A Framework for Reliability-Based Fatigue Safety Factors for Flexible Risers

2007 ◽  
Author(s):  
B. J. Leira ◽  
K. A. Farnes ◽  
R. T. Igland ◽  
J. Martin ◽  
D. Percy ◽  
...  
Keyword(s):  
Reliability Analysis ◽  
Safety Factors ◽  
Fatigue Lifetime ◽  
Specific Target ◽  
Parametric Studies ◽  
Flexible Risers ◽  
Corrosive Environments ◽  
Wave Induced

In the present paper, a procedure for reliability analysis of wave-induced fatigue in the tensile and pressure armours of flexible risers is described. The procedure is based on performing a number of parametric studies with respect to variables that influence the fatigue lifetime. The results of these parametric studies are subsequently combined with models describing the statistical scatter of the same parameters. By application of this procedure, the safety factors which are required in order to reach specific target reliability levels can be computed. Different SN-curves which correspond to different corrosive environments are considered.

Fatigue Safety Factors for Flexible Risers Based on Case Specific Reliability Analysis

2005 ◽  
Author(s):  
Bernt J. Leira ◽  
Ragnar T. Igland ◽  
Gro S. Baarholm ◽  
Knut A. Farnes ◽  
Dick Percy
Keyword(s):  
Reliability Analysis ◽  
Limit State ◽  
State Function ◽  
Safety Factors ◽  
Fatigue Lifetime ◽  
Statistical Variation ◽  
Parametric Studies ◽  
Flexible Risers ◽  
Corrosive Environments ◽  
Wave Induced

In the present paper, fatigue safety factors for flexible risers are assessed. A procedure for reliability analysis of wave-induced fatigue is first described. The procedure is based on performing a number of parametric studies with respect to variables that influence the fatigue lifetime. The results of these parametric studies are subsequently combined with models describing the statistical scatter of the same parameters. By application of this procedure, the safety factors which are required in order to reach specific target reliability levels can be computed. Such safety factors are computed for three specific flexible riser configurations. Different SN -curves which correspond to different corrosive environments are considered. The percentwise contribution from each parameter to the total statistical variation of the limit state function is also quantified.

Fatigue Safety Factors for the Tensile and Pressure Armours of Flexible Risers

2007 ◽  
Author(s):  
Bernt J. Leira ◽  
Ragnar T. Igland ◽  
Naiquan Ye ◽  
Elizabeth A. Passano
Keyword(s):  
Limit State ◽  
State Function ◽  
Flexible Riser ◽  
Safety Factors ◽  
Fatigue Lifetime ◽  
Statistical Variation ◽  
Parametric Studies ◽  
Flexible Risers ◽  
Corrosive Environments ◽  
Wave Induced

In the present paper, fatigue safety factors for metallic layers of flexible risers are assessed. A procedure for reliability analysis of wave-induced fatigue is first described. The procedure is based on performing a number of parametric studies with respect to variables that influence the fatigue lifetime. The results of these parametric studies are subsequently combined with models describing the statistical scatter of the same parameters. By application of this procedure, the safety factors which are required in order to reach specific target reliability levels can be computed. Example of calculation of such safety factors for the tensile and pressure armours of some specific flexible riser configurations are given. Different SN-curves which correspond to different corrosive environments are considered. The percentwise contribution from each parameter to the total statistical variation of the limit state function is also quantified.

Reliability Analysis of Ultimate Longitudinal Strength for Ships in Yangtze River

2016 ◽  
Author(s):  
Le Deng ◽  
Ji Guo ◽  
Chuang Fang ◽  
Lu-yao Zou
Keyword(s):  
Reliability Analysis ◽  
Ultimate Strength ◽  
Yangtze River ◽  
Bending Moment ◽  
Analysis Method ◽  
Safety Factors ◽  
Hull Girder ◽  
Longitudinal Strength ◽  
Partial Safety Factors ◽  
Wave Induced

With Consideration of the uncertainties of materials yield strength, still water bending moment and wave-induced bending moment, the failure equation is established based on reliability analysis method. The reliabilities of 33 ships navigating in Yangtze River are calculated using improved FOSM method, according to which the target reliability is obtained, and the partial safety factors for hull girder ultimate strength, still water bending moment and wave-induced bending moment are given. As a result the formula for probability assessment of ultimate strength is established. Verification of sample ships shows that the formula is accurate and useful.

Safety Factors for Fatigue Analysis of Flexible Pipes Based on Structural Reliability

2012 ◽  
Author(s):  
Fernando dos Santos Loureiro Filho ◽  
Edison Castro Prates de Lima ◽  
Luís Volnei Sudati Sagrilo ◽  
Fernando Jorge Mendes de Sousa ◽  
Carlos Alberto Duarte de Lemos
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Fatigue Analysis ◽  
Design Criterion ◽  
Flexible Riser ◽  
Safety Factors ◽  
Common Procedure ◽  
Flexible Pipes ◽  
Campos Basin ◽  
Flexible Risers

Structural reliability–based methodology [1,2] has been proposed for fatigue analysis of flexible pipes tension armours. In this methodology a design criterion is verified using a standard reliability analysis approach and checking if the fatigue failure probability is equal to or less than a target value. The use of reliability analysis in the every day design practice is not yet a common procedure. Hence, in this paper we present the calibration of safety factors for Brazilian environmental conditions to be used in the standard fatigue analysis of flexible riser tension armours. The calibration is performed in order to guarantee the same target probability of failure. The safety factors are calibrated considering four flexible risers, two connected to FPSOs and the other two to semi-submersibles located in different water depths in Campos Basin offshore Brazil.

scholarly journals Reliability analysis of wake-induced collision of flexible risers

2017 ◽  
Vol 62 ◽  
pp. 49-56 ◽  
Author(s):  
Ping Fu ◽  
Bernt J. Leira ◽  
Dag Myrhaug
Keyword(s):  
Reliability Analysis ◽  
Flexible Risers

scholarly journals Safety Standard for Special Class Damslopes Based on Reliability Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Lingzhi Huang ◽  
Zheng Si ◽  
Xiaoqi Du ◽  
Lifeng Wen ◽  
Bin Li
Keyword(s):  
High Risk ◽  
Reliability Analysis ◽  
Special Class ◽  
Slope Failure ◽  
Safety Margin ◽  
Class Ii ◽  
Class I ◽  
Safety Factors ◽  
Safety Standard ◽  
Risk Levels

The risk of slope failure is determined by the degree of damage caused by the slope slide. For the special-high slope of some high-risk water conservancy and hydropower projects, the standard should be appropriately raised. Thus, the safety standard for these slopes is explored on the basis of reliability analysis. The slopes with high risk of failure are divided into special class I and special class II slopes depending on the risk levels and acceptable risk standards. The concept of reliability theory-based relative ratio of the safety margin is utilized to establish the relationship between annual failure probability and safety factor, thereby obtaining the reasonable safety factors for different slopes. Results show that the values of safety factors for special class I and special class II are 1.40 and 1.35, respectively. These results can provide a reference for exploring the safety standards of dams with a height of more than 200 m.

Flexible Armor Wires: Fatigue Load Frequency Effects and an Accelerated Pitting Methodology

2014 ◽  
Author(s):  
Venkat R. Krishnan ◽  
Stefanie Asher ◽  
Krassimir Doynov ◽  
Yan-Hui Zhang
Keyword(s):  
Corrosion Fatigue ◽  
Fatigue Testing ◽  
Experimental Program ◽  
Work Effort ◽  
Flexible Pipe ◽  
Endurance Tests ◽  
Flexible Risers ◽  
Flexible Armor ◽  
Corrosive Environments ◽  
Fatigue Endurance

Corrosion fatigue in the tensile armor layer is a design consideration for both flexible risers and flowlines offshore. Recently, the industry has experienced a handful of in-service flexible pipe replacements due to corrosion fatigue of armor wires. That experience motivated the work effort summarized herein. This paper presents the preliminary results from an experimental program undertaken by ExxonMobil to evaluate and suggest improvements to the currently established fatigue testing methodology for armor wires in corrosive environments. In particular, the results from a frequency scanning test program for armor wires and a methodology for artificially generating pitted armor wire specimens for fatigue endurance tests are presented.

Fatigue Lifetime Design of Pantograph V500 Based on Reliability

2011 ◽  
Vol 135-136 ◽  
pp. 540-546
Author(s):  
Dong Li Song ◽  
Wei Hua Zhang ◽  
Ping He
Keyword(s):  
Reliability Analysis ◽  
Failure Rate ◽  
Fatigue Lifetime ◽  
General Management ◽  
Reliability Level ◽  
Service Conditions ◽  
Mean Time

Reliability analysis of structure fatigue has two assignments: a. To forecast lifetime of the structure on given reliability level, b. To evaluate reliability level of the structure on given service conditions, material features and designing dimensions. It aims at evaluating the structure’s designing quality and providing a basis for designing improvement or manufacturing. At mean time, it provides instruction to updating management by parameter of failure rate under given fatigue lifetime.Lastly, in form of tables, this paper presents the predicting results of fatigue lifetime of pantograph V500 based on different reliability levels at 500km/h and the predicting results of reliability level of Pantograph V500 under lifetime of 1,200,000km which provide direction of design, manufacturing and general management for Pantograph V500.

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