• 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.

• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.24-30
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• 2011

Conventional slope stability analysis is focused on calculating minimum factor of safety or maximum probability of failure. To minimize inherent uncertainty of soil properties and analytical model and to reflect various analytical models and its failure shape in slope stability analysis, slope stability analysis method considering simultaneous failure probability for multi failure mode was proposed. Linear programming recently introduced in system reliability analysis was used for calculation of simultaneous failure probability. System reliability analysis for various analytical models could be executed by this method. For application analysis for embankment, the results of this method shows that system stability of embankment calculate quantitatively.

• Computational Structural Engineering
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• v.11 no.4
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• pp.341-350
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• 1998

본 논문은 교통하중에 대한 강사장교의 체계신뢰성에 기초한 체계적이며 실용적인 내하력평가 및 여용성평가 모형을 제안하였다. 고량 주형과 주탑의 조합상관 한계상태에 기초한 내하력평가를 위하여 개선된 조합상관식에 기초한 LRFR(Load and Resistance Factor Rating) 방법과 신뢰성에 기초한 시스템수준의 평가를 위해서 목표체계신뢰성지수의 항으로 표현되는 등가시스템저항강도에 의한 접근방법을 제안하였다. 또한 시스템의 여용성을 정의하기 위해서 체계신뢰성해석의 결과와 내하력평가 결과를 이용한 실제적인 시스템여용성 평가방법을 적용하였다. 제안한 체계신뢰성에 기초한 평가방법은 기존의 요소신뢰성 방법에 비해 구조물의 여용성을 충분히 반영하는 상당히 합리적이며 실제적인 결과를 보여주는 실용적인 방법으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.79-88
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• 1987

This study is intended to propose a system reliability analysis model for R.C. bridge superstructures based on the systems reliability theory. Approximately assuming that the ultimate capacity of the superstructures is reached, when two adjacent girders fail subsequently, a practical system reliability model is proposed, which is based on a point estimate for Level II parallel-series system modelling. The sensitivity analysis of system reliabilities for the variation of the coefficients of correlations between the failure modes is performed by applying the proposed model for R.C. T beam bridges. It is observed that the point estimate method for the proposed model corresponds to the average value of the Ditlevsen's bound, and the system reliability index, ${\beta}_s$, varies quite sensitively according to the variation of the cofficients of correlations. Systems reliabilities of a few existing T beam bridges are analyzed by applying the proposed practical system reliability method of this study, and, in addition, the preferable direction of the development of the reliability-based code calibration using the system target reliability index concept are suggested.

• Computational Structural Engineering
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• v.4 no.2
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• pp.119-129
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• 1991

This study is directed for the development of an efficient Importance Sampling Technique for system reliability analysis of bridge structures. Many methods have been proposed for structural reliability assessment such as the First-order Second-Moment Method, the Advanced Second-Moment Method, Monte Carlo Simulation, etc. The Importance Sampling Technique can be employed to obtain accurate estimates for the system reliability with reasonable computation effort. Based on the results of example analysis, it may be concluded that Importance Sampling Technique is a very effective tool for the system reliability analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.3
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• pp.273-279
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• 2007

Probabilistic Risk Assessment considering statistically random variables is performed for the preliminary design of an Arch Bridge. Component reliabilities of girders have been evaluated using the response surfaces of the design variables at the selected critical sections based on the maximum shear and negative moment locations. Response Surface Method (RSM) is successfully applied for reliability analyses lot this relatively small probability of failure of the complex structure, which is hard to be calculated by Monte-Carlo Simulations or by First Order Second Moment method that can not easily calculate the derivative terms in implicit limit state functions. For the analysis of system reliability, parallel resistance system composed of girders is modeled as a parallel series connection system. The upper and lower probabilities of failure for the structural system have been evaluated and compared with the suggested prediction method for the combination of failure modes. The suggested prediction method for the combination of failure modes reveals the unexpected combinations of element failures in significantly reduced time and efforts, compared with the previous permutation method or conventional system reliability analysis method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.51-59
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• 1993

This paper develops practical and realistic reliability models and methods for the evaluation of system-reliability and system reliability-based rating of various types of box-girder bridge superstructures. The strength limit state model for box-girder bridges suggested in the paper are based on not only the basic flexural strength but also the strength interaction equations which simultaneously take into account flexure, shear and torsion. And the system reliability problem of box-girder superstructure is formulated as parallel-series models obtained from the FMA(Failure Mode Approach) based on major failure mechanisms or critical failure states of each girder. In the paper, an improved IST(Importance Sampling Technique) simulation algorithm is used for the system reliability analysis of the proposed models. This paper proposes a practical but rational approach for the evaluation of capacity rating in terms of the equivalent system-capacity rating corresponding to the estimated system-reliability index which is derived based on the concept of the equivalent FOSM(First Order Second Moment) form of system reliability index. The results of the reliability evaluation and rating of existing bridges indicate that the reserved reliability and capacity rating at system level are significantly different from those of element reliability or conventional methods especially in the case of highly redundant box-girder bridges.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.73-80
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• 2010

Conventional slope stability analysis is focused on calculating minimum factor of safety or maximum probability of failure. To minimize inherent uncertainty of soil properties and analytical model and to reflect various analytical models and its failure shape in slope stability analysis, slope stability analysis method considering simultaneous failure probability for multi failure mode was proposed. Linear programming recently introduced in system reliability analysis was used for calculation of simultaneous failure probability. System reliability analysis for various analytical models could be executed by this method. Optimum design to determine angle of a simple slope is executed for multi failure mode using linear programming. Because of complex consideration for various failure shapes and modes, it is possible to secure advanced safety by using simultaneous failure probability.

• Magazine of the Korea Concrete Institute
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• v.7 no.3
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• pp.187-198
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• 1995

This paper develops practical and reallstic reliabllity models and methods for the evaluation of system rehability and system rellabllity based ratlng of R.C box glrder bridge superstructures. The precise prediction of reberved carrying capacity of bridge as d system is extremely difficult especially when the brldges are highly redundant and slgnlficantly deter 1or;itcd or dainagetl. Thls papel proposes a nt2w approach for the evaluation of reseived system c,drrying capaaty of br~dges in terms ot equ~vdleiit system strength, which may b~ ddcflned as a brtdge system strength correipcmdlng tu the system rehability of the bridge. This cm be ticrAvcd from an Inverse process bami or1 the con~ept of FOSM(F1rst Order Second Moment) form of system reliabihty index. The sf rength llmt state models for K C box girder br~dges suggested In the paper dre based on the basi~ bending and shear strength And thc system reliatxllty pro,~lerri of box gritier super structure 1s formuldted as parallel serles models obtalncd f ~ o m thc FMA(Fdilure blode Rp proath) based on major failure mc>clmusrns or c~itlcal fdure ,>tatcs of each nuder .WOSM(Ad-vanced First Order Second Moment) and IST(1mportance Sampling Technique) simulation algorithm are used for the reliability analysis of the proposed models.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.241-250
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• 1991

The reliability analysis for web frame of tanker is carried out by the probabilistic finite element method combined with the classical reliability method such as MVFOSM and AFOSM which can be used for calculating the probability of failure for the complicated structures in which the limit state equation is implicitly expressed. As random variables external load, elastic modulus, sectional moment of inertia and field stress are chosen and Parkinson's iteration algorithm in AFOSM is used for reliability analysis. By adding only the covariance data of the random variables to the input data set required for conventional finite element method, the present method can easily calculate the probability of failure at every element end as well as the covariances of structural reponses such as displacements at every element end and member forces at every element, even for the complicated ship structure.