Buckling Of Pipe Research Articles

Cyclic Deformation Behavior and Buckling of Pipeline With Local Metal Loss in Response to Axial Seismic Loading

Buried pipelines may be corroded, despite the use of corrosion control measures such as protective coatings and cathodic protection, and buried pipelines may be deformed due to earthquakes. Therefore, it is necessary to ensure the integrity of such corroded pipelines against earthquakes. This study has developed a method to evaluate earthquake resistance of corroded pipelines subjected to seismic motions. Pipes were subjected to artificial local metal loss and axial cyclic loading tests to clarify their cyclic deformation behavior until buckling occurred under seismic motion. As the cyclic loading progressed, displacement shifted to the compression side due to the formation of a bulge. The pipe buckled after several cycles. To evaluate the earthquake resistance of different pipelines with varying degrees of local metal loss, a finite-element analysis method was developed that simulates cyclic deformation behavior. A combination of kinematic and isotropic hardening was used to model the material properties. The associated material parameters were obtained by small specimen tests that consisted of a monotonic tensile test and a low-cycle fatigue test under a specific strain amplitude. This method enabled the successful prediction of cyclic deformation behavior, including the number of cycles required for the buckling of pipes with varying degrees of metal loss.

Buckling of Tubing Inside Casing

Summary Oil wells typically have multiple concentric casing strings. For a set of two concentric strings, if the inner pipe has a compressive axial force, it will typically buckle within the outer string. The buckling of pipe can be important in the analysis of a well-completion design because the buckled pipe can develop bending stresses that may be significant. Most analyses of this problem assume that the outer casing is rigid. In reality, this external casing is also elastic and would displace owing to the loads generated by contact with the inner pipe. Further, if both strings have compressive axial forces, both strings will buckle, and the resulting buckled configuration must fit together so that contact forces between the two strings are positive and the pipes do not each occupy the same space. If the two strings have an external, cylindrical rigid wellbore, then any contact forces with this wellbore must also be positive, and the buckled pipe system must lie within this wellbore. The only known solution to the multiple concentric pipe-buckling problem is that of Christman (1976), who proposed a composite pipe based on the summed properties of the individual pipes. This analysis does not conform to the requirements posed in the preceding paragraph. This paper presents the various ways that two concentric pipes can interact when one or both pipes are in compression and would then have a tendency to buckle. The contact forces between the pipes and with the external wellbore are explicitly calculated, and contact or noncontact conditions are determined. All results are analytical so that they can easily be used in spreadsheets or hand calculations. Several examples of calculations are presented to illustrate how these results might be used.

Modeling the Deformation Response of High Strength Steel Pipelines—Part II: Effects of Material Characterization on the Deformation Response of Pipes

The material model proposed in Part I (Neupane et al., 2012, “Modeling the Deformation Response of High Strength Steel Pipelines—Part I: Material Characterization to Model the Plastic Anisotropy,” ASME J. Appl. Mech., 79, p. 051002) is used to study the deformation response of high strength steel. The response of pipes subjected to frost upheaval at a particular point is studied using an assembly of pipe elements, while buckling of pipes is examined using shell elements. The deformation response is obtained using two different material models. The two different material models used were the isotropic hardening material model and the combined kinematic hardening material model. Two sets of material stress-strain data were used for the isotropic hardening material model; data obtained from the longitudinal direction tests and data obtained from the circumferential direction tests. The combined kinematic hardening material model was calibrated to provide an accurate prediction of the stress-strain behavior in both the longitudinal direction and the circumferential direction. The deformation response of a pipe model using the three different material data sets was studied. The sensitivity of the response of pipelines to the choice of a material model and the material data set is studied for the frost upheaval and local buckling.

The experimental study of Buckling of Steel Pipe under External High Water Pressure for Water Supply Tunnel Constructed in Deep Underground

The experimental study of Buckling of Steel Pipe under External High Water Pressure for Water Supply Tunnel Constructed in Deep Underground

European Research and Analysis of Buckling

European Research and Analysis of Buckling

Experimental Investigation on Buckling of Plastic Pipe Reinforced by Winding Steel Wires Under External Pressure

Plastic pipe reinforced by cross helically wound steel wires (PSP) is a new type of plastic-matrix steel composite pipes developed in China recently. PSPs may collapse when they are subjected to an external pressure load. To obtain the buckling behavior of PSPs and provide basic data for Chinese National Standard of PSPs, the testing devices of external hydraulic pressure and vacuum were designed for short-term buckling and creep buckling tests, and corresponding tests had been carried out. The critical buckling pressure, the methods to increase the critical buckling pressure, the relationship between creep deformation and time under different pressures, and the variation of the critical buckling time with critical creep buckling pressures of the PSP were obtained. The results show that the short-term critical buckling pressure of the PSP is higher than that of the HDPE with the same diameter and wall thickness. The critical buckling pressure of the PSP with the same pressure class decreases gradually with the increase of pipe diameter. The resistance to buckling can be increased by installing stiffening rings on the PSP. Furthermore, the PSP shows time-dependent buckling behavior, because of the time-dependent behavior of the matrix. Even if the external pressure load is lower than the short-term critical buckling pressure of the PSP, the buckling failure may still occur, and the time of buckling failure gradually shortens with the increase in the external pressure.

Effects of Boundary Conditions and Friction on Static Buckling of Pipe in a Horizontal Well

Summary A comprehensive buckling model, a group of fourth-order nonlinear ordinary differential equations, was derived by applying the principle of virtual work. Lateral friction force is included in this model. The equations were normalized to make the solutions independent of the wellbore size, type of pipe, and mud. The critical sinusoidal buckling load of tubing with different boundary conditions typically seen in drilling and well-completion applications was analyzed on the basis of the analytical solution of the linearized buckling equation. The results show that the effect of the boundary conditions can be neglected when the dimensionless length of tubing is greater than 5π. The authors further investigated the effects of friction on sinusoidal buckling by applying the principle of virtual work. The critical conditions for initiating sinusoidal buckling were determined by a group of three nonlinear equations. A perturbation solution of these nonlinear equations was obtained. It was found that the critical loads for sinusoidal buckling will increase by 30 to 70% for friction coefficients between 0.1 and 0.3. The authors also conducted an experimental study. The experimental results, including both data obtained by the authors and results published by other researchers, support the proposed model.

Selfstressed bowstring footbridge in FRP

An original structural concept of footbridge, Taylor-made for fibre reinforced polymer (FRP) is proposed in this work. The bowstring bridge is obtained by elastic buckling of straight pipes (glass fibre). The bows are stabilized with cables and zigzag stays (carbon fibre). Crossbars at the intersection nodes of the cables with the stays support the bridgedeck. The selfstress state in the structure depends on the pipes and on the geometry. A finite element study describes the behavior of such a non-linear structure and highlights its specificities, among which variability in the stresses from one element to the other. A formfinding process based on the method of force density is then developed, to ensure an equal distribution of prestresses in the composite retainers. This method allows the optimization of the design of the structure. Preliminary static and dynamic studies show the structural interest of the concept, and its future is discussed.

Helical Buckling of Pipe With Connectors and Torque

SummaryIt has been generally recognized that connectors (tool joints and couplings) should have some effect on the buckling of pipe. For instance, the connector outside diameter may be as much as 50% greater than the pipe-body diameter. As a result, the radial clearance of the connector can be substantially smaller than the radial clearance of the pipe body.The analysis of buckling has received extensive attention in the last 20 years. The effect of connectors on pipe stresses has received somewhat less attention. Lubinski (1977) used the beam-column equations to analyze the effect of connectors on pipe-bending stresses for a pipe in tension in a 2D constant-curvature wellbore. Bending stresses were significantly magnified by the connector standoff. Paslay and Cernocky (1991) completed this analysis by analyzing the pipe in compression. Mitchell (2000) extended these results to 3D helical buckling.Torque adds a new dimension to the buckling problem. Without torque, buckling occurs only for positive effective axial force (compressive axial force plus pressure effects). A pipe with applied torque can buckle in tension (Greenhill 1883). The contact force between pipe and wellbore can be increased or decreased, depending on the direction of the applied torque. And, of course, pipe used in rotary drilling always has applied torque'so buckling analysis without torque is not complete.This paper looks at 3D buckling of pipes with connectors with applied torque. The problem formulation is similar to Lubinski et al.'s (1962) buckling analysis: the wellbore is vertical and straight. The beam-column equations considered in the plane-buckling analysis are used, but now there are deflections out of the plane. A solution for helical buckling is developed that produces pipe sag, maximum dogleg angle, contact force, and bending-stress magnification as a function of pipe effective axial force and torque. An application problem is solved, and the relative effects of compressive axial force and torque on sag between connectors, contact loads, and maximum bending stress are examined.Applications include the analysis of bottomhole assemblies, drillpipe, casing, and tubing. The final results are simple enough to be suitable for spreadsheet calculations.

Application of Plastic Buckling of Pipes with Flange to a Structural Fastening System

One-sided fastening systems using plastic buckling of the thin-walled pipes with flange are studied in this paper. Plastic buckling occurs in the thin-walled pipe area of the blind nut with flange, when an axial compressive load is applied to the blind nut. As one-sided fastening is applied for the case such as the inner hollow part, estimations of buckling load and the proper displacement are important. The buckling deformation is studied by the nonlinear finite element analysis, and the numerical results are in good agreement with experimental observations for the buckling load and displacement. Effects of geometrical parameters of the thin pipe area are investigated for the buckling load and displacement by FEM. In order to evaluate the tensile strength of the fastening systems, unloading and reloading is carried out consistently by analyses. Effects of the tensile strength with the length and thickness of the thin-walled pipe area of the blind nut are also investigated

Lateral Buckling of Pipe With Connectors in Horizontal Wells

Summary The effect of connectors on pipe buckling has only recently received attention. For nonbuckled pipe, Lubinski analyzed the effect of connectors on pipe in tension in a curved borehole, and Paslay and Cernocky extended this analysis to pipe in compression. The first analysis of buckled pipe with connectors was done by Mitchell, who developed a 3D analysis of helical buckling. These papers indicate that bending stresses are greater because of connector standoff. Laterally buckled pipe with connectors is analyzed for the first time in this paper. It presents an analytic solution of the beam-column equations in 3D in a horizontal wellbore with pipe weight. Pipe deflections, contact loads, and bending stresses are determined with explicit formulas. Sag between connectors is calculated so that pipe body contact with the wellbore between connectors can be determined. Applications include the analysis of bottomhole assemblies, drillpipe, casing, and tubing. The solutions are simple formulas that are suitable for hand calculations.

Lateral Buckling of Pipe With Connectors in Curved Wellbores

Summary Connectors should clearly have an effect on pipe loading. For nonbuckled pipe, Lubinski analyzed the effect of connectors on pipe in tension in a curved borehole and Paslay and Cernocky extended this analysis to pipe in compression. Recently, helically buckled and laterally buckled pipes with connectors have been analyzed. In these papers, analytic solutions of the beam-column equations were developed in 3D, and critical loads were determined for buckling initiation. Conditions for positive contact forces were determined and compared to previous buckling criteria, such as Dawson-Paslay. In this paper, the wellbore curvature effects studied by Lubin-ski, Paslay, and Cernocky are included in the buckling effects. The modifications necessary to analyze lateral buckling are made for a curved wellbore. The resulting model gives a buckling criterion similar to He and Kyllingstad's results for pipe without connectors. The buckling model is integrated with the Paslay-Cernocky analysis to resolve some of the odd bending-stress results developed by their model. Pipe deflections, contact loads, and bending stresses are determined with explicit formulas. Sag between connectors is calculated so that pipe contact with the wellbore between connectors can be determined. Conditions for positive contact forces are determined and compared to previous buckling criteria, such as Paslay-Dawson and He-Kyllingstad. Applications include the analysis of bottomhole assemblies (BHAs), drillpipe, casing, and tubing. The solutions are simple formulas that are suitable for hand calculations.

Application of Plastic Buckling of Pipes to a Structural Fastening System

The one-sided fastening systems of structures using plastic buckling of the thin pipe are studied in this paper. The plastic buckling occurs in a predetermined annealed area of the thin pipe when the axial compressive load is applied to the thin pipe. Estimations of buckling deformation, load and post-buckling behavior are very important, because the buckling deformations are used as the backside head of fastening the objects, and the post-buckling behavior affect the reliability and the strength of fastening system. The whole fastening process is studied by the nonlinear finite element analysis consistently. In order to evaluate the deformation behavior of pipes in fastening the objects, effects of the parameters such as the length and thickness of the pipe, the band and position of annealed area of the pipe are investigated. Two types of deformation modes of the pipe are found in the analysis, the position of annealed area of the pipe is dominant for the deformation mode, and the optimal values of the parameters are obtained in the analysis.

NONLINEAR BUCKLING OF MARINE ELASTICA PIPES TRANSPORTING FLUID

This paper addresses the nonlinear buckling and post-buckling behavior of an extensible marine elastica pipe conveying fluid. The mathematical model employed in the nonlinear buckling analysis is developed based on the extensible elastica theory and the large strain formulation, so that the high extensibility of the pipe due to large axial strains is tackled thoroughly. The boundary value problem of the model is solved by the shooting method, and the numerical elastica solutions are obtained. For stability examination, the method of adjacent nonlinear equilibrium is exploited. It is revealed that the fundamental mode of nonlinear buckling of the pipe is reached when the pipe experiences either the critical top tension or the critical weight. Postbuckling behavior of the pipe is recognized to be unstable. The investigation is extended to studying various parameters that impinge on the limit states of the pipe. These parameters are the dimensionless quantities that relate to density of pipe material, densities of external and internal fluids, applied top tension, Poisson's ratio, slenderness ratio, vessel offset, seawater depth, current-drag coefficients, current velocity, and internal flow velocity.

Helical Buckling of Pipe With Connectors in Vertical Wells

Summary The effect of connectors on pipe buckling is acknowledged, but has received little attention. Lubinski analyzed the effect of connectors on pipe in tension in a curved borehole, while Paslay and Cernocky extended this analysis to pipe in compression. These papers indicate that bending stresses are greater due to connector standoff. However, these papers do not consider a buckled pipe. This paper presents an analytic solution of the beam-column equations in three dimensions for a helically buckled pipe with connectors in a vertical well. For low axial compression, the solution approximates helically buckled pipe without connectors, however, at higher axial forces, the effects of connectors on contact forces and bending stress becomes significant. Sag between connectors is calculated so that pipe body contact between connectors can be determined. Applications include the analysis of bottomhole assemblies, drillpipe, casing, and tubing. The solutions are simple formulas that are suitable for hand calculations.

Nonlinear deformation and buckling of curvilinear pipes loaded by external pressure

The problem of loading of a thin-walled elastic pipe (a toroidal shell) by external pressure is examined in a geometrically nonlinear formulation. A numerical algorithm is used to study the nonlinear deformation of the shell and the stability of its equilibrium states when its cross section has undergone a significant change in shape. Results are presented from a determination of the critical stresses of curvilinear pipes with allowance for moments in the subcritical state. These results are compared with the approximate solution.

Thermal buckling and progressive ovalization of pipes: experiences at the TTS sodium test facility and their analysis

Two remarkable thermally induced deformation mechanisms of pipes which may have serious effects on structural integrity, thermal buckling and progressive ovalization, were observed on the horizontal piping of the sodium test facility, called TTS, with which cyclic thermal transient tests of structures had been conducted. The thermal buckling, which was caused by thermal stratification, occurred at a circumferentially welded region of the pipe where a noticeable geometrical imperfection existed. The buckling was analyzed comprehensively for this pipe, using both the finite element method and a simplified method based on Gellin's analysis results. The predictions were reasonable and gave confidence in accounting for the sodium leakage encountered at the TTS. It was also demonstrated by the finite element analyses that the progressive ovalization of the pipe cross-section from a circular to a downward triangular shape can be caused by cyclic thermal stratification under the existence of cover gas in the pipe.

Helical Buckling of Pipes in Extended Reach and Horizontal Wells—Part 2: Frictional Drag Analysis

Abstract This paper studies the frictional drag of helically buckled pipes (drillstring and tubing) in extended reach and horizontal wells to correctly predict the actual bit weight or packer load, in cases where helical buckling of pipes may have occurred. Helical buckling of pipes in such wells may occur, since large axial loads are often required. The differential equation of axial force balance with consideration of the axial friction for helically buckled pipes is resolved, and the solution shows that when the pipes are helically buckled, the frictional drag will become very large. The actual bit weight for drilling or packer load for well completion may therefore become much smaller than estimated under the unbuckled pipe conditions. The analytical solution is also shown to agree with the results from laboratory experiments, which simulate the real wellbore-pipe conditions. An example is provided to show the calculation procedure and the importance of the results.

Helical Buckling of Pipes in Extended Reach and Horizontal Wells—Part 1: Preventing Helical Buckling

Abstract This paper studies the helical buckling of pipes (drillstring and tubing) in extended reach and horizontal wells, theoretically and experimentally, resulting in new equations to correctly predict and effectively prevent the helical buckling of pipes in such wells. The theoretical study shows that the so-called helical buckling load that appears in the current literature is only the average axial load in the helical buckling development process. The laboratory experiments confirm the theoretical analysis. The new helical buckling load equations are formulated by combining the theoretical analysis and the experimental results, thereby resolving the existing assumption-and result inconsistency in the current literature. The new equation predicts the true helical buckling load to be about 1.3 times the so-called helical buckling load in the current literature, and about 1.8 times the critical buckling load that predicts the onset of sinusoidal buckling. Consequently, larger bit weights or packer setting loads can be applied to increase the drilling rate or to ensure a proper seal, before the helical buckling of the pipes can occur.

Buckling of polymer pipes under internal pressure

In this work, the buckling phenomenon of slender pressurized pipes under concentrically applied indirect axial force is experimentally and theoretically investigated. The axial force is applied via a frictionless piston. The deformation trend of a polyvinylchloride pipe sample under this compressive axial force is monitored by means of a number of strain gauges. The strain readings are processed by a computer equipped with strain processing software. The buckling modes as well as the buckling load of the system are thus experimentally determined. To describe the stability behaviour of the pipe analytically, several theoretical models are employed and the buckling phenomenon in such a pressurized pipe is analytically ascertained. Numerical values for the critical buckling loads are also obtained. The experimental and theoretical buckling studies are correlated. Through these correlations, the buckling of pressurized pipes under indirect axial pressure is substantiated and an appropriate theoretical model to describe the phenomenon is established.