• Title, Summary, Keyword: Stochastic assessment

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An Objective Method of Risk Assessment Based on Stochastic Modelling (확률 기반의 위험등급평가 객관화 방안)

  • Shin, Sang-Sik;Lee, Kil-Soo;Cho, Heung-Gi
    • Journal of the Korean Society for Quality Management
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    • v.41 no.3
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    • pp.465-474
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    • 2013
  • Purpose: To provide a variety of stable military supplies, risk should be avoided or removed. This paper aims to provide an objective method of risk assesment for risk matrix to evaluate risk level. Methods: According to previous results of risk assesment through risk matrix, some parameters and probability density functions, which include characteristics of military supplies, are selected and Risk matrix is modelled based on that. Results: Results show that a proposed method can evaluate objectively risk level through the stochastic modelling and provide well-balanced risk assessments by categorizing into 3 levels such as high, middle and low level risk. Conclusion: A current risk assessment method includes substantial subjectivity of risk assessment and as a problem about military supplies comes up, we can not show any appropriate evidences for decision of risk assessment. We propose an objective scheme employing stochastic modelling with parameters and probability density functions.

Calculation of the Area of Severity for Voltage Sag Assessment (순간전압강하 평가를 위한 가혹지역의 계산)

  • Park, Chang-Hyun;Hong, Jun-Hee
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.6
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    • pp.1034-1040
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    • 2010
  • This paper presents a calculation method of the area of severity for the stochastic assessment of voltage sags. In general, the annual expected numbers of voltage sags at an individual load point can be estimated stochastically. However, in order to assess the system voltage sag performance considering many sensitive load points together, it is necessary to determine and analysis the area of severity for the load points. The area of severity to voltage sags is the network region where the fault occurrences will simultaneously lead to voltage sags at different load points. In this paper, the concept of the voltage sag assessment and the calculation method of the area of severity are addressed. The analysis of the area of severity is performed on the IEEE 30-bus test system by using the proposed method. The method is useful for the stochastic assesment of voltage sags and the establishment of systematic plans for voltage sag mitigation.

Probabilistic Structural Safety Assessment Considering the Initial Shape and Non-linearity of Steel Cable-Stayed Bridges (강사장교의 초기형상과 비선형성을 고려한 확률론적 구조안전성 평가)

  • Bang, Myung-Seok;Han, Sung-Ho;Lee, Woo-Sang;Lee, Chin-Ok
    • Journal of the Korean Society of Safety
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    • v.25 no.3
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    • pp.91-99
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    • 2010
  • In this study, the advanced numerical algorithm is developed which can performed the static and dynamic stochastic finite element analysis by considering the effect of uncertainties included in the member stiffness of steel cable-stayed bridges and seismic load. After conducting the linear and nonlinear initial shape analysis, the advanced numerical algorithm is the assessment tool which can performed structural the response analysis considering the static linearity and non-linearity of before or after induced intial tensile force, and examined the reliability assessment more efficiently. The verification of the developed numerical algorithm is evaluated by analyzing the regression analysis and coefficient of correlation using the direct monte carlo simulation. Also, the dynamic response characteristic and coefficient of variation of the steel cable-stayed bridge is calculated by considering the uncertainty of random variables using the developed numerical algorithm. In addition, the quantitative structural safety of the steel cable-stayed bridges is evaluated by conducting the reliability assessment based upon the dynamic stochastic finite element analysis result.

Seismic fragility assessment of isolated structures by using stochastic response database

  • Eem, Seung-Hyun;Jung, Hyung-Jo
    • Earthquakes and Structures
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    • v.14 no.5
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    • pp.389-398
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    • 2018
  • The seismic isolation system makes a structure isolated from ground motions to protect the structure from seismic events. Seismic isolation techniques have been implemented in full-scale buildings and bridges because of their simplicity, economic effectiveness, inherent stability and reliability. As for the responses of an isolated structure due to seismic events, it is well known that the most uncertain aspects are the seismic loading itself and structural properties. Due to the randomness of earthquakes and uncertainty of structures, seismic response distributions of an isolated structure are needed when evaluating the seismic fragility assessment (or probabilistic seismic safety assessment) of an isolated structure. Seismic response time histories are useful and often essential elements in its design or evaluation stage. Thus, a large number of non-linear dynamic analyses should be performed to evaluate the seismic performance of an isolated structure. However, it is a monumental task to gather the design or evaluation information of the isolated structure from too many seismic analyses, which is impractical. In this paper, a new methodology that can evaluate the seismic fragility assessment of an isolated structure is proposed by using stochastic response database, which is a device that can estimate the seismic response distributions of an isolated structure without any seismic response analyses. The seismic fragility assessment of the isolated nuclear power plant is performed using the proposed methodology. The proposed methodology is able to evaluate the seismic performance of isolated structures effectively and reduce the computational efforts tremendously.

Reliability Assessment of Elevators Using Life Data of the Components (부품의 수명 데이터를 이용한 승강기의 신뢰성 평가)

  • Sohn, S.H.;Sohn, H.J.;Kim, S.J.;Yang, B.S.;Yoon, M.C.
    • Journal of the Korea Society For Power System Engineering
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    • v.14 no.6
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    • pp.61-66
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    • 2010
  • Engineering asset management (EAM) requires the accurate assessment of current and the prediction of future asset health condition. Suitable mathematical models that are capable of predicting time-to-failure and the probability of failure in future time are essential. In general reliability models, lifetime of component and system is estimated using failure time data. This paper deals with the reliability assessment of elevators using life of main components. Especially this work is concerned with the stochastic nature of life of elevator components. First, we investigate the Weibull statistical analysis of lifetime data for the components. The final goal is to establish the mathematical model for reliability assessment. This work provides more perspectives to future research in the fields of reliability and maintainability.

A stochastic adaptive pushover procedure for seismic assessment of buildings

  • Jafari, Mohammad;Soltani, Masoud
    • Earthquakes and Structures
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    • v.14 no.5
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    • pp.477-492
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    • 2018
  • Recently, the adaptive nonlinear static analysis method has been widely used in the field of performance based earthquake engineering. However, the proposed methods are almost deterministic and cannot directly consider the seismic record uncertainties. In the current study an innovative Stochastic Adaptive Pushover Analysis, called "SAPA", based on equivalent hysteresis system responses is developed to consider the earthquake record to record uncertainties. The methodology offers a direct stochastic analysis which estimates the seismic demands of the structure in a probabilistic manner. In this procedure by using a stochastic linearization technique in each step, the equivalent hysteresis system is analyzed and the probabilistic characteristics of the result are obtained by which the lateral force pattern is extracted and the actual structure is pushed. To compare the results, three different types of analysis have been considered; conventional pushover methods, incremental dynamic analysis, IDA, and the SAPA method. The result shows an admirable accuracy in predicting the structure responses.

Assessment of ride safety based on the wind-traffic-pavement-bridge coupled vibration

  • Yin, Xinfeng;Liu, Yang;Chen, S.R.
    • Wind and Structures
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    • v.24 no.3
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    • pp.287-306
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    • 2017
  • In the present study, a new assessment simulation of ride safety based on a new wind-traffic-pavement-bridge coupled vibration system is developed considering stochastic characteristics of traffic flow and bridge surface. Compared to existing simulation models, the new assessment simulation focuses on introducing the more realistic three-dimensional vehicle model, stochastic characteristics of traffic, vehicle accident criteria, and bridge surface conditions. A three-dimensional vehicle model with 24 degrees-of-freedoms (DOFs) is presented. A cellular automaton (CA) model and the surface roughness are introduced. The bridge deck pavement is modeled as a boundless Euler-Bernoulli beam supported on the Kelvin model. The wind-traffic-pavement-bridge coupled equations are established by combining the equations of both the vehicles in traffic, pavement, and bridge using the displacement and interaction force relationship at the patch contact. The numerical simulation shows that the proposed method can simulate rationally useful assessment and prevention information for traffic, and define appropriate safe driving speed limits for vulnerable vehicles under normal traffic and bridge surface conditions.

A Study on Estimation of the Probability Distribution of Fatigue Crack Growth Life for Steels (강의 피로균열전파수명의 확률분포 추정에 관한 연구)

  • 김선진;윤성환;전창환;정규연;안석환
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.40-45
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    • 2000
  • Presented are the estimation of the probability distribution of fatigue crack growth life and reliability assessment of structures by simulating material resistance to fatigue crack growth along a crack path. The material resistance is treated as a Weibull stochastic process. A non-Gaussian stochastic fields simulation method proposed by Shimozuka, et al is applied with the statistical data obtained experimentally. Test results are obtained for $\Delta$K constant amplitude load in tension with stress ratio of R=0.2 and three specimen thicknesses of 6, 12 and 18mm. This simulation method is useful to estimate the probability distribution of fatigue crack growth life and the smallest life.

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Development of Probability Distribution Estimation Program for Fatigue Crack Growth Lives (피로균열전파수명의 확률분포추정 프로그램 개발)

  • 김선진;안석환;윤성환
    • Journal of the Korean Society of Marine Engineering
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    • v.25 no.5
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    • pp.1058-1064
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    • 2001
  • In this paper, the development of probability distribution estimation program for fatigue crack growth lives was summarize. The probability distribution estimation program of life was developed to increase the reliability of life estimation. In this study, it is considered that the cause of scatter in fatigue crack growth data is due to material inhomogeneity. The material resistance to fatigue crack growth is modelled as a spatial stochastic process, which varies randomly along the crack path. We developed the GUI program to estimate the probability distribution and reliability using the non-Gaussian stochastic process method. This program can be used for the reliability assessment.

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A Study on Estimation of the Probability Distribution of Fatigue Crack Growth Life for Steels (강의 피로균열전파수명의 확률분포 추정에 관한 연구)

  • 김선진;윤성환;전창환;김일석
    • Journal of Ocean Engineering and Technology
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    • v.14 no.4
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    • pp.73-78
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    • 2000
  • Presented are the estimation of the probability distribution of fatigue crack growth life and reliability assessment of structures by simulating material resistance to fatigue crack growth along a crack path. The material resistance is treated as a Weibull stochastic process. A non-Gaussian stochastic fields simulation method proposed by shimozuka, et al is applied with the statistical data obtained experimentally. Test results are obtained for $\delta K$ constant amplitude load in tension with stress ratio of R=0.2 and three specimen thicknesses of 6,12 and 18mm. This simulation method is useful to estimate the probability distribution of fatigue crack growth life and the smallest life.

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