• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.4
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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.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.4
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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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• v.52 no.2
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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.

• Proceedings of the KSME Conference
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• 2000.11a
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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.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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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.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.3
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• pp.211-216
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• 2008

Recently a lot of researches have been conducted on the progressive collapse of structures which is the total collapse of structures initiated by localized damage. Most of the previous studies on the field of progressive collapse have followed deterministic approach without considering uncertainty involved in design variables, which results in unknown reliability of the analysis results. In this study the sensitivity analyses are carried out with design variables such as yield strength, live load, damping ratio, and elastic modulus on the vertical deflection of the joint from which a column is suddenly removed. The Monte Calro simulation, tornado diagram method, and the first order second moment method(FOSM) are applied for the sensitivity study. According to the nonlinear static analysis results, the vertical deflection is most affected by the variation of yield strength of beams. The nonlinear dynamic analyses show that the behaviour of model structures is highly sensitive to variation of the yield strength of beams and the structural damping ratio.

• Communications for Statistical Applications and Methods
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• v.25 no.5
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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.

• Journal of the Korean Operations Research and Management Science Society
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• v.37 no.1
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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.

• Journal of Korean Society of Steel Construction
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• v.21 no.2
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• pp.155-164
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• 2009

In this study, a computationally efficient parallel axial-flexural plastic hinge model is proposed for nonlinear dynamic progressive collapse analysis of welded steel moment frames. To this end, post-yield flexural behavior and the interaction of bending moment and axial force of the double-span beams in the column's missing event was first investigated by using material and geometric nonlinear parametric finite element analysis. A piece-wise linear parallel point hinge model that captures the moment-axial tension interaction was then proposed and applied to nonlinear dynamic progressive collapse analysis of welded steel moment frames with the use of the OpenSees Program. The accuracy as well as the efficiency of the proposed model was verified based on the inelastic dynamic finite element analysis results. The importance of including the catenary action effects for proper progressive collapse resistant analysis and design was also emphasized.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.29 no.3
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• pp.298-305
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• 1984

The competitive relationship between orchardgrass (Dactylis glomerata L.) and ladino clover (Trifolium repens L.) was studied under aerial and soil partitions and N, P fertilizer combinations. Orchardgrass and ladino clover were grown in field with one of non competition, shoot competition only, root competition only, full competition and competition between same species. Under basal application of K fertilizer N and P were applied in treatment combinations of blank, N only (l5kg/10a), P only (l5kg/10a), and both NP at planting and each cutting. The forage yield in mixture was between yield of pure orchard grass stand and the 'expected yield', which was a mean of both pure stands. The forage yield in pure ladino was the lowest. During the experiment there was a progressive decline in clover yield either pure stand or mixture. Since orchardgrass was 'over-compensated' to low-yielding clover, the yield of mixture was more than non competition. Orchard grass was more competitive than ladino clover as seasons advanced. The aggressivity of orchardgrass was higher in root competition than in shoot competition comparing to clover. Nitrogen fertilizer increased orchardgrass yield, while phosphate did ladino clover yield and root weight of both species. But the additional effect of P to N was not significant in dry weight and LAI.