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.

Limit States Design—An Innovation in Design Standards for Steel Structures

1974 ◽  
Vol 1 (1) ◽  
pp. 1-13 ◽  
Author(s):  
D. J. Laurie Kennedy
Keyword(s):  
Design Method ◽  
Steel Structures ◽  
Probability Of Failure ◽  
Simple Design ◽  
Design Standards ◽  
Limit States ◽  
Working Stress ◽  
Wide Range ◽  
Ultimate Resistance ◽  
Two Sides

The greater rationality of limit states design as compared to working stress design is developed to show that limit states design leads to a more consistent probability of failure and that neither overly safe and therefore uneconomic structures nor structures with insufficient safety should result from this design methodology.This rationality is extended in the limit states design method in that the performance of the structure and its components is checked against the various limit states at the appropriate load levels. Thus the limit states of serviceability are checked at specified load levels and of strength and stability at the factored load levels.Functions are presented for the two sides of the inequality:[Formula: see text]A comparative design of a 20-storey structure selected to provide a wide range of variables shows that limit states design as proposed results in a structure comparable to that designed by working stress method with a moderate saving in the weight of steel. Some simple design examples are worked out to show the basic similarities between working stress design and limit states design and that the two methods are of about equal complexity or simplicity. It is believed, because the designer will have to check the ultimate resistance against the effect of the factored loads, that he will develop a greater awareness of the behavior of the material and members with which he is working.

scholarly journals Integrity Management of Marine Structures; With Emphasis on Design for Structural Robustness

2018 ◽  
Author(s):  
Torgeir Moan
Keyword(s):  
Structural Damage ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Offshore Structures ◽  
Design Standards ◽  
Limit States ◽  
Fabrication Errors ◽  
Integrity Management ◽  
Operational Errors ◽  
And Control

Based on relevant accident experiences with oil and gas platforms, a brief overview of structural integrity management of offshore structures is given; including an account of adequate design criteria, inspection, repair and maintenance as well as quality assurance and control of the engineering processes. The focus is on developing research based design standards for Accidental Collapse Limit States to ensure robustness or damage tolerance in view damage caused by accidental loads due to operational errors and to some extent abnormal structural damage due to fabrication errors. Moreover, it is suggested to provide robustness in cases where the structural performance is sensitive to uncertain parameters. The use of risk assessment to aid decisions in lieu of uncertainties affecting the performance of novel and existing offshore structures, is briefly addressed.

Partial and total factors of safety in anchored sheet pile design

1991 ◽  
Vol 28 (6) ◽  
pp. 812-817 ◽  
Author(s):  
A. J. Valsangkar ◽  
A. B. Schriver
Keyword(s):  
Design Method ◽  
Water Pressure ◽  
Design Approach ◽  
Foundation Engineering ◽  
Sheet Pile ◽  
Depth Of Penetration ◽  
Limit States ◽  
Working Stress ◽  
Conventional Methods ◽  
Sheet Pile Wall

Recently, the limit states design approach has been recommended in geotechnical design. The Canadian Foundation Engineering Manual (1985) details the new approach for design of foundations, slopes, and retaining structures. Some recent research has indicated that the use of the limit states design approach leads to conservative designs when compared with conventional methods of design. Results of a parametric study are presented in this paper. The study investigated the influence of sheet pile wall geometry, type of water-pressure distribution considered, and different methods of analysis on the required depth of penetration of an anchored sheet pile wall. Modifications are suggested to make the new design method compatible with the conventional methods of design. Key words: factor of safety, working stress design, ultimate limit states design, anchored sheet pile wall.

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.

scholarly journals Strain-Based Pipeline Design Criteria Review

1998 ◽  
Author(s):  
Aaron S. Dinovitzer ◽  
Raymond J. Smith
Keyword(s):  
State Of The Art ◽  
Design Criteria ◽  
Design Standards ◽  
Limit States ◽  
Design Standard ◽  
Offshore Pipeline ◽  
The Usa ◽  
Pipeline Design ◽  
Classification Society

The new Canadian limit states pipeline design standard (CSA Z662-96, Appendix C - Limit States Design) incorporates deformation or strain-based design criteria to prevent pipe rupture and or buckling and limit ovality due to bending. These criteria are different and in some instances, much more conservative than those contained in the Canadian offshore pipeline design standard (chapter 11 of CSA Z662-96) and similar standards used in other countries. This study was completed to review the ovality, buckling (including wrinkling) and rupture criteria included in current Canadian pipeline design standards (CSA Z662-96) and define its basic differences with respect to other standards. The deformation or strain based design criteria formulations in Z662 are compared with those contained in design standards, industry association recommendations and classification society rules from Norway, Britain, Germany, Australia and the USA to illustrate their differences and relative levels of conservatism. In addition, current and on-going research efforts were reviewed to identify the state-of-the-art in pipeline strain-based design, since this research could form the basis for future amendments to existing pipeline design standards. Based on the findings of this review, recommended changes to the limit states pipeline design formulation are given to better reflect the strain-based (non-linear or post-yield) design and assessment approaches included in the Canadian offshore or foreign pipeline design approaches. In addition, an analytical basis for pipeline ovality and buckling design criteria are recommended.

scholarly journals Providing safety and reliability in the design of the offshore ice-resistant stationary oil and gas structures

Vestnik MGSU ◽  
2015 ◽  
pp. 167-177
Author(s):  
Valentin Aleksandrovich Polit’ko ◽  
Igor’ Grigor’evich Kantarzhi
Keyword(s):  
Oil And Gas ◽  
Design Method ◽  
Economic Consequences ◽  
International Standards ◽  
Limit States ◽  
Structure Reliability ◽  
The Social ◽  
Safety And Reliability ◽  
Offshore Oil And Gas ◽  
Offshore Oil

Safety and reliability factors, assumed in Russian and international standards, as well as the main provisions of design of offshore oil and gas structures are considered in the article. The reasons for structures destruction are classified. The analysis showed that the main design provisions and methodology of calculations related to provision of safe and reliable operation of offshore oil and gas structures by different standards are not fundamentally different: the required degree of reliability of the structure is set depending on the social and economic consequences of possible hydrodynamic accidents; calculations are based on the limit states design method using partial safety factors; etc. However, the factors accounting the degree of the structure reliability, partial safety coefficients and load combinations coefficients differ in different standards and methodologies.

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.

Scenario Based Risk Management for Arctic Shipping and Operations

2014 ◽  
Author(s):  
Sören Ehlers ◽  
Pentti Kujala ◽  
Brian Veitch ◽  
Faisal Khan ◽  
Jarno Vanhatalo
Keyword(s):  
Oil And Gas ◽  
The Arctic ◽  
Risk Level ◽  
Limit States ◽  
Operational Conditions ◽  
Holistic Treatment ◽  
Environmental Consequences ◽  
Extreme Load ◽  
Arctic Shipping ◽  
Ice Loads

Arctic oil and gas explorations and Arctic shipping must ensure the safety and protection of this sensitive environment in spite of the challenging operational conditions. However, current regulations and assessment methods do not predict the associated risk level reliably. In other words, ships transiting ice-covered waters are not designed according to physical measures, such as accurate limit states under ice loading, but according to economic and empirical design measures. Similarly, offshore installations should be designed according to the accurate limit states, but the actual ice loads are uncertain so this is not possible at present. Risk-based design methodologies using first principal methods offer a way to advance safe operations and transport of natural resources within and out of the Arctic Sea. This paper introduces a holistic treatment of the design relevant features and their identification to improve safe Arctic operations and transport. The focus is on design relevant Arctic aspects related to extreme and accidental ice events. The approach includes estimating ice loads, including extreme load events, assessing structural consequences of the loading events, assessing associated potential environmental consequences, and establishing a risk based design framework for managing risks.

STRUCTURAL RELIABILITY ANALYSIS BASED ON P-BOXES

2020 ◽  
Vol 92 (6) ◽  
pp. 51-58
Author(s):  
S.A. SOLOVYEV ◽  
Keyword(s):  
Probability Distribution ◽  
Reliability Analysis ◽  
Structural Reliability ◽  
Epistemic Uncertainty ◽  
Random Variable ◽  
Strength Criterion ◽  
Structural Elements ◽  
Structural Element ◽  
Limit States ◽  
Distribution Shape

The article describes a method for reliability (probability of non-failure) analysis of structural elements based on p-boxes. An algorithm for constructing two p-blocks is shown. First p-box is used in the absence of information about the probability distribution shape of a random variable. Second p-box is used for a certain probability distribution function but with inaccurate (interval) function parameters. The algorithm for reliability analysis is presented on a numerical example of the reliability analysis for a flexural wooden beam by wood strength criterion. The result of the reliability analysis is an interval of the non-failure probability boundaries. Recommendations are given for narrowing the reliability boundaries which can reduce epistemic uncertainty. On the basis of the proposed approach, particular methods for reliability analysis for any structural elements can be developed. Design equations are given for a comprehensive assessment of the structural element reliability as a system taking into account all the criteria of limit states.

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