• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.04a
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• pp.88-96
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• 1995

Seismic design provisions in Korea has developed based on seismic provisions in United States (e.g., ATC 3-06). Current seismic design provisions in U .S. is moving toward adopting enhanced concept for design. Federal Emergence Management Agency (FEMA) Provides the NEHRP recommended Provisions for the Development of Seismic Regulations for New Buildings which can be used as a source document for use by any interested members of the building community. Current seismic design provisions in U .S. generally use a uni-level force. These provisions can not be satisfied if the limit state design is concerned. Limit state can be defined as a state causing undesirable performance o( a structure (e .g., serviceability, ultimate, buckling, etc.). Even if there are provision for controlling drift by two levels, it is still difficult to satisfy limit states using uni-level force. Architectural Institute of Japan (AIJ) uses a hi-level forces Int seismic loadings which can satisfy serviceability and ultimate limit state. However, the seismic parameters used in AIJ guideline are basically determined by subjective manner of code committee member and professions. These parameters need to be determined based on target quantities (target reliability, target energy dissipation, target displacement, target stress level, etc.). This study develops the method to determine the sesmic design parameters based on a certain taget level. Reliability is used as a target level and load factors in ANSI/ASCE 7-88 are selected as design parameters to be determined.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.567-569
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• 1992

Design sensitivity analysis is proposed for the optimal shape design of three dimensional magnetostatic problems. The direct differentiation method is introduced for design sensitivity analysis and the boundary element method with reduced magnetic scalar potential as the state variable is used to analyze the magnetic characteristics. In the direct differentiation method, the design sensitivity, defined as the total derivative of the objective function with respect to the design variables, is calculated based on the variation of the state variable with respect to the design variable. And the variation of He state variable is calculated by differentiating the both sides of the system matrix equation obtained by applying boundary element method. Through the numerical example with simple electromagnet, the usefullness is proved.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.8
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• pp.850-857
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• 1992

Design sensitivity analysis is proposed for the optimal shape design of three-dimensional magnetostatic problems. The direct differentiation method is introduced for design sensitivity analysis and the boundary element method with reduced magnetic scalar potential as the state variable is used to analyze the magnetic characteristics. In the direct differentiation method, the design sensitivity, defined as the total derivative of the objective function with respect to the design variables, is calculated based on the variation of the state variable with respect to the design variable. And the variation of the state variable is calculated by differetiating the both sides of the system matrix equation obtained by applying boundary element method. Through the numerical example with simple electromagnet, the usefulness is proved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.40-43
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• 2000

A process optimal design methodology applicable to steady-state forming with a strain-hardening material is presented. in this approach the optimal design problem is formulated on the basis of a rigid-viscoplastic finite element process model and a derivative based approach is adopted as an optimization technique The process model the schemes for the evaluation of the design sensitivity considering the effect of strain-hardening and an iterative procedure for design optimization are described. the validity of the proposed approach is demonstrated through application to die shape optimal design in extrusion.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.2
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• pp.102-108
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• 2017

Proper design guides are proposed for a practical dual-active bridge (DAB) converter based on the mathematical model on the steady state. The DAB converter is popular in bidirectional application due to its zero-voltage capability and easy bidirectional operation for seamless control, high efficiency, and performance. Some design considerations are taken to overcome the limitation of the DAB converter. The practical design methodology of power stage is discussed to minimize the conduction and switching losses of the DAB converter. Small-signal model and frequency response are derived and analyzed based on the generalized average method, which considers equivalent series resistance, to improve the dynamics, stability, and reliability with voltage regulation of the practical DAB converter. The design of closed-loop control is discussed by the derived small-signal model to obtain the pertinent gain and phase margin in steady-state operation. Experimental results of a 3.3 kW prototype of DAB converter demonstrate the validity and effectiveness of the proposed methods.

• Journal of the Korean Society of Safety
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• v.29 no.5
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• pp.97-103
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• 2014

To ensure durability and light weight of bridges, high-strength concrete is required for long-span deck slabs. Such a technology eventually extends the life of bridges and improves the economic efficiency. The results of this study suggests a formula for calculating the minimum thickness of long-span deck slabs built with high strength concrete. The minimum thickness is proposed based on the limit states indicated in the CEB-FIP Model Code and the Korean Highway Bridge Design Code(limit state design). The design compressive strength of concrete used for the study is 80MPa. Moreover, the required thickness for satisfying the flexural capacity and limiting deflection is estimated considering the limit state load combination. The formula for minimum thickness of deck slabs is proposed considering the ultimate limit state(ULS) and the serviceability limit state(SLS) of bridges, and by comparing the Korean Highway Bridge Design Code and similar previous studies. According to the research finding, the minimum thickness of long-span deck slab is more influenced by deflection limit than flexural capacity.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.129-136
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• 2005

The deterministic analysis method has generally used to evaluate the slope stability and it evaluates the slope stability with decision value that is a representative value of design variables. However, one of disadvantages in the deterministic approach is there is not able to consider the uncertainty of soil strength properties, even though it is the biggest influential parameter of the slope stability. On the other hand, the limit state design(LSD) can take a consideration of uncertainties and computes both the reliability index and the probability of failure. LSD method is capable of overcoming the disadvantages of deterministic method and evaluating the slope stability more reliably. In this study, both the mean value and standard deviation of the internal land's representative soil strength properties applied to process the LSD method. The major purpose of this study is to gauge the general applicability of the limit state design in soil slope and to weigh the comparative validity of the proposed partial safety factor. In order to reach the aim of this study, the partial safety factor and resistance factor which totally satisfied the slope's overall safety factor were calculated by the load and resistance safety factor design (LRFD).

• 전기의세계
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• v.31 no.1
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• pp.43-49
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• 1982

This paper intends to compare and illustrate the feedback effects of the state feedback scheme to a positional control system by the use of the state observer. As a case study, the dynamic properties of a proposed positional control system lie derived, first, and the design of an optimal state feedback control system by the actual states is intended as a primary case study. For the illustration of the feedback effects with the asymptotic state observer, unobservability of some state variables are assumed and an optimal state feedback design is carried by using the estimated states which is reconstructed through the observer. That is, when some of the states of the system to be controlled are not avalable, an observer is constructed to estimate the unaccessable states. Adigital computer is used for the comparative study of the feedback effects in both cases. The resultant response of the proposed system have shown quite reasonable satisfaction oncontrol quality.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.11 no.1
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• pp.26-31
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• 1975

Mordern Ocean-going ships utilize stabilization techniques in order to minimize the effects of oscillations due to the unwanted disturbances. In this paper, as an elementary design of automatic control system with linear-state vari;tble feedback and series compensator for ship stabilization, analysis and design is limited to the linear time-invariant single input and output system. In order for the Controlled system to meet the requirements of stability, accuracy and transient response, a model of the automatic control system is proposed. For the analysis and design of this model, the state-space method, that is, the mordern way, or an alternative to the transfer function method of describing a linear system that utilize the state variables and state equations, is applied.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.50-56
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• 2000

This paper presents the design of an optimal state feedback controller for container cranes under some design specifications. To do this, the nonlinear equation of a container crane system is linearized and then augmented to eliminate the steady-state error, and some constraints are derived from the design specifications. Designing the controller involves a constrained optimization problem which classical gradient-based methods have difficulties in handling. Therefore, a real-coding genetic algorithm incorporating the penalty strategy is used. The responses of the proposed control system are compared with those of the unconstrained optimal control system to illustrate the efficiency.