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1.
T.A. Netto 《Applied Ocean Research》2009,31(2):75-81
Internal corrosion in pipelines is often caused by water, sediment, or chemical contaminants present in the multi-phase flow. This normally occurs at the bottom of the pipe and at low points in the pipeline where sediment and water can settle out of the product being transported, therefore creating narrow and long defects. The effect of corrosion defects on the collapse pressure of offshore pipelines was studied through combined small-scale experiments and nonlinear numerical analyses based on the finite element method. After calibrated in view of the experimental results, the model was used to determine the collapse pressure as a function of material and geometric parameters of different pipes and defects. An extensive parametric study using two and three-dimensional numerical models was carried out encompassing different defect geometries and their interaction with pipe ovalization. This paper reports these results which are subsequently used to develop a simple procedure for estimating the collapse pressure of pipes with narrow defects. 相似文献
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海底管道是海洋石油主要的运输方式，但海底管道在外部静水压力作用下很可能发生局部屈曲压溃，造成灾难性后果。安装止屈器可有效阻止屈曲传播，保证管道安全，整体式止屈器在实际中应用最为广泛。整体式止屈器存在通过减小止屈器体积以节约成本进行优化的可能性，因此，在保证止屈器止屈效果的前提下，可通过减小止屈器的体积，以达到减轻重量、节约成本、减少安装难度等多种目的。研究过程中使用ABAQUS进行模型的仿真模拟，比较了广义弧长法的优缺点，决定选用更方便的静水流体单元法，计算得到不同止屈器的穿越压力以及相应的体积，对比各止屈器的穿越压力变化和体积变化，实现结构优化的目标。基于以上研究，可以得出减少止屈器体积的结构优化方案具有可行性的结论。 相似文献
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The present paper is concerned with determining the effect of thickness variation on collapse pressure of seamless pipes. There exists extensive information on the effects external pressure has on pipelines. A substantial amount of literature deals with results of analysis, numerical modelling and testing of pipes those are gradually subject to external pressure. This knowledge has been incorporated into standards which are intended for designing linepipe operating in deepwater locations. One such example is the DNV-OS-101 (DNV, 2007) Submarine Pipeline Systems standard. This code only addresses pipes with a nominally uniform wall thickness making it inadequate for designing seamless pipe which is prone to thickness variation arising from the manufacturing process. The DNV (2007) code effectively ignores the problem as it simply provides a vague statement regarding a conservative value of wall thickness that should be used in the design calculations.The present paper uses finite element analysis (FAE) modelling to predict the external pressure acting on the pipes. The present paper explains the manner in which FEA models will be used to study the effect wall thickness variation will have on the pressure at which the pipe will collapse. An improvement to the DNV (2007) code is then suggested by interpreting the results of the FEA models. The case study that follows provides insight on the savings the improved method is projected to offer. 相似文献
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The paper presents a non-linear buckling analysis of ring stiffened cylindrical shells subject to external pressure. The collapse pressure is calculated by assuming failure to occur when the material reaches a plastic stress state defined by the Ilyushin criterion. It is shown in the paper that use of the non-linear theory can reduce the estimated first yield by up to 25% in comparison to the linear buckling analysis used up to now. Comparison of predicted failure loads are in good agreement with the lower bound of test results. 相似文献
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非黏结柔性管道骨架层由不锈钢材料互锁缠绕而成,主要用于抵抗外压防止软管发生压溃失效.骨架层失效是柔性软管故障的最大风险,骨架层失效模式主要分为压溃失效和拉伸失效.采用非线性有限元方法并且考虑几何大变形、材料非线性、接触和摩擦等非线性效应的影响,对"S"型骨架层结构建立三维有限元模型,进行了单外压作用下的压溃失效分析和单一轴向拉力作用下的拉伸失效分析,而后开展轴向拉力和外压载荷组合作用下骨架层压溃失效分析.结果表明轴向拉力会一定程度上降低骨架层压溃承载力,相关结论可以为柔性软管结构设计和完整性评价提供参考. 相似文献
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海上施工栈桥作为一种可以快速装配的施工辅助设施,在跨海大桥建设中得到广泛应用。为研究海上施工栈桥在极端波浪作用下的结构性能,基于波浪增量分析(IWA)理论,提出海上施工栈桥承载性能评估方法。以某在役海上施工栈桥为例,考虑杆件弹塑性和节点局部柔性建立结构非线性分析模型,评估了海上施工栈桥在不同方向极端波浪荷载作用下的结构承载性能及倒塌失效模式。研究表明,随着极端波高逐渐增大,栈桥依次出现首次屈服、塑性铰和倒塌起始三种非线性行为点,结构将依次经历正常使用、可以使用、临近倒塌和倒塌破坏四个承载性能状态;波浪入射方向对于海上施工栈桥的承载性能和倒塌失效模式影响较大;海上施工栈桥的主要薄弱部位位于钢管桩桩底及其与支撑框架下横撑相交的节点处,应在设计中重点关注。 相似文献
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The paper presents a theoretical and an experimental investigation into the plastic collapse of circular steel corrugated cylinders under external hydrostatic pressure. The experimental investigation gives a detailed study of 9 steel corrugated cylinders which were tested to destruction. Six of these cylinders failed by plastic non-symmetric bifurcation buckling and three failed by plastic axisymmetric deformation. The results of these tests were used, together with the results obtained from previous tests, to present a design chart for the plastic collapse of these vessels. The design chart was obtained by a semi-empirical approach, where the thinness ratios of the vessels were plotted against their plastic knockdown factors. The process of using the design chart is to calculate the theoretical elastic instability pressure for a perfect vessel by the finite element method and also to calculate the thinness ratio for this vessel. Using the appropriate value of the thinness ratio, the plastic knockdown factors are obtained from the design chart. To obtain the actual collapse pressure of the vessel, the theoretical elastic instability pressure for a perfect vessel is divided by the plastic knockdown factor. This work is of importance in ocean engineering. A large safety factor must also be introduced. 相似文献
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非黏结柔性管道作为深水油气开发领域的关键设备,是连接海底井口和海洋平台的主要纽带。海洋油气开发水深已经超过了3 000 m,高静水压力是深水软管设计和安全评价的主要挑战,明确深水柔性管道压溃失效机理,并准确地预测柔性管道的压溃压力可以为柔性管道结构设计和安全评价提供依据,柔性管道的压溃压力与骨架层的几何形状以及骨架层之间复杂的相互作用有关,准确高效地预测压溃压力变得极具挑战性。针对柔性管道失效机理研究和压溃压力预测方法进行了总结,指出当前柔性管道压溃失效分析中薄弱的环节,为我国非黏结柔性管道的结构设计和安全评价提供参考。 相似文献
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This paper reports on experimental work carried out on nine thin-walled circular cylinders which were tested to destruction under external hydrostatic pressure. Seven of the cylinders failed through non-symmetric bifurcation buckling and two failed through axisymmetric collapse. The results were used from these tests, together with the results from other experiments, to produce a design chart which could be used for designing against the occurence of elastic and inelastic shell instability. 相似文献
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Zhang Wenge Li Dexiang
Associate Professor Dalian Railroad Institute Dalian .
Engineer Dalian New Shipyard Dalian 《中国海洋工程》1997,(4)
-The first-yield collapse of submarine pipelines with an initial out-of-roundness imperfection un-der combined bending and external pressure load is formulated by means of the Von.Mises yield criterion.The formula reduces to Timoshenko and Gere's expression in the case of external pressure load alone.Theinfluence curves of various parameters on the yield strength are presented,the collapse of submarinepipelines in a deep water region is numerically predicted,and the effect of pre-yield nonlinear bending onthe yield strength is also examined. 相似文献
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DUAN Menglan GAO Zhaojie LIU Chuntu Senior Engineer China Classification Society Beijing China. Research Professor 《中国海洋工程》1998,(3)
To investigate the low temperature fatigue crack propagation behavior of offshore structuralsteel A131 under random ice loading,three ice failure modes that are commonly present in the Bohai Gulfare simulated according to the vibration stress responses induced by real ice loading.The test data are pro-cessed by a universal software FCPUSL developed on the basis of the theory of fatigue crack propagationand statistics.The fundamental parameter controlling the fatigue crack propagation induced by randomice loading is determined to be the amplitude root mean square stress intensity factor K_(arm).The test resultsare presented on the crack propagation diagram where the crack growth rate da/dN is described as thefunction of K_(arm).It is evident that the ice failure modes have great influence on the fatigue crack propaga-tion behavior of the steel in ice-induced vibration.However,some of the experimental phenomena and testresults are hard to be physically explained at present.The work in this paper is an init 相似文献
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Inelastic buckling of thick-walled circular conical shells under external hydrostatic pressure 总被引：1，自引：0，他引：1
The paper reports on a theoretical and an experimental study into the collapse of three thick-walled circular conical shells, which were tested to failure under external hydrostatic pressure. All three vessels failed by plastic non-symmetric bifurcation buckling. Two theoretical analyses were carried out, both based on the finite element method. One of the theoretical analyses was based on inelastic non-symmetric bifurcation buckling and the other analysis was based on plastic axisymmetric buckling. Both of these theoretical analysis and the experimental observations appeared to indicate that there is a link between plastic non-symmetric bifurcation buckling and plastic axisymmetric buckling. 相似文献
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Pipes inevitably encounter high ambient pressure and bending moment during the deepwater pipe-laying process,which can lead to elliptical buckling and even deterioration failure.For the safety of pipe-laying operation,available formalas for the pipe stability are established on the basis of the assumption of uniform deformation along the tube length and symmetrical buckling.This method can predict the nonlinear rcsponse of elliptical collapse of steel circular tubes for different ratios of diameter to thickness (D/t) under pure bending or combined bending and external pressure.In these formulas,the strain-displacement relationship is deduced from the nonlinear ring theory,and the Ramberg-Osgood constitutive model is applied to simulate the inelastic material behavior.Meanwhile,the principle of virtual work is adopted to derive the equilibrium equations.A set of equations is solved by the Newton-Raphson method,and the iterative scheme contains nested iteration for the constitutive relation.In order to check the effectiveness of this theoretical method,illustrative examples are presented in this paper.Besides,the numerical simulation is carried out by use of ANSYS.A comparison of the results shows that the theoretical method can provide reasonable prediction for engineering practice. 相似文献
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腐蚀是管道常见的缺陷形式之一,会极大降低管道的压溃压力,同时深海环境下高静水外压易引发管道压溃失效,威胁管道的安全运行,因此准确预测管道压溃压力显得尤为重要。采用数值模拟方法研究了含腐蚀缺陷的高强钢厚壁管道压溃失效模式,分析了管材、管道径厚比、腐蚀深度、长度和宽度等参数对高强钢厚壁管道压溃压力的影响规律。分析结果表明:管道径厚比愈大,对厚壁管道的承压能力提升愈显著;腐蚀缺陷的存在对管道压溃压力具有减小作用;随着管道材料等级的提升,压溃压力有明显提高。提出了相应的压溃压力预测公式,为厚壁管道完整性评价提供了参考依据。 相似文献
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In-service pipelines are often subject to external disturbances that produce dent defects, and the presence of dent defects often affects the pipeline's ultimate bearing capacity. This paper analyzes the equilibrium state of dent pipelines under external force for in-service pipelines with type II dent defects. A simplified calculation model for the shell is established through a series of assumptions and simplifications. Firstly, the pipe ring is crushed and analyzed to obtain the crushing power of the pipe ring, and then the pipe generator is subjected to deformation analysis to obtain the generator dissipating power. According to the principle of virtual work, the relationship between the external force power and the internal power dissipation power in equilibrium state is obtained.Under the condition of internal pressure, the type II dent defect is analyzed, and the relationship between the external force and the depth of the dent defect and its corresponding analytical expression are obtained. Under the condition of no internal pressure, the dent defect under different constraints is analyzed, and the analytical expression of the applied load under different constraints is obtained. 相似文献
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该文研究了海洋平台输液管道振动流的行为特性。依据振荡流体力学基本原理 ,建立了输液管道非定常、不可压缩、粘性振动流的物理模型和数学模型。推导出了关于流场速度、压力系数的微分方程组 ,得到了不同条件下流动的速度和压力分布。结果表明流体诱发的海洋平台输液管道振动流的行为特性受管道结构形状及流体性质的影响。比较等截面管道的变分解和数值解 ,说明本文所选用的方法用于研究海洋平台输液管道振动流是有效的。 相似文献
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Carl T. F. Ross Andrew P. F. Little Leonidas Chasapides Jeff Banks Daniele Attanasio 《Ocean Engineering》2004,31(2):239-252
The paper reports on the buckling of three ring-stiffened prolate domes under external hydrostatic pressure. The study was partly theoretical and partly experimental, where in the case of the latter, the finite element was used. Comparison between experiment and theory was good. The effect of ring stiffening the domes was to increase their buckling resistances by factors varying from 4.43 to 5.72. 相似文献
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为了探索不同径厚比海底管道的压溃屈曲特性,本文分别采用挪威船级社（Det Norske Veritas,DNV）规范、有限元模拟和深海压力舱模型试验,研究不同径厚比海底管道承载外部水压的能力,并就DNV规范压溃屈曲计算公式对不同径厚比管道的适用性进行了讨论,优化了小径厚比海底管道压溃屈曲的设计方法。研究表明：小径厚比管道的压溃屈曲临界压力对管道径厚比的变化更敏感;DNV规范计算小径厚比管道的压溃屈曲临界压力偏小,在进行深海管道的压溃屈曲设计时,建议采用模型试验结合有限元模拟的方法,计算管道实际可提供的压溃屈曲承载力。 相似文献
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近海海床表层多为软黏土或淤泥质土,为探究海床表层软土对海上风电宽浅式筒型基础承载特性的影响,以中国广东某海域风电场为背景,通过有限元分析的方法,研究竖向、水平、弯矩荷载作用下软土层厚度和土体强度对基础极限承载力、破坏模式以及筒基土压力分布的影响。研究结果表明:当软土层厚度小于H/2(H为筒裙高度)时,单向荷载作用下宽浅式筒型基础极限承载力随软土层厚度的增加呈线性减小的趋势;当软土层厚度大于H/2后,承载力降低速率逐渐增大。表层软土的存在,使得塑性区范围缩小,软土层内土体塑性破坏更加明显。竖向荷载作用下,随软土层厚度的增大,筒顶承载先减小后增大,筒内侧摩阻力先增大后减小;水平荷载和弯矩作用下,筒侧被动土压力的降低是引起软土覆盖地基中基础承载能力降低的主要因素。 相似文献