• Title, Summary, Keyword: Reliability-Based Design

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Probabilistic Structure Design of Automatic Salt Collector Using Reliability Based Robust Optimization (신뢰성 기반 강건 최적화를 이용한 자동채염기의 확률론적 구조설계)

  • Song, Chang Yong
    • Journal of the Korean Society of Industry Convergence
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    • v.23 no.5
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    • pp.799-807
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    • 2020
  • This paper deals with identification of probabilistic design using reliability based robust optimization in structure design of automatic salt collector. The thickness sizing variables of main structure member in the automatic salt collector were considered the random design variables including the uncertainty of corrosion that would be an inevitable hazardousness in the saltern work environment. The probabilistic constraint functions were selected from the strength performances of the automatic salt collector. The reliability based robust optimum design problem was formulated such that the random design variables were determined by minimizing the weight of the automatic salt collector subject to the probabilistic strength performance constraints evaluating from reliability analysis. Mean value reliability method and adaptive importance sampling method were applied to the reliability evaluation in the reliability based robust optimization. The three sigma level quality was considered robustness in side constraints. The probabilistic optimum design results according to the reliability analysis methods were compared to deterministic optimum design results. The reliability based robust optimization using the mean value reliability method showed the most rational results for the probabilistic optimum structure design of the automatic salt collector.

Barrier Function Method in Reliability Based Design Optimization (장애함수법에 의한 신뢰성기반 최적설계)

  • Lee, Tae-Hee;Choi, Woon-Yong;Kim, Hong-Sun
    • Proceedings of the KSME Conference
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    • pp.1130-1135
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    • 2003
  • The need to increase the reliability of a structural system has been significantly brought in the procedure of real designs to consider, for instance, the material properties or geometric dimensions that reveal a random or incompletely known nature. Reliability based design optimization of a real system now becomes an emerging technique to achieve reliability, robustness and safety of these problems. Finite element analysis program and the reliability analysis program are necessary to evaluate the responses and the probabilities of failure of the system, respectively. Moreover, integration of these programs is required during the procedure of reliability based design optimization. It is well known that reliability based design optimization can often have so many local minima that it cannot converge to the specified probability of failure. To overcome this problem, barrier function method in reliability based design optimization is suggested. To illustrate the proposed formulation, reliability based design optimization of a bracket is performed. AMV and FORM are employed for reliability analysis and their optimization results are compared based on the accuracy and efficiency.

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Reliability Based Design Optimization of the Softwater Pressure Tank Considering Temperature Effect (온도영향을 고려한 연수기 압력탱크의 신뢰성 최적설계)

  • Bae Chul-Ho;Kim Mun-Seong;Suh Myung-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.10
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    • pp.1458-1466
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    • 2004
  • Deterministic optimum designs that are obtained without consideration of uncertainties could lead to unrealiable designs. Such deterministic engineering optimization tends to promote the structural system with less reliability redundancy than obtained with conventional design procedures using the factor of safety. Consequently, deterministic optimized structures will usually have higher failure probabilities than unoptimized structures. This paper proposes the reliability based design optimization technique fur apressure tank considering temperature effect. This paper presents an efficient and stable reliability based design optimization method by using the advanced first order second moment method, which evaluates a probabilistic constraint for more accuracy. In addition, the response surface method is utilized to approximate the performance functions describing the system characteristics in the reliability based design optimization procedure.

Reliability-Based Optimization of Continuous Steel Box Girder Bridges (신뢰성에 기초한 강상형 연속교의 단면 최적설계)

  • 조효남;이두화;정지승;민대홍
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.145-154
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    • 1997
  • The results of optimum design by the deterministic approach adopted in the current design codes depend upon the safety levels of the applied code. But, it is now generally recognized that structural problems are nondeterministic and, consequently, that engineering optimum design must cope with uncertainties. Therefore, it is not an overstatement to affirm that the combination of reliability-based design procedures and optimization techniques is the only means of providing a powerful tool to obtain a practical optimum design solution. In the paper, reliability based optimum design procedure as a rational approach to optimum structural design is presented. The design constraints are formulated based on the ASD, LRFD and reliability theories. The reliability analysis is based on an advanced first-order second moment approach. Uncertainties in the structural strength and loading due to inherent variability as well as modeling and prediction errors are included in failure due to combined bending and shear. For the realistic reliability-based optimization of continuous steel box girder bridges, interactive non-linear limit state model is formulated based on the von Mises's combined stress yield criterion. Comparative results are presented when the ASD criteria are used for the optimum design of a structure under reliability constraints. In addition, this study comparatively shows the results of the optimum design for various criteria of design codes.

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A Study on Reliability Based Design Criteria for Erection Members (가설부재의 신속성 설계기준에 관한 연구)

  • 민경주
    • Journal of the Korean Society of Safety
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    • v.6 no.3
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    • pp.56-63
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    • 1991
  • This study investigates reliability based design criteria for the erection members, and proposes practical algorithm which is based on Ellingwood's algorithm for the reliability analysis and the derivation of reliability based criteria. The magnitude of the uncertainties associated with load effects are chosen primarily by considering our level of practice. And thus the uncertainties so obtained are applied for the reliability analysis and the derivation of reliability based design criteria. A target reliability($\beta$$_{o}$=2.0) is selected as an appropriate value by analyzing the reliability levels of our current USD and WSD design standards. Them a set of load and resistance factors corresponding to the target reliability is proposed as a reliability based design provision, and furthermore a set of allowable stresses for steel having same level of reliability with the corresponding LRFD criteria is also prepared for the current WSD design provision. It may be concluded that the proposed LRFD reliability based design provisions and the corresponding allowable stresses give more rational design than the current code for erection membars.s.s.

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A Study on the Dynamic Reliability Analysis of the Shell Structure under Random Loads (불규칙 하중을 받는 Shell 구조물의 동적 신뢰성 해석에 관한 연구)

  • 배동명
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.33 no.4
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    • pp.334-345
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    • 1997
  • Reliability-based design approaches are needed for cylindrical shell structure whose design and operational experiences are few and which are subjected to external loads of random loads. In designing new type of structure, it is very difficult to evaluate the safety factors due to lack of previous design data and operational experience. To solve the above mentioned problem, much attention is being focussed on rational reliability based design approaches. This paper deals with weight-optional reliability-based design of cylindrical shell structure subjected to structural reliability constraints taking into account of the effect of local buckling and interactive behavior between local and global buckling. Present mentioned is compared with the exiting optional design method based only on safety factors. Numerical simulation reveals that the present method leads to lighter structure (4% reduction in weight compared to the existing optimal design) with the same reliability index. For larger structures with more number of structural members and possible failure modes, the present W0RBD procedure will be an efficient tool in designing cost-effective rationalized economic design.

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Reliability-based design optimization using reliability mapping functions

  • Zhao, Weitao;Shi, Xueyan;Tang, Kai
    • Structural Engineering and Mechanics
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    • v.62 no.2
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    • pp.125-138
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    • 2017
  • Reliability-based design optimization (RBDO) is a powerful tool for design optimization when considering probabilistic characteristics of design variables. However, it is often computationally intensive because of the coupling of reliability analysis and cost minimization. In this study, the concept of reliability mapping function is defined based on the relationship between the reliability index obtained by using the mean value first order reliability method and the failure probability obtained by using an improved response surface method. Double-loop involved in the classical RBDO can be converted into single-loop by using the reliability mapping function. Since the computational effort of the mean value first order reliability method is minimal, RBDO by using reliability mapping functions should be highly efficient. Engineering examples are given to demonstrate the efficiency and accuracy of the proposed method. Numerical results indicated that the proposed method has the similar accuracy as Monte Carlo simulation, and it can obviously reduce the computational effort.

A Study on Optimum Reliability of P.S.C Box Girder Bridge (최적신뢰성에 의한 P.S.C Box Girder교의 연구)

  • Jung, Chul-Won;Yu, Han-Shin;Na, Ki-Hyun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.3 no.4
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    • pp.139-144
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    • 1999
  • Based on the recent developments of the reliability-based structural analysis and design as well as the extending knowledge on the probabiliistic characteristics of load and resistances, the probability based design criteria have been successfully developed for many standards. Since the probabilistic characteristics depend highly on the local load and resistances, it is recognized to develop the design criterion compatible with domestic requirements. The existing optimum design methods, which are generally based on the structural theory and certain engineering experience, do not realistically consider the uncertainties of load and resistances and the basic reliability concepts. This study is directed to propose a optimum design based Expected Total Cost Minimization on P.S.C Box Girder Bridge system which could possibly replace optimum design based traditional provisions of the current code, based on the Neldel-Mead Method reliability theory.

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Midship Section Design of Ship Structures Based on Reliability Analysis (신뢰성 해석에 기초한 선체 중앙단면 설계)

  • Lee, Joo-Sung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.5
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    • pp.507-512
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    • 2011
  • This study is concerned with the reliability analysis and its based design of midship section against the ultimate bending strength. Eight bulk carriers and seven oil tankers over 100m length are chosen for the present study. Target reliability indices for the two ship types have been derived based on the results reliability analysis of the present ship models. Reliability-based structural design codes are proposed for use in design of midship section of bulk carriers and oil tankers. The design codes proposed in this study have been successfully applied to re-design of midship section of the present ship types. It has been found that the proposed codes can provide more uniform structural design results.

Reliability Optimum Design of Slab System based on Lagrange Multipliers (Lagrange Multipliers에 의한 슬래브시스템의 신뢰성 최적설계)

  • Kim, Hyeon-Seak;Lee, Jeung-Bin;Jung, Chul-Won
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.1 no.1
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    • pp.113-124
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    • 1997
  • Based on the recent developments of the reliability-based structural analysis and design as well as the extending knowledge on the probabilistic characteristics of load and resistances, the probability based design criteria have been successfully developed for many standards. Since the probabilistic characteristics depend highly on the local load and resistances, it is recognized to develop the design criterion compatible with domestic requirements. The existing optimum design methods, which are generally based on the structural theory and certain engineering exprience, do not realistically consider the uncertainties of load and resistances and the basic reliability concepts. This study is directed to propose a optimum design based Expected Total Cost Minimization on two-way slab system which could possibly replace optimum design based traditional provisions of the current code, based on the AFOSM reliablity theory.

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