• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.555-562
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• 2016

The objective of the present study is to evaluate the shear transfer capacity of transverse reinforcement at the concrete interfaces with smooth construction joint. The transverse reinforcing bars were classified into two groups: V-type for the arrangement perpendicular to the interface and X-type for inclined-crossing arrangement. The transverse reinforcement ratio at the interface varied from 0.0045 to 0.0135 for V-type and 0.0064 to 0.0045 for X-type. The mechanism analysis proposed for monolithic concrete interface, derived based on the upper-bound theorem of concrete plasticity, was modified to evaluate the shear friction capacity of concrete interfaces with smooth construction joint. Test results showed that the specimens with X-type reinforcement had lower amount of relative slippage at the interface and higher shear friction capacity than the companion specimens with V-type reinforcement. This observation was independent of the unit weight of concrete. The mean and standard deviation of the ratios between the experimental shear friction strength of smooth construction joints and predictions obtained from the proposed model are 1.07 and 0.14, respectively.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.611-620
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• 2016

In the construction of nuclear power plants, only 420 MPa reinforcing bars are allowed and, therefore, so many large-diameter bars are placed, which results in steel congestion. Consequently, re-bar works are difficult and the quality of RC structures may be deteriorated. To solve the steel congestion, 550 MPa bars are necessary. Among many items for verifying structural performance of reinforced concrete with 550 MPa bars, the 43 mm hooked bars are examined in this study. All specimens failed by side-face blowout and the side cover explosively spalled at maximum loads. The bar force was initially transferred to the concrete primarily by bond along a straight portion. At the one third of maximum load, the bond reached a peak capacity and began to decline, while the hook bearing component rose rapidly. At failure, most load was resisted by the hook bearing. For confined specimens with hoops, the average value of test-to-prediction ratios by KCI code is 1.45. The modification factor of confining reinforcement which was not allowed for larger than 35 mm bars can be applied to 43 mm hooked bars. For specimens with 70 MPa concrete, the average value of test-to-prediction ratios by KCI code is 1.0 which is less than the values of the other specimens. The effects of concrete compressive strength should be reduced. An equation to predict anchorage capacity of hooked bars was developed from regression analysis including the effects of compressive strength of concrete, embedment length, side cover thickness, and transverse reinforcement index.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.282-289
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• 2017

The flexural behavior tests of UHPC segmental Box girder which has 160MPa compressive strength and 15.4m length were carried out. The test variables are area of prestressing wires, volume fraction of steel fibers and longitudinal reinforcing bars in upper flange and web. PS tendons which has 32 strands of 15.2mm diameter in lower flange, 24 strands and 14 strands in lower flange were arranged and volume fraction of 2%, 1.5% and 1.0% is used in box girder concrete. UHPFRC box girder which has 32 strands in lower flange showed the over reinforcement and brittle behavior. UHPFRC box girder which has 24 strands showed the similar peak load as 32 strands girder and ductile behavior as large deflection. UHPFRC box girder which has 14 strands showed half of the peak load of 24 strands box girder and ductile behavior. After the application of the formular for the reinforcement index to the behavior of the UHPFRC box girders, reinforcement index does not determine the characteristic of behavior of UHPFRC box girder exactly. So the index should consider the dimension precisely and modify the reference value corresponding to the 0.005 strain of the prestressing strands.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.520-526
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• 2019

I-type girders are widely applied as very economical sections in plate girder bridges. There has been research on developing composite laminated panels, curved plates reinforced with closed-end ribs, and new forms of ribs and compression flanges for steel box girders. However, there is a limitation in analyzing the exact cause of local buckling caused by an I-type girder's webs. Therefore, an I-type girder's web was modeled using the finite element analysis program LUSAS 17.0 before and after reinforcement. We checked for the minimum thickness criteria presented in the Korea highway bridge design code, and the cause of buckling after performing a linear elastic buckling analysis of dead and live loads was analyzed. Before reinforcement, an eigenvalue (λ₁) at the 1st mode was 0.7025, the critical buckling load was smaller than the applied load, and there is a buckling. After reinforcement, when applying vertical and horizontal stiffeners to the web part of the girder at support, a Nodal line was formed, the eigenvalue was 1.5272, and buckling stability was secured. To improve buckling trace of the girder at the support, an additional plate was applied to the web at the support to ensure visual and structural safety, but buckling occurs at center of web. The eigenvalue (λ₁) was 3.5299, and this method is efficient for reinforcing the web of the support.

• Korean Journal of Human Ecology
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• v.6 no.1
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• pp.111-127
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• 1997

This study was to examine home economics (HE) teachers' and the 1st-grade students' needs perception toward the purposes of HE education in middle school which has been practced since 1995 for both male and female students. This study, attempted (1) to analyze needs priority among the educational purposes of HE subject in relation to three systems of actions; (2) to compare differences between HE teachers' and students' perception concerning the degree of importance and achievement of the educational purposes of HE subject: and (3) to examine what they conceive as the problems In the current HE education. The survey was conducted with the samples of 600 1st-grade middle school students and 101 middle school HE teachers during the period of February-March 1996. The questionnaire used in this study was a modified version which had already been developed along with the 6th HE curriculum. For data analyses, SAS program was utilized to get Means and to perform both discrepancy test and t-test. The findings of this study were summarized as follows: first, with respect to each group's perception of the importance of the purposes related to three systems of action, HE teachers emphasized the importance of the purposes related to emancipatory action, while students placed more emphasis on the purposes related to technical action. Second, in terms of the degree of achievement, students had more positive perception on the degree of achievement of the purposes related to technical action than HE teachers did. Both groups marked low level of recognition on the degree of achievement of the purposes related to emancipatory action. Third, with respect to needs priority, HE teachers placed the first priority on emancipatory action, the second on technical action, and the last on communicative action: in the case of students, the first priority was on technical action, the second on communicative action, and the last on emancipatory action. In addition, the analysis of the opinions on the 6th curriculum revealed that most respondents found it necessary to secure adequate amount of classes for HE education. Also they shared the recongnition that HE curriculum should be renovated into the one which would fully appreciate the purposes of HE education from the perspective of the practical concerns of action which are distinct from the functional and technical concerns of passive learning. The findings of this study can serve as basic data for establishing the new purposes of HE education which put more emphasis on the purposes related to emancipatory action: as well as for developing an enhanced curriculum and reinforcing the identity of HE education.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.528-536
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• 2016

The aim of this study was to understand the difference between the image of social-workers and nurses perceived by middle school and high school students, and determine the experience related to social workers and the role of social workers projected in the media. The subjects of this study were 386 students of middle and high school located in S city. Data were collected from Oct. 15, 2013 to Nov. 23, 2013 and analyzed using the SPSS win 18.0 program. A comparison of the image of nurses and social workers in two groups showed that middle school students tended to have a more positive image of nurses than high school students, and the image of nurses appeared to be more positive than that of social workers. As a result of analyzing the contents exposed in media, the students received most of their information on social workers from TV. Therefore, it is necessary to have a strategy to help students choose a major or a job by reinforcing mass media monitoring based on TV, which may have a major impact on the image of social workers and provide them with the correct information on the profession.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.1
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• pp.21-28
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• 2012

In this paper, we present the analytical study results pertaining to the buckling of the orthotropic plates and local buckling of structural compression members composed of orthotropic plate components. Fiber reinforced polymeric plastic (FRP) materials, have many advantages over conventional structural materials such as steel and concrete. The advantages of the FRP materials are high specific strength and stiffness, high corrosion resistance, right weight, etc. Among the various manufacturing methods, pultrusion process is one of the best choices for the mass production of structural plastic members. Since the major reinforcing fibers are placed along the axial direction of the member, this material is usually considered as an orthotropic (tranversely isotropic, more specifically) material. However, pultruded fiber reinforced plastic structural members have low modulus of elasticity and are composed of orthotropic thin plate components the members are prone to buckle. Therefore, stability is an important issue in the design of the pultruded FRP structural members. In this paper, the buckling of orthotropic plates and the local buckling of pultruded FRP structural members are investigated by following the previous research results and the local buckling strength of the member produced in the domestic manufacturer is found.

• Journal of Bio-Environment Control
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• v.19 no.2
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• pp.63-69
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• 2010

This study was implemented to clarify the effect of a supplementary pole on the increment of safety snow-depth for the single-span plastic greenhouses which had been run as standardized facilities for 10 to 15 years till April, 2007. In the previous work, some of the basic ideas of the use of a temporary pole were discussed, but application was restricted to both 2-D and the cases which took rafter's specifications into no consideration, and there was also much less experimental information available. So, by modeling the house as the 3-D frame structure, the present study attempted to provide a comprehensive review of the pole's effect through structural analyses as well as measurements. Structural analyses abnormally revealed that the pole regardless of its interval had a negative effect on the structural stability. The results was certainly inconsistent with practical experience and hence implied a necessity of reinforcing the roof purlin. Accordingly, with the purlin being sufficiently reinforced, the plastic greenhouse with the pole's interval of 3~4 m had two times safety snow-depth more than that of the plastic greenhouse without the pole. And the safety snow-depth of five types of the single-span plastic greenhouses according to the pole's intervals was presented.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.8 no.4
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• pp.119-127
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• 2013

The purpose of this study is an attempt to explore the impact of working environment of visiting instructor on the empowerment for multi-cultural families. In this light, this study aims to provide some inevitable and necessary foundational data for reinforcing the empowerment of visiting instructor in order to essentially improve the quality and effectiveness of this governmental service. To accomplish this goal, this study selected eighteen multi-cultural service centers which locate near to the capital city due to each center serves relatively a large populations of multi-cultural families and took a survey from visiting instructor 286 survey forms. It used SPSS WIN 15.0 program for analyzing data, and the following is a list of tests used in this research: t-test,One-way ANOVA, correlation analysis, multiple regression analysis. The conclusive consequences from the research are following. In the case of analyzing the difference of empowerment for multi-cultural families, the project showed that the nationality, the forms of religion, the level of education, the number of child, the state of economic made a difference. As this project explored the impact of working environment on job stress, it showed that job characteristics and organizational commitment's compensation system and the development of education negatively effects on job stress. Therefore, as this project investigated how the working environment impacts on the empowerment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.403-414
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• 1994

Nonlinear analysis of RC containment structure under thermal load and pressure is presented to trace the behaviour after an assumed LOCA. The temperature distribution varying with time through the wall thickness is determined by transient finite element analysis with the two time level scheme in time domain. The layered shell finite elements are used to represent the containment structures in nuclear power plants. Both geometric and material nonlinearities are taken into account in the finite element formulation. The constitutive relation of concrete is modeled according to Drucker-Prager yield criteria in compression. Tension stiffening model is used to represent the tensile behaviour of concrete including bond effect. The reinforcing bars are modeled by smeared layer at the location of reinforcements accounting elasto-plastic axial behaviors. The steel liner model under Von Mises yield criteria is adopted to represent elastic-perfect plastic behaviour. Geometric nonlinearity is formulated to consider the large displacement effect. Thermal stress components are determined by the initial strain concept during each time step. The temperature differential between any two consecutive time steps is considered as a load incremental. The numerical results from this study reveal that nonlinear temperature gradient based on transient thermal analysis will produces excessive large displacement. Nonlinear behavior of containment structures up to ultimate stage can be traced reallistically. The present study allows more realistic analysis of concrete containment structures in nuclear power plants.