• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.64-67
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• 2004

In recent years, the use of FRP composites to repair and strengthen existing reinforced concrete (RC) structures has been widely used. When the columns of existing RC structures are wrapped with FRP composites, the core concrete of such columns is confined not only by the FRP composites but also by the existing steel reinforcing ties (or spirals). Therefore, it is necessary to understand correctly the compressive response of concrete confined with both steel spirals and FRP composites in order to predict the behavior of such RC columns. This paper proposes a model to predict the compressive stress-strain curves of concrete confined with FRP and steel reinforcing ties.

• Computers and Concrete
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• 제10권6호
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• pp.575-586
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• 2012

In the present paper the problem of monotonically compressed concrete columns is studied numerically, accounting for transverse steel reinforcement and concrete cracking. The positive confinement effect of the ties on the core concrete is modeled explicitly and studied in the case of distributed or concentrated vertical load. The main aim is to investigate the influence of transverse reinforcement steel characteristics on the column load carrying capacity and ductility, in order to provide an evaluation about some standards requirements about the class and ductility of steel to be used for ties. The obtained results show that the influence of transverse reinforcement steel class of ductility is negligible both on the column load carrying capacity and on its ductility. Also the dissipated energy is basically unchanged. In view of these evidences, some standards requirements about the steel class of ductility to be used for ties appear to be rather questionable.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.561-568
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• 1997

Conventional confinement reinforcement for rectangular columns consist of closely spaced perimeter hoops, overlapping hoops, and crossties. One of the potential alternatives to conventional reinforcement is a welded reinforcement grid, prefabricated to required size and volumetric ratio of transverse reinforcement. An experimental investigation was carried out to investigate the strength and deformability of reinforced concrete columns confined with welded reinforcement grids. The comparisons of the envelopes of experimental force-displacement hysteric relationships for columns confined by welded grids with analytically generated force-displacement curves for columns confined with conventional ties. In general, inelastic deformability beyond the peak, as indicate by the slope of the cuvers, was similar to those indicated by columns with conventional ties. The superior performance of columns with welded grids may be attributed to the improved confinement characteristics of grids associated with increased rigidity of welded ties.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 가을 학술발표회 논문집
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• pp.57-62
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• 1990

This paper is to study the effect of rectilinear confinement in high-strength concrete subjected to a monotonically increasing compressive axial loads. To investigate behavior of columns rectilinearly confined with lateral ties and longitudinal rebars, twelve specimens including two plain concrete specimens were tested. The main variables in this study are volumetric ratio of lateral ties, cistribution of lateral ties, yield strength of logitudinal steel, ratio of area of longitudinal steel to the area of cross section. The test results were not only compared with an empirical model for the stress-strain curve of rectilinearly confined high-strength concrete but also the existing model. The empirical model used calculating column capacity shows better agreement with the test results tham the existing model.

• 한국구조물진단유지관리공학회 논문집
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• 제3권1호
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• pp.137-146
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• 1999

Analysis of R/C columns requires modeling of the plastic hinge region, as well as nonlinear material characteristics. This becomes a challenging task in view of the nonlinearity of both steel and concrete. Furthermore, formation and progression of plasticity in the hinge is a difficult phenomenan to simulate, especially under reversed cyclic loading and decaying strength conditions. This research provide one analytical model employed in column analysis, including the analysis procedure for establishing inelastic force-deformation relationships. The analytical results show good correlation with experimental data. The employed procedure with the adopted analytical models can be used to compute inelastic displacements of concrete columns with welded reinforcement grids. The inelastic deformability beyond the peak was similar to those indicated by columns with conventional ties. The superior performance of columns with welded grids may be attributed to the improved confinement characteristics of grids associated with increased rigidity of welded ties.

• International Journal of Contents
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• 제15권2호
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• pp.29-37
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• 2019

This study investigates how adolescents' smartphone attachment, social anxiety, and offline and smartphone network sizes are related to their friendship in regards to maintaining either a strong or weak bond. Based on an online survey involving 402 adolescent smartphone users in South Korea, this study found that smartphone attachment was positively related to a strong ties friendship maintenance and negatively related to weak ties friendships. Similarly, social anxiety was found to be negatively associated with friendship maintenance for both strong and weak - tie relationships. More importantly, this study revealed that the types and size of social networks moderated the relationships among adolescents with smartphone attachment, social anxiety, and friendship maintenance through smartphones.

• 산경연구논집
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• 제8권6호
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• pp.97-109
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• 2017

Purpose - This study aimed to investigate the effect of entrepreneurial temperament (ET) such as innovativeness, risk-taking, and proactiveness in entrepreneur's lifetime before start-up and the effect of social capital (SC) such as network ties and trustworthiness on entrepreneurial intention. Research design, data, and methodology - We examined the components of ET (innovativeness, risk-taking, and proactiveness) and components of SC (network ties and trustworthiness) through existing prior research and investigated the factors that affected entrepreneurial intention. The first hypothesis of this study was that entrepreneurial temperament will have a significant impact on network ties of social capital, and the second hypothesis assumed that entrepreneurial temperament will have a significant effect on the trustworthiness of social capital. Finally, the second hypothesis assumed that social capital will have a significant impact on entrepreneurial intentions. We collected 175 data using questionnaires for people who have not yet started a start-up. And we used the Structure Equation Modeling (SEM) to evaluate the collected data and to test the research model by the two step research procedure. Results - As a result, the innovativeness and proactiveness of ET have a significant effect on network ties and trustworthiness of SC, but the effect of risk-taking on risk-taking of SC is not significant. On the other hand, network ties and network ties of SC was revealed a significant effect on the EI. Conclusions - The implications of this article could be observed as mentioned in this paper. First, we found that entrepreneurial innovativeness and proactiveness are helpful in constructing SCs, but not risk-taking. These results demonstrated that ET of entrepreneurs is important factor in the formation of social capital. Second, the SC that an entrepreneur built before the start-up has a meaning for EI. In conclusion, ET was affected partially to EI mediated SC. It is academic in that ET and SC are independent from each other and have a mediating role between ET and EI, unlike those directly affecting EI. Although some important implications were found in this study, this study had some limitations and we hope that future research will be complemented.

• 콘크리트학회논문집
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• 제13권3호
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• pp.261-267
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• 2001

본 연구는 고축력을 받는 고강도 콘크리트 기둥부재의 연성을 확보하기 위한 띠철근 양 산정시 띠철근 강도가 연성에 미치는 영향이 현저하게 나타나기 시작하는 축력비 및 연성과 주근의 관계를 파악하기 위한 실험적 연구이다 본 연구의 목적을 이루기 위해 띠철근 항복강도, 축력비, 주근 양 및 배치형태 등을 주요 변수로 하여 총 12개의 시험체를 제작하였다. 시험체의 크기는 20$\times$20$\times$80 cm이며 실험구간은 중앙부 40 cm 이다. 실험결과 띠철근의 항복강도가 연성에 영향을 현저히 미치기 시작하는 축력비는 0.4 $f_{ck}$ $A_{g}$이었으며 현 ACI318-99 내진기준에 따라 띠철근 양을 산정할 때 저축력하에서 고강도 띠철근을 사용할 경우 띠철근 간격이 크고 띠철근 강도의 영향이 미비하여 부재는 취성적인 거동을 보일 위험이 있다. 고축력하에서 고강도 띠철근은 주근의 좌굴억제에도 상당히 효율적이었다. 특히 0.4 $f_{ck}$ $A_{g}$이상의 고축력하에서 고강도 띠철근이 응력을 충분히 발휘하기 위해서는 띠철근 체적비 및 배근형태, 주근의 배치형태, 축력비 등을 함께 고려하여야 할 것이라고 사료된다.다.

• Journal of Electrical Engineering and Technology
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• 제2권3호
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• pp.342-345
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• 2007

This paper presents an engineering approach to derive the optimum price levels of transacted power. In this paper, with the assumption that power import is possible through the system connection in Northeast Asia regions, the upper price limit of imported power deserving economic efficiency was derived with respect to the time and amount of power import. The proposed approach was demonstrated based on the data from the National Power Development Planning in 2004 with the WASP model.

• 한국의류학회지
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• 제33권7호
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• pp.1025-1037
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• 2009

This study- 1) identifies the distribution of customer equity in luxury brands, 2) identifies customer equity dimensions of luxury brands, 3) identifies the properties that influence the customer equity of a luxury brand, and 4) compares the differences in the properties of the luxury brands that influence customer equity by brand type and relationship duration. In this research, the survey method was conducted in Seoul and 500 responses were used for analysis. For the data analysis, descriptive statistics (i.e. frequency and percentage), t-test, factor analysis, and multiple-regression analysis were used through the utilization of the SPSS 12.0 program. The results of this study are as follows: First, the distribution of customer equity are found to be 50.8% of the customer equity distributes under 1 million Korean won and 34.8% between 1 million won and 3 million won. Second, the luxury brand dimension consists of 6 factors, 'differentiated brand image', 'personal ties', 'qualitative trust relation', 'rational price value', 'store value', and 'convenience value'. Third, the higher 'differentiated brand image', 'personal ties', 'qualitative trust relation', 'store value', and 'convenience value' were related to a higher customer equity. Fourth, in the case of the consumer group having a long-term relationship, the higher' differentiated brand image', 'personal ties', and 'store value' were related to a higher customer equity. Also, in the case of the consumer group of the traditional luxury brands, the higher 'personal ties', 'differentiated brand image', 'qualitative trust relation', and 'store value' were related to a higher customer equity.