• Earthquakes and Structures
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• v.27 no.1
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• pp.31-39
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• 2024

The reliability-based seismic design of steel frames is a complex process that incorporates seismic demand with a structural capacity to attain safe buildings aligned with specified constraints. This paper introduces an efficient base shear force formulation to support the reliability-based design process of steel frames. The introduced base shear force equation combines the seismic demand statistics with the reliability objective to calculate a fictitious base shear force for linear static analysis. By concentrating on the seismic demand and promising to meet a certain level of reliability, the equation converts the reliability-based seismic design problem to a deterministic one. Two code-compliant real-size steel moment frames are developed according to different reliability objectives to demonstrate the competency of the proposed formula. The nonlinear dynamic analysis method is used to assess the seismic reliability of the constructed frames, and the numerical results validate the credibility of the suggested formulation. The base shear force calculation method regarding seismic reliability is the main finding of this study. The ease of use makes this approach a potent tool for design professionals and stakeholders to make rapid risk-informed decisions regarding steel moment frame design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.1 s.173
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• pp.215-224
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• 2000

In order to reduce the variation effects of uncertainties in the engineering environments, new robust optimization method, which considers the uncertainties in design process, is proposed. Both design variables and system parameters are considered as random variables about their nominal values. To ensure the robustness of performance function, a new objective is set to minimize the variance of that function. Constraint variations are handled by introducing probability constraints. Probability constraints are solved by the advanced first order second moment (AFOSM) method based on the reliability theory. The proposed robust optimization method has an advantage that the second derivatives of the constraints are not required. The suggested method is examined by solving three examples and the results are compared with those for deterministic case and those available in literature.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.113-116
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• 1995

In this study, we formulate production costing problem with environmental and operational constraints into an optimization problem of LP form. In the process of formulation, auxiliary constraints on which reflect unit loading order are constructed to reduce the size of optimization problem by economic operation rules. As a solution of the optimization problem in LP form, we use Karmarkar's method which performs much faster than simplex method in solving large scale LP problem. The proposed production costing algorithm is applied to IEEE Reliability Test System, and performs production simulation under environmental and operational constraints. Test and computer results are given to show the accuracy and usefulness of the proposed algorithm in the field of power system planning.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.243-250
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• 1998

In this paper, for the fuzzy constraints not only fuzziness of the constraints relation but also uncertainties of the response of the structures, allowable limits of the constraints and structural design variables, etc. are considered,. so that the fuzzy optimization of the structures can involve more wide scope of the problem and the fuzzy optimal problem is more generalized. In the decision making of the structural design scheme, every possible cases of the fuzzy variables, random variables and fuzzy-random variables, etc. for the uncertainties of the optimization problem are all considered, so the most general method of the decision making is presented. And a numerical example for the three bar truss is offered to demonstrate the reliability and execution possibility proposed method in this paper.

• Journal of the Korea Safety Management & Science
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• v.7 no.1
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• pp.159-166
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• 2005

It is not difficult to see the road repairing. There are many and various machines which crush road surface. The efficiency and power of the machine depend on crushing head-shape, crushing interval, crushing load, crushing stress, machine's dropping height and roller's kind. The objective of this study is to select the optimal model among ten models of crushing machine with constraints such as crushing depth, variation, and crushed particle size. And then this paper provides the valid theoretical base on selected model. The data for this study are chosen from the site of construction in Kangnung during three months (2004. 6. 1${\~}$2004. 8. 31). The provided methodology in this paper will be fruitful not only for the selection of crushing machine but also for the aspects of construction period, cost, work efficacy according to the condition from the various sites of construction.

• Steel and Composite Structures
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• v.51 no.2
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• pp.203-223
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• 2024

This study shows functionally graded material structural topology optimization under buckling constraints. The SIMP (Solid Isotropic Material with Penalization) material model is used and a method of moving asymptotes is also employed to update topology design variables. In this study, the quadrilateral element is applied to compute buckling load factors. Instead of artificial density properties, functionally graded materials are newly assigned to distribute optimal topology materials depending on the buckling load factors in a given design domain. Buckling load factor formulations are derived and confirmed by the resistance of functionally graded material properties. However, buckling constraints for functionally graded material topology optimization have not been dealt with in single material. Therefore, this study aims to find the minimum compliance topology optimization and the buckling load factor in designing the structures under buckling constraints and generate the functionally graded material distribution with asymmetric stiffness properties that minimize the compliance. Numerical examples verify the superiority and reliability of the present method.

• Journal of the military operations research society of Korea
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• v.5 no.2
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• pp.73-80
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• 1979

In military applications of equipment, it is of the utmost importance that the equipment operates without breakdown for a specified length of time. We can increase the reliability of a system by adding redundant components to the basic nonredundant system. This study introduces a dynamic programming algorithm of finding optimum redundant design that maximizes the system reliability with constraints.

• Journal of Applied Reliability
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• v.2 no.2
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• pp.113-119
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• 2002

The estimation of mean lifetimes in presence of interval censoring with replacement procedure are examined when the distributions of lifetimes are exponential. It is assumed that, due to physical restrictions and/or economic constraints, the number of failures is investigated only at several inspection times during the lifetime test. The maximum likelihood estimator is found in an implicit form. The Cramer-Rao lower bounds of the estimates are found in places of variances and by simulations the properties of the estimates are examined.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.9 no.14
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• pp.45-48
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• 1986

This paper studies reliability growth model in redundancy allocation of Parallel-series system in which several series system is linked parallelly, The model is generalized by system redundancy of sub-system that have components redundancy. The stage of components in each sub-system is established differently. At the same time by assigned the different number of constraints to the sub-system, this paper deals with rather practical reliability growth model.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.13 no.22
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• pp.25-34
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• 1990

This paper is to maximize the reliability subject to certain constraints on amounts of resources available for control of the parameters. The lagrange multiplier method is used to optimize t-th lognormal stress-lognormal strength problem. This optimization problem can be reduced to a search problem in one variable. A numerical example is presented to illustrate the optimization problem.