Assessment on Design Factors of China’s Natural Gas Pipeline Based on Reliability-Based Design Method

2016 ◽  
Author(s):  
Zhenyong Zhang ◽  
Yawei Zhou ◽  
Jinyuan Zhang
Keyword(s):  
Natural Gas ◽  
Design Method ◽  
Large Diameter ◽  
Small Diameter ◽  
Research Report ◽  
Design Code ◽  
Limit States ◽  
Reliability Based Design ◽  
Location Class ◽  
Design Factors

Although the traditional method based on stress analysis is simple and convenient, the main limitation is that it does not reflect the actual failure mechanisms (or limit states). A pipeline network database of about 40 thousand kilometers comprising 258 design cases that represent combinations of steel grade, diameter, pressure, and location class is established, in order to evaluate and improve the design factors specified in the Chinese standard “Code for design of gas transmission pipeline engineering” (GB 50251). Referring to the research report “Target Reliability Levels for the Design and Assessment of Onshore Natural Gas Pipelines” accomplished by C-FER in 2005, the critical wall thicknesses and corresponding equivalent design factors are calculated by using reliability-based method to meet specified reliability targets. The research shows that the equivalent design factors obtained by Reliability-Based Design (RBD) method tend to increase as the pipe diameters get larger. The new design factors are smaller than those specified in the design code for pipelines with small diameter in location class 1 and 2, and larger than those in the design code for the other pipelines. Therefore, design factors are modified in each location class. The new factors are specific to pipes with small diameter (D ≤ 508mm), medium diameter (508mm < D < 711mm), and large diameter (711mm ≤ D ≤ 1219mm), thus enhancing the rationality and practicability of design factors.

Application of High-Grade Steels to Onshore Natural Gas Pipelines Using Reliability-Based Design Method

2006 ◽  
Author(s):  
Joe Zhou ◽  
Brian Rothwell ◽  
Wenxing Zhou ◽  
Maher Nessim
Keyword(s):  
High Pressure ◽  
Wall Thickness ◽  
Design Method ◽  
Large Diameter ◽  
Economic Assessment ◽  
High Grade ◽  
Gas Pipelines ◽  
Natural Gas Pipelines ◽  
Reliability Based Design ◽  
Design Factors

Two example onshore gas pipelines were designed using a reliability-based approach. The first example (1219 mm, 17.2 MPa) represents a high-pressure large-diameter pipeline; the second example has a smaller diameter (762 mm) and lower pressure (9.9 MPa). Three steel grades (X70, X80 and X100) were used to develop three design solutions for each example. The wall thickness-related life cycle costs of the designs were evaluated. The design outcomes show that the reliability targets for both examples can be met using X100 steels and high equivalent design factors (0.93 for the first example and 0.9 for the second example). Moreover, ruptures and excessive plastic deformation of a defect free pipe were found to be insignificant integrity threats even when the design uses X100 and relatively high equivalent design factors such as 0.85 and 0.9. The economic assessment results show that the X100 design is the most economical option for the high-pressure large-diameter example. However, using X100 does not show a clear economic advantage over using X80 for the second example mainly because the wall thickness for the design using X100 is governed by the maximum D/t ratio constraint. The study also demonstrates the advantages of the reliability-based approach as a valuable tool in assessing the feasibility and potential benefits of using high-grade steels on a pipeline project.

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.

Reliability-based design criteria for timber bridges in Ontario

1986 ◽  
Vol 13 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Andrzej S. Nowak ◽  
Raymond J. Taylor
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Structural Safety ◽  
Design Code ◽  
Bridge Design ◽  
Limit States ◽  
Acceptance Criterion ◽  
Reliability Based Design ◽  
Load And Resistance Factor ◽  
Timber Bridges

The new Ontario Highway Bridge Design Code (OHBDC) is based on limit states theory and therefore uses a load and resistance factor format. This paper deals with the development of the basis for the timber bridge design provisions (OHBDC). Three structural systems are considered: sawn timber stringers, laminated nailed decks, and prestressed laminated decks. The latter system has been successfully used in Ontario for the last 7 years.The acceptance criterion in calculation of load and resistance factors is structural reliability. It is required that bridges designed using the new code must have a reliability equal to or greater than a preselected target value. Reliability is measured in terms of the reliability index. The safety analysis is performed for a structural system rather than for individual members. The live load model was developed on the basis of available truck survey data. Material properties are based on extensive in-grade test results. Numerical examples are included to demonstrate the presented approach. Key words: bridge deck, design code, prestressed timber, reliability, reliability index, stringers, structural safety, timber bridges.

Reliability Based Design and Assessment for Location-Specific Failure Threats With Application to Natural Gas Pipelines

2006 ◽  
Author(s):  
Maher Nessim ◽  
Wenxing Zhou ◽  
Joe Zhou ◽  
Brian Rothwell
Keyword(s):  
Natural Gas ◽  
Individual Risk ◽  
Gas Pipelines ◽  
Limit States ◽  
Integrity Assessment ◽  
Natural Gas Pipelines ◽  
Risk Criteria ◽  
Reliability Based Design ◽  
Unstable Slope ◽  
The Individual

The acceptance criteria used in Reliability Based Design and Assessment (RBDA) are defined as a set of reliability targets (where reliability is defined as 1.0 minus the probability of failure). Because of the linear nature of pipeline systems, reliability targets are defined on a per km-year basis. Such targets are directly applicable to failure causes (or limit states) that are equally likely to occur anywhere along a segment of the pipeline (e.g. equipment impact or yielding/rupture of defect-free pipe under internal pressure). They are, however, not directly applicable for design and assessment situations involving limit states that apply at known specific locations. Examples include design for geotechnical loads on a particular unstable slope or integrity assessment of specific corrosion defects based on in-line inspection data. In previous work, reliability targets for natural gas pipelines have been developed on the basis of appropriate societal and individual risk criteria. This paper describes an approach to adapt these targets, and demonstrate compliance with them, for location-specific limit states. The approach is based on using separate checks to ensure that the individual and societal risk criteria underlying the targets are met. An example is included to demonstrate application of the approach to design a pipeline on an unstable slope.

Target Reliability Levels for Pipeline Limit States Design

1996 ◽  
Author(s):  
T. J. E. Zimmerman ◽  
Q. Chen ◽  
M. D. Pandey
Keyword(s):  
Reliability Analysis ◽  
Oil And Gas ◽  
Design Method ◽  
Risk Level ◽  
Design Standards ◽  
Limit States ◽  
Working Stress ◽  
Partial Safety Factors ◽  
Pipeline Design ◽  
Design Factors

The limit states design appendix currently being developed for inclusion in the Canadian Standards Association pipeline design code, Z662, Oil and Gas Pipeline Systems contains preliminary partial safety factors that were selected on the basis that they result in designs similar to those produced using the existing working stress design standards. This paper suggests an approach for selecting partial factors for limit states design of pipelines based on formal reliability analysis. Such an approach recognizes that consistent safety levels can be achieved for different pipeline sections by varying the target reliability as a function of the severity of failure consequences, where consequences are measured in terms of public safety, economic costs, and damage to the environment. Where the consequences of failure are more severe, higher reliability is required. Where the consequences are less severe, lower reliability can be tolerated, with the same risk level being achieved. This paper reviews the limit states design method and discusses the selection of target reliability levels and the reliability analysis procedures used to calibrate partial design factors.

Reliability Based Design and Assessment for Location-Specific Failure Threats With Application to Natural Gas Pipelines

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Maher Nessim ◽  
Wenxing Zhou ◽  
Joe Zhou ◽  
Brian Rothwell
Keyword(s):  
Natural Gas ◽  
Individual Risk ◽  
Gas Pipelines ◽  
Limit States ◽  
Integrity Assessment ◽  
Natural Gas Pipelines ◽  
Risk Criteria ◽  
Reliability Based Design ◽  
Unstable Slope ◽  
The Individual

The acceptance criteria used in reliability based design and assessment are defined as a set of reliability targets (where reliability is defined as 1.0 minus the probability of failure). Because of the linear nature of pipeline systems, reliability targets are defined on a per kilometer-year basis. Such targets are directly applicable to failure causes (or limit states) that are equally likely to occur anywhere along a segment of the pipeline (e.g., equipment impact or yielding/rupture of defect-free pipe under internal pressure). They are, however, not directly applicable for design and assessment situations involving limit states that apply at known specific locations. Examples include design for geotechnical loads on a particular unstable slope or integrity assessment of a corrosion defect at a specific location (as determined by in-line inspection). In previous work, reliability targets for natural gas pipelines have been developed on the basis of appropriate societal and individual risk criteria. This paper describes an approach to adapt these targets and demonstrate compliance with them, for location-specific limit states. The approach is based on using separate checks to ensure that the individual and societal risk criteria underlying the targets are met. An example is included to demonstrate application of the approach to design a pipeline on an unstable slope.

Limit States Design and Assessment of Onshore Pipelines

2012 ◽  
Author(s):  
Maher Nessim
Keyword(s):  
Natural Gas ◽  
Development Stage ◽  
Simple Design ◽  
Safety Factors ◽  
Limit States ◽  
Natural Gas Pipelines ◽  
Reliability Based Design ◽  
Wide Range ◽  
Assessment Standard ◽  
Expected Outcomes

In 2005, guidelines for the application of reliability-based design and assessment (RBDA) to natural gas pipelines were developed under PRCI sponsorship. The methodology underlying these guidelines has since been adopted as a non-mandatory Annex in the CSA Z662 standard (Annex O). The benefits of reliability-based methods include consistent safety levels, optimized solutions that make best use of available resources and flexibility in addressing non-standard problems. The key limitations of the methodology are that it requires specialized expertise, good data and a significant analysis effort. One approach that has been successfully used to simplify the application of reliability-based methods is to develop simple design and assessment rules that are designed to meet specified safety levels. In this approach, which is referred to here as limit states design and assessment, the checking rules incorporate safety factors that are “calibrated” to meet pre-selected reliability targets, within a specified tolerance, over a wide range of possible design and assessment cases. Probabilistic analyses are performed as part of the development stage, but the resulting checks are deterministic. The basic elements required to calibrate limit states design and assessment checks have been developed as part of the RBDA methodology, making the development of a limit states approach feasible. This paper provides an overview of an ongoing Joint Industry Project to develop a limit states design and assessment standard that addresses the key threats to the safety of onshore pipelines. The benefits and limitations of this approach are discussed in comparison to the full RBDA approach, and the expected outcomes of the project are described.

Limit states and reliability-based design for a non-codified problem of aqueduct buoyancy

2006 ◽  
Vol 43 (8) ◽  
pp. 869-883
Author(s):  
Gil Robinson ◽  
James Graham ◽  
Ken Skaftfeld ◽  
Ron Sorokowski
Keyword(s):  
Design Methods ◽  
Model Parameters ◽  
Safety Factors ◽  
Design Code ◽  
Limit States ◽  
Reliability Based Design ◽  
Simulation Techniques ◽  
Working Stress ◽  
Engineering Problems ◽  
Partial Safety Factors

Limit states design methods and engineering judgement have been used to assess buoyancy issues for remediation of the 85 year old Shoal Lake Aqueduct in Manitoba. The study demonstrates how these methods can be applied to non-codified engineering problems. Four separate buoyancy analyses were completed using (i) partial safety factors from the Ontario Highway Bridge Design Code, (ii) project-specific partial safety factors, (iii) Monte Carlo simulation techniques, and (iv) working stress design (WSD) methods. Engineering judgement was required to develop a buoyancy model, interpret data for modeling parameters, and provide meaningful values for parameters that could not be measured. Results from the analyses show that more uniform reliability is provided when measured variability of the model parameters is accounted for. The reliability is not quantifiable when working stress design methods are used. Key words: limit states, probability, non-codified problem, aqueduct, buoyancy.

Developments in the design of welded HSS truss joints with RHS chords

1983 ◽  
Vol 10 (1) ◽  
pp. 92-103 ◽  
Author(s):  
Jeffrey A. Packer
Keyword(s):  
Design Method ◽  
Simple Procedure ◽  
Steel Structures ◽  
Design Code ◽  
Limit States ◽  
Hollow Section ◽  
Recent Developments

Recent developments in design proposals for rectangular hollow section truss joints are reviewed for statically loaded, single chord, planar truss connections having one compression bracing member and one tension bracing member welded to the chord face, with either a small gap or an overlap at the connection. After comparison with the results of many joint tests, undertaken both in isolation and in complete trusses in other countries, a relatively simple procedure for the design of such joints is advocated. The design method is presented in a format compatible with the Canadian Standards Association Limit States Design Code for Steel Structures.

Seismic Design Method for Reliability-Based Rehabilitation of Buildings

2006 ◽  
Vol 22 (1) ◽  
pp. 189-214 ◽  
Author(s):  
Marco A. Montiel ◽  
Sonia E. Ruiz
Keyword(s):  
Seismic Design ◽  
Design Method ◽  
Limit States ◽  
Confidence Levels ◽  
Reliability Based Design ◽  
Seismic Design Code ◽  
Conventional Structure ◽  
Factor Design ◽  
Seismic Design Method ◽  
Story Building

A reliability-based design method for the rehabilitation of buildings with energy-dissipating devices is proposed. The design method is formulated within the demand and capacity factor design (DCFD) format. The proposed approach is based on verifying that the confidence levels (associated with the serviceability and the ultimate limit states) corresponding to the rehabilitated structure are equal to or larger than the confidence levels associated with a similar conventional structure that is designed in accordance with a reference seismic design code. The method is illustrated with a five-story building rehabilitated with steel TADAS energy-dissipating plates.

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