• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.5
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• pp.263-270
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• 2021

In this study, a reliability-based design optimization of a 130-m class fixed-type offshore platform, to be installed in the North Sea, was carried out, while considering environmental, material, and manufacturing uncertainties to enhance its structural safety and economic aspects. For the reliability analysis, and reliability-based design optimization of the structural integrity, unity check values (defined as the ratio between working and allowable stress, for axial, bending, and shear stresses), of the members of the offshore platform were considered as constraints. Weight of the supporting jacket structure was minimized to reduce the manufacturing cost of the offshore platform. Statistical characteristics of uncertainties were defined based on observed and measured data references. Reliability analysis and reliability-based design optimization of a jacket-type offshore structure were computationally burdensome due to the large number of members; therefore, we suggested a method for variable screening, based on the importance of their output responses, to reduce the dimension of the problem. Furthermore, a deterministic design optimization was carried out prior to the reliability-based design optimization, to improve overall computational efficiency. Finally, the optimal design obtained was compared with the conventional rule-based offshore platform design in terms of safety and cost.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.125-130
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• 2011

Since conventional optimization that is classified as a deterministic method does not consider the uncertainty involved in a modeling or manufacturing process, an optimum design is often determined to be on the boundaries of the feasible region of constraints. Reliability-based design optimization is a method for obtaining a solution by minimizing the objective function while satisfying the reliability constraints. This method includes an optimization process and a reliability analysis that facilitates the quantization of the uncertainties related to design variables. Moment-based reliability analysis is a method for calculating the reliability of a system on the basis of statistical moments. In general, on the basis of these statistical moments, the Pearson system estimates seven types of distributions and determines the reliability of the system. However, it is technically difficult to practically consider the Pearson Type IV distribution. In this study, we propose an enhanced Pearson Type IV distribution based on a kriging model and validate the accuracy of the enhanced Pearson Type IV distribution by comparing it with a Monte Carlo simulation. Finally, reliability-based design optimization is performed for a system with type IV distribution by using the proposed method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.102-110
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• 2010

The reliability evaluation may be a efficient method for estimating of the quantitative structural safety considering the effect of uncertainties included in high-speed railway bridges. The expected life-cycle cost(LCC) based upon the reliability evaluation will reasonably offer the safety level and design criteria of high-speed railway bridges. Therefore, this study determined the expected life-cycle cost and optimal design method of high-speed railway bridges on the basis of the result of the numerical analysis and reliability evaluation. For this, after creating various design method based upon the standard design of high-speed railway bridges, the numerical analysis is conducted on each of the alternative design methods. The reliability evaluation by the design strength limit state function is conducted considering the effect of external uncertainties on the basis of the numerical analysis result. The expected life-cycle cost of high-speed railway bridges is calculated on the basis of the reliability evaluation result by each of the alternative design methods. Also, the optimal design method is determined using the calculated expected life-cycle cost. In addition, The result of reliability evaluation and expected life-cycle cost of optimal design method are examined considering the effect of internal uncertainties. It is expected that the result of this study can be used as a basic information for the systematic safety evaluation and optimal structure design of high-speed railway bridges.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.19 no.40
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• pp.69-79
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• 1996

하드웨어 설계 과정에서 신뢰성 담당자들에게 당면한 문제는 요구된 임무에 필요한 기능적 요구사항의 달성 가능성과 요구된 임무를 달성할 확률의 예측여부 및 이의 적합성을 판단하는 것이다. 첫번째의 문제는 기존의 신뢰성 공학의 방법을 사용하여 해결되지만 두번째의 문제는 잦은 사후 설계 변경을 필요로 하기 때문에 항상 시스템 전체에서의 최적을 고려하여 이루어지지 못하고 있다. 본 논문에서는 그러한 잦은 사후 설계 변경등으로 인한 취약한 점을 극복하기 위한 방법론으로 하드웨어 설계 신뢰성 공학을 다루며 그 분석 도구로서 목표달성 나무(Goal-tree)의 사용과 그 응용을 제시하고자 한다.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.82-91
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• 2002

방파제에 대한 신뢰성 설계 방법은 유럽과 일본을 중심으로1980년대 중반 이후로 발전되어 왔다. 유럽에서는 van der Meer(1988a)가 방파제 피복재의 설계에 확률론적인 방법을 도입하였고, Burcharth(1991)는 사석방파제에 대하여 부분안전계수(partial safety factor)를 이용한 신뢰성 설계 방법을 제시하였다 최근 Burcharth and Sørensen(1999)은 PIANC (Permanent International Association of Navigation Congress) Working Groups의 결과를 요약하여 사석방파제와 직립방파제에 대한 부분안전계수들을 확립하였다. (중략)

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2001.05a
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• pp.198-208
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• 2001

CORBA, DCOM, Java RMI 등과 같은 분산 객체 기술이 분산 응용의 신뢰성을 직접적으로 향상시키지는 못한다. 이러한 분산 객체 기술에 고장 감내성을 추가하여 신뢰성 있는 시스템을 구축하기 위해서 객체 단위의 복제 그룹 관리와 고장 탐지 및 회복 메커니즘이 필요하다. 본 논문에서는 신뢰성 있는 고장 감내성 Java RMI 객체를 개발하기 위하여 고장 탐지와 그룹 관리를 위한 그룹 관리자와 원격 인터페이스를 설계하고, 고장 감내성 클래스를 정의한다. 또한 고장 감내성 객체의 투명한 그룹 참여를 위하여 Naming 클래스와 RMIRegistry를 확장한다. 응용 개발자는 고장 감내성 클래스를 상속함으로써 외부의 도움 없이 간단히 고장 감내성 응용 객체를 개발하여 신뢰성을 높일 수 있다. 100M Ethernet으로 연결된 Linux kernel2.2.1의 PentiumIII머신 3대와 Solaris2,6의 Sun Spar치머신을 클라이언트한 시스템을 사용하고 JDK 1.2.2를 이용하여 설계한 객체를 구현하여 다양한 객체고장 에 대해 복구되는 것을 확인하였다. 성능 평가는 그룹크기에 따른 함수의 응답속도와 메시지 크기에 따른 응답속도를 비교하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.33-40
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• 2005

The reliability of flight control system(FCS) for Unmanned Air Vehicle(UAV) is underestimated because of the design restrictions such as small size, low cost and light weight. However because the failure of FCS may cause the loss of aircraft, the reliability of FCS must be analysed and validated whether it meet the reliability requirements in design phase.In this paper the failure rate of subsystems was divided with its function based on the design experience of FCS. The redundancy models which satisfy the system reliability requirements were suggested. These results may be utilized in the hardware design of FCS.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.173-178
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• 1992

This paper is in principle concerned with the reliability analysis and its based design of midship section against the ultimate bonding strength. Bulk carriers and oil tankers over 100m length are considered for this study. Target reliability indices are derived with the results of reliability analysis of the present ship models. Reliability-based structural design code formats are proposed for use in design of midship section of bulk carriers and oil tankers. The proposed design formats have been success fully applied to re-design of midship section of the present ship types and show the reasonable results. It has been found that the proposed code formats in this paper are useful for the re-deign of midship section of such ship types.

• Journal of the KSME
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• v.55 no.10
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• pp.45-49
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• 2015

원자력 발전소를 구성하는 기본 요소들인 부품과 소재의 신뢰성을 보증하고 향상시키는 기계분야 관련 기술에 대해 개략적으로 설명하고자 한다. 원자력 발전소 부품 소재의 설계, 제작, 조달, 시험 등 전체적인 공정에 걸쳐 수행되어야 하는 품질 보증 체계, 신뢰성을 확보하기 위해 준수해야 하는 관련 기계분야 기술기준의 신뢰성, 최신 신뢰성 관련 연구 동향 등으로 구분하여 요약 제시하고자 한다. 최종적으로 원자력 부품 소재의 신뢰성 향상 방안을 제안하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.18-27
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• 2006

The conventional reliability based design optimization(RBDO) methods require high computational cost compared with the deterministic design optimization(DO) methods, therefore it is hard to apply directly to large-scaled problems such as an aerodynamic shape design optimization. In this study, to overcome this computational limitation the efficient RBDO procedure with the two-point approximation(TPA) and adjoint sensitivity analysis is proposed, that the computational requirement is nearly the same as DO and the reliability accuracy is good compared with that of RBDO. Using this, the 3-D aerodynamic shape design optimization is performed very efficiently.