• 복합신소재구조학회 논문집
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• 제5권4호
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• pp.1-10
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• 2014

A progressive failure analysis procedure for composite laminates is developed in here and in the companion paper. An anisotropic plastic constitutive model for fiber-reinforced composite material, is developed, which is simple and efficient to be implemented into computer program for a predictive analysis procedure of composites. In current development of the constitutive model, an incremental elastic-plastic constitutive model is adopted to represent progressively the nonlinear material behavior of composite materials until a material failure is predicted. An anisotropic initial yield criterion is established that includes the effects of different yield strengths in each material direction, and between tension and compression. Anisotropic work-hardening model and subsequent yield surface are developed to describe material behavior beyond the initial yield under the general loading condition. The current model is implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS), and is presented in the companion paper. The accuracy and efficiency of the anisotropic plastic constitutive model are verified by solving a number of various fiber-reinforced composite laminates with and without geometric discontinuity. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

• 복합신소재구조학회 논문집
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• 제5권4호
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• pp.11-17
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• 2014

A progressive failure analysis procedure for composite laminates is completed in here. An anisotropic plastic constitutive model for fiber-reinforced composite material is implemented into computer program for a predictive analysis procedure of composite laminates. Also, in order to describe material behavior beyond the initial yield, the anisotropic work-hardening model and subsequent yield surface are implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS). The accuracy and efficiency of the anisotropic plastic constitutive model and the computer program PACS are verified by solving a number of various fiber-reinforced composite laminates with and without geometric discontinuity. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

• Structural Engineering and Mechanics
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• 제52권2호
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• pp.291-306
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• 2014

In this paper the progressive collapse resisting capacity of steel moment frames with MR dampers is evaluated, and a preliminary design procedure for the dampers to prevent progressive collapse is suggested. Parametric studies are carried out using a beam-column subassemblage with varying natural period, yield strength, and damper force. Then the progressive collapse potentials of 15-story steel moment frames installed with MR dampers are evaluated by nonlinear dynamic analysis. The analysis results of the model structures showed that the MR dampers are effective in preventing progressive collapse of framed structures subjected to sudden loss of a first story column. The effectiveness is more noticeable in the structure with larger vertical deflection subjected to larger inelastic deformation. The maximum responses of the structure installed with the MR dampers designed to meet a given target dynamic response factor generally coincided well with the target value on the conservative side.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.413-419
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• 2000

An efficient method for calculating the nonlinear stiffness of the Progressive Multi-Leaf Spring is developed and evaluated. It utilizes the interaction between the main and help spring that induces the nonlinearity. The main and the help springs are modeled as multi-leaf cantilever beams, and, then, they are integrated as one by connecting the two models for each side of the Progressive Multi-Leaf Spring at the center-bolt. The results from the developed model are evaluated by use of the commercial FEA program, ABAQUS. The nonlinear spring coefficients calculated by FEM analysis yield the numbers very close to the numbers calculated for the spring coefficients by used of the developed method. From the comparative evaluations, the developed method is accurate enough and very efficient in calculation time for evaluating the nonlinear spring property of the Progressive Multi-Leaf Spring.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.307-312
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• 2008

Local damage may cause sequential collapse of structure, which is called progressive collapse. Current progressive collapse analysis is based on the mean value of design variables. This deterministic approach has a low reliability as it doesn't consider uncertainty of variables. In this study the sensitivity of design variables for progressive collapse of structure is evaluated by Monte Calro simulation and Tornado diagram. The analysis results show that the behaviour of model structures is highly sensitive to variation of the yield force of beams and the structural damping ratio.

• 한국전산구조공학회논문집
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• 제21권3호
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• pp.211-216
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• 2008

최근 구조물의 국부적인 손상이 전체적인 붕괴로 이어지는 연쇄붕괴 현상에 관한 연구가 활발히 진행되고 있다. 연쇄붕괴에 관한 기존의 연구는 대부분 해석변수의 불확실성을 포함하지 않는 확정론적인 방법이므로, 해석결과에 대한 신뢰도를 알 수 없다. 본 논문에서는 재료의 항복강도, 활하중의 크기, 감쇠비, 탄성계수 등치 설계변수들이 기둥이 제거됨에 따라 발생하는 수직변위에 영향을 미치는 민감도를 분석하였다. 이를 위하여 몬테카를로 시뮬레이션, 일계이차법, 토네이도 다이어그램의 세 가지 해석기법을 적용하였다. 비선형정적 해석결과에 의하면 난수로 설정한 해석변수들 중에서 보의 항복강도가 수직변위의 변동폭이 가장 컸으며, 비선형동적해석의 경우 보의 항복강도와 감쇠비가 서로 유사한 변동폭을 가지는 것으로 나타났다.

• Communications for Statistical Applications and Methods
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• 제25권5호
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• pp.569-575
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• 2018

Pareto distribution is important to analyze data in actuarial sciences, reliability, finance, and climatology. In general, unknown parameters of the Pareto distribution are estimated based on the maximum likelihood method that may yield inadequate inference results for small sample sizes and high percent censored data. In this paper, a new approach based on the regression framework is proposed to estimate unknown parameters of the Pareto distribution under the progressive Type-II censoring scheme. The proposed method provides a new regression type estimator that employs the spacings of exponential progressive Type-II censored samples. In addition, the provided estimator is a consistent estimator with superior performance compared to maximum likelihood estimators in terms of the mean squared error and bias. The validity of the proposed method is assessed through Monte Carlo simulations and real data analysis.

• 한국경영과학회지
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• 제37권1호
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• pp.1-18
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• 2012

The present study provides some extensions over a recent work in Won (2011) which investigates properties of the static newsvendor problem under a schedule involving progressive multiple discounts under the assumption that demand is given exogenously. Khouja (1995, 1996) formulated the extended versions over the classical newsvendor model with various discount policies including all-units discount and/or multiple discounts and found that the extended newsvendor models with discount schedules yield higher optimal expected profits than the classical newsvendor model with no-discounts. In this study, we establish a robust conjecture as a stronger statement than Khouja's findings with regard to the general relationship among the expected profits of newsvendor models in the sense that the conjecture holds for every order quantity as well as the optimal order quantity. The conjecture encourages the newsvendor facing quantity discounts to safely implement her own discounts policy to customer or accept quantity discounts offered by the supplier even if the optimal order quantity cannot be ordered due to additional restrictions such as budget or warehouse capacity constraints because the newsvendor models with quantity discounts always yield higher expected profit than the classic newsvendor model without quantity discounts regardless of the order quantity. Results from wide experiments with various probability distributions of demand strongly support our conjecture.

• 한국강구조학회 논문집
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• 제21권2호
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• pp.155-164
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• 2009

본 논문에서는 용접철골모멘트골조의 비선형 동적 연쇄붕괴 해석을 위해 인장-휨 거동을 반영한 효율적인 병렬 소성힌지를 제안하였다. 본 목적을 위해 재료적/기하학적 비선형 유한요소해석을 이용한 변수연구를 통해 기둥이 손실된 2경간 보의 항복후 휨거동과 모멘트-축인장력 상호작용을 살펴보았다. 유한요소해석결과를 토대로 보의 모멘트-축인장력 상호작용 관계를 일련의 선형으로 근사화한 소성힌지모델을 제안하고, 이를 OpenSees 프로그램에 적용하여 용접철골모멘트골조의 비선형 동적 연쇄붕괴해석을 수행하였다. 비선형 동적 유한요소해석을 통하여 본 연구에서 제안한 힌지모델의 효율성과 정확도를 검증하였다. 또한 본 연구 결과는 연쇄붕괴 해석 및 설계에 적절한 현수작용효과의 포함여부가 중요함을 보여준다.

• 한국작물학회지
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• 제29권3호
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• pp.298-305
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• 1984

오차드그라스와 라디노클로버의 경합관계를 밝히기 위하여 기존초지에서 분주하여 동일한 밀도로 단·혼파조합을 조성하고 경합구로서 지상 및 지하를 투명아크릴판으로 격리처리하고 질소 및 인산비료를 시용하여 시비에 따른 반응을 조사하였다. 년4회 예취를 통한 목초수량에서 라디노클로버는 오차드그라스에 비하여 현저히 낮았고 LAI, 초고, 분얼력에서도 약세였다. 특히 혼파시에는 라디노클로버가 하부에 위치하며 수평엽의 초형을 가져 광리용 이 불량하였고 경합이 진행됨에 따라 점차적인 수량감소가 있었다. 이들의 경합상태를 지상부 경합과 지하부 경합으로 나누어 보았을 때 지하교 경합에서 라디노의 상대적 열세가 더욱 심하였고 이는 오차드그라스의 왕성한 근군확장과 양수분리용에서 유리하였기 때문이었다. 질소의 시비는 오차드의 경합력을 더욱 촉친하였고 인산의 시용은 라디노의 생육에 유리하게 작용하였으나 오차드에 미치지 못하였다. 혼파구의 수량은 오차드그라스의 단파수량보다 적었으나 두 초종의 평균인 'Expected Yield' 보다는 높아 혼파는 유리하였고 경합의 형태는 오차드그라스에 의한 '과잉보상'으로 오차드그라스는 라디노에 비하여 23.5％ 가량 우점도를 나타내었다.