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考虑沟槽深度及土体吸力影响的SCR与海床土体循环作用分析 总被引：1，自引：0，他引：1
悬链线立管与海床土体的相互作用对立管的疲劳寿命影响很大,而管土作用的机理又十分复杂,海底沟槽以及海床土体吸力都会对立管力学特性产生影响,文章以Aubeny等提出的管土作用完整P-y曲线为基础,在有限元分析软件ANSYS中采用非线性弹簧模拟海床土体,计算中考虑了土体吸力;模拟了三种位移幅值下管土循环作用时沟槽深度的变化,分析了沟槽段各点弯矩及应力随深度的变化规律,同时对比了三种情况下管道最深点的弯矩及应力随加载时间的变化关系,为进一步分析管土循环作用提供了参考。 相似文献
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深水海洋立管具有柔性,特别是极端海况条件下,相邻立管之间可能发生互相干涉而增大立管的应力,从而影响其疲劳寿命.钢悬链线立管相比顶张力立管,有效张力较小,对环境载荷作用更加敏感,更容易发生碰撞.基于动力学分析软件OrcaFlex建立有限元模型,从允许碰撞的角度出发,对串列布置于张力腿平台上的两根钢悬链线立管进行整体碰撞分析,研究立管间距、尾流模型、拖曳力系数、海流流速和柔性接头刚度对立管碰撞的影响,阐述对碰撞范围、上下游立管相对运动速度、最大碰撞速度和最大碰撞能量的影响规律,为实际工程中立管的空间布置和结构优化设计提供参考. 相似文献
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Steel catenary riser is a long-established option for subsea projects in deep-water regions. Sustained pulling force of steel catenary risers on subsea flowlines in combination with cyclic thermal load throughout the system lifetime may lead to progressive global axial displacement of subsea pipelines which has been termed as ‘walking’. One of the challenges in the deep-water industry is long-term walking of subsea flowlines in a cumulative manner. Common practice methods for walking mitigation are quite expensive operations. State-of-the-art mitigation strategies are proposed in the paper by means of modifying pipe pieces before the installation operation. Bowed pipe pieces and miter joints are two recommended approaches for walking mitigation. The presented mitigation strategies are relatively cost-effective solutions for the pipe-walking challenge and they are able to considerably cease the potential cyclic walking. Comprehensive FE analyses in ABAQUS software are performed to evaluate the proposed deformed pipelines response subject to two loading conditions. Through-life integrity of the suggested pre-deformed pipeline is assessed in terms of effective axial force, local buckles and excessive axial strains. A comparison of the presented method with conventional techniques shows the effectiveness of the proposed configuration. The proposed methods can significantly reduce effective axial force throughout the subsea pipeline by means of artificially introduced deformations. The cumulative walking of the presented method is practically zero. In addition, the influence of combined triggering mechanisms to the walking phenomenon is assessed when the pipeline is located on a sloping seabed and it is subject to non-uniform thermal loads. A parametric study is performed to improve confidence in design and provide a reasonably practical technique with an optimal shape. 相似文献
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对海洋钢悬链线立管(SCR)与土体的相互作用研究越来越得到业界的重视,不同计算方法得到的结果准确性如何尚未做过对比分析.文章采用有限元法和有限差分法对管—土的相互作用进行了数值计算.在有限差分法中采用弹簧单元,在有限元法中采用接触单元模拟悬链线立管与海床土体的相互作用,得到端部施加不同位移载荷下的立管弯矩、土体反力、触底点位置并与实验结果作比较.分析了端部位移载荷大小对触地点(TDP)位置及对土体反力的影响.文中采用的方法在模拟静态端部位移加载下的管—土相互作用与实验结果吻合较好.为进一步模拟循环载荷下管—土相互作用奠定了基础. 相似文献
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The most critical issue in the steel catenary riser design is to evaluate the fatigue damage in the touchdown zone accurately. Appropriate modeling of the riser-soil resistance in the touchdown zone ca... 相似文献
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A method to identify vortex-induced forces and coefficients from measured strains of a Steel Catenary Riser (SCR) undergoing vessel motion-induced Vortex-induced Vibration (VIV) is proposed. Euler–Bernoulli beam vibration equations with time-varying tension is adopted to describe the out-of-plane VIV responses. Vortex-induced forces are reconstructed via inverse analysis method, and the Forgetting Factor Least Squares (FF-LS) method is employed to identify time-varying vortex-induced force coefficients, including excitation coefficients and added mass coefficients. The method is verified via a finite element analysis procedure in commercial software Orcaflex. The time-varying excitation coefficients and added mass coefficients of an SCR undergoing vessel motion-induced VIV are investigated. Results show that vessel motion-induced VIV is excited at the middle or lower part of the SCR and in the acceleration period of in-plane velocity, where most of the excitation coefficients are positive, while during the deceleration period, the excitation coefficients becomes too small to excite VIVs. Parameter γ [1] has strong correlation with excitation coefficients. In addition, time-varying tensions contribute significantly to the variations of added mass coefficients under the condition that the ratio of dynamic top tension to pretension exceeds the range of 0.7–1.3. Moreover, chaotic behaviors are observed in vortex-induced force coefficients and are more evident with the increase of vessel motion velocity. This behavior may attribute to the randomness existing in in-plane velocity and its coupling with out-of-plane vibrations. 相似文献
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向量式有限元法是基于向量式力学和数值计算的一种创新性的结构行为分析方法。文章采用三种弹簧模型模拟海床,将向量式有限元法用于钢悬链线立管触地段与海床土体相互作用研究中,编制相应Matlab求解程序,计算了端部施加一定位移下立管的位形和弯曲应力,并与他人基于有限差分法及ABAQUS的模拟结果进行对比,同时运用该方法分析了弹簧模型、土体刚度、土体吸力系数等参数对立管触地段变形和弯曲应力的影响。结果表明向量式有限元法在模拟静态端部位移加载下的管-土相互作用是准确和可行的,能够直接求解变形和内力,具有相对简洁性,此方法是对立管力学行为的模拟,符合实际运动变形过程。为模拟管-土相互作用提供了新方法,同时为进一步研究实际循环载荷下管-土相互作用奠定了基础。 相似文献
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The subsea survey results using remote operating vehicles (ROV) show that trenches with a depth of several riser diameters can be developed underneath the steel catenary risers (SCR). Therefore, an important question in respect of the riser–seabed interaction is, how the trench formation beneath the riser affects the riser fatigue performance in the touchdown zone. A common methodology reported in literature to study the impact of trench formation on riser fatigue life is the insertion of an artificial mathematical expression of the riser profile into the seabed. This study shows that such methodology can be inconsistent and leading to contradictory results. The current paper has employed ABAQUS finite element software and coded a non-linear soil hysteretic model to automatically simulate the variable seabed stiffness and the gradual trench development through the touchdown zone. In this method, the seabed model parameters are initially adjusted to extreme values allowing trench with desired depth to be developed over a moderate number of displacement cycles of the SCR. The design wave scatter diagram is then applied, simulating a generic Spar system, after switching the model parameters to values with normal range. The paper presents the impact of trenches of different depths on the fatigue performance of SCRs in the touchdown zone. 相似文献
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随着海上浮式移动钻井设施作业水深的不断增加,钻井立管受水面浮体运动与海洋环境载荷的影响将更加复杂,如何通过有效的定位方法来保证水面平台与水下立管的联合作业安全是深海环境下油气开发面临的重要挑战。针对浮式移动设施水下钻井、修井的位置保持问题,本文在动力定位模式下设计一种考虑钻井立管顶、末端角度响应的控位方法,以满足立管安全运行限制域的要求。联合水面浮体与水下立管的低频运动特性分析与建立水面浮体运动偏移与立管顶、末端角度的相对运动关系与模型。在动力定位控位策略中引入最小化钻井立管角度响应的目标函数及其约束条件进行最优化动态期望位置规划,并通过“海洋石油981”深水钻井平台及其立管系统进行了仿真验证。 相似文献
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梁辉 《船舶与海洋工程学报》2009,8(2):163-167
钢悬链线立管作为一种全新的深水立管系统已经在国外多个项目中应用,总结了有关深水钢悬链线立管触地区域管土相互作用的研究进展,主要包括STRIDE和CAluSIMA工业合作计划的研究数据和其他的相关论文,能够为国内深水钢悬链线立管的研究提供参考. 相似文献
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To meet the increasing applications of the deepwater steel lazy-wave riser (SLWR), the riser abandonment and recovery (A&R) is a great challenge for SLWR installation and its mechanical analysis is necessary and significant. This paper is focused on the abandonment and recovery process which is of great importance to the installation feasibility and analysis. A comprehensive mechanical model based on the nonlinear large deformation beam theory for simulating the deepwater SLWR is proposed. And a simple and suitable model for analyzing the A&R cable is developed. The presented model with detailed boundary conditions is able to deal with three different A&R methods. Numerical analysis is conducted by the finite difference method to investigate the riser configurations and somev important mechanical parameters of the pipeline and cable which exert influences on the riser's performance and the A&R cable's requirement. Parametric comparison study is conducted to analyze the advantage of different method. The proposed model can help on development of deepwater SLWR A&R design and analysis. 相似文献
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深水管中管钢悬链线立管的非线性动力分析 总被引：1，自引：0，他引：1
立管技术是深水资源开发的关键技术之一。管中管钢悬链线立管具有同心的外管与内管，其外管提供机械保护，内管提供油气通道，内、外管之间按照一定的距离安装扶正器以保护绝热材料，在深水油气开发中具有较大的应用价值。充分考虑在位立管承受的复杂载荷条件泡括动边界、波浪与海流载荷、立管自重、海水浮力、管内外静压力），以及整体和局部非线性因素（包括摩擦、滑移、接触、间隙等），采用时域有限元软件ABAQUS实现管中管钢悬链线立管的建模与非线性动力分析。 相似文献
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In this paper a recently proposed formulation for the multilayered pipe beam element is extended to dynamic analysis of risers. Derivations of hydrostatic and hydrodynamic loadings due to internal and external fluid acting on each element layer are presented. Mass and damping matrices, associated to each element layer, are properly derived by adding their respective contributions to the expression of the virtual work due to external loading. The finite element implementation allows for the numerical representation of either bonded or unbonded multilayered risers, including small slip effects between layers. A number of numerical examples have been carried out and the results show the accuracy and efficiency of the new element formulation, even in large scale riser analysis. Moreover, we establish a few benchmarks using multilayered pipes and risers. 相似文献
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悬链线立管会在半潜平台运动带动下出现涡激振动现象,对立管疲劳寿命造成影响.借助海工结构物动力分析软件Orcaflex建立立管模型,使用Iwan-Blevins尾流振子模型进行数值模拟.通过与试验结果对比验证了该方法的可行性.同时建立实尺度悬链线立管模型,并考虑背景海流的影响,分析平台垂荡、纵荡运动下的立管涡激振动响应和疲劳损伤.研究表明,平台运动产生的非定常流场将引起悬链线立管发生涡激振动现象,并在背景洋流激励的基础上增大疲劳损伤,在立管结构实际工程设计时应予以关注. 相似文献
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针对缓波型柔性立管存在的波型较陡和浮子段张力较大的问题,对其进行优化,将单波构型优化为双波构型,运用集中质量法对改进前后的2种结构形式进行分析,确认双波构型在静力和动力响应下的张力及弯曲特性更优。在此基础上,对双波型柔性立管进行敏感性分析。在静力状态下,悬挂点和第2段浮子段末端对浮子段间隔和浮子段长度敏感;在动力响应下,悬挂段到第1段浮子段的张力变化和最小弯曲半径对浮子段间隔和大悬挂角非常敏感。研究得到的敏感性参数结论可作为缓波型柔性立管总体布置设计的参考。为提升缓波型柔性立管的性能,可合理增加浮子段与浮子段的间隔和悬挂角,但同时要满足规范的要求,避免关键部位动力响应过大。 相似文献