• Journal of the Korea Institute of Building Construction
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• v.19 no.6
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• pp.539-547
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• 2019

Recently, the international community signed a climate change agreement to prevent global warming. Yet currently, the fossil fuels have been widely used in to supply building energy for cooling and heating. The Green Building certification (G-SEED), an energy efficiency rating for new or existing buildings requires that buildings meet certain conditions. Insulation is used as a building material to reduce the energy supply to buildings and to improve the thermal insulation, and it accounts for more than 90% of the total heat resistance provided by the building surface components that meet the energy-saving design standards of new buildings. In this investigation, a performance evaluation study was conducted through an experimental study by directly extracting the foam polystyrene insulation on-site during the remodeling of a building that was in the range of 22~38 years old. Through tests, it was found that the thermal conductivity of the extrusion method insulation (XPS) was reduced by 48% and the compressive strength of XPS decreased by 36% compared to KS M 3808, which is the initial quality standard. For bead method insulation (EPS) with a thickness of 50mm, the thermal conductivity, the compressive strength, and flexural failure load were similar to the initial quality standard. Therefore, in the calculation of the primary energy requirement per unit area per year, the performance of bead method insulation can be estimated simply by considering the thickness of the insulation, while a correction factor that considers its performance deterioration should be applied when extrusion method insulation is used.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.148-156
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• 2020

The paper is a summary of the results of the basic pullout test which is conducted to evaluate the anchorage capacity of high strength headed bars that is mechanical anchored vertically on steel fiber reinforced concrete members. The main experimental parameters are volume fraction of steel fiber, concrete strength, anchorage length, yield strength of headed bars, and shear reinforcement bar. Both sides of covering depth of the specimen are planned to double the diameter of the headed bars. The hinged point is placed at the position of each 1.5𝑙_dt and 0.7𝑙_dt around the headed bars, and the headed bars are drawn directly. As a result of pullout test experiment, concrete fracture and steel tensile rupture appear by experimental parameters. The compressive strength of concrete is 2.7~5.4% higher than that of steel fiber with the same parameters, while the pullout strength is 20.9~63.1% higher than that of steel fiber without the same parameters, which is evaluated to contribute greatly to the improvement of the anchorage capacity. The reinforcements of shear reinforcements parallel to the headed bars increased 1.7~7.7% pullout strength for steel fiber reinforced concrete, but the effect on the improvement of the anchorage capacity was not significant considering the increase in concrete strength. As with the details of this experiment, it is believed that the design formula for the anchorage length of KCI2017and KCI2012 are suitable for the mechanical development design of SD600 head bar that is perpendicular to the steel fiber reinforced concrete members.

• Journal of Information Technology Services
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• v.11 no.2
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• pp.275-289
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• 2012

Although the specification of packaging box is one of the most important process to be considered before deciding cost in terms of production and logistics, there are no efficient services in our country at this time as such the making decision only through the empirical knowledge. In this research, we have developed the packaging specification design system based on the web online packaging IT service. The developed system was advanced from the existing-inefficient process of deciding the specification of packaging box, and which can decide the specification of packaging box considering the efficiency of logistics through use of IT based tool. Therefore, this study shows applied cases of normalized packaging process through the obtained packaging design simulation program. The packaging specification design system can provide the simulation and user interface. Those could calculate the specification of packaging box(packaging box size, packaging box quantity, packaging box pattern, packaging compressive strength, packaging cost etc.) considering the efficiency of logistics.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.745-752
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• 2009

This paper presents the optimized mixing design of lightweight aerated concrete using hydrogen peroxide. Design of experiments in order to the optimized mixing design was applied and commercial program (MINITAB) was used. Statistical analysis was used to Box-Behnken (B-B) method in response surface analysis. The influencing factors of experimental are unit cement content, water ratio and hydrogen peroxide ratio. According to the analysis of variance, at the hardened state, water ratio and hydrogen peroxide ratio affects on dried density, compressive strength and bending strength of lightweight aerated concrete, but unit cement content affects on only dried density. In the results of response surface analysis, to obtain goal performance, the optimized mixing design for lightweight aerated concrete using hydrogen peroxide were unit cement content of 800 kg/$m^3$, water ratio of 44.33% and hydrogen peroxide ratio of 10%.

• Journal of the Korean Geotechnical Society
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• v.31 no.7
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• pp.41-52
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• 2015

Volcanic rocks in Jeju Island have vesicular structure caused by various environmental factors, and indicate the differences in geological and mechanical characteristics from region to region. In addition, the bedrock of Jeju Island shows stratified structure, that is, soft layers composed of pyroclastic rocks or cavities are irregularly developed between the basalt layers by several times of volcanic activity. In this study, various physical tests and unconfined compressive strength test were conducted for intact rocks sampled in northwestern onshore and offshore of Jeju Island. The results obtained in the tests were compared with the physical and mechanical characteristics of intact rocks sampled in southeastern offshore of Jeju Island. As a results, it was confirmed that the physical and mechanical characteristics of basalts sampled in northwestern Jeju Island were similar to those of basalts sampled in southeastern offshore of Jeju Island. In addition, it was possible to estimate approximate design parameters from the correlation of mechanical properties with physical properties of basalts in Jeju Island.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.427-434
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• 2016

The purpose of this study is to propose a mixture proportioning approach based on the replacement level of natural sand for reducing $CO_2$ emissions from artificial lightweight aggregate concrete(LWAC) production. To assess the effect of natural sand on the reduction of $CO_2$ emissions and compressive strength of LWAC, a total of 379 specimens compiled from different sources were analyzed. Based on the non-linear regression analysis using the database and the previous mixture proportioning method proposed by Yang et al., simple equations were derived to determine the concrete mixture proportioning and the replacement level of natural sand for achieving the targeted performances(compressive strength, initial slump, air content, and $CO_2$ reduction ratio) of concrete. Furthermore, the proposed equations are practically applicable to straightforward determination of the $CO_2$ emissions from the provided mixture proportions of LWAC.

• Fire Science and Engineering
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• v.18 no.3
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• pp.51-56
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• 2004

A fire outbreak in a reinforcement concrete structure looses the organism by the different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So concrete reinforcement structure is damaged partial or whole structure system. Therefore diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. In this study, it was presented data for the accurate diagnosis and selection of repair and reinforcement system for the deteriorated concrete heated highly, various concrete such as standard design compressive strength, fine aggregate and admixture were exposed to a high temperature environment. And fundamental data were measured engineering properties such as explosive spatting, ultrasonic pulse velocity and compressive strength.

• Composites Research
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• v.30 no.6
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• pp.331-337
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• 2017

The composite lattice structures have advantages of high specific stiffness and strength and are mainly applied to the structures of launch vehicles that carry the compressive load. However, since these structures are manufactured by filament winding technology, there are some defects and voids found in the knots. For these reasons, the stiffness and strength of the lattice structures have to be compared with finite element model for predicting design load. But, the full scale test is difficult because time and space are limited and the shape of structure is complex, and hence the simple and reliable test methods for examination of stiffness are needed. In this paper, subelements of composite lattice structures were prepared and compressive and bending test were conducted for examination of stiffness of helical and hoop rib. Test methods for subelements of composite lattice structures that has curved and twisted shape were supposed and compared with finite element analysis results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.44-54
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• 2012

The structural designs of RC flat plates that have no flexural stiffness by boundary beams may be governed not by strength conditions but by serviceabilities. Specially, since over-loading and tensile cracking in early-aged slabs significantly increase the immediate and long-term deflections of a flat plate system, a construction sequence and its impact on the slab deflections may be decisive factors in designs of flat plate systems. In this study, the procedure of calculating slab deflections with considering construction sequences, concrete cracking, and long-term effects is proposed. Using the proposed method, the parametric study for deflections of flat plates is performed. With various conditions for slab construction cycle, the number of shored floors, tensile or compressive reinforcement ratio, compressive strength of concrete, construction live load, and slab thickness, the immediate deflection during construction and long-term deflections after completion are analyzed. The calculated results are compared with the serviceability limits offered by the structural design code.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.84-90
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• 2013

In this study we propose an effective method, Coating processing methods, which can improve the quality of recycled aggregate relatively easily without new equipment investment and complex treatment process and verify the improved effect using the devised method, Coating processing methods. To attain the research aim we used adequately diluted silicate solution for coating and carried out several property valuation for twelve types of material with different coating method. Also we formed concrete with coated aggregates which showed the best property. In conclusion the aggregates with the method of repeated impregnation in the silicate and drying showed the most excellent quality while other coating methods also resulted in an improvement of aggregate quality but failed to meet the KS Standard. Lastly with the optimal material we could obtain the approved compressive strength from the concrete allowing it to be utilized for road facility of which standard compressive strength of design is under 24MPa.