• Title, Summary, Keyword: Probability of failure

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Reliability Estimation of Buried Gas Pipelines in terms of Various Types of Random Variable Distribution

  • Lee Ouk Sub;Kim Dong Hyeok
    • Journal of Mechanical Science and Technology
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    • v.19 no.6
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    • pp.1280-1289
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    • 2005
  • This paper presents the effects of corrosion environments of failure pressure model for buried pipelines on failure prediction by using a failure probability. The FORM (first order reliability method) is used in order to estimate the failure probability in the buried pipelines with corrosion defects. The effects of varying distribution types of random variables such as normal, lognormal and Weibull distributions on the failure probability of buried pipelines are systematically investigated. It is found that the failure probability for the MB31G model is larger than that for the B31G model. And the failure probability is estimated as the largest for the Weibull distribution and the smallest for the normal distribution. The effect of data scattering in corrosion environments on failure probability is also investigated and it is recognized that the scattering of wall thickness and yield strength of pipeline affects the failure probability significantly. The normalized margin is defined and estimated. Furthermore, the normalized margin is used to predict the failure probability using the fitting lines between failure probability and normalized margin.

Effect of Boundary Conditions of Failure Pressure Models on Reliability Estimation of Buried Pipelines

  • Lee, Ouk-Sub;Pyun, Jang-Sik;Kim, Dong-Hyeok
    • International Journal of Precision Engineering and Manufacturing
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    • v.4 no.6
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    • pp.12-19
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    • 2003
  • This paper presents the effect of boundary conditions in various failure pressure models published for the estimation of failure pressure. Furthermore, this approach is extended to the failure prediction with the aid of a failure probability model. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with each corrosion defect in buried pipelines for long exposure period with unit of years. A failure probability model based on the von-Mises failure criterion is adapted. The log-normal and standard normal probability functions for varying random variables are adapted. The effects of random variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress, material ultimate tensile strength and pipe thickness on the failure probability of the buried pipelines are systematically investigated for the corrosion pipeline by using an adapted failure probability model and varying failure pressure model.

Estimation of Failure Probability Using Boundary Conditions of Failure Pressure Model for Buried Pipelines (파손압력모델의 경계조건을 이용한 매설배관의 파손확률 평가)

  • Lee, Ouk-Sub;Kim, Eui-Sang;Kim, Dong-Hyeok
    • Proceedings of the KSME Conference
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    • pp.310-315
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    • 2003
  • This paper presents the effect of boundary condition of failure pressure model for buried pipelines on failure prediction by using a failure probability model. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with various corrosion defects for long exposure periods in years. A failure pressure model based on a failure function composed of failure pressure and operation pressure is adopted for the assessment of pipeline failure. The effects of random variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress, material ultimate tensile strength and pipe thickness on the failure probability of the buried pipelines are systematically studied by using a failure probability model for the corrosion pipeline.

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Failure Probability of Corrosion Pipeline with Varying Boundary Condition

  • Lee, Ouk-Sub;Pyun, Jang-Sik
    • Journal of Mechanical Science and Technology
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    • v.16 no.7
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    • pp.889-895
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    • 2002
  • This paper presents the effect of external corrosion, material properties, operation condition and design thickness in pipeline on failure prediction using a failure probability model. The predicted failure assessment for the simulated corrosion defects discovered in corroded pipeline is compared with that determined by ANSI/ASME B31G code and a modified B31G method. The effects of environmental, operational, and random design variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress and pipe thickness on the failure probability are systematically studied using a failure probability model for the corrosion pipeline.

Failure Probability Model of Buried Pipeline (매설배관의 파손 확률 모델)

  • Lee, Eok-Seop;Pyeon, Jang-Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.11
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    • pp.116-123
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    • 2001
  • A failure probability model based on Von-Mises failure criterion and the standard normal probability function is proposed. The effects of varying boundary conditions such as nearby cavity, backfill, load cycle and corrosion on failure probability of the buried pipes are systematically investigated. The location of cavity is found to affect failure probability of buried pipeline within a certain limit. It is noted that the flexibility of backfill plays a great role to change the failure probability of buried pipeline. Furthermore, the corrosion gives less effects than other boundary conditions such as cavity, load as cavity, load cycle, and backfill to the failure probability of buried pipeline.

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Effect of Ground Subsidence on Reliability of Buried Pipelines (지반침하가 매설배관의 건전성에 미치는 영향)

  • 이억섭;김동혁
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.1
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    • pp.173-180
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    • 2004
  • This paper presents the effect of varying boundary conditions such as ground subsidence, internal pressure and temperature variation for buried pipelines on failure prediction by using a failure probability model. The first order Taylor series expansion of the limit state function incorporating with von-Mises failure criteria is used in order to estimate the probability of failure mainly associated with three cases of ground subsidence. Using stresses on the buried pipelines, we estimate the probability of pipelines with von-Mises failure criterion. The effects of varying random variables such as pipe diameter, internal pressure, temperature, settlement width, load for unit length of pipelines, material yield stress and pipe thickness on the failure probability of the buried pipelines are systematically studied by using a failure probability model for the pipeline crossing ground subsidence regions which have different soil properties.

Probability of performance failure of storm sewer according to accumulation of debris (토사 적체에 따른 우수관의 성능불능확률)

  • Kwon, Hyuk-Jae
    • Journal of Korean Society of Water and Wastewater
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    • v.24 no.5
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    • pp.509-517
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    • 2010
  • Statistical distribution of annual maximum rainfall intensity of 18 cities in Korea was analyzed and applied to the reliability model which can calculate the probability of performance failure of storm sewer. After the analysis, it was found that distribution of annual maximum rainfall intensity of 18 cities in Korea is well matched with Gumbel distribution. Rational equation was used to estimate the load and Manning's equation was used to estimate the capacity in reliability function to calculate the probability of performance failure of storm sewer. Reliability analysis was performed by developed model applying to the real storm sewer. It was found that probability of performance failure is abruptly increased if the diameter is smaller than certain size. Therefore, cleaning the inside of storm sewer to maintain the original diameter can be one of the best ways to reduce the probability of performance failure. In the present study, probability of performance failure according to accumulation of debris in storm sewer was calculated. It was found that increasing the amount of debris seriously decrease the capacity of storm sewer and significantly increase the probability of performance failure.

A reliability analysis method for rock slope controlled by weak structural surface

  • Zhou, Jia-wen;Jiao, Ming-yuan;Xing, Hui-ge;Yang, Xing-guo;Yang, Yu-chuan
    • Geosciences Journal
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    • v.21 no.3
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    • pp.453-467
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    • 2017
  • Catastrophic landslides maybe occur in rock slope due to the effect of strong earthquakes or heavy rainfall. The stability of rock slope is usually controlled by different scales of weak structural surfaces, which are uncertain and randomly exist in the rock slope. According to the geological characteristics of rock slope, two typical failure modes - plane and wedge are possible. A second-order second-moment (SOSM) method is presented to calculate the reliability index and the failure probability of rock slope, which is an improvement over the first-order second-moment (FOSM) method, and performance functions are built up with the classic limit equilibrium method. The presented method is applied to analyze the failure probability of two rock slopes at the Jinping I Hydropower Station and is compared with the Monte Carlo method and the FOSM method. The computed results show that for plane failure, the reliability index and the failure probability determined by the presented method are 0.563 and 28.7%, respectively, and the reliability index and the failure probability determined by Monte Carlo method are 0.677 and 24.9%, respectively. However, for the FOSM method, the reliability index and failure probability are -0.025 and 51.0%, respectively. For both plane failure and wedge failure, the difference between the presented method and the Monte Carlo method is very small, but the failure probability of plane failure determined by FOSM method is larger than that of the other two methods. The presented method can provide a useful tool to evaluate the failure probability of rock slope.

The Reliability Estimation of Buried Pipeline Using the FAD and FORM (파손평가선도(FAD)와 FORM을 이용한 매설배관의 건전성 평가)

  • Lee, Ouk-Sub;Kim, Dong-Hyeok
    • Journal of the Korean Society of Safety
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    • v.20 no.4
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    • pp.20-28
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    • 2005
  • In this paper, the methodology for the reliability estimation of buried pipeline with longitudinal gouges and dent is presented and the limit state of buried pipeline is formulated by failure assessment diagram(FAD). The reliability of buried pipeline with defects has been estimated by using a theory of failure probability. The failure probability is calculated by using the FORM(first order reliability method) and Monte Carlo simulation. The results out of two procedures have been compared each other. It is found that the FORM and Monte Carlo simulation give similar results for varying boundary conditions and various random variables. Furthermore, it is also recognized that the failure probability increases with increasing of dent depth, gouge depth, gouge length, operating pressure, pipe outside radius and decreasing the wall thickness. And it is found that the analysis by using the failure assessment diagram gives highly conservative results than those by using the theory of failure probability.

Estimating Parameters of Field Lifetime Data Distribution Using the Failure Reporting Probability (고장 보고율을 이용한 현장 수명자료 분포의 모수추정)

  • Kim, Young Bok;Lie, Chang Hoon
    • Journal of Korean Institute of Industrial Engineers
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    • v.33 no.1
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    • pp.52-60
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    • 2007
  • Estimating parameters of the lifetime distribution is investigated when field failure data are not completelyreported. To take into account the reality and the accuracy of the estimates in such a case, the failure reportingprobability is incorporated in estimating parameters, Firstly, method of maximum likelihood estimate (MLE) isused to estimate parameters of the lifetime distribution when failure reporting probability is known, Secondly,Expectation and Maximization (EM) algorithm is used to estimate the failure reporting probability and parame-ters of the lifetime distribution simultaneously when failure reporting probability is unknown. For both cases,procedures of estimation are illustrated for single Weibull distribution and mixed Weibull distribution. Simula-tion results show that MLE obtained by the proposed method is more accurate than the conventional MLE.