• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.169-177
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• 2017

Rather than causing damage from heat, blast, and radiation of a regular nuclear weapon, recently, it is predicted that North Korea has been inventing high altitude electromagnetic pulse (HEMP) missile in order to incapacitate electronic equipment. HEMP shielding facility is used for military purpose today. Despite the electromagnetic shielding effects from high quality compression plates, problems may include such as the possibility of electromagnetic influx resulting in the welding of the compression plates, and difficulties and high cost of construction. Therefore, in this study, a high electrical conducting material was added to the concrete experimental subject to ensure the shielding effect through electromagnetic waves to for the concrete structure, instead of building a shielding facility separately for the structure. Also, among the experimental subjects, 100 ${\mu}m$ of Iron-Aluminum alloy metal spraying coat was applied to two types with the highest shielding effect, and to two types with the lowest shielding effect. The result of the experiment indicates that experimental subjects added with a high electrical conductivity material did not meet the minimum shielding criteria of MIL-STD-118-125-1 standard, but all the experimental material applied to the metal spraying coating satisfied the minimum shielding criteria. In conclusion, it is considered that 100 µm of Iron-Aluminum alloy metal spraying coat contains high efficiency in the HEMP shielding.

• Journal of the Korean Institute of Gas
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• v.18 no.2
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• pp.73-80
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• 2014

The objective of this paper is to assess the service life and retrain methods of specimens, which were subjected to carbonation attack, obtained from mix proportion of Sam-cheok LNG storage tank under construction. As the results, accelerated-carbonation penetration depths of 7, 28, 56 ages indicated 4.45, 9.19, 13.37mm, and even considering for cover depths of steel of LNG storage tank under real operation, it was enough. In addition, with carbonation velocity coefficient calculated by carbonation penetration depths, the service life to design cover depth(70, 80, 90, 100mm) of PC outer tank of LNG storage tank was 779, 1017, 1287, 1589 years and 466, 609, 771, 951 years, respectively, considering the $CO_2$ concentration in air which account for the 0.03% and 0.05%. Also, the restrain methods to carbonation attack were feasible through controlling the factors affecting the changes of hydration products such as $Ca(OH)_2$, ion composition in pore solution and matter mobility of organization structures within hardened concrete.

• Journal of the Mineralogical Society of Korea
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• v.19 no.4 s.50
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• pp.239-246
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• 2006

KAERI Underground Research Tunnel (KURT) was recently constructed through the site investigation from the yea. of 2003 at KAERI site, Dukjin-dong, Yuseong-gu, Daejeon city. The geo-logic setting of the site has been slightly metamorphosed. There are small fractures developed in the rock and several kinds of secondary filling minerals exist in the fractures. We examined mineralogical characteristics of fracture-filling calcite, which is not only largely distributed, but also can significantly affect the radionuclides migration. The calcite is found along fractures like other secondary minerals, forming thick veins in part. Most calcite-filled fractures contain quartz, iron oxides, and dolomite as minor minerals. The calcite crystals show an characteristic appearance with an uniformly oriented growth, coated with goethite on the edge and the etch-pit sites of their surface. Some calcite crystals have been newly formed by the precipitation of elements dissolved from the tunnel shotcrete wall, and their morphology changed according to the chemistry and flow of groundwater. The calcite can modify the groundwater chemistry and significantly affect the sorption behavior of radionuclides. The characteristic crystal structure and surface morphology of the calcite examined in the KURT site will be used as important basic data for the radionuclide migration experiment in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.508-517
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• 2018

This study evaluated the construction costs of 11 design cases to decrease the horizontal forces applied to an abutment. They include two kinds of abutment types, which are used to improve the backfill materials for reversed T-shaped abutment and geosynthehtic reinforced abutment for railways (RAR). In the first economic analysis, the internal friction angles of the backfill materials were increased from ${\Phi}=35^{\circ}$ to ${\Phi}=40^{\circ}$ and $50^{\circ}$ for a reversed T-shaped abutment. The second analysis examined cases with the design of a geosynthehtic RAR. When the friction angles were $40^{\circ}$ or $50^{\circ}$ after improvement of the backfill material, the reduction in the construction cost of the abutment was not as large (2.0-3.9%), even though the horizontal forces on the abutment were decreased by 18-48%. However, in the case of applying the RAR, a maximum cost reduction of 30% was achieved by decreasing the horizontal force to zero. The cost reduction results from the decreased wall thickness, base slab size, and the number of pile foundations for the abutment, as well as changing the material.

• Journal of Energy Engineering
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• v.21 no.2
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• pp.119-123
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• 2012

Although LNG storage tanks are very delicate with chloride attack owing to its operating inshore location, specific integrity management system for chloride attack has not been studied so far. As the design warranty life time, about 25 years, has come, to prevent paying huge amount of construction cost and required resources for new alternative storage tanks and manage the life time of operating storage tanks, the basic data of chloride attack is necessary. This study intended to build up basic data for following detailed study to develop technologies for life time management of LNG storage tanks, NT Build 492 method in North Europe was used to test chloride diffusion coefficient for the newly-constructing concrete outer tank. Results of these tests lead us to the conclusion that 90 days diffusion coefficients show 46% of 28 days' due to a large quantity of fly ash mixing and much similar to estimation from concrete process table. It seems resonable to conclude that 90 days specimens are recommended estimating the chloride diffusion coefficient for LNG storage tanks to enhance the reliabilities.

• Journal of the Korean Wood Science and Technology
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• v.36 no.4
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• pp.26-36
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• 2008

As the height of the light-framed building increases, the lateral load and overturn-moment are increased and the possibility of the building overturn becomes larger. Because the shear wall resists lateral load in light-framed building, the reinforcement of shear wall is required. In order to reinforce the light-framed shear wall, using lag screw fastener type (B-HD) and using bolt type (S-HD) hold-down connectors were applied for test. And domestic larch lumbers, $38{\times}140mm$ and $89{\times}140mm$, KS 2nd grade, were used for the stud. The North American OSB panels were used for sheathing panel. Static loads, load speed 6 mm/min, were applied on top of the wall. As a result, shear strength of the wall that using hold-down connector was improved sufficiently. And when applying the S-HD type hold-down connector, stud should be reinforced against weakening by drilled hole. As increasing the number of lag screw, the number of bolt and the product allowable strength, the strength of shear wall that using hold-down connector was also increased. When applying hold-down connector to light-framed building using 38 mm stud, it must be reinforced by enlarging the thickness of stud like as 38 mm doubled column.

• Land and Housing Review
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• v.5 no.4
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• pp.315-323
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• 2014

In this study, thermal transmittance which is a parameter to measure the thermal performance was evaluated for an internal insulation versus an external insulation. Then the ISO regulation was applied to evaluate it, and the superiority of an external insulation was verified by the thermal transmittance values. The three zones of apartment housing were selected to evaluate the performance. (1) The junction of an outer wall and a protruded slab : If there is no a thermal bridge protection system, then the values are about same in the two insulation systems, so the protection system should certainly be installed. If it is installed, then the value for the external insulation is 2 times lower than internal system. (2) The junction of a side wall and a flat slab: The value is 0.509W/mK for the internal insulation and about zero for the external insulation. (3) The junction of an outer wall and a division wall: The value is 0.451W/mK for the internal insulation and also about zero for the external insulation. A domestic regulation that could evaluate a thermal transmittance has to be established by applying the ISO regulation for the evaluation of external insulation systems in apartment housing in the future. Additionally, the government must decide which length should be used for the national standard.

• Journal of Wetlands Research
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• v.16 no.3
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• pp.327-336
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• 2014

Submerged thin walls are extreme case of submerged rectangular blocks, and could be used for many purposes in rivers or coastal zones, e.g. to tsunami. To understand flow characteristics including flow and pressure fields around a specific submerged thin wall a numerical model was applied which includes computation of hydrodynamic pressure on ${\sigma}$-coordinate. ${\sigma}$-coordinate has strong merits for simulation of subcritical flow over mild-sloped beds. On the other hand ${\sigma}$-coordinate is quite poor to treat sharp structures on the bed. There have been a few trials to incorporate dynamic pressure in ${\sigma}$-coordinate by some researchers. One of the previous approaches includes process of sloving the Poisson equation. However, the above method includes many high-order terms, and requires long cpu for simulation. Another method SOLA was developed by Hirt et al. for computation of dynamic pressure, but it was valid for straight grid system only. Previous SOLA was modified for ${\sigma}$-coordinate for the present purpose and was adopted in a model system, CST3D. Computed flow field shows reasonable behaviour including vorticity is much stronger than the upstream and downstream of the structure. The model was verified to laboratory experiments at a 2DV flume. Time-average flow vectors were measured by using one-dimensional electro-magnetic velocimeter. Computed flow field agrees well with the measured flow field within 10 % error from the speed point of view at 5 profiles. It is thought that the modified SOLA scheme is useful for ${\sigma}$-coordinate system.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.413-416
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• 2008

The concrete used most in construction materials. There is an overcrowded iron dimensions use of the concrete at time of the other concrete theory on the reinforcing rod back which did congestion and compares it with this, and there are more few dimensions of the aggregate than concrete, and quantity of aggregate passage is superior in mortar than concrete. If a volume rate of the aggregate writes mortar than concrete against this, therefore, unit amount increases, and quantity of paste increases and quantity of dry shrinkage than increase concrete. However, I let I regulate lay priest distribution of the aggregate, and the results rates increase and reduce unit amount and decrease quantity of dry shrinkage, and separation resistance and the gap passage characteristics are judged because it can be it in a substitute document of very superior concrete. I came to carry out the study that I watched to let I was useful a little more and do the improvement repair of a become building wall body, a basement pillar and repair reinforcement of the assistant in the reinforcing rod back, the old age when I made congestion here. I regulated lay priest distribution of the aggregate in the study and regulated substitution rate of the aggregate (40%, 50%, 60%) and divided W/C 30%, 40% standards and produced mortar and I compared quantity of air by this, slump, compression robbery and showed it this time.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.2
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• pp.83-91
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• 2017

In order to cope with the abnormally high waves during the storm surge due to climate change, various methods have been proposed for interlocking adjacent caissons to enhance stability of harbor structures. Among the methods, it was studied the method based on an open-cell caisson having reduction effect increasing the cohesion with adjunction caissons by filling materials such as crushed rocks in an inter-cell formed by two facing open-cells which consist of transverse walls. It is necessary to investigate the shear behaviors of an inter-cell to secure the stability using calculating shear forces on inter-cell under oblique wave loadings. It was analyzed the shear force share ratio with the length of internal and external wall and the number of internal walls. Numerical results show that 60~70% of the shear load is transmitted to adjacent caisson through the internal walls, more than 30% is through the external wall. It was applicable in the assumption that filling materials was uniformly distributed in inter-cells, and further studies were worth consideration on other conditions under construction.