Application of Deterministic and Probabilistic Methods in Pipeline Lateral Buckling Design

2012 ◽  
Author(s):  
Hammam Zeitoun ◽  
Maša Branković ◽  
Edwin Shim ◽  
EuJeen Chin ◽  
Benjamin Anderson
Keyword(s):  
Structural Reliability ◽  
Design Guidelines ◽  
Probabilistic Methods ◽  
Design Solution ◽  
Design Parameters ◽  
Pipeline System ◽  
Limit States ◽  
Lateral Buckling ◽  
Current Design ◽  
Subsea Pipelines

Subsea pipelines lateral buckling design has significantly evolved over the last years as more pipeline projects have moved into more challenging environments and into high temperature / high pressure (HT/HP) design application. Knowledge and understanding of pipeline lateral buckling has improved with design application resulting in refined and enhanced design approaches. Using current design approaches, it is now quite acceptable to control lateral buckle formation along the pipeline by using buckle triggers or to allow uncontrolled lateral buckles, provided that the various design limit states are satisfied. A number of design methodologies can be used to check the acceptability of uncontrolled buckling or to design for controlled buckling including deterministic, probabilistic buckle formation and full Structural Reliability Assessment (SRA) methods. Using SRA or probabilistic methods is usually an attractive design option as lateral buckling design involves dealing with a large number of uncertainties and variation in design parameters. These methods help to ensure the reliability of the proposed buckle initiation scheme. However, the use of these methods is also associated with a number of challenges such as the need to identify key parameters influencing the design and quantifying their uncertainties. Deterministic design approaches on the other hand are simpler to apply. However, they do not provide means to quantify the reliability of the proposed buckling scheme or the design risks. The choice of input parameters in a deterministic design is also relatively subjective which can possibly result in an overly conservative or unconservative design solution depending on the adopted design approach, selected design parameters and pipeline system being considered. Design guidelines and recommended practices such as SAFEBUCK (20) offer comprehensive guidelines to design for lateral buckling. However when faced with a range of complex variables, the designer needs to be aware of the effect of these parameters on the overall design. This paper describes the application of Deterministic and Probabilistic design approaches in lateral buckling design. The paper starts by describing these approaches, their advantages and limitations. The paper then explores a number of key uncertainties and variation in design parameters that the designer is faced with and its effect on the pipeline response.

Assessment of Parameters Influencing Lateral Buckling of Deep Subsea Pipe-in-Pipe Pipeline System Using Finite Element Modeling

2014 ◽  
Author(s):  
M. Masood Haq ◽  
S. Kenny
Keyword(s):  
Boundary Conditions ◽  
Load Capacity ◽  
External Pressure ◽  
Design Parameters ◽  
Parameter Study ◽  
Pipeline System ◽  
Limit States ◽  
Lateral Buckling ◽  
Global Buckling ◽  
External Forces

The operational requirements for subsea pipeline systems have progressed towards higher design temperatures and pressures (HTHP). To address flow assurance requirements, pipe-in-pipe systems have been developed. For pipelines laid on the seabed, or with partial embedment, the potential for lateral buckling; in response to operational loads, external forces and boundary conditions, has become a major factor in engineering design. The effective axial force is a key factor governing the global lateral buckling response that is influenced by parameters such as internal and external pressure, and operating and ambient temperature. Other design parameters that influence lateral buckling include global imperfections or out-of-straightness, pipe/soil interaction characteristics and installation conditions. Global buckling reduces the axial load capacity of the pipeline that may impair operations and exceed serviceability limit states. Results from a numerical parameter study on lateral buckling response of a subsea pipe-in-pipe (PIP) pipeline are presented. The parameters examined include pipe embedment, pipe out-of-straightness (OOS), soil shear strength, soil peak and residual forces and displacements, variation in soil properties distributed along the pipeline route, and external pressure associated with the installation depth. The observed pipe response was a complex relationship with these parameters and kinematic boundary conditions.

Validation of Residual Curvature Installation for Lateral Buckling Management Using Structural Reliability Analysis (SRA)

2017 ◽  
Author(s):  
Martin Teigen ◽  
Malik M. Ibrahim
Keyword(s):  
Finite Element ◽  
Reliability Analysis ◽  
Structural Reliability ◽  
Control Method ◽  
Multivariate Interpolation ◽  
Design Parameters ◽  
Bending Moments ◽  
Lateral Buckling ◽  
Residual Curvature ◽  
Subsea Pipelines

The method of using residual curvature during pipeline installation, primarily for the purpose of lateral buckling control, has caught an increasing amount of attention over the past few years [1], [9]. The use of residual curvature sparked a particular interest after positive experiences from a 26 km long pipeline on Statoil’s Skuld project (2012) in the Norwegian Sea [7]. As such, a range of technical papers elaborating on the topic have recently been published [6], [7], [9]. Some of this work has identified some particularly novel applications for the residual curvature method including freespan mitigation to reduce the requirement for seabed intervention, allowing for direct pipeline tie-ins, use with s-lay installation and even for steel catenary risers [10], [11]. However, these applications are currently only identified and not yet proven successful in any published work. This technical paper focusses on validating the use of residual curvature for the purpose of lateral buckling control in subsea pipelines installed by reel-lay. The residual curvature method demonstrates high buckling reliability without the use of subsea structures or additional installation equipment, with a controlled buckle response and favourable operational bending moments [1]. The residual curvature method has been shown less sensitive to some design parameters than other lateral buckling control methods [6]. However, published work also show that high strains will develop for short residual curvature lengths, high pipe-seabed frictions and for certain levels of residual strains [6]. Previous research has predicted the behaviour of residual curvature as a means of controlling lateral buckling in a deterministic approach [6], [7], [9]. However, performing a lateral buckling design with a probabilistic approach can offer a more realistic design and demonstrate higher reliability. There is a range of research on probabilistic approaches for lateral buckling design of subsea pipelines, but there is little published work on the same approach for residual curvature in particular. For this reason, this paper suggests a method for determining the likelihood of buckling and the associated bending moments via structural reliability analysis (SRA). A numerical model combining Finite Element (FE) Analysis and a Monte Carlo simulation is applied. A similar approach has already been presented by others for a different lateral buckling control method, and involves forming a database of finite element solutions followed by multivariate interpolation for the stochastic variables [16]. The multivariate interpolation necessitates a permutation of the cases in an FE result database. In order to keep the simulation efficient, only a limited number of variables are treated as stochastic. The variables that are considered as stochastic are those that have been determined that the lateral buckling response due to residual curvature is sensitive to. The variations of the remaining parameters are also accounted for but in a simpler way. The suggested SRA is used to assess the reliability of a pipeline that resembles the Skuld pipeline. The proposed SRA validates that residual curvature is a reliable lateral buckling control method irrespective of great variations in the design parameters that cannot be quantified easily, such as target residual strain. The proposed SRA also serves as a cost attractive solution in the qualification testing, by potentially relieving the installation contractor from the expensive exercise of performing an additional straightening trial.

Overview of the Lateral Buckling and Walking Designs of Deepwater Pipelines in Offshore Brazil

2019 ◽  
Author(s):  
Rafael F. Solano ◽  
Carlos O. Cardoso ◽  
Bruno R. Antunes
Keyword(s):  
Oil And Gas ◽  
Design Guidelines ◽  
Mitigation Measures ◽  
Design Parameters ◽  
Clayey Soils ◽  
Lateral Buckling ◽  
Buckling Behavior ◽  
The World ◽  
Global Buckling ◽  
Subsea Pipelines

Abstract Last two decades have been marked by a significant evolution on the design of HP/HT subsea pipelines around the world. The HotPipe and SAFEBUCK JIPs can be seen as the first deepened developments in order to obtain safe design guidelines for subsea pipelines systems subjected to global buckling and walking behaviors. The adopted design approach have been to allow exposed pipeline buckles globally on seabed in a safe and controlled manner. Otherwise, the walking phenomenon has been in general mitigated constraining axial displacements by means of anchoring systems. After several design and installation challenges concerning lateral buckling and pipeline walking behaviors, nowadays there is a significant amount of deepwater pipelines operating with buckle initiators (triggers) as well as walking mitigation devices in offshore Brazil. Oil and gas pipelines, short gathering lines and long export lines, installed by reeling and J-lay methods, in other words different kinds of subsea pipelines have operated on very soft clayey soils and have formed planned lateral buckles as well as rogue buckles. This paper presents the main characteristics and design challenges of the deepwater pipelines subjected to the lateral buckling behavior, also highlighting mitigation measures to constrain the walking phenomenon of some pipelines. The relevant design results are highlighted as type and number of buckle triggers, buckle spacing, type and locations of walking mitigations. Envelopment of the main design parameters are mapped in order to identify some trends. Finally, survey images of operating pipelines are presented confirming behaviors predicted in the design phase.

Front steering design guidelines formulation for e-scooters considering the influence of sitting and standing riders on self-stability and safety performance

2021 ◽  
pp. 095440702199217
Author(s):  
Milan Paudel ◽  
Fook Fah Yap
Keyword(s):  
Preventive Measures ◽  
Recent Trend ◽  
Dynamic Performance ◽  
Design Guidelines ◽  
Safety Performance ◽  
Design Parameters ◽  
Single Track ◽  
Standing Posture ◽  
Last Mile ◽  
Current Design

E-scooters are a recent trend and are viewed as a sustainable solution to ease the first and last mile problem in modern transportation. However, an alarming rate of accidents, injuries, and fatalities have caused a significant setback for e-scooters. Many preventive measures and legislation have been put on the e-scooters, but the number of accidents and injuries has not reduced considerably. In this paper, the current design approach of e-scooters has been analyzed, and the most common range of design parameters have been identified. Thereafter, validated mathematical models have been used to quantify the performance of e-scooters and relate them with the safety aspects. Both standing and seated riders on e-scooters have been considered, and their influence on the dynamic performance has been analyzed and compared with the standard 26-in wheel reference safety bicycle. With more than 80% of the accidents and injuries occurring from falling or colliding with obstacles, this paper tries to correlate the dynamics of uncontrolled single-track vehicles with the safety performance of e-scooters. The self-stability, handling, and braking effect have been considered as major performance matrices. The analysis has shown that the current e-scooter designs are not as stable as the reference safety bicycle. Moreover, these e-scooters have been found unstable within the most common range of legislated riding velocity. The results corroborate with the general perception that the current designs of e-scooters are less stable, easy to lose control, twitchy, or wobbly to ride. Furthermore, the standing posture of the rider on the e-scooter has been found dangerous while braking to avoid any disturbances such as potholes or obstacles. Finally, the front steering design guidelines have been proposed to help modify the current design of e-scooters to improve the dynamic performance, hence the safety of the e-scooter riders and the surroundings.

Reliability-Based Limit States Design for Onshore Pipelines

2002 ◽  
Author(s):  
Maher Nessim ◽  
Tom Zimmerman ◽  
Alan Glover ◽  
Martin McLamb ◽  
Brian Rothwell ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Traditional Approach ◽  
Large Diameter ◽  
Small Diameter ◽  
Mechanical Damage ◽  
Design Approach ◽  
Design Parameters ◽  
Pipe Failure ◽  
Limit States ◽  
Current Design

The traditional approach to pipelines design is to select a wall thickness that maintains the hoop stress below the yield strength multiplied by a safety factor. The main design condition implied by this approach is yielding (and by extension burst) of the defect-free pipe. Failure statistics show that this failure mode is virtually impossible as the majority of failures occur due to equipment impact and various types of defects such as corrosion and cracks. Recent investigations show that these failure causes are much more sensitive to wall thickness than to steel grade. As a consequence, current design methods produce variable levels of safety for different pipelines — small-diameter, low-pressure pipelines for example have been shown to have higher failure risks due to mechanical damage than large-diameter, high-pressure pipelines. In addition, the current design approach has been shown to have limited ability to deal with new design parameters, such high steel grades, and unique loading conditions such as frost heave and thaw settlement. The paper shows how these limitations can be addressed by adopting a reliability-based limit states design approach. In this approach, a pipeline is designed to maintain a specified reliability level with respect to its actual expected failure mechanisms (known as limit states). Implementation involves identifying all relevant limit states, selecting target reliability levels that take into account the severity of the failure consequences, and developing a set of design conditions that meet the target reliability levels. The advantages of this approach include lower overall cost for the same safety level, more consistent safety across the range of design parameters, and a built-in ability to address new design situations. Obstacles to its application for onshore pipelines include lack of familiarity with reliability-based approaches and their benefits and lack of consensus on how to define reliability targets. The paper gives an overview of the reliability-based design approach and demonstrates its application using an example involving design for mechanical damage.

The Influence of the Bourdon Effect on Pipe Elbow

2016 ◽  
Author(s):  
Diana Abdulhameed ◽  
Samer Adeeb ◽  
Roger Cheng ◽  
Michael Martens
Keyword(s):  
Internal Pressure ◽  
Cross Section ◽  
High Stress ◽  
Bending Moment ◽  
Design Parameters ◽  
Pipeline System ◽  
Pipe Elbow ◽  
Stress Levels ◽  
Current Design ◽  
Thrust Forces

Pipe elbows are frequently used in a pipeline system to change the directions. Thermal expansion and internal pressure results in bending moments on the bends causing ovalization of the initial circular cross-section. The ability of the bend to ovalize will result in an increase in the bend flexibility when compared to straight pipes [1]. In case of bends subjected to internal pressure, the pipe will start to straighten out due to the difference between the intrados and extrados surface areas. The internal pressure causes unbalanced thrust forces tending to open up the elbow depending on its stiffness and surrounding constraints. These forces tending to cause ovalization of the cross section and causing the tendency of pipe bends to open up are termed the “Bourdon effect”. If these unbalanced thrust forces are not taken into consideration, unanticipated deformations and high stress levels could occur at the elbow location that may not be accounted for in traditional stress analysis [2]. A better understanding of the influence of the Bourdon effect on the elbow design parameters is required. Past studies have investigated the behaviour of pipe elbows under closing bending moment and proposed factors that account for the increased flexibility and high stress levels resulted from ovalization. These factors are used in the current design codes [3],[4] &[5] and known as the flexibility factor and stress intensification factor. In this investigation, pipe elbows with different nominal pipe size and various bend radiuses to internal pipe radius ratios (R/r) are studied to get a better understanding of the Bourdon effect and its influence on the pipe stresses and deformations. Differential equilibrium equations are solved to derive a mathematical model to evaluate the unbalanced thrust forces resulted from the Bourdon effect on a pipe elbow. The forces evaluated from the derived model are compared to finite element model results and showed excellent agreement. A comparison between the CSA-Z662 code and the FEA results is conducted to investigate the applicability of the stress intensification factors used in the current design code for different loading cases. The study showed that the external bending moment direction acting on the pipe has a significant effect on the distribution of stresses on the pipe elbow and significantly depending on the level of applied internal pressure.

scholarly journals Reliability of Concrete Elements Designed for Alternative Load Combinations Provided in Eurocodes

10.14311/382 ◽  
2003 ◽  
Vol 43 (1) ◽  
Author(s):  
M. Holický ◽  
J. Marková
Keyword(s):  
Structural Design ◽  
Structural Reliability ◽  
Reliability Theory ◽  
Probabilistic Methods ◽  
European Standard ◽  
Limit States ◽  
Design Procedures ◽  
Characteristic Features ◽  
Concrete Elements ◽  
Ultimate Limit

The basic European standard for design of buildings and other engineering works, EN 1990 "Basis of structural design", provides alternative design procedures, for which national choice is allowed. One of the most important questions concerns three fundamental combinations of actions for persistent and transient design situations in the Ultimate limit states. Simple examples of reinforced concrete elements show, that the alternative load combinations may lead to considerably different reliability levels. Probabilistic methods of structural reliability theory are used to identify characteristic features of each combination and to formulate recommendations. However, further calibration studies are urgently needed in order to prepare National annexes to EN 1990 on time.

Serviceability Limit Verification for Structural Elements of Steel Hall

2017 ◽  
Author(s):  
Izabela Skrzypczak ◽  
Grzegorz Oleniacz
Keyword(s):  
Structural Reliability ◽  
Probabilistic Methods ◽  
Steel Beam ◽  
Structural Elements ◽  
Specific Design ◽  
Limit States ◽  
Time Period ◽  
Reliability Indicator ◽  
Design Requirements ◽  
Probabilistic Measures

In recent years, the importance of assessing structural reliability has increased significantly. This is confirmed by the recommendations of the PN-EN 1990 standard. This standard gives the principles and requirements to ensure the safety, serviceability and durability of the structure. It sets out the basis for calculation and verification of the structure and provides guidance to ensure their reliability. Reliability of structure is its ability to meet specific design requirements, taking into account the planned period of use. The planned period of use should be understood as a time period approved in the project, in which the structure or part of it is to be used for their intended purpose, without the need for major repairs. Typically, reliability is expressed by probabilistic measures as indicator of reliability or probability of failure. The aim of this study is to present the results of of roof girder deflection surveying and modeling their reliability. A general algorithm for determining the value of the reliability indicator for the bending steel beam with FORM method will be presented. Verification of the differences between the indicator of reliability obtained by simplified probabilistic methods and compare them with the values recommended in the Eurocode 0 standard will be also shown. For the analyzed steel beam the serviceability limit states were considered.

Risk Design for Stable ‘Thin-Walled’ Pipelines Subject to Global Buckling and Excessive Bending From Seabed and Pipelay Induced Out-of-Straightness

2008 ◽  
Author(s):  
E. A. Maschner ◽  
N. Y. Wang
Keyword(s):  
External Loading ◽  
Limit States ◽  
Lateral Buckling ◽  
Seabed Topography ◽  
Current Design ◽  
Bending Capacity ◽  
Global Buckling ◽  
Sensitivity Studies ◽  
Structural Risk ◽  
Thin Walled

Relatively thin walled moderate water depth pipelines prone to lateral buckling can have very limited bending capacity in terms of their through-life load, strain and fatigue limit states. For such pipelines effective force mitigation schemes are often impracticable and the use of intermittent rock dump constraint if available, expensive. An alternative option is to design the pipeline to be stable along its length under operational and external loading. However a multitude of uncertainties can impact on such an assessment among them the concrete weight coat properties (stiffness and weight), residual lay tension, field joint SCF, corrosion rate, seabed topography, pipe embedment with associated non-linear pipe soil interactions and the size and frequency of external impacts. This paper reports on a methodology for achieving quantitatively low risk designs meeting regulatory approval through in-place 3D finite element sensitivity studies coupled with structural risk assessments. A current design project utilizing this approach is described along with analytical equations governing excessive seabed and pipelay induced out-of-straightness and lateral buckling initiations. Ultimately this enabled specification of practical limits on pipelay imposed out-of-straightness to safeguard the heavy weight coated pipeline and its field joints during operation.

Lateral Buckling of Deepwater Pipelines in Operation

2012 ◽  
Author(s):  
Yetzirah Urthaler ◽  
Ryan Watson ◽  
Jonathan Davis
Keyword(s):  
Gulf Of Mexico ◽  
Lessons Learned ◽  
Design Solution ◽  
Pipeline System ◽  
Fe Model ◽  
Lateral Buckling ◽  
Operating Environments ◽  
Pipeline Systems ◽  
Fe Model Calibration

Deepwater pipeline systems are regularly designed to operate under high pressure and high temperature (HPHT) conditions. These operating environments typically mean that the systems are susceptible to Euler buckling, more commonly referred to as lateral buckling. An effective design solution, promoted by the SAFEBUCK JIP [1],[2] and now regularly adopted within the industry, is to accommodate the thermal expansion with planned buckle sites, thereby controlling the loads within the system. Traditionally, operators have spent a great deal of resources in designing, manufacturing and installing pipeline systems. However, it is equally important to demonstrate that the system is fit for service and that operational loads do not exceed the extreme design cases. In some instances, there have been a number of instances where lateral buckling has caused full bore rupture in offshore pipelines. In order to verify the long-term integrity of a pipeline system, it is essential to confirm the location, mode shape and amplitude of both the planned and rogue (unplanned) lateral buckles. This can be accomplished via pipeline surveys. Recent pipeline survey work was conducted on a pipeline system in the Gulf of Mexico. The data exhibited some areas of unexpected performance, which highlights the fact that operating uncertainty exists and that lateral buckling is an unstable phenomenon. The design Finite Element (FE) models were calibrated using the measured buckle shapes, and the fatigue life was estimated using recorded operational pressure and temperature data. The survey work performed has proven invaluable when assessing the long-term integrity of the pipeline system. This paper presents a review of the methods used for surveying a pipeline system in the Gulf of Mexico, a summary of the results obtained from the subsequent analysis and pipeline FE model calibration, as well as ‘lessons learned’ for future projects with similar design challenges.

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