• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.116-122
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• 2003

Monte Carlo method is one of the powerful engineering tools especially to solve the complex non-linear problems. The Monte Carlo method gives approximate solution to a variety of mathematical problems by performing statistical sampling experiments on a computer. One of the methods to predict the time dependent failure probability of one of the bridge components or the bridge system is a lifetime function. In this paper, FORTRAN program is developed to predict the failure probability of bridge components or bridge system by using both system reliability and lifetime function. Monte Carlo method is used to generate the parameters of the lifetime function. As a case study, the program is applied to the concrete-steel bridge to predict the failure probability.

• Journal of Korean Society of Steel Construction
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• v.14 no.2
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• pp.365-373
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• 2002

In this paper, the system reliability concept was presented to predict the lifespan of bridges. Lifetime distribution functions (survivor functions) were used to model real bridges to predict their remaining life. Using the system reliability concept and lifetime distribution functions (survivor functions), a program called LIFETIME was developed. The survivor functions give the reliability of component at time t. The program was applied to an existing Colorado state highway bridge to predict the failure probability of the time-dependent system. The bridge was modeled as a system, with failure probability computed using time-dependent deteriorating models.

• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.627-639
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• 2002

Bridge construction is almost complete in many countries. Thus, the government and highway agencies change their focus from constructing to maintaining. Effectively maintaining bridges require predicting their lifespan using a system reliability viewpoint. Likewise, maintenance models based on the system reliability concept should be developed. Thus, this study developed maintenance models for preventive maintenance and essential maintenance using system reliability and lifetime distributions. The optimal maintenance strategy for an existing bridge was obtained using the developed maintenance models.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.19-25
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• 2016

Engineering structures including civil infrastructures require a life-cycle cost and benefit during their service lives. The service life of a structure can be extended through appropriate inspection and maintenance actions. In general, this service life extension requires more life-cycle cost and cumulative benefit. For this reason, structure managers need to make a rational decision regarding the service life management considering both the cost and benefit simultaneously. In this paper, the probabilistic decision tool to determine the optimal service life based on cost-benefit analysis is presented. This decision tool requires an estimation of the time-dependent effective cost-benefit under uncertainty to formulate the optimization problem. The effective cost-benefit is expressed by the difference between the cumulative benefit and life-cycle cost of a deteriorating structure over time. The objective of the optimization problem is maximizing the effective cost-benefit, and the associated solutions are the optimal service life and maintenance interventions. The decision tool presented in this paper can be applied to any deteriorating engineering structure.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.467-474
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• 2002

이 연구에서는 점탄성감쇠기가 설치된 구조시스템의 통합최적설계 방법을 제시하였다. 최적화를 위한 목적함수로는 구조시스템이 유발하는 사회적 비용을 의미하는 총 생애주기비용을 사용함으로써, 구조제어 시스템의 성능에 기반한 경제적 유익을 극대화하도록 하였다. 구조물의 층별 기둥 강성 및 점탄성감쇠기의 사용량 등을 설계변수로 하여 생애주기비용함수를 정의하였으며, 통합시스템을 동시에 최적화하기위한 방법으로 유전자 알고리즘을 적용하였다. 동일한 초기비용을 사용하며 통합최적설계를 수행하지 않은 설계를 통해 얻어진 지진응답과 비교한 결과, 제안하는 통합 설계방법은 보다 우수한 진동제어효과를 발휘하는 것으로 나타났다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.162-165
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• 2010

합리적인 교량 대안선정을 위해서는 설계 시 경제성, 경관성, 안전성 및 기능성, 유지관리 용이성, 시공성 등 다양한 속성을 고려하여야 한다. 이 중 경제성은 초기비용뿐만 아니라 공용수명에 걸쳐 발생하는 유지관리비용, 보수 보강비용, 해체 폐기비용 등의 합인 총 생애주기비용에 대해 최소의 비용으로 최상의 가치를 창출하도록 하여야 한다. 본 연구에서는 건설계획과정에서 대표적으로 고려될 수 있는 대안으로 세 가지 교량 형식(강상자형교, 소수주형교, PSC-I형 거더교)을 대상구조물로 선정하고 교량의 공용수명은 상태등급곡선으로부터 추정한 내하율 곡선을 사용하여 산정하였다. LCC최적설계를 위해 설계변수, 제약조건, 목적함수를 구성하였고, 총 생애주기비용을 공용수명으로 나눈 연간생애주기비용을 사용하여 하여 합리적인 교량의 경제성 분석을 수행하였다.

• Journal of the Korean Society for Railway
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• v.8 no.5
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• pp.439-443
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• 2005

The biggest challenge bridge agencies face is the maintenance of bridges, keeping them safe and serviceable, with limited funds. To maintain the bridges effectively, there is and urgent need to predict their remaining life from a system reliability viewpoint. In this paper, a model using lifetime functions to evaluate the overall system probability of survival of a rail road bridge is proposed. In this model, the rail load bridge is modeled as a system. Using the model, the lifetime of the rail road bridge is predicted.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.115-122
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• 2010

The importance of the life cycle cost (LCC) analysis for bridges has been recognized over the last decade. However, it is difficult to predict LCC precisely since the costs occurring throughout the service life of the bridge depend on various parameters such as design, construction, maintenance, and environmental conditions. This paper presents a methodology for the optimal life cycle cost design of a bridge. Total LCC for the service life is calculated as the sum of initial cost, damage cost, maintenance cost, repair and rehabilitation cost, user cost, and disposal cost. The optimization method is applied to design of a bridge structure with minimal cost, in which the objective function is set to LCC and constraints are formulated on the basis of Korean Bridge Design Code. Initial cost is calculated based on standard costs of the Korea Construction Price Index and damage cost on damage probabilities to consider the uncertainty of load and resistance. Repair and rehabilitation cost is determined using load carrying capacity curves and user cost includes traffic operation costs and time delay costs. The optimal life cycle cost design of a bridge is performed and the effects of parameters are investigated.

• Journal of the Korean Society for Railway
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• v.8 no.6 s.31
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• pp.544-549
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• 2005

Nowadays, most of bridge networks are complete or close to completion. The biggest challenge railroad./highway agencies and departments of transportation face is the maintenance of these networks, keeping them safe and serviceable, with limited funds. To maintain the bridges effectively, there is an urgent need to predict their remaining life from a system reliability viewpoint. And, it is necessary to develop the maintenance models based on system reliability concept. In this paper, maintenance models are developed for preventive maintenance and essential maintenance by using system reliability and lifetime distributions. The proposed model is applied to an existing railroad bridge. The optimal maintenance strategy of this bridge is obtained in terms of services life extension and cumulative maintenance cost.

• KDI Journal of Economic Policy
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• v.9 no.2
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• pp.39-70
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• 1987

본고(本稿)에서는 정부투자기관(政府投資機關)의 적정보수(適正報酬) 수준(水準)에 관한 이론(理論)을 제시(提示)하고 이를 배경으로 하여 25개 정부투자기관의 보수실태를 민간기업(民間企業) 및 공무원(公務員)의 경우와 대비(對比)하여 실증적으로 분석 평가하고자 하였다. 정부투자기관의 보수수준(報酬水準)은 "민간(民間) 공공대등(公共對等)의 원칙(原則)"을 반영하여야 한다는 것이 본고(本稿)의 주장(主張)이며, 이에 따라 본고(本稿)에서는 1985년 3월의 시점에서 공공(公共) 민간(民間) 각 부문 종사자들의 직종별(職種別) 학력별(學歷別) 생애임금(生涯賃金)(퇴직금(退職金) 포함(包含)) 수준(水準)을 추계하여 비교하였고, 동시에 부문별(部門別) 임금함수(賃金函數)를 추정(推定)하여 임금격차(賃金隔差) 구조상(構造上)의 부문간 상이여부(相異與否)를 검증(檢證)하였다. 검증(檢證)에 의하면 민간기업(民間企業)(500인(人) 이상(以上))에 비하여 정부투자기관의 평균생애임금(平均生涯賃金)은 사무관리직(事務管理職)의 경우 21%, 생산기능직(生産技能職)의 경우 39% 높았다. 동시(同時)에 정부투자기관 상호간(相互間)의 생애임금(生涯賃金) 격차(隔差)도 적지 않았다. 반면에 학력(學歷) 성(性) 직종(職種)에 따른 임금격차는 민간기업에 비하여 정부투자기관이 훨씬 적었다. 보수체계(報酬體系)에 있어서는 사무직의 경우 각종 수당(手當)이 민간기업에서는 총급여(總給與)의 25%를 차지하였으나 투자기관에서는 총급여(總給與)의 53%에 달하였다. 한편 공무원(公務員)의 평균생애임금(平均生涯賃金)은 민간기업의 수준보다 낮아 사무관리직(事務管理職)의 경우 민간기업 수준의 71%, 생산기능직(生産技能職)의 경우 민간기업 수준의 90%에 불과하였다. 본고(本稿)의 결과에 의하면 공공부문(公共部門)의 보수정책(報酬政策)에는 개선(改善)의 여지가 적지 않다고 하겠다.