• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1579-1586
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• 2020

Dissimilar metal joints (DMJs) are more common in the application of piping system of many industries. A 2- D and 3-D finite element analysis (FEA) is carried out on dissimilar metal Single Edged Notch Bending (DMSENB) specimens fabricated from ferritic steel, austenitic steel and Inconel - 182 alloy to study the behavior of DMJs with constraints by using linear elastic fracture mechanics (LEFM) principles. Studies on DMSENB specimens are conducted with respect to (i) dissimilar metal joint width (DMJW) (geometrical constraints) (5 mm, 10 mm, 20 mm, 30 mm and 50 mm) (ii) strength mismatch (material constraints) and (iii) crack lengths (16 mm, 20 mm and 24 mm) to study the DMJ behavior. From the FEA investigation, it is observed that (i) SIF increases with increase of crack length and DMJWs (ii) significant constraint effect (geometry, crack tip and strength mismatch) is observed for DMJWs of 5 mm and 10 mm (iii) stress distribution at the interfaces of DMSENB specimen exhibits clear indication of strength mismatch (iv) 3-D FEA yields realistic behavior (v) constraint effect is found to be significant if DMJW is less than 20 mm and the ratio of specimen length to the DMJW is greater than 7.4.

• Wind and Structures
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• 제5권1호
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• pp.49-60
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• 2002

This paper describes a simple method for evaluating the design wind loads for the structural frames of circular flat roofs with long spans. The dynamic response of several roof models were numerically analyzed in the time domain as well as in the frequency domain by using wind pressure data obtained from a wind tunnel experiment. The instantaneous displacement and bending moment of the roof were computed, and the maximum load effects were evaluated. The results indicate that the wind-induced oscillation of the roof is generally dominated by the first mode and the gust effect factor approach can be applied to the evaluation of the maximum load effects. That is, the design wind load can be represented by the time-averaged wind pressure multiplied by the gust effect factor for the first mode. Based on the experimental results for the first modal force, an empirical formula for the gust effect factor is provided as a function of the geometric and structural parameters of the roof and the turbulence intensity of the approach flow. The equivalent design pressure coefficients, which reproduce the maximum load effects, are also discussed. A simplified model of the pressure coefficient distribution is presented.

• 한국보육지원학회지
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• 제14권1호
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• pp.167-186
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• 2018

Objective: The purpose of this study was to explore the structural analysis of the relationships among principals and fellow teacher's emotional support, teacher's active motivation for choosing the teaching profession, self-leadership, and child care efficacy and commitment. Methods: Data were collected from 465 child care teachers and analyzed by means of structural equational modeling(SEM). Results: First, principals and fellow teacher' emotional support was found to have a direct effect on teacher's child care commitment, as well as an indirect effect through teacher's self-leadership. Second, teacher's active motivation for choosing the teaching profession was found to have a direct effect on teacher's child care commitment, as well as an indirect effect through self-leadership and child care efficacy. Third, teacher's self-leadership was found to have a direct effect on teacher's child care commitment, as well as an indirect effect through child care efficacy. Fourth, teacher's child care efficacy was to found have a direct effect on teacher's child care commitment. Conclusion: These results suggest the need for a great deal of utility to improve teacher's child care commitment.

• Structural Engineering and Mechanics
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• 제33권2호
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• pp.113-136
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• 2009

The seismic induced interaction between multistory structures with unequal story heights (inter-story pounding) is studied taking into account the local response of the exterior beam-column joints. Although several parameters that influence the structural pounding have been studied sofar, the role of the joints local inelastic behaviour has not been yet investigated in the literature as key parameter for the pounding problem. Moreover, the influence of the infill panels as an additional parameter for the local damage effect of the joints on the inter-story pounding phenomenon is examined. Thirty six interaction cases between a multistory frame structure and an adjacent shorter and stiffer structure are studied for two different seismic excitations. The results are focused: (a) on the local response of the critical external column of the multistory structure that suffers the hit from the slab of the adjacent shorter structure, and (b) on the local response of the exterior beam-column joints of the multistory structure. Results of this investigation demonstrate that the possible local inelastic response of the exterior joints may be in some cases beneficial for the seismic behaviour of the critical column that suffers the impact. However, in all the examined cases the developing demands for deformation of the exterior joints are substantially increased and severe damages can be observed due to the pounding effect. The presence of the masonry infill panels has also been proved as an important parameter for the response of the exterior beam-column joints and thus for the safety of the building. Nevertheless, in all the examined inter-story pounding cases the presence of the infills was not enough for the total amelioration of the excessive demands for shear and ductility of the column that suffers the impact.

• 산업융합연구
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• 제20권2호
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• pp.21-27
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• 2022

본 연구목적은 일반고 학생들의 자기주도 학습, 온라인 수업 환경, 그리고 학습만족도 간의 구조관계를 탐색하는 것이다. 연구 대상은 세종 B고교 3학년의 219명이며, 상관관계와 구조방정식 모형을 분석했다. 연구결과는 다음과 같다, 첫째, 자기주도 학습과 온라인 수업 환경 및 학습만족도 간에는 중간 이상의 상관관계를 있었다. 둘째로, 측정변인들 간의 구조모형의 적합도 지수도 양호했다. 자기주도 학습은 온라인 수업 환경에 영향을 주고, 온라인 수업환경은 학습만족도에 정적으로 영향을 주지만, 자기주도 학습은 학습만족도에 유의한 영향력은 없었다. 본 연구의 시사점은 학습자의 온라인 수업만족도는 학생의 자기주도 학습능력이 교사의 훌륭한 수업환경의 조성이 이루어질 때 시너지 효과를 얻음을 알 수 있다. 추후 온라인 학습만족도에 대하여 다양한 학습자의 개인, 가정 및 학교요소를 종합적으로 투입하는 분석할 것을 제안했다.

• Earthquakes and Structures
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• 제14권3호
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• pp.229-239
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• 2018

Under strong ground motion, pounding can be caused because of the different dynamic properties between two adjacent buildings. Using different structural systems in two adjacent structures makes a difference in the lateral stiffness and thus changes the pounding force between them. In this paper, the effect of the structural system of adjacent buildings on the amount of force applied by pounding effects has been investigated. Moment resisting frame systems (MRFs), lateral X-bracing system (LBS), shear wall system (SWS) and dual system (DS) have been investigated. Four different cases has been modelled using finite element (FE) method. The number of stories of the two adjacent buildings is different in each case: case 1 with 6 and 4 stories, case 2 with 9 and 6 stories, case 3 with 15 and 6 stories and case 4 with 10 and 10 stories. The structures have been modelled three-dimensionally. Non-linear time history analysis has been done on the structures using the finite element software SAP2000. In order to model pounding effects, the non-linear gap elements have been used.

• 소성∙가공
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• 제32권3호
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• pp.129-135
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• 2023

The use of engineering plastic products in internal combustion engine and electric cars to improve stiffness and reduce weight is increasing significantly. Among various lightweight materials, engineering plastics have significant advantages such as cost reduction, improved productivity, and weight reduction. In particular, engineering plastics containing glass fibers are used to enhance stiffness. However, the stiffness of glass fibers can increase or decrease depending on their orientation. Before developing plastic products, optimal designs are determined through injection molding and structural analysis to enhance product reliability. However, reliable analysis of products with variable stiffnesses caused by anisotropy cannot be achieved via the conventional isotropic structural analysis, which does not consider anisotropy. Therefore, based on the previously reported study "the Effect of Impacted Fracture in Glass Fiber Orientation with Injection Molding & Structural Coupled Analysis," this study aims to investigate the structural analysis and degradation mechanisms of various polymers. In particular, this study elucidates the actual mechanism of plastic fracture by analyzing various fracture conditions and their corresponding simulations. Furthermore, the objective of this study is to apply the injection molding and structural coupled analysis mechanism to develop engineering plastic products containing glass fibers. In addition, the study aims to apply and improve the plastic fracture mechanism in actual products by exploring anisotropy and stiffness reduction owing to the unfilled polymer weld line.

• 인터넷정보학회논문지
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• 제15권6호
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• pp.77-84
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• 2014

본 연구는 대학에서 이러닝을 활용 수업의 효과에 영향을 미치는 요인들을 탐색하고 요인들 간의 인과관계를 파악하고자 하였다. 이를 위해 2013년 2학기를 기준으로 이러닝 기반의 수업인 사이버 강의에 참여한 학생들 2,091명 중 유효했던 1,732명을 연구 대상으로 하였다. 연구방법은 확인적 요인분석과 구조방정식모형 분석을 활용하였다. 확인적 요인분석을 통해 이러닝 학습효과, 컨텐츠만족요인, 시스템기능요인, 운영지원요인의 네 개의 잠재변인을 도출할 수 있었다. 이들 잠재변인들 간의 구조방정식 모델 분석을 통한 결과는 다음과 같다. 첫째, 이러닝 학습효과와 관련된 주요 요인으로 컨텐츠 요인, 기능요인, 운영지원 요인으로 구분할 수 있었다. 둘째, 이러닝 학습효과에는 운영지원, 컨텐츠 요인이 직접적 영향을 미치는 것으로 나타났다. 하지만 기능요인은 유의하지 않은 것으로 나타났다. 셋째, 컨텐츠 요인에는 기능 및 운영요인이 유의한 영향을 미치는 것으로 나타났다. 넷째, 기능요인 및 운영지원요인은 컨텐츠 요인을 매개로하여 이러닝 학습효과에 간접적 영향을 미치는 것으로 나타났다.

• Smart Structures and Systems
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• 제3권3호
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• pp.341-356
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• 2007

A good understanding of normal modal variability of civil structures due to varying environmental conditions such as temperature and wind is important for reliable performance of vibration-based damage detection methods. This paper addresses the quantification of wind-induced modal variability of a cable-stayed bridge making use of one-year monitoring data. In order to discriminate the wind-induced modal variability from the temperature-induced modal variability, the one-year monitoring data are divided into two sets: the first set includes the data obtained under weak wind conditions (hourly-average wind speed less than 2 m/s) during all four seasons, and the second set includes the data obtained under both weak and strong (typhoon) wind conditions during the summer only. The measured modal frequencies and temperatures of the bridge obtained from the first set of data are used to formulate temperature-frequency correlation models by means of artificial neural network technique. Before the second set of data is utilized to quantify the wind-induced modal variability, the effect of temperature on the measured modal frequencies is first eliminated by normalizing these modal frequencies to a reference temperature with the use of the temperature-frequency correlation models. Then the wind-induced modal variability is quantitatively evaluated by correlating the normalized modal frequencies for each mode with the wind speed measurement data. It is revealed that in contrast to the dependence of modal frequencies on temperature, there is no explicit correlation between the modal frequencies and wind intensity. For most of the measured modes, the modal frequencies exhibit a slightly increasing trend with the increase of wind speed in statistical sense. The relative variation of the modal frequencies arising from wind effect (with the maximum hourly-average wind speed up to 17.6 m/s) is estimated to range from 1.61% to 7.87% for the measured 8 modes of the bridge, being notably less than the modal variability caused by temperature effect.

• 대한건축학회논문집:구조계
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• 제35권4호
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• pp.167-174
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• 2019

Cable-stayed structures provide a lot of possibilities toward the development of innovative structural forms regarding their expressiveness and uniqueness. Such cable-stayed structures, as form-active structures, can obtain a family of alternatives by changing parameters for defining geometric shapes. The concept of graphic statics is utilized to explain the relationship between the load path and structural forms because the load path of cable structures has something to do with their structural geometry. Moreover, this structural geometry has a dominant effect on both structural efficiency and structural elegancy. The proposed design method in this study will help designers conceive innovative structural forms considering structural safety, material efficiency, and structural art altogether.