• Title/Summary/Keyword: 신뢰한계

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Stochastic Reliability Analysis of Armor Units of Rubble-Mound Breakwaters Subject to Multiple Loads (다중하중에 따른 경사제 피복재의 추계학적 신뢰성 해석)

  • Lee, Cheol-Eung
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.24 no.2
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    • pp.138-148
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    • 2012
  • A stochastic reliability analysis model has been developed for evaluating the time-dependent stability performance of armor units of rubble-mound breakwaters subjected to the multiple loads of arbitrary magnitudes which could be occurred randomly. The initial structural capacities and the damage rates of armor units of rubble-mound breakwaters could be estimated as a function of the incident wave height with a given return period by using the modified Hudson's formula and Melby's formula. The structural stability performances of armor units of rubble-mound breakwaters could be analyzed in detail through the lifetime reliability investigations according to the limit states such as the serviceability or ultimate limit state and the conditions of multiple loads. Finally, repair intervals for the structural management of armor units of rubble-mound breakwaters could quantitatively be evaluated by a new approach suggested in this paper that has been based on the target probability for repair and the accumulated probabilities of failure obtained from the present stochastic reliability analysis model.

Structure Reliability Analysis using 3rd Order Polynomials Approximation of a Limit State Equation (한계상태식의 3차 다항식 근사를 통한 구조물 신뢰도 평가)

  • Lee, Seung Gyu;Kim, Sung Chan;Kim, Tea Uk
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.26 no.3
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    • pp.183-189
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    • 2013
  • In this paper, uncertainties and failure criteria of structure are mathematically expressed by random variables and a limit state equation. A limit state equation is approximated by Fleishman's 3rd order polynomials and the theoretical moments of an approximated limit state equation are calculated. Fleishman introduced a 3rd order polynomial in terms of only standard normal distiribution random variables. But, in this paper, Fleishman's polynomial is extended to various random variables including beta, gamma, uniform distributions. Cumulants and a normalized limit state equation are used to calculate a theoretical moments of a limit state equation. A cumulative distribution function of a normalized limit state equation is approximated by a Pearson system.

Reliability Analysis Model for Deflection Limit State of Deteriorated Steel Girder Bridges (처짐한계상태함수를 이용한 노후 강거더 교량의 신뢰성해석 모델 구축)

  • Eom, Jun-Sik
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.2
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    • pp.47-53
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    • 2014
  • The paper investigates the limit state of deflection for short and medium span steel girder bridges. Deflection depends on stiffness of steel girders and integrity of the reinforced concrete slab (composite action). Load and resistance parameters are treated as random variables. A probabilistic model is developed for prediction of the deflection. The structural performance can be affected by deterioration of components, in particular corrosion of steel girders. In addition, the creep of concrete can greatly influence the deflection of composite structures. Therefore, the statistical models for creep and corrosion of structural steel are incorporated in the model. Structures designed according to the AASHTO LRFD Code are considered. Load and resistance models are developed to account for time-variability of the parameters. Monte Carlo simulations are used to estimate the deflections and probabilities of serviceability failure. Different span lengths and girder spacing are considered for structures designed as moment-controlled and deflection-controlled. A summary of obtained results is presented.

A Study on Optimal Design of Accelerated Life Tests (가속수명시험의 최적 설계)

  • Jeong, Hai-Sung
    • Journal of Applied Reliability
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    • v.7 no.2
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    • pp.57-72
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    • 2007
  • This paper suggests an approach for using ALTA 7 PRO to design accelerated life test plans. Conducting a accelerated life test requires finding life distributions at different stress levels and determining an appropriate life-stress relationship. Moreover, a test plan needs to be developed. In its optimal test plan, stress levels are determined and the proportions of test units are assigned at each stress level so that asymptotic variance of the maximum likelihood estimate of a (log) percentile of the life distribution at the design stress is minimized. Examples are presented for usage.

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On the Six-sigma Approach in Dependability Management System IEC60300 (신뢰성경영시스템에서의 식스시그마 접근법)

  • Kim, Jong-Gurl;Kim, In-Hee;Kim, Hyung-Man
    • Proceedings of the Safety Management and Science Conference
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    • 2010.11a
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    • pp.639-649
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    • 2010
  • 신뢰성 기술은 제품이 고장 없이 일정기간 사용할 수 있게 하는 기술로 시장점유율과 고객만족을 높이는 효과적이고 전략적인 필수 요소이다. 검사시점의 적합성에 대한 평가가 아닌 제품 및 시스템의 설계에서부터 폐기까지의 제품수명주기에 대한 신뢰성 평가를 다루는 제품의 신뢰성인증과 신뢰성경영시스템 인증 확보가 시급한 과제이다. 이를 위한 제품 수명의 평균과 분산을 효과적으로 관리할 수 있는 신뢰성 식스시그마 기술개발과 확보가 중요 현안과제이다. 정규분포를 가정한 대부분의 품질경영시스템에서의 식스시그마 접근법은 비정규 분포를 따르는 신뢰성특성과 실험계획기법 등을 고려해야 하는 신뢰성 식스시그마에서의 적용의 한계가 많다. 본 연구에서는 품질혁신 방법론인 식스시그마 기법을 토대로 신뢰성경영시스템에서 맞는 식스시그마 구축의 방향성을 제시하고자 한다.

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Target Reliability Index of Single Gravel Compaction Piles for Limit State Design (한계상태설계를 위한 단일 쇄석다짐말뚝의 목표신뢰도지수)

  • You, Youngkwon;Lim, Heuidae;Park, Joonmo
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.2
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    • pp.5-15
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    • 2014
  • Target reliability index in the limit state design indicated the safety margin and it is important to determine the partial factor. To determine the target reliability index which is needed in the limit state design, the six design and construction case histories of gravel compaction piles (GCP) were investigated. The limit state functions were defined by bulging failure for the major failure mode of GCP. The reliability analysis were performed using the first order reliability method (FORM) and the reliability index was calculated for each ultimate bearing capacity formulation. The reliability index of GCP tended to be penportional to the safety factor of allowable stress design and average value was ${\beta}$=2.30. Reliability level that was assessed by reliability analysis and target reliability index for existing structure foundations were compared and analyzed. As a result, The GCP was required a relatively low level of safety compared with deep and shallow foundations and the currd t reliability level were similar to the target reliability in the reinforced earth retaining-wall and soil-nailing. Therefore the target reliability index of GCP suggested as ${\beta}_T$=2.33 by various literatures together with the computed reliability level in this study.

System Reliability-Based Safety Assessment of Steel Cable-Stayed Bridges (체계신뢰성방법에 기초한 강사장교의 안전도평가)

  • 조효남;임종권;박경훈
    • Computational Structural Engineering
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    • v.11 no.4
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    • pp.351-360
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    • 1998
  • 본 논문에서는 실용적 체계신뢰성에 기초한 강사장교의 안전도평가를 위한 체계적인 모형을 제안하였다. 공용중인 강사장교의 시스템 안전도평가를 위하여 요소신뢰성해석을 위한 케이블, 주형 그리고 주탑의 한계 상태모형과 각 요소들간의 조합파괴를 포함하는 주파괴경로를 정의할 수 있는 체계신뢰성해석 모형을 제안하였다. 요소신뢰성해석을 위한 수치해석기법으로는 AFOSM(Advanced First Order Second Moment) 방법을 사용하였고, 체계신뢰성해석을 위해서는 부분 ETA(partial Event Tree Analysis) 모형을 사용하였다. 제안된 방법의 타당성을 고찰하기 위하여 진도대교의 안전도 평가에 적용하였다. 부분 ETA 모혀을 사용한 체계신뢰성 평가 방법은 기존의 요소신뢰성 방법에 비해 구조물의 여용성을 충분히 반영하는 상당히 합리적이며 실제적인 결과를 보여주는 실용적인 방법으로 판단된다.

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A Study on Data Reliability Used on the Internet (웹에서 사용되는 데이터 신뢰성에 관한 연구)

  • Lee, Seok-Ki;Kim, Jae-Jung;Kwack, Kae-Dal;Shin, Seung-Jung
    • Proceedings of the Korea Information Processing Society Conference
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    • 2009.11a
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    • pp.957-958
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    • 2009
  • 이 글은 신뢰성 문제와 관련된 현대 정보사회의 특성을 되짚어 본 다음, 정보보호와 신뢰성의 관계에 대해 살펴보고 웹 정보를 중심으로 신뢰성의 개념, 신뢰성 평가의 방법, 웹 사이트의 신뢰성 요인, 범주별 웹 사이트 신뢰도 등에 대해 이용자들을 대상으로 조사, 분석하고자 한다. 웹 사이트의 신뢰성 평가 항목과 조사 대상자의 표본 수가 제한되어 있다는 한계를 갖고 있으므로 이 부분은 향후 지속적인 조사와 연구를 통해 보완해 나갈 필요가 있다

A study for null lens design of autostigmatic type and the limitation of measurement accuracy for ultra precision manufacturing of large aspherical surface (대형 비구면의 초정밀 가공을 위한 자동무수차점 방식의 널 렌즈 설계 및 측정 정밀도의 한계에 관한 연구)

  • Kim, Kil-Seon;Rim, Cheon-Seog
    • Korean Journal of Optics and Photonics
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    • v.16 no.1
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    • pp.71-78
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    • 2005
  • A null lens system of autostigmatic type, consisting of two mirrors, is designed for testing a large aspherical mirror. The system is theoretically analyzed to determine the limitation of measurement accuracy according to the manufacturing and alignment errors. We confirmed that irregularity of the null lens surface is the principal factor among tolerances in limiting measurement accuracy. Consequently, we can predict that measurement accuracy will be from 5λ/100 to 4λ/1000 according to the amount of this irregularity. That is, we can present the limitation of possible measurement accuracy with actual alignment and manufacturing errors.

Safety Analysis of Storm Sewer Using Probability of Failure and Multiple Failure Mode (파괴확률과 다중파괴유형을 이용한 우수관의 안전성 분석)

  • Kwon, Hyuk-Jae;Lee, Cheol-Eung
    • Journal of Korea Water Resources Association
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    • v.43 no.11
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    • pp.967-976
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    • 2010
  • AFDA (Approximate Full Distribution Approach) model of FORM (First-Order Reliability Model) which can quantitatively calculate the probability that storm sewer reach to performance limit state was developed in this study. It was defined as a failure if amount of inflow exceed the capacity of storm sewer. Manning's equation and rational equation were used to determine the capacity and inflow of reliability function. Furthermore, statistical characteristics and distribution for the random variables were analyzed as a reliability analysis. It was found that the statistical distribution for annual maximum rainfall intensity of 10 cities in Korea is matched well with Gumbel distribution. Reliability model developed in this study was applied to Y shaped storm sewer system to calculate the probability that storm sewer may exceed the performance limit state. Probability of failure according to diameter was calculated using Manning's equation. Especially, probability of failure of storm sewer in Mungyeong and Daejeon was calculated using rainfall intensity of 50-year return period. It was found that probability of failure can be significantly increased if diameter is decreased below the original diameter. Therefore, cleaning the debris in sewer pipes to maintain the original pipe diameter should be one of the best ways to reduce the probability of failure of storm sewer. In sewer system, two sewer pipes can flow into one sewer pipe. For this case, probability of system failure was calculated using multiple failure mode. Reliability model developed in this study can be applied to design, maintenance, management, and control of storm sewer system.