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Traditionally, the design of mooring lines and risers of floating production systems (FPS) has been performed separately, by different teams, employing uncoupled analysis tools that do not consider the nonlinear interaction between the platform hull and the mooring lines and risers. Design processes have been focused on fulfilling the design criteria of the respective component (mooring/riser) alone, with few or no consideration to the other component, and little interaction between the design teams. Nowadays the importance of employing analysis tools based on coupled formulations is widely recognized, and analysis strategies have been proposed to consider feedback between mooring lines and risers within their respective design processes.In this context, this work details a proposal of one single and fully integrated design methodology for mooring systems and risers for deep-water FPS. In this methodology, the design stages of both risers and mooring lines are incorporated in a single spiral, allowing the full interaction of different teams; mooring design implicitly considers the riser integrity, and vice-versa, leading to gains in efficiency and cost reduction.Different analysis strategies are employed, taking advantage of uncoupled and coupled numerical models. The models generated at the initial/intermediate design stages can be reused in subsequent stages: simpler models are used in the initial stages, and more refined models are gradually introduced, to reach an ideal balance between computational cost and accuracy of results. In the advanced stages, the exchange of information between mooring/riser also allows the definition of criteria for the selection of governing/critical loading cases to be revised and verified in detail. This leads to the reduction of the original loading case matrix, allowing a feasible use of time-consuming fully coupled analysis.Results of a case study illustrating the application of some of the main processes of the methodology are included. 相似文献
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A linearized aero-hydro-servo-elastic floating wind turbine model is presented and used to perform integrated design optimization of the platform, tower, mooring system, and blade-pitch controller for a 10 MW spar floating wind turbine. Optimal design solutions are found using gradient-based optimization with analytic derivatives, considering both fatigue and extreme response constraints, where the objective function is a weighted combination of system cost and power quality. Optimization results show that local minima exist both in the soft-stiff and stiff-stiff range for the first tower bending mode and that a stiff-stiff tower design is needed to reach a solution that satisfies the fatigue constraints. The optimized platform has a relatively small diameter in the wave zone to limit the wave loads on the structure and an hourglass shape far below the waterline. The shape increases the restoring moment and natural frequency in pitch, which leads to improved behaviour in the low-frequency range. The importance of integrated optimization is shown in the solutions for the tower and blade-pitch control system, which are clearly affected by the simultaneous design of the platform. State-of-the-art nonlinear time-domain analyses show that the linearized model is conservative in general, but reasonably accurate in capturing trends, suggesting that the presented methodology is suitable for preliminary integrated design calculations. 相似文献
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We present an optimization study for the conceptual design of wind turbine floaters of the TetraSpar type. The optimization variables include all geometric dimensions of the floater, keel, mooring lines and tower design. A gradient based optimization method is applied to a mass proportional objective cost function. The objective function accounts for the different weight components of the floater, including secondary steel, the wind turbine tower, and the mooring system. A frequency domain response method is utilized, so that each design evaluation also takes into account the dynamic response for 12 wind speeds with associated wave conditions. Nineteen constraints are applied for static and dynamic response, natural frequencies, and fatigue at the bottom of the tower. Two reference designs are presented, namely one with a soft–stiff tower and one with a stiff–stiff tower. Due to the anti-phase coupling of the floater pitch and tower vibration, the soft–stiff tower needs a stronger floater stiffness in pitch. This design thus has a larger water plane area moment than the more compact stiff–stiff floater, which is found to be the least economical. A constraint analysis is next presented based on Lagrange multipliers and a relative cost index. We find that the strongest cost influence is exerted by the 3P tower frequency constraint for the stiff-stiff and soft-stiff designs. Finally, a third design variant with a free optimizable tower frequency is introduced. This design is found to be 11% cheaper than the soft–stiff design and highlights the potential cost savings of tower designs within the 3P region. 相似文献
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This paper addresses the need for systematic evaluation of the station keeping systems of deepwater drilling semi-submersibles. Based on the selected drilling semi-submersible configuration, the mooring systems were analyzed and designed for a range of water depths using different mooring line materials. These were steel wire rope, polyester rope and HMPE (high modulus poly ethylene). The mooring analysis was carried out using the advanced fully coupled time domain analysis method in the computer software package HARP. Diffraction analysis was first applied to solve the hydrodynamic properties of the vessel and then the motion equations of the complete dynamic system including the drilling rig, the mooring lines and risers were developed and solved in the time domain. Applying the advanced analysis method, a matrix of mooring systems was developed for operating in water depths of 1 000 m, 1 500 m, and 2 000 m using various mooring materials. The development of mooring systems was conducted in accordance with the commonly adopted mooring design code, API RP 2SK and API RP 2SM. Fresh attempts were then made to comparatively evaluate the mooring system’s characteristics and global performance. Useful results have been obtained in terms of mooring materials, water depths, and key parameters of mooring configurations. The results provide in-depth insight for the design and operation of deepwater mooring systems in the South China Sea environment. 相似文献
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拖曳锚系泊作为目前海洋工程使用最为广泛的系泊方式,因其较低的制造和安装成本使其成为小型浮式平台系泊方式的首选。目前拖曳式系泊设计大多根据以往工程经验进行选择设计,由于经验设计中并没过多的泥面表面及以下锚链安装信息,因此在设计之初很难对系泊材料用量准确计算。不同重量的拖曳锚在同样的嵌深和同样的锚倾角条件下,所能提供的系泊力大不相同。同时,不同重量的拖曳锚的在相同土壤条件下拖曳嵌入轨迹不同,因而最大埋深不同。上述两方面原因导致不同重量的拖曳锚提供的系泊力不一样。因此,需要达到同样的系泊效果,泥线以下反悬链线和卧底链的长度在不同重量锚的系泊系统中是不同的。参照系泊成本各个分项在其生命周期各阶段的占比,材料制造成本与安装成本占据系泊成本的大部分,且安装成本往往正比于材料成本。因此降低系泊锚链的材料成本对整个系泊系统的成本降低起到了巨大的优化作用。通过结合拖曳锚的极限平衡法拖曳轨迹理论方程,以不同重量的拖曳锚在粘性土壤中的不同拖曳距离下提供额定系泊力时所需要的材料重量为系泊成本评价依据,从而得到浮式结构物系泊系统的一种设计优化方法。 相似文献
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张力腿平台采用特殊的垂直系泊系统,属于半顺应半刚度式平台,平台主体-系泊系统-立管之间的耦合动力响应是张力腿平台设计的关键,直接影响平台的安全性和可靠性。文中首先采用数值模拟和模型试验相结合的手段对一座工作水深为500m的张力腿平台运动响应和系泊特性进行了对比验证,模型缩尺比为1:40,试验在上海交通大学海洋工程国家重点实验室进行,数值计算采用SESAM软件。在试验验证的基础上重点对一腱断裂的前、后平台水动力性能进行了对比分析,重点关注有义波高、特征周期以及浪向角等因素对六自由度运动响应以及张力腿张力特性的影响。 相似文献
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本文应用水弹性理论研究单点系泊系统立管的强度问题。讨论了有固定强迫漂移运动的立管水弹性计算方法,提出了适用于深海多节铰支立管计算公式,并编成计算程序,对 SALS 系统立管进行了计算检验。 相似文献
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研究基于可靠度的方法,对深海复合材料悬链线立管进行优化设计分析。对于正交各向异性层合复合材料结构而言,叠层顺序不同、各层铺角变化以及层间厚度差异等都会影响到结构的承载能力,因此,有必要引进可靠度作为优化设计指标。首先,根据经典层合板理论计算整体模型的等效属性,建立悬链线立管整体分析模型,得到关键截面响应,以此作为局部分析模型的约束;然后,运用试验设计方法构建Kriging近似模型;最后,利用蒙特卡罗撒点方法对比分析确定性优化与可靠性优化的结果。研究表明:优化后的深海复合材料立管在满足应力强度设计的要求下可有效降低结构重量,所提出的基于可靠度的优化设计复合材料悬链线立管具有可行性。 相似文献
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浮体系泊系统在海洋工程水池进行模型试验时,由于水池尺度有限,首先对系泊线进行等效截断设计,是被动式混合模型试验的重要一步。截断设计时,基于细长杆理论,模拟系泊线的非线性动力特性,将计算所得时域内的系泊力转换到频域响应,选择有代表性的频率及响应建立目标函数,结合NSGA II优化算法,确定最优截断系泊参数,计算快速准确。针对一作业水深420m的FPSO单点系泊系统,进行水平截断设计。截断前后系泊系统和单根系泊线的静力特性吻合很好。截断系泊系统在不同环境载荷作用下的总体响应和系泊动力,都与截断前一致。证明了截断设计的合理性和准确性,为后续的模型试验工作打下了基础。 相似文献
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以某LR2型油船实船系泊、拖带设备选型及技术方案确定过程为依据,结合设计过程中针对该船特殊甲板结构区域系泊设备布置及为完全满足新规范要求改进舾装设备所采取的优化措施,对此类油船实船设计如何更好地满足近年来新生效的系泊、拖带相关规范和规则要求进行研究。对LR2型油船系泊、拖带设计相关的重点内容、关键技术及为获得最优设计方案所采取的技术措施进行解析和归纳。所得成果能为以后此类油船的系泊、拖带设计提供参考。 相似文献
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The development of the LBR-5 “Stiffened Panels Software” is included in the development of a new design methodology to ease and to improve preliminary studies of naval structures and floating hydraulic structures. It allows, as of the first draft, an optimization of the scantling of the structure's constituent elements. The ultimate target is to link standard design tools (steel structure CAD, hull form, hydrostatic curves, floating stability, weight estimation, etc.) with a rational optimization design module and a minimum construction cost (or minimum weight) objective function. It is developed to be a user-oriented tool. The optimization module is composed of three basic modules (OPTI, CONSTRAINT and COST) and a group of sub-modules (in external databases). Among these the user selects a set of relevant sub-modules (i.e. geometrical and structural constraints). Since the present optimization deals with least construction costs (as objective function), and uses an explicit objective function (not empirical), the user must specify labor costs (unitary material costs, welding, cutting, etc.). This paper is the second part of a series of two articles. The previous paper focused on the ‘Module-Oriented Optimization’ methodology and on the rational constraints (Rigo, Marine Structures 2001). This paper presents the optimization algorithm based on convex linearization and a dual approach (OPTI module). It also includes the optimization of a FSO unit as a detailed example. 相似文献
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The real-time monitoring of underwater risers, cables, and mooring lines by multiple sensors is in great demand but still very challenging. In this study, a new real-time riser monitoring method based on an Extended Kalman Filter (EKF) is proposed. It estimates the overall shape of riser in real-time utilizing the measured signals from multiple bi-axial (inclination and heading) inclinometers along the riser. The novel EKF algorithm is shown to be robust against sensor noises and successfully reproduces the actual riser profiles at each time step, which has been verified by multiple tests through numerical simulations. For verification, a turret-moored FPSO (Floating Production Storage and Offloading) with a SCR (Steel Catenary Riser) is employed in four different random waves and currents. Subsequent algorithms are also developed so that the corresponding bending and axial stresses along the riser can also be estimated in real time from the obtained riser shape, which can further be used for the real-time estimation of fatigue-damage accumulation. 相似文献
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The integrity of mooring chains is essential to the safety of a range of offshore platforms. However, mooring line failures are occurring earlier than their design lives, with a high number of these failures occurring due to fatigue. Early in the fatigue life of the component fatigue initiation processes occur, where the fatigue hotspot is sensitive to the mean load and there is plastic strain accumulation from the multiaxial stress-strain responses of the material, leading to cyclic plastic damage accumulation. The traditional SN approach suggested by mooring standards does not consider these effects, and it is proposed that this lack of consideration under low-cycle fatigue conditions is the reason for the current non-conservative fatigue assessments of mooring chains. This paper aims to develop a fatigue approach based on a critical plane multiaxial fatigue criterion for mooring chains that can consider the damage-induced by the cyclic plasticity and the mean load effect, to investigate the importance of incorporating low-cycle fatigue into the mooring chain life prediction. To develop the critical plane approach, the multiaxial stress-strain states are extracted for the critical plane at the fatigue hotspot from a finite element model of a mooring chain. This is then correlated with a fatigue life prediction provided by conventional fatigue design data. It uses a simulation of an FPSO as a case study to demonstrate the importance of low cycle fatigue, which shows that the mean load effect is significant in reducing the fatigue life for mooring chain applications, while the effect of fatigue damage-induced cyclic plasticity is limited. The fatigue damage accumulation predicted by the critical plane approach is significantly higher than that of the traditional SN approach and should be accounted for in mooring line design. 相似文献
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Philippe Rigo 《Marine Structures》2001,14(6):611-629
The development of the LBR-5 “Stiffened Panels Software” is included in the development of a new design methodology to ease and to improve preliminary studies of naval structures and floating hydraulic structures. The ultimate target is to link standard design tools (steel structure CAD, hull form, hydrostatic curves, floating stability, weight estimation, etc.) with a rational optimization design module and a minimum construction cost (or minimum weight) objective function. This paper is the first part of a series of two articles. It focuses on the ‘Module-Oriented Optimization’ methodology and on the rational constraints. The second paper presents the optimization technique using convex linearization and a dual approach, and the optimization of an FSO unit as an example (Rigo and Fleury, Marine Stuructures, 2001). LBR-5 allows, as of the first draft, an optimization of the scantling of the structure's constituent elements. Relevant limit states of the structure are taken into account thanks to a 3D rational analysis of the structure based on the general rules of solid-mechanics and structure behaviour. The optimization module is composed of 3 basic modules (OPTI, CONSTRAINT and COST) and a group of sub-modules (in external databases). Among these the user selects a set of relevant sub-modules (i.e. geometrical and structural constraints). Since the present optimization deals with least construction costs (as objective function), and uses an explicit objective function (not empirical), the user must specify labor costs (unitary material costs, welding, cutting, etc.). 相似文献