• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.1-1
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• 2000

본 논문에서는 3축이 연성되어 비선형 운동 방정식으로 표현되는 3축 안정화 인공위성 시스뎀에 입릭외란과 시스템의 불확실성이 존재할 경우에도 자제 정밀도를 유지하는 제어기를 설계한다. 비선헝 운동 방정식으로 표현되는 운동 방정식을 선형화하고 PID제어기를 구성하였다 선형화에 의한 시스템의 불확실성과 입력 외란을 신경회로망으로 추정하여 외란의 엉향을 제거하도록 구성된 PR제어기의 제어입력을 수정한다 수정된 제어입력은 외란을 상쇠시켜 시스템 출력에서 외란의 효과를 제거하게 된다. 신경회로망은 제어입력과 시스템 출력, 기준 운동 방정식간의 관계를 이용하여 외간과 시스템의 불확실성을 추정하며, 역전파 알고리즘을 사용한 학습 알고리즘으로 신경 회로망을 교육한다. 제안된 신경회로망을 이용한 외란 제거 제어기는 시뮬레이션을 통하여 자세 정밀도의 향상을 검증한다

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.88-95
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• 2009

Input shaping has been a very effective control method for reducing payload swing in industrial bridge and gantry cranes. However, conventional input shapers often degrade performance when applied to tower cranes because of the nonlinear coupled dynamics between rotational and radial motions in tower cranes. To alleviate this problem, a new input shaper for tower cranes is developed by means of dynamic modeling, analysis and optimization. This work investigates the tower crane dynamics along with parameters of the tower crane varied. A performance index for input shaper design is proposed so as to reduce the coupled residual vibration of a tower crane using only rotational motion of tower crane. The proposed new input shaper is verified to be effective through simulations and experiments.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.349-357
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• 2019

Finite element method (FEM) is utilized in the development of products to realistically analyze and predict the mechanical behavior of materials in various fields. However, the approach based on the numerical analysis of glass fiber reinforced plastic (GFRP) composites, for which the fiber orientation and strain rate affect the mechanical properties, has proven to be challenging. The purpose of this study is to define and evaluate the mechanical properties of glass fiber reinforced plastic composites using the numerical analysis models of Digimat, a linear, nonlinear multi-scale modeling program for various composite materials such as polymers, rubber, metal, etc. In addition, the aim is to predict the behavior of realistic polymeric composites. In this regard, the tensile properties according to the fiber orientation and strain rate of polybutylene terephthalate (PBT) with short fiber weight fractions of 30wt% among various polymers were investigated using references. Information on the fiber orientation was calculated based on injection analysis using Moldflow software, and was utilized in the finite element model for tensile specimens via a mapping process. LS-Dyna, an explicit commercial finite element code, was used for coupled analysis using Digimat to study the tensile properties of composites according to the fiber orientation and strain rate of glass fibers. In addition, the drawbacks and advantages of LS-DYNA's various anisotropic material models were compared and evaluated for the analysis of glass fiber reinforced plastic composites.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.5
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• pp.75-83
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• 2003

The ultimate goal of this research is to improve highway system performance in earthquakes by evaluating the effectiveness of retrofitting bridges with column jacketing. The objective of the study is to determine if steel jacketing increases the ductility capacity of bridge columns and hence improves the fragility characteristics of the bridge. Analytical fragility curves are used to adjust the empirical fragility curves obtained for the unretrofitted bridges using seismic damage data collected following past earthquakes. The adjustment was carried out by increasing the median values of the empirical curves through comparison with the median values of the corresponding fragility curves obtained analytically, both before and after being retrofit.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.389-398
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• 2010

The flexural strength of composite HSB I-girders under a positive moment was investigated using the moment-curvature analysis method to evaluate the applicability of the current AASHTO LRFD design specifications to such girders. A total of 2,391 composite I-girder sections that satisfied the section proportion limits of the AASHTO LRFD specifications was generated by the random sampling technique to consider a wide range of section properties. The flexural capacities of the sections were calculated inthe nonlinear moment-curvature analysis in which the HSB600 and HSB800 steels were modeled as an elasto-plastic strain-hardening material, and the concrete, as a CEB-FIP model. The effects of the ductility ratio and the compressive strength of the concrete slab on the flexural strength of the composite girders made of HSB and SM520-TMC steels were analyzed. The numerical results indicated that the current AASHTO LRFD equation can be used to calculate the flexural strength of composite girders made of HSB600 steel. In contrast, the current AASHTO LRFD equation was found to be non-conservative in its prediction of the flexural strength of composite HSB800 girders. Based on the numerical results of this study for 2,391 girders, a new design equation for the flexural strength of composite HSB800 girders in a positive moment was proposed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.5
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• pp.473-480
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• 2011

Recently, the resizing algorithms based on the displacement participation factors have been developed for sizing members to satisfy stiffness criteria. It is proved that this resizing algorithms made for utilizing worker's stiffness design are practical and rational due to the simplicity and convenience of the method. The resizing algorithm can be practically and effectively applied to drift design of buildings. However, the researches on the change of inelastic behavior by the resizing algorithm has been insufficient. To identify the effect on the inelastic behavior of buildings by the resizing method, this study used the reinforced concrete shear wall-frame example. Through the application of the resizing method, the weights of shear wall in the lower class and the weights of columns and beams in the upper class increased respectively. And the initial stiffness of the building increased and the ductility of the buildings had similar with that of the initial structure.

• Journal of Korean Association for Spatial Structures
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• v.10 no.4
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• pp.49-57
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• 2010

This study is the research appling the representative Displacement-Based Design which is the basic concept of Direct Displacement Based Design proposed by Chopra and Goel to original Reinforced Concrete structure and determining the thickness of retrofit Steel Jacket about the Maximum design ground acceleration, and developing the more improved Algorithm as well as program by the Retrofit Design method and Nonlinear analysis by the Performance design method before and after reinforcement appling the determined retrofit thickness. To predict the target displacement of retrofitted columns, a nonlinear analysis model of reinforced concrete columns has been developed to be based on the nonlinear fiber cross-sectional and segmental analysis model, and the seismic displacement level of retrofitted columns is estimated by two procedures, the direct displacement-based design method and the displacement coefficient method. In examples of seismic retrofit design, the current seismic improved design method gives good results in improvements of displacement levels and displacement ductilities of retrofitted columns.

• Journal of Korean Society of Steel Construction
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• v.21 no.2
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• pp.105-113
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• 2009

To improve braced frame performance, the connection strength, stiffness, and ductility must be directly considered in the frame design. The resistance of the connection must be designed to resist seismic loads and to help provide the required system ductility. In addition, the connection stiffness affects the dynamic response and the deformation demands on the structural members and connections. In this paper, current design models for gusset plate connections are reviewed and evaluated usingthe results of past experiments. Current models are still not sufficient to provide adequate connection design guidelines and the actual stress and strain states in the gusset plate are very nonlinear and highly complex. Design engineers want simple models with beam and column elements to make an approximate estimation of system and connection performance. The simplified design models are developed and evaluated to predict connection stiffness and system behavior. These models produce reasonably accurate and reliable estimation of connection stiffness.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.385-395
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• 2011

The flexural strength of composite HSB hybrid I-girders under positive moment is investigated by the moment-curvature analysis method to evaluate the applicability of the current AASHTO LRFD design specification to such girders. The hybrid girders are assumed to have the top flange and the web fabricated from HSB600 steel and the bottom flange made of HSB800 steel. More than 6,200-composite I-girder sections that satisfy the section proportion limits of AASHTOL RFD specifications are generatedby the random sampling technique to consider a statistically meaningful wide range of section properties. The flexural capacities of the sections are calculated by the nonlinear moment-curvature analysis in which the HSB600 and HSB800 steels are modeled as an elastoplastic, strain-hardening material and the concrete as CEB-FIP model. The effects of ductility ratio and compressive strength of concrete slab on the flexural strength of composite hybrid girders make of HSB steels are analyzed. Numerical results indicated that the current AASHTO-LRFD equation can be used to calculate the flexural strength of composite hybrid girders fabricated from HSB steel.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.989-1000
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• 2002

As advanced earthquake design methods using nonlinear static analysis are developed, it is required to estimate precisely the cyclic behavior of reinforced concrete members that is characterized by strength, deformability, and energy dissipation. In a recent study, a simplified method which can estimate accurately the energy dissipation capacity of flexure-dominated RC members subjected to repeated cyclic load was developed. Based on the previously developed method, in the present study, simple equations that can be used for calculating the energy dissipation capacity were derived and verified by the comparison with experimental results. Through parametric study using the proposed equations, effects of axial load, reinforcement ratio, rebar arrangement, md ductility on the dissipated energy were investigated. The proposed equations can accurately estimate the energy dissipation capacity compared with the existing empirical equations, and therefore they will be useful for the nonlinear static analysis/design methods.