• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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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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• v.10 no.6
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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.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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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.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.1
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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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• v.15 no.2
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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.

• The Journal of Industrial Distribution & Business
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• v.8 no.6
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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.

• Journal of the Korea Concrete Institute
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• v.13 no.3
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• pp.261-267
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• 2001

The objective of this experimental study is to find the allowable level of axial load to give the proper flexural ductility according to the yield strength of lateral ties, and the distribution and amount of longitudinal bars used in confined high-strength concrete columns. Twelve concrete columns with a 20 cm square section and 80 cm high were tested under hi-axial loads. It was observed that the ductility tends to be improved at the axial loads not less than 0.4f$\_$ck/A$\_$g/. The utilization of high-strength ties in accordance with the ACI 318-99 can cause the brittle failure due to the wide tie spacing. Under the high level of axial loads not less than 0.4f$\_$ck/A$\_$g/. it is necessary for the buckling prevention of the longitudinal bars and the proper ductility improvement to use the high-strength ties with the consideration of the volumetric ratio and confinement type of the lateral ties, and the distribution of the longitudinal bars.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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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.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.7
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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.