Buckling of Clad Pipes Under Bending and External Pressure

2011 ◽  
Author(s):  
Daniel Vasilikis ◽  
Spyros A. Karamanos
Keyword(s):  
Numerical Solutions ◽  
Local Buckling ◽  
External Pressure ◽  
Structural Behaviour ◽  
Nonlinear Finite Elements ◽  
Buckling Resistance ◽  
Manufacturing Procedure ◽  
Thin Walled ◽  
Bending Response ◽  
Outer Pipe

The present paper concerns the structural behaviour of clad pipes. This is a double wall pipe, composed by two pipes that are in contact through an appropriate manufacturing procedure; a thick-walled carbon steel “outer pipe”, and a thin-walled corrosion-resistant inner pipe, referred to as “liner” pipe. To predict the bending response and the buckling curvature of the thin-walled liner, it is necessary to account for its contact with the confining thick-walled outer pipe. Because of this confinement, existing numerical solutions or analytical predictions for the bending buckling resistance of unconfined thin-walled tubes are inadequate to predict the buckling resistance of the bent liner. In the present work, the problem is solved numerically, using nonlinear finite elements to simulate the clad pipe, accounting for the interaction between the liner and the outer pipe. First, the manufacturing process of the clad pipe is simulated to determine the liner hoop prestressing. Subsequently, bending curvature is applied (with and without the presence of external pressure). Stresses and strains are monitored throughout the deformation stage with emphasis on possible detachment of the liner from the outer pipe and the formation of local buckling on the liner wall.

Lobar Buckling of Thin-Walled Cylindrical and Truncated Conical Shells Under External Pressure

1974 ◽  
Vol 18 (04) ◽  
pp. 272-277
Author(s):  
C. T. F. Ross
Keyword(s):  
Finite Element ◽  
Circular Cylinder ◽  
Numerical Solutions ◽  
External Pressure ◽  
Element Solution ◽  
Conical Shells ◽  
Varying Thickness ◽  
Complex Boundary ◽  
Thin Walled ◽  
Unsymmetrical Loading

Numerical solutions have been produced for the asymmetric instability of thin-walled circular cylindrical and truncated conical shells under external pressure. The solutions for the circular cylinder have shown that the assumed buckling configurations of Nash [l]2 and Kaminsky [2] were quite reasonable for fixed ends. Comparison was also made of the finite-element solution of conical shells with other analyses. From these calculations, it was shown that the numerical solutions were superior to the analytical ones, as the former could be readily applied to vessels of varying thickness or those subjected to unsymmetrical loading or with complex boundary conditions.

Mechanics of Confined Thin-Walled Cylinders Subjected to External Pressure

2013 ◽  
Vol 66 (1) ◽  
Author(s):  
Daniel Vasilikis ◽  
Spyros A. Karamanos
Keyword(s):  
Mechanical Response ◽  
Surrounding Medium ◽  
External Pressure ◽  
Numerical Results ◽  
Maximum Pressure ◽  
Imperfection Sensitivity ◽  
Nonlinear Finite Elements ◽  
Good Comparison ◽  
Practical Engineering ◽  
Thin Walled

Motivated by practical engineering applications, the present paper examines the mechanical response of thin-walled cylinders surrounded by a rigid or deformable medium, subjected to uniform external pressure. Emphasis is given to structural stability in terms of buckling, postbuckling, and imperfection sensitivity. The present investigation is computational and employs a two-dimensional model, where the cylinder and the surrounding medium are simulated with nonlinear finite elements. The behavior of cylinders made of elastic material is examined first, and a successful comparison of the numerical results is conducted with available closed-form analytical solutions for rigidly confined cylinders. Subsequently, the response of confined thin-walled steel cylinders is examined. The numerical results show an unstable postbuckling response beyond the point of maximum pressure and indicate severe imperfection sensitivity on the value of the maximum pressure. A good comparison with limited available test data is also shown. Furthermore, the effects of the deformability of the surrounding medium are examined. In particular, soil embedment conditions are examined, with direct reference to the case of buried thin-walled steel pipelines. Finally, based on the numerical results, a comparison is attempted between the present buckling problem and the problem of “shrink buckling.” The differences between those two problems of confined cylinder buckling are pinpointed, emphasizing the issue of imperfection sensitivity.

Wrinkling of Lined Steel Pipes Under Bending

2013 ◽  
Author(s):  
Daniel Vasilikis ◽  
Spyros A. Karamanos
Keyword(s):  
Carbon Steel ◽  
Large Strains ◽  
Corrosion Resistant ◽  
Steel Pipes ◽  
Nonlinear Finite Elements ◽  
Offshore Pipeline ◽  
Secondary Bifurcation ◽  
Thin Walled ◽  
Oil Gas ◽  
Outer Pipe

Lined pipes are used in energy pipeline applications (oil, gas, etc.); a corrosion-resistant thin-walled liner is fitted inside a carbon-steel outer pipe. The paper focuses on wrinkling of lined pipes (sometimes also referred to as “mechanical clad” pipes), which are candidates for offshore pipeline applications. The lateral confinement of the liner pipe due to the deformable outer pipe and its interaction with the outer pipe has a decisive influence on the wrinkling behaviour of the thin-walled liner. The problem is solved numerically, using nonlinear finite elements to simulate the lined pipe and its interaction with the outer pipe. Nonlinear geometry with large strains is taken into account, and the material of both pipes is elastic-plastic. Stresses and strains are monitored throughout the deformation stage with emphasis on possible detachment of the liner from the outer pipe and the formation of wrinkles. It is shown that the behaviour is characterized by a first bifurcation in a uniform wrinkling pattern, followed by a secondary bifurcation and finally a localization of the buckled pattern. The values of curvature at which liner wrinkling occurs are determined. The numerical results are compared with available experimental results.

ELASTIC BUCKLING OF THIN-WALLED CIRCULAR TUBES CONTAINING AN ELASTIC INFILL

2006 ◽  
Vol 06 (04) ◽  
pp. 457-474 ◽  
Author(s):  
M. A. BRADFORD ◽  
A. ROUFEGARINEJAD ◽  
Z. VRCELJ
Keyword(s):  
Axial Compression ◽  
A Priori ◽  
Local Buckling ◽  
Steel Tube ◽  
Transcendental Equation ◽  
Buckling Mode ◽  
Buckling Stress ◽  
Elastic Tubes ◽  
Thin Walled ◽  
Energy Formulation

Circular thin-walled elastic tubes under concentric axial loading usually fail by shell buckling, and in practical design procedures the buckling load can be determined by modifying the local buckling stress to account empirically for the imperfection sensitive response that is typical in Donnell shell theory. While the local buckling stress of a hollow thin-walled tube under concentric axial compression has a solution in closed form, that of a thin-walled circular tube with an elastic infill, which restrains the local buckling mode, has received far less attention. This paper addresses the local buckling of a tubular member subjected to axial compression, and formulates an energy-based technique for determining the local buckling stress as a function of the stiffness of the elastic infill by recourse to a transcendental equation. This simple energy formulation, with one degree of buckling freedom, shows that the elastic local buckling stress increases from 1 to [Formula: see text] times that of a hollow tube as the stiffness of the elastic infill increases from zero to infinity; the latter case being typical of that of a concrete-filled steel tube. The energy formulation is then recast into a multi-degree of freedom matrix stiffness format, in which the function for the buckling mode is a Fourier representation satisfying, a priori, the necessary kinematic condition that the buckling deformation vanishes at the point where it enters the elastic medium. The solution is shown to converge rapidly, and demonstrates that the simple transcendental formulation provides a sufficiently accurate representation of the buckling problem.

Elastic buckling of thin-walled polyhedral pipe liners encased in a circular pipe under uniform external pressure

2018 ◽  
Vol 123 ◽  
pp. 214-221 ◽  
Author(s):  
Zhaochao Li ◽  
Yan Tang ◽  
Fujian Tang ◽  
Yizheng Chen ◽  
Genda Chen
Keyword(s):  
External Pressure ◽  
Circular Pipe ◽  
Elastic Buckling ◽  
Uniform External Pressure ◽  
Thin Walled

scholarly journals Rational Modeling of Ultimate Pipe Strength Under Bending and External Pressure

2000 ◽  
Author(s):  
André C. Nogueira ◽  
Glenn A. Lanan
Keyword(s):  
Deep Water ◽  
Limit State ◽  
Local Buckling ◽  
External Pressure ◽  
Pressure Effects ◽  
Combined Loading ◽  
Empirical Prediction ◽  
Limit State Design ◽  
Controlled Conditions ◽  
Offshore Pipeline

The capacity of pipelines to resist collapse or local buckling under a combination of external pressure and bending moment is a major aspect of offshore pipeline design. The importance of this loading combination increases as oil and gas projects in ultra deep-water, beyond 2,000-m water depths, are becoming reality. The industry is now accepting, and codes are explicitly incorporating, limit state design concepts such as the distinction between load controlled and displacement controlled conditions. Thus, deep-water pipeline installation and limit state design procedures are increasing the need to understand fundamental principles of offshore pipeline performance. Design codes, such as API 1111 (1999) or DNV (1996, 2000), present equations that quantify pipeline capacities under combined loading in offshore pipelines. However, these equations are based on empirical data fitting, with or without reliability considerations. Palmer (1994) pointed out that “it is surprising to discover that theoretical prediction [of tubular members under combined loading] has lagged behind empirical prediction, and that many of the formula have no real theoretical backup beyond dimensional analysis.” This paper addresses the ultimate strength of pipelines under combined bending and external pressure, especially for diameter-to-thickness ratios, D/t, less than 40, which are typically used for deep water applications. The model is original and has a rational basis. It includes considerations of ovalization, anisotropy (such as those caused by the UOE pipe fabrication process), load controlled, and displaced controlled conditions. First, plastic analysis is reviewed, then pipe local buckling under pure bending is analyzed and used to develop the strength model. Load controlled and displacement controlled conditions are a natural consequence of the formulation, as well as cross section ovalization. Secondly, external pressure effects are addressed. Model predictions compare very favorably to experimental collapse test results.

Remaining Local Buckling Resistance of Corroded Pipelines

2010 ◽  
Author(s):  
Qishi Chen ◽  
Heng Aik Khoo ◽  
Roger Cheng ◽  
Joe Zhou
Keyword(s):  
Finite Element ◽  
Wall Thickness ◽  
Phase 1 ◽  
Compressive Strain ◽  
Research Work ◽  
Local Buckling ◽  
Model Verification ◽  
Metal Loss ◽  
General Corrosion ◽  
Buckling Resistance

This paper describes a multi-year PRCI research program that investigated the local buckling (or wrinkling) of onshore pipelines with metal-loss corrosion. The dependence of local buckling resistance on wall thickness suggests that metal-loss defects will considerably reduce such resistance. Due to the lack of experimental data, overly conservative assumptions such as a uniform wall thickness reduction over the entire pipe circumference based on the defect depth have been used in practice. The objective of this research work was to develop local buckling criteria for pipelines with corrosion defects. The work related to local buckling was carried out in three phases by C-FER and the University of Alberta. The first phase included a comprehensive finite element analysis to evaluate the influence of various corrosion defect features and to rank key parameters. Based on the outcome of Phase 1 work, a test matrix was developed and ten full-scale tests were carried out in Phase 2 to collect data for model verification. In Phase 3, over 150 parametric cases were analyzed using finite element models to develop assessment criteria for maximum moment and compressive strain limit. Each criterion includes a set of partial safety factors that were calibrated to meet target reliabilities selected based on recent research related to pipeline code development. The proposed criteria were applied to in-service pipeline examples with general corrosion features to estimate the remaining load-carrying capacity and to assess the conservatism of current practice.

Sign in / Sign up

Export Citation Format

Share Document