• 한국공간구조학회논문집
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• 제20권4호
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• pp.83-91
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• 2020

In this study, a tuned mass damper(TMD) was installed to control the displacement response to earthquakes by generalizing to six analysis models according to the shape of the upper structure based on the case of various large spatial structures around the world. The six analysis models are ribbed type, latticed type, elliptical type, gable type, barrel type, and stadium type composed of 3D arch trusses. In this paper, ribbed type, latticed type and elliptical type were analyzed. The mass of each TMD was set to 1% of the total structural mass. Result of analyzing the optimal number and position of the analysis model, the displacement response control was the most excellent in the model with 6 and 8 TMDs, and the displacement response decreased in most cases. The displacement response control was better with installing the TMD at the edge point than focusing the TMD at the center of the analysis model. However, when 10 or more TMDs are installed or concentrated in the center, large loads intensively act on the structure, resulting in increased displacement. Therefore, although it is slightly different depending on the shape, it is judged that the displacement response control is the best to install 6 and 8 TMDs at the close to the edge point.

• 한국공간구조학회논문집
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• 제20권4호
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• pp.73-81
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• 2020

In this study, a tuned mass damper(TMD) was installed to control the displacement response to earthquakes by generalizing to six analysis models according to the shape of the upper structure based on the case of various large spatial structures around the world. The six analysis models are ribbed type, latticed type, elliptical type, gable type, barrel type, and stadium type composed of 3D arch trusses. In this paper, ribbed type, latticed type and elliptical type were analyzed. The mass of each TMD was set to 1% of the total structural mass. Result of analyzing the optimal number and position of the analysis model, the displacement response control was the most excellent in the model with 6 and 8 TMDs, and the displacement response decreased in most cases. The displacement response control was better with installing the TMD at the edge point than focusing the TMD at the center of the analysis model. However, when 10 or more TMDs are installed or concentrated in the center, large loads intensively act on the structure, resulting in increased displacement. Therefore, although it is slightly different depending on the shape, it is judged that the displacement response control is the best to install 6 and 8 TMDs at the close to the edge point.

• 지구물리와물리탐사
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• 제27권2호
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• pp.108-118
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• 2024

이 논문에서는 타원판의 자력과 자력 변화율 텐서 반응식을 유도하였다. 화성암 관입이나 킴벌라이트 구조 등은 축 대칭성을 가지면서 단면이 타원인 경우가 많다. 타원 단면의 넓이가 변하는 타원 기둥은 타원판의 조합으로 모사할 수 있다. 타원판의 자력 반응은 이전 논문(Rim, 2024)에서 유도한 중력 변화율 텐서에 자화 방향에 대한 정보를 포함시킨 포아송 관계식을 이용하여 유도하였다. 타원판의 자력 변화율 텐서는 벡터 자력을 미분하여 유도하는데 타원판의 인력 퍼텐셜을 각 축방향으로 3회 미분한 총 10개의 삼중 미분 함수를 구하는 것과 동일하다. 미분의 순서는 바꾸는 것이 가능하므로 결과적으로 자력 변화율 텐서는 타원판의 인력 퍼텐셜을 3회 미분한 후, 복소 평면에서 타원판의 경계를 폐곡선으로 하는 경로를 따라 선적분으로 변환하여 유도된다. 이 논문에서 복소 평면에서 선적분으로 유도한 자력 및 자력 변화율 텐서 반응식은 립쉬츠-한켈 적분으로 유도한 원판의 자력 및 자력 변화율 텐서 반응식과 완벽하게 일치함을 보였다.

• Steel and Composite Structures
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• 제29권1호
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• pp.39-51
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• 2018

Position of a circular or elliptical cutout within an orthotropic plate has great influence on its buckling behavior. This paper aims at finding the optimal position (both location and orientation) of a single circular/elliptical cutout, within an orthotropic rectangular plate, that maximizes the critical buckling load. We consider linear buckling of simply supported orthotropic plates under uniaxial edge loads. To obtain the optimal positions of the cutouts, we have employed a MATLAB optimization routine coupled with buckling computation in ANSYS. Our results show that the position of the cutout that maximizes the buckling load has great dependence on the material properties, laminate configurations, and the geometrical parameters of the plate. These optimal results, for a number of plate geometries and cutout sizes, are reported in this paper. These results will be useful in the design of perforated orthotropic plates against buckling failure.

• 한국언어정보학회지:언어와정보
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• 제3권1호
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• pp.21-37
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• 1999

The purpose of this paper is to propose a theory for the interpretation of VP-ellipsis. Although there have been various proposals such as Sag(1976), Williams(1977), Darlymple et al.(1991), there remain many problems, especially with respect to the interpretation of pronouns. Assuming that a coordinate sentence forms a kind of discourse, we propose a theory which consists of two subparts, i. e. a revised HPSG for the syntactic treatment and a so-called 'default-inheritance' mechanism for the interpretation of elliptical parts. By means of this theory, we can explain various elliptical constructions of Fiengo and May(1994), in which pronouns are interpreted ambiguously within the elliptical conjuncts of coordinate sentences according to the related syntactic and the discourse structures.

• Smart Structures and Systems
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• 제10권1호
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• pp.47-65
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• 2012

The presence of crack-like defects in mechanical and structural elements produces failures during their service life that in some cases can be catastrophic. So, the early detection of the fatigue cracks is particularly important because they grow rapidly, with a propagation velocity that increases exponentially, and may lead to long out-of-service periods, heavy damages of machines and severe economic consequences. In this work, a non-destructive method for the detection and identification of elliptical cracks in shafts based on stress wave propagation is proposed. The propagation of a stress wave in a cracked shaft has been numerically analyzed and numerical results have been used to detect and identify the crack through the genetic algorithm optimization method. The results obtained in this work allow the development of an on-line method for damage detection and identification for cracked shaft-like components using an easy and portable dynamic testing device.

• Wind and Structures
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• 제30권5호
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• pp.525-532
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• 2020

This work numerically investigates the effects of Reynolds number Re_D (= 100 - 150), cross-sectional aspect ratio AR = ( 0.25 -1.0), and attack angle α (= 0° - 90°) on the forces, Strouhal number, and wake of an elliptical cylinder, where Re_D is based on the freestream velocity and cylinder cross-section height normal to the freestream flow, AR is the ratio of the minor axis to the major axis of the elliptical cylinder, and α is the angle between the cylinder major axis and the incoming flow. At Re_D = 100, two distinct wake structures are identified, namely 'Steady wake' (pattern I) and 'Karman wake followed by a steady wake (pattern II)' when AR and α are varied in the ranges specified. When Re_D is increased to 150, an additional wake pattern, 'Karman wake followed by secondary wake (pattern III)' materializes. Pattern I is characterized by two steady bubbles forming behind the cylinder. Pattern II features Karman vortex street immediately behind the cylinder, with the vortex street transmuting to two steady shear layers downstream. Inflection angle α_i = 32°, 37.5° and 45° are identified for AR = 0.25, 0.5 and 0.75, respectively, where the wake asymmetry is the greatest. The α_i effectively distinguishes the dependence on α and AR of force and vortex shedding frequency at either Re_D. In Pattern III, the Karman street forming behind the cylinder is modified to a secondary vortex street. At a given AR and α, Re_D = 150 renders higher fluctuating lift and Strouhal number than Re_D = 100.

• Steel and Composite Structures
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• 제42권4호
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• pp.427-446
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• 2022

Cutouts in the beams or plates are often unavoidable due to inspection, maintenance, ventilation, structural aesthetics purpose, and sometimes to lighten the structures. Therefore, there will be a substantial reduction in the strength of the structure due to the introduction of the cutouts. However, these cutouts can be reinforced with the different patterns of ribs (stiffener) to enhance the strength of the structure. The present study highlights the influence of the elliptical cutout reinforced with a different pattern of ribs on the stability performance of such stiffened composite panels subjected to non-uniform edge loads by employing the Finite element (FE) technique. In the present formulation, a 9-noded heterosis element is used to model the skin, and a 3-noded isoparametric beam element is used to simulate the rib that is attached around a cutout in different patterns. The displacement compatibility condition is employed between the plate and stiffener, and arbitrary orientations are taken care by introducing respective transformation matrices. The effect of shear deformation and rotary inertia are incorporated in the formulation. A new mesh configuration is developed to house the attached ribs around an elliptical cutout with different patterns. Initially, a study is performed on the panels with different stiffener schemes for various ply orientations and for different stiffener depth to width ratios (d_s/b_s) to determine an optimal stiffener configuration. Further, various parametric studies are conducted on an obtained optimal stiffened panel to understand the effect of cutout size, cutout orientation, panel aspect ratio, and boundary conditions. Finally, from the analysis, it can be observed that the arrangement of the stiffener attached to a panel has a major impact on the buckling capacity of the stiffened panel. The stiffener's depth to width ratio also significantly influences the buckling characteristic.

• Steel and Composite Structures
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• 제25권3호
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• pp.375-388
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• 2017

This paper presents a combined experimental, numerical, and analytical study on elliptical concrete-filled steel tubular (E-CFT) and rebar-stiffened elliptical concrete-filled steel tubular (RE-CFT) subjected to axial loading. ABAQUS was used to establish 3D finite element (FE) models for the composite columns and the FE results agreed well with the experimental results. It was found that the ultimate load-bearing capacity of RE-CFT stub columns was 20% higher than that of the E-CFT stub columns. Such improvement was attributed to the reinforcement effects from the internal rebar-stiffeners, which effectively enhanced the confinement effect on the core concrete, thereby significantly improved both the ultimate bearing capacity and the ductility of the E-CFT columns. Based on the results, equations were also established in this paper to predict the bearing capacities of E-CFT and RE-CFT stub columns under axial loading. The predicted results agreed well with both experimental and numerical results, and had much higher accuracy than other available methods.

• 대한기계학회논문집A
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• 제27권1호
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• pp.126-137
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• 2003

Many research works have been performed on the J-T approach for elastic-plastic crack-tip stress fields in a variety of plane strain specimens. To generalize the validity of J-T method, further investigations are however needed fur more practical 3D structures than the idealized plane strain specimens. The present study deals mainly with 3D finite element (FE) modeling of welded plate and straight pipe, and accompanying elastic, elastic-plastic FE analyses. Manual 3D modeling is almost prohibitive, since the models contain semi-elliptical interfacial cracks which require singular elements. To overcome this kind of barrier, we develop a program generating the meshes fur semi-elliptical interfacial cracks. We then compare the detailed 3D FE stress fields to those predicted with J-T two parameters. The validity of J-T approach is thereby extended to 3D yield-strength-mismatched weld joints, and useful information is inferred fur the design or assessment of pipe welds.