• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.2
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• pp.86-93
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• 2007

This paper proposes two fast calculation methods of ATC. These two methods evaluate ATC with thermal constraints(Thermal ATC) and ATC with voltage stability constraints(Voltage ATC) respectively. The ATC with thermal constraints was based on the linear incremental power flow to account for the line flow thermal loading effects when the n-1 security constraints were included. The ATC with voltage stability constraints used two-bus equivalents of the system to find the maximum load at a load bus before reaching the voltage stability problem. The methods were tested on the IEEE 30bus systems and the results obtained were compared with those found by some other methods.

• Structural Engineering and Mechanics
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• v.71 no.3
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• pp.233-244
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• 2019

Steel jacketing technique is a retrofitting method often employed for static and seismic strengthening of existing reinforced concrete columns. When no continuity is given to angle chords as they cross the floor, the jacket is considered "indirectly loaded", which means that the load acting on the column is transferred partially to the external jacket through interface shear stresses. The evaluation of load transfer mechanism between core and jacket is not straightforward to be modeled, due to the absence of knowledge of a proper constitutive law of the concrete-to-steel interface and to the difficulties in taking into account the mechanical nonlinearities of materials. This paper presents an incremental analytical/numerical approach for evaluating the compressive response of RC columns strengthened with indirectly loaded jackets. The approach allows calculating shear stresses at the interface between core and jacket and predicting the axial capacity of retrofitted columns. A proper constitutive law is proposed for modelling the interaction between the steel and the concrete. Based on plasticity rules and the non-linear behaviour of materials, the column is divided into portions. After a detailed parametric analysis, comparisons are finally made by theoretical predictions and experimental results available in the literature, showing a good agreement.

• Earthquakes and Structures
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• v.23 no.1
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• pp.13-21
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• 2022

Masonry constructions exhibit uncertain behaviors under dynamic effects such as seismic action. Complex issues arise in the idealization of structural systems of buildings having different material types and mechanical properties. In this study, the structural behavior of a vaulted masonry building constructed using full clay brick and lime-based mortar and sitting on consecutive arches was investigated by experimental and numerical approaches. The dimensions of the structure built in the laboratory were 391 × 196 cm, and its height was 234 cm. An incremental repetitive loading was applied to the prototype construction model. Along the gradually increasing loading pattern, the load-displacement curves of the masonry structure were obtained with the assistance of eight linear displacement transducers. In addition, crack formation areas, and relevant causes of its formation were determined. The experimental model was idealized using the finite element method, and numerical analyses were performed for the area considered as linear being under similar loading effect. From the linear analyses, the displacement values and stress distribution of the numerical model were obtained. In addition, the effects of tie members, frequently being used in the supports of curved load-bearing elements, on the structural behavior were examined. Consequently, the experimental and numerical analysis results were comparatively evaluated.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.75-82
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• 2004

Many researcher's efforts have made a significant advancement of space frame structure with various portion, and it becomes the most outsanding one of space structures. However, with the characteristics of thin and long term of spacing, the unstable behavior of space structure is shown by initial imperfection, erection procedure or joint, especially space frame structure represents more. This kind of unstable problem could not be set up clearly and there is a huge difference between theory and experiment. Moreover, the discrete structure such as space frame has more complex solution, this it is not easy to derive the formulation of design about space structure. In this space frame structure, the character of rise-span ratio or load mode is represented by the instability of space frame structure with initial imperfection, and snap-through or bifurcation might be the main phenomenon. Therefore, in this study, space frame structure which has a lot of aesthetic effect and profitable for large space covering single layer is dealt. And because that the unstable behavior due to variation of inner force resistance in the elastic range is very important collapse mechanism, I would like to investigate unstable character as a nonlinear behavior with a geometric nonlinear. In order to study the instability. I derive tangent stiffness matrix using finite element method and with displacement incremental method perform nonlinear analysis of unit space structure, star dome and 3-ring star dome considering rise-span $ratio(\mu}$ and load $ratio(R_L)$ for analyzing unstable phenomenon.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.129-132
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• 2001

Fiber waviness is one of manufacturing defects encountered frequently in thick composite structures. It affects significantly on the behavior as well as strength of thick composites. The effects of fiber waviness on tensile/compressive nonlinear elastic behavior and strength of thick composite with fiber waviness are studied theoretically and experimentally. FEA(Finite Element Analysis) models are proposed to predict tensile/compressive nonlinear behavior and strength of thick composites. In the FEA models, both material and geometric nonlinearities were incorporated into the model using energy density, iterative mapping and incremental method. Also Tsai-Wu criteria was adopted to predict the strength of thick composites with fiber waviness. Tensile and compressive tests were conducted on the specimens with uniform fiber waviness. It was observed that the degree of fiber waviness in composites significantly affected the nonlinear behavior and strength of the composites

• Journal of Welding and Joining
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• v.10 no.1
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• pp.35-42
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• 1992

In this study, the stress concentration phenomenon for the dissimilar joints(ceramic-metal) bonded by thermal treating using a soft-insert metal(copper) was investigated with the aid of FEM(finite element method) under the load condition of uniform tension. The analysis was carried out by the supposing that stress states are plane stress or plane strain and elastic or elastic-plastic. And the Von Mises yield criterion and the incremental theory as plastic flow were adopted in this analysis. As the summarized results obtained, the stress concentration phenomenon was severer as the soft insert metal was thicker, in plane strain than in plane stress and in elastic-plastic state than in elastic state. Furthermore, the inducing mechanism of stress concentration was well expressed by the constraint forces(Fc) generated between the soft and the hard material.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.224-231
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• 1993

This paper is concerned with the influence of changes in stochastic parameters of the important resistance variables such as the strength modelling parameter and material and geometric properties, on the system safety level of TLP structures. The effect of parameters governing the post-ultimate behaviour is also addressed. An extended incremental load method is employed for the present study, which has been successfully applied to the system reliability analysis of continuous structures. The Hutton Field TLP and its one variant called herein TLP-B, are chosen as TLP models in this paper. The results of several parameteric studies lead to useful conclusions relating to the importance of reducing uncertainties in strength formulae and relating the importance of component post-ultimate behaviour to the systems reliability of such structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.45-52
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• 2003

A finite element procedure to estimate ultimate strength of space frames considering spread of plasticity is presented. The improved displacement field is introduced based on inclusion of second order terms of finite rotations. All the nonlinear terms due to bending and torsional moment as well as axial force are precisely considered. The concept of plastic hinge is introduced and the incremental load/displacement method is applied for the elasto-plastic analysis. The initial yield surface is defined based on the residual stress and the full plastification surface is considered under the combined action of axial force, bending and torsional moments. The elasto-plastic stiffness matrices are derived using the flow rule and the normality condition of the limit function. Finite element solutions for ultimate strength of space frames are compared with available solutions and experimental results.

• Journal of Surface Science and Engineering
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• v.28 no.6
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• pp.343-351
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• 1995

Titanium nitride films have been prepared on various substrates (silicon wafer, HSS) by cathode arc ion plating process to measure microhardness, adhesion and wear-resistant behaviors by changing the substrate bias voltages (0∼-300V), thickness and roughness. Microhardnesses were measured by micro vickers hardness tester, the adhesion strengths were evaluated by acoustic signals through the scratch test with incremental applied load. As the substrate bias voltages were increased, the ｛111｝ orientation was predominant, the microhardnesses and adhesion strengths of tool steel were observed to be stronger than those of without subatrate bias voltage. Adhesion strengths of the substrate bias were 4-7 times higher than those of without the substrate bias, confirmed by SEM with EDX. Wear resistances were used pin-on-disk tribotester and TiN costing reduced the abrasive wear. As the substrate bias was increased, the weight loss and the friction coefficient was decreased.

• Journal of Korean Society of Steel Construction
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• v.8 no.4 s.29
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• pp.31-42
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• 1996

본 연구에서는 박벽 구조물의 기하학적 비선형 해석을 수행하기 위하여 개선된 하중 및 변위 증분의 조합법이 제시되었다. 제안된 알고리즘은 기존의 하중 및 변 변위 증분의 조합법 이 고정된 증분량을 갖는 점을 개선하여, 수렴정도에 따라 증분량을 변화시킴으로써, 여러개의 임계점을 갖는 비선형 거동을 보다 효율적으로 추적하도록 하였다. 또한 하중 및 변위 증분법을 전환점을 첫 단계의 기울기에 비례한 값으로 대체함으로써 사용자의 편리를 도모하였다. 트러스, 공간 뼈대, 아치, 쉘 구조물 등의 기하학적 비선형 해석 예제를 통하여, 본 연구에서 제시한 개선된 하중 및 변위 증분의 조합법의 적용성을 입증하였다.