Probabilistic and Deterministic Approach to the Setting of In-Line Inspection Intervals

2011 ◽  
Author(s):  
Marcus McCallum ◽  
Chas Jandu ◽  
Andrew Francis
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Corrosion Damage ◽  
Time Dependent ◽  
Metal Loss ◽  
Deterministic Approach ◽  
Robust Method ◽  
Optimum Frequency ◽  
Detection Tool ◽  
Pipeline Wall

All pipelines are susceptible to the possibility of corrosion damage. Corrosion is a time dependent process that leads to localised gradual thinning of the pipeline wall and if allowed to continue will eventually cause failure of the pipewall. Due to the progressive nature of corrosion the likelihood of failure increases with time. One means of mitigating the likelihood of such failures is to perform an in-line inspection using a metal loss detection tool. The frequency of inspection is an important parameter to operators since if it is too high, excessive costs will be incurred and if it is too low, failure involving loss of supply, threats to safety and the environment may follow. Operators therefore seek the optimum frequency. This paper describes a robust method for optimizing inspection intervals based on the use of structural reliability analysis.

scholarly journals Time-Dependent Reliability Analysis of Reinforced Concrete Beams Subjected to Uniform and Pitting Corrosion and Brittle Fracture

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1820
Author(s):  
Mohamed El Amine Ben Seghier ◽  
Behrooz Keshtegar ◽  
Hussam Mahmoud
Keyword(s):  
Reinforced Concrete ◽  
Brittle Fracture ◽  
Reliability Analysis ◽  
Pitting Corrosion ◽  
Structural Reliability ◽  
Time Dependent ◽  
State Function ◽  
Rc Beams ◽  
Highly Nonlinear ◽  
Reliability Method

Reinforced concrete (RC) beams are basic elements used in the construction of various structures and infrastructural systems. When exposed to harsh environmental conditions, the integrity of RC beams could be compromised as a result of various deterioration mechanisms. One of the most common deterioration mechanisms is the formation of different types of corrosion in the steel reinforcements of the beams, which could impact the overall reliability of the beam. Existing classical reliability analysis methods have shown unstable results when used for the assessment of highly nonlinear problems, such as corroded RC beams. To that end, the main purpose of this paper is to explore the use of a structural reliability method for the multi-state assessment of corroded RC beams. To do so, an improved reliability method, namely the three-term conjugate map (TCM) based on the first order reliability method (FORM), is used. The application of the TCM method to identify the multi-state failure of RC beams is validated against various well-known structural reliability-based FORM formulations. The limit state function (LSF) for corroded RC beams is formulated in accordance with two corrosion types, namely uniform and pitting corrosion, and with consideration of brittle fracture due to the pit-to-crack transition probability. The time-dependent reliability analyses conducted in this study are also used to assess the influence of various parameters on the resulting failure probability of the corroded beams. The results show that the nominal bar diameter, corrosion initiation rate, and the external loads have an important influence on the safety of these structures. In addition, the proposed method is shown to outperform other reliability-based FORM formulations in predicting the level of reliability in RC beams.

The Research on Time-Dependent Reliability Analysis for RC Structures Based on the Theory of Stochastic Processes

2011 ◽  
Vol 243-249 ◽  
pp. 5650-5655
Author(s):  
Cheng Yu Xia ◽  
Qing You Liu ◽  
Li Qin Qian
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Time Dependent ◽  
Time Varying ◽  
Rc Structures ◽  
Calculating Method ◽  
Specific Analysis ◽  
The Mean ◽  
Compression Member ◽  
Strong Ability

This paper proposes a new calculating method for the reliability analysis of the time-varying structure，and applies the calculating method to optimize the design for the concrete structure . The RC compression member was taken as an example in the specific analysis in by the mean of resistance and structural reliability with time t. The results show that, this mode has a strong ability of analyzing adequately all kinds of random variant in procedure of structure failures.

Pipeline Integrity Reliability Analysis Levels

2016 ◽  
Author(s):  
Sherif Hassanien ◽  
Len Leblanc ◽  
Javier Cuervo ◽  
Karmun Cheng
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Failure Modes ◽  
Oil And Gas ◽  
Prediction Models ◽  
Metal Loss ◽  
Operating Pressure ◽  
Reliability Engineering ◽  
Reliability Methods ◽  
Types Of Information

Reliability engineering science is a mature discipline that has been used extensively in industries such as aviation, nuclear energy, automobiles, and structures. The application of reliability principles (especially structural reliability) in oil and gas transmission pipelines is still an active area of development. The advent of high resolution in-line inspections tools (ILI) facilitates a formal application/utilization of reliability methods in pipeline integrity in order to safely manage deformation, metal loss, and crack threats. At the same time, the massive amount of ILI data, their associated uncertainties, and the availability/accuracy of failure prediction models present a challenge for operators to effectively implement the use of reliability analysis to check the safety of integrity programs within available timeframes. On the other hand, approximate reliability techniques may affect the analysis in terms of both accuracy and precision. In this paper, a Pipeline Integrity Reliability Analysis (PIRA) approach is presented where the sophistication of the reliability analysis is staged into three levels: PIRA levels I, II and III. The three PIRA levels correspond to different representations of integrity uncertainties, uses of available validated/calibrated data, uses of statistical models for operating pressure and resistance random variables, implementation of reliability methods, and consideration of failure modes. Moreover, PIRA levels allow for improved integration of reliability analysis with the existing timelines/stages of traditional integrity programs, such that integrity data are updated as the integrity program progresses. The proposed integrity reliability approach allows for the delivery of safety checks leveraging all types of information available at any given point in time. In addition, the approach provides a full understanding of the strengths and weaknesses of each PIRA level. Pipeline corrosion case studies are provided herein to illustrate how the PIRA Levels can be applied to integrity programs.

scholarly journals DEVELOPED PROBABILISTIC REDUCTION FACTORS FOR LOPHIRA ALATA (EKKI) TIMBER JOISTS SUBJECTED TO CREEP-RUPTURE

2016 ◽  
Vol 36 (1) ◽  
pp. 39-44
Author(s):  
JM Kaura ◽  
A Lawan ◽  
AA Salihu
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Significant Loss ◽  
Creep Rupture ◽  
Time Dependent ◽  
Load Duration ◽  
Design Variables ◽  
Reliability Method ◽  
Load Carrying ◽  
Strength And Stiffness

Wood experiences a significant loss of strength and stiffness when loaded over period of time. This phenomenon is known as creep-rupture. Several models were developed for the estimation of the reduction of load carrying capacity of timber with time. In this paper, the results of time dependent structural reliability analysis of timber joist produced with Lophiraalata (Ekki) timber specie was presented. Three load duration models were considered in the study, namely: The Model proposed by Wood, Gerhards model, and Nielsen. The timber joist was designed in accordance with the Eurocode 5. The uncertainties in all the basic design variables were fully accommodated in the time dependent reliability analysis. The entire process was implemented using a developed MATLAB program employing First Order Reliability Method (FORM). Time dependent mathematical models for modification of safety index to account for the effect of load duration were proposed. The use of both Gerhards and Nielsen model, for the design of Lophiraalata timber members was recommended.  http://dx.doi.org/10.4314/njt.v36i1.6

Use of Structural Reliability Analysis for Uprating Above Ground Installations

2002 ◽  
Author(s):  
A. Francis ◽  
C. S. Jandu ◽  
M. A. McCallum
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Failure Modes ◽  
Time Dependent ◽  
Operating Pressure ◽  
Stress Concentrations ◽  
Safe Operation ◽  
The Uk ◽  
Design Factors ◽  
Increased Pressure

In support of an extensive programme to increase the operating pressure of the UK National Transmission System (NTS) Advantica Technologies Limited have developed a structural reliability based methodology which is used to demonstrate the safe operation of Above Ground Installations (AGIs) at increased pressure levels. The approach is based on Advantica’s methodology for demonstrating the safe operation of pipeline sections at high design factors. It incorporates the effects of stress concentrations occurring at Tees and bends within complex pipework systems, and addresses the credible failure modes, including shakedown, corrosion and fatigue, taking account of pressure and thermal loadings. Particular attention is given to the time-dependent nature of the failure modes and the mitigating effect of the pre-service hydrostatic test and weld inspections is included.

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