减少不确定性的同时又不降低安全标准,有效提高了疲劳计算的精确度,从而可以降低相关近海结构建设和维护成本。文中的计算方法已被成功地应用于北海及墨西哥湾数座近海结构在风和波浪荷载作用下的疲劳评估。