共查询到20条相似文献，搜索用时 156 毫秒
1.
Because non-buried submarine pipelines under cyclic thermal loading are prone to global buckling,sleepers are commonly laid along the pipeline route to induce a series of relatively small and controllable lateral buckling.A finite element model which can simulate the transformation of pipeline laid on a sleeper from vertical buckling to lateral buckling is established in this work.The parameters of sleeper affecting pipeline buckling modes are analysed,and a new kind of sleeper is proposed aimed... 相似文献
2.
The buckling of submarine pipelines may occur due to the action of axial soil frictional force caused by relative movement of soil and pipeline, which is induced by the thermal and internal pressure. The likelihood of occurrence of this buckling phenomenon is largely determined by soil resistance. A series of large-scale model tests were carried out to facilitate the establishment of substantial data base for a variety of burial pipeline relationships. Based on the test data, nonlinear soil spring can be adopted to simulate the soil behavior during the pipeline movement. For uplift resistance, an ideal elasticity plasticity model is recommended in the case of H/D (depth-to-diameter ratio)>5 and an elasticity softened model is recommended in the case of H/D≤5. The soil resistance along the pipeline axial direction can be simulated by an ideal elasticity plasticity model. The numerical analyzing results show that the capacity of pipeline against thermal buckling decreases with its initial imperfection enlargement and increases with the burial depth enhancement. 相似文献
3.
One of the main concerns for pipeline on-bottom stability design is to properly predict ultimate soil resistance in severe ocean environments.A plane-strain finite element model is proposed to investigate the ultimate soil resistance to the partially-embedded pipeline under the action of ocean currents.Two typical end-constraints of the submarine pipelines are examined,i.e.freely-laid pipes and anti-rolling pipes.The proposed numerical model is verified with the existing mechanical-actuator experiments.The magnitude of lateral-soil-resistance coefficient for the examined anti-rolling pipes is much larger than that for the freely-laid pipes,indicating that the end-constraint condition significantly affects the lateral stability of the untrenched pipeline under ocean currents.The parametric study indicates that,the variation of lateral-soil-resistance coefficient with the dimensionless submerged weight of pipe is affected greatly by the angle of internal friction of soil,the pipe-soil friction coefficient,etc. 相似文献
4.
Owing to the complex environmental conditions, suspension could induce complicated forces on submarine pipelines and even cause vortex-induced vibration, resulting in fatigue damage of pipelines. Through aiming at the 28-inch submarine pipeline in the East China Sea, the pipeline was segmented according to the similarity, considering the factors of pipe assembly, typhoon, current, wave and seabed topography. The effects of span length on natural frequency in each section of submarine pipeline were analyzed by finite element model. The maximum safe span length allowed by each pipeline section was verified by fatigue cumulative damage theory, and the fatigue life of each pipeline section were predicted. The results showed that each order natural frequency of the pipeline decreased with the increase of span length. The calculated results of empirical formulas were much smaller than those of the FEM analysis. The increase of the gap between the suspended pipeline and the seabed was beneficial to enhance the fatigue life of the suspended pipeline. 相似文献
5.
Experiments on Interaction Between Current-Induced Vibration and Scour of Submarine Pipelines on Sandy Bottom 总被引：2，自引：0，他引：2
SHEN Zhonghan 《中国海洋工程》2000,14(4):423-434
In order to understand the dynamic behavior of submarine pipelines exposed to current andthe mechanism of the interaction between current-induced vibration and scour of pipelines on a sandy bot-tom,an experimental investigation is conducted with a small scale model.A test model which can be testedin the flume is set up by taking into account the typical working conditions of the pipelines and by ap-plying the similarity theory.The interactions between the shape of the scour hole and the behavior of thepipeline as well as the flow patterns of the current are detailed,and the interaction mechanism outlined.The effect of vibration of the pipeline on the development of dynamic scour at different stages is foundout.The proposed experimental method and test results provide an effective means for design of marinepipelines against scouring. 相似文献
6.
Owing to the complexity of the pipe-in-pipe (PIP) riser system in structure, load and restraint, many problems arise in the structural analysis of the system. This paper presents a new method for nonlinear static finite element stress analysis of the PIP riser system. The finite element (FE) model of the PIP riser system is built via software AutoPIPE 6.1. According to the specialties of a variety of components in the PIP riser system, different elements are used so as to model the system accurately. Allowing for the complication in modeling the effects of seabed restraint, a technique based on the bilinear spring concept is developed to calculate the soil properties. Then, based on a pipeline project, the entire procedure of stress analysis is discussed in detail, including creation of an FE model, processing of input data and analysis of results. A wide range of loading schemes is investigated to ascertain that the stresses remain within the acceptable range of the pipe material strength. Finally, the effects of the location of flanges, the thermal expansion of submarine pipelines and the seabed restraint on stress distribution in the riser and expansion loop are studied, which are valuable for pipeline designers. 相似文献
7.
Seismic load has a significant effect on the response of a free spanning submarine pipeline when the pipeline is con-structed in a seismically active region. The model experiment is performed on an underwater shaking tahle to simulate the response of submarine pipelines under dynamic input. In consideration of the effects of the terrestrial and submarine pipeline , water depth, support condition, distance from seabed, empty and full pipeline, and span on dynamic response, 120 groups of experiments are conducted. Affecting factors are analyzed and conclusions are drawn for reference. For the con-trol of dynamic response, the span of a submarine pipeline is by far more important than the other factors. Meanwhile, the rosponse difference between a submarine pipeline under sine excitation and that under random excitation exists in ex-periments. 相似文献
8.
Li Yucheng Zhang Ningchuan
Professor Dalian University of Technology Dalian . Lecturere Delian University of Technology Dalian 《中国海洋工程》1994,(1)
- A composite pipeline is defined as a main big pipe composed of one or several small pipes. The flow behaviour around a submarine composite pipeline is more complicated than that around a single submarine pipeline. A series model test of composite pipelines in a wave-current coexisting field was conducted by the authors. Both in-line and lift forces were measured, and the resultant forces were also analyzed. The results of lift forces and resultant forces are reported in this paper. It is found that the lift force coefficients for composite pipelines are well related to the KC number. The lift force coefficients for an irregular wave-current coexisting field are smaller than those for a regular wave-current coexisting field. The frequency of lift force is usually twice the wave frequency or higher. The authors test indicates that the resultant forces are about 10 to 20 percent larger than in-line forces (horizontal forces). The effect of water depth is analyzed. Finally, the relationship between lift f 相似文献
9.
《中国海洋工程》1989,(4)
Based on the Karman-Donnell shell equations, a two-timing perturbation technique together with Fourier series expansion is used to solve an imperfection sensitivity problem of submarine pipelines with dimple shaped initial deflection under external pressure combined with axial load. The relationship between limit load and initial postbuckling coefficient as well as imperfection parameter is obtained. It shows that these submarine pipelines are imperfection-sensitive to a dimple shaped imperfection over a large range of a geometrical parameter and that the effect of the dimple shaped imperfection on limit load depends only upon its linear buckling mode component of the corresponding Fourier series expansion. 相似文献
10.
Study on Interaction Relationship for Submarine Pipeline with Axial Corrosion Defects 总被引：2，自引：0，他引：2
Corrosion is one of the main reasons to cause the operation accident of submarine oil and gas transmission pipelines. As the major corrosion pattern in submarine pipelines, the effects of corrosion clusters consisting of the adjacent corrosion defects on failure pressure are investigated through non-linear large-deformation finite element method. Typically, the failure behavior and limit strength of submarine pipeline with axial groove-groove corrosion defect pair exposed to internal pressure are analyzed. The effects of corrosion depth and axial spacing between a pair of corrosion defects on failure pressure are concluded. An interaction relationship for corrosion defects in pipelines, as well as prediction formulations for assessing the remaining strength of corroded pipelines are proposed. The expressions based on the proposed interaction relationship give more accurate results than the methods used in the existing design guidelines. 相似文献
11.
As an important part of lifeline engineering in the development and utilization of marine resources, the submarine fluid-filled pipeline is a complex coupling system which is subjected to both internal and external flow fields. By utilizing Kennard’s shell equations and combining with Helmholtz equations of flow field, the coupling equations of submarine fluid-filled pipeline for n=0 axisymmetrical wave motion are set up. Analytical expressions of wave speed are obtained for both s=1 and s=2 waves, which correspond to a fluid-dominated wave and an axial shell wave, respectively. The numerical results for wave speed and wave attenuation are obtained and discussed subsequently. It shows that the frequency depends on phase velocity, and the attenuation of this mode depends strongly on material parameters of the pipe and the internal and the external fluid fields. The characteristics of PVC pipe are studied for a comparison. The effects of shell thickness/radius ratio and density of the contained fluid on the model are also discussed. The study provides a theoretical basis and helps to accurately predict the situation of submarine pipelines, which also has practical application prospect in the field of pipeline leakage detection. 相似文献
12.
- With the rapid development of the offshore oil industries, submarine oil / gas pipelines have been widely used. Under the complicated submarine environmental conditions, the dynamic characteristics of pipelines show some new features due to the existence of both internal and external flows. The paper is intended to investigate the vortex-induced vibration of the suspended pipeline span exposed to submarine steady flow. Especially, the effects of the flow inside the pipeline are taken into account. Its influences on the amplitude of pipeline response, and then on the fatigue life, are given in terms of the velocity of the internal flow. 相似文献
13.
Zhang Jianguo Yan Chi Yan Shuwang
Lecturer Dept. of Hydraulic Eng. Tianjin University Tianjin Associate Professor Dept. of Hydraulic Eng. Tianjin University Tianjin Professor Dept. of Hydraulic Eng. Tianjin University Tianjin 《中国海洋工程》1996,(1)
This paper describes the model tests for determining the axial friction and the lateral resistance of sand to pipeline by using fine sand and prototype pipeline, and the calculation method based on limit analysis theory is verified. The effect of cyclic loading is considered in the test. 相似文献
14.
Li Yucheng Zhang Ningchuan Professor Dalian University of Technology Dalian . Lecturer Dalian University of Technology Dalian 《中国海洋工程》1994,(3)
-A composite pipeline is defined as a pipeline system composed of one big pipe and one or several small pipes. Based on the theory of wave- current interaction and physical model test, the hydrodynamic characteristics of the submarine composite pipeline in wave-current coexisting field (both regular and irregular waves) are investigated. The so-called "modified diameter method" is used for analyzing the in-fine hydrodynamic coefficients of the composite pipeline, which are well related to KC number. The comparison of test data for regular and irregular waves shows that in the region of 90 > KC> 20, the results in these two cases can be unified. The effect of water depth is analyzed in details. The relationships between CD, CM and KC , which are based on the results of present research, may be used as a reference in engineering design. 相似文献
15.
Scour of the Seabed Under A Pipeline in Oscillating Flow 总被引：3，自引：0，他引：3
The scour of the seabed under a pipeline is studied experimentally in this paper. Tests are carried out in a U-shaped oscillatory water tunnel with a box imbedded in the bottom of the test section. By use of the standard sand, clay and plastic grain as the seabed material, the influence of the bed material on the scour is studied. The relationship between the critical initial gap-to-diameter ratio above which no scour occurs and the parameters of the oscillating flow is obtained. The self-burial phenomenon, which occurs for the pipeline not fixed to two sidewalls of the test section, is not observed for the fixed pipeline. The effect of the pipe on sand wave formation is discussed. The maximum equilibrium scour depths for different initial gap-to-diameter ratios, different Kc numbers and different bed sands are also given in this paper. 相似文献
16.
By using the atmosphere-ocean coupled model (CGCM) which is composed of a 2-level global atmospheric general circulation model and a 4-layer Pacific oceanic general circulation model developed in the Institute of Atmospheric Physics of Chinese Academy of Sciences, and two model climatological fields got from the two independent models' numerical integrations respectively, the Pacific sea surface temperature anomalies (SSTA) from 1988 to 1989 are simulated in this paper with observed atmospheric general circulation data and sea surface temperature fields as initial conditions and monthly coupling scheme. In order to remove systematic biases of the model climatological fields, interaction variables between atmosphere and ocean are also corrected simultaneously. The experiments show that the simulation results can be improved effectively if these interaction variables are corrected in spite of the fact that there always exist systematic biases in independent numerical simulations of atmospheric part and oc 相似文献
17.
As there are no specific guidelines on design of subsea pipelines crossing active seismic faults, methods for land buried pipelines have been applied to. Taking the large seismic fault movement into account, this paper proposes improved methods for seismic designs of subsea pipelines by comprehensively investigating the real constraining of soil on the pipelines, the interaction processes of soil with the pipeline, the plastic slippage of the soil, and the elastic-plastic properties of the pipeline materials. New formulas are given to calculate the length of transition section and its total elongation. These formulas are more reasonable in mechanism, and more practical for seismic design of subsea pipelines crossing active faults. 相似文献
18.
Subsea pipelay has a relatively long history. In recent years, there has been a domestic need for the laying of large diameter thin wall pipes. A land-based trial for the large diameter thin wall specimen pipe is described in this paper. Re-gression analysis is performed for the trial data and the formula derived can express the trial data very well. Numerical analysis is adopted to compute various trial conditions. Then the numerical model is revised with the trial results, which are consistent with each other. After summarization of the results of trial and numerical analysis, the characteristics are described of the spatial configuration during the laying of the pipe and it is concluded that the maximum strain appears around the center of the raised pipeline. In the end, a reference Standard, which limits the maximum stress below the yield stress is provided. 相似文献
19.
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
20.
The spoiler is a kind of device to disturb current and promote burying.At present,all submarine pipeline spoilers at home and abroad are parallel spoilers,that is,the plane of the spoiler is parallel to the vertical plane of the pipeline axis.According to the results of indoor experiments,when the pipeline with the forward spoiler is installed perpendicular to the direction of water flow,the spoiler will accelerate the seabed erosion and cause the pipeline to endure downward pressure,which will eventually cause the pipeline self-buried to form a protection.However,when the pipeline direction is consistent with the flow direction,the self-buried behavior and protective effect is vanished.By aiming at the defect that the forward spoiler cannot be self-buried when the direction of the pipeline and the flow are basically parallel,the spoiler burying aid device perpendicular to the pipeline axis has been innovatively developed,and the hydrodynamic changes and sediment erosion characteristics near the pipeline after the installation of the device were studied based on the experiment.Results reveal that although the perpendicular spoiler cannot generate downforce,it can greatly increase the turbulent kinetic energy of the flow and the rate of sediment erosion.The larger the angle between the pipeline axis and the spoiler plane is,the larger the increase in turbulent energy will be.The increase in turbulent energy near the bed surface can reach up about 70%when the angle is 90°,while serious sediment erosion mainly occurs along both sides of the pipeline with a distance of about 2?4 times the pipe diameter.In the future,we can further explore the influence of the perpendicular spoiler size and installation position on the pipeline downforce and the effect of burying promotion.At the same time,field tests on the perpendicular spoiler burying aid device currently developed will conduct to observe the actual effect of perpendicular spoiler promoting pipeline scouring and burying,and improve submarine pipeline safety protection technology. 相似文献