• Journal of the Korean GEO-environmental Society
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• v.17 no.5
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• pp.27-36
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• 2016

Low Impact Development (LID) techniques are eco-friendly storm water management process for water circulation restoration and non-point pollutant reduction. In this study, four LID techniques (Small constructed wetland, Infiltration trench box, Infiltration trench, Vegetated swale) were selected and installed as a real size at the real site. All facilities were evaluated as monitoring under the real environmental climate situation and an artificial rain with exceeding design rainfall. In various rainfall, runoff reduction efficiency and non-point pollutant removal efficiency are increased to the bigger Surface Area of LID (SA)/Catchment Area (CA) ratio and the bigger Storage Volume of LID (SV)/Catchment Area (CA) ratio. Runoff did not occur at all rainfall event (max. 17.2 mm) in infiltration trench and vegetated swale. But Small constructed wetland was more efficient at less than 10 mm, a efficiency of infiltration trench box was similar at different rainfall. Although different conditions (such as structural material of LID, rainfall flow rate, antecedent dry periods), LID techniques are good effects not only water circulation improvement but also water quality improvement.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.10
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• pp.979-988
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• 2012

The 3D structure of GDL for fuel cells was measured using high-resolution X-ray tomography in order to study material transport in the GDL. A computational algorithm has been developed to remove noise in the 3D image and construct 3D elements representing carbon fibers of GDL, which were used for both structural and fluid analyses. Changes in the pore structure of GDL under various compression levels were calculated, and the corresponding volume meshes were generated to evaluate the anisotropic permeability of gas within GDL as a function of compression. Furthermore, the transfer of liquid water and reactant gases was simulated by using the volume of fluid (VOF) and pore-network model (PNM) techniques. In addition, the simulation results of liquid water transport in GDL were validated by analogous experiments to visualize the diffusion of fluid in porous media. Through this research, a procedure for simulating the material transport in deformed GDL has been developed; this will help in optimizing the clamping force of fuel cell stacks as well as in determining the design parameters of GDL, such as thickness and porosity.

• Journal of Korean Society of Steel Construction
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• v.29 no.2
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• pp.111-122
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• 2017

In this paper, the applicability of a 1900mm-deep concrete-filled U-shaped composite beam to composite ordinary moment frames (C-OMFs) was investigated based on existing test results from smaller-sized specimens and supplemental numerical studies since full-scale seismic testing of such a huge sized beam is practically impossible. The key issue was the web local buckling of concrete-filled U section under negative bending. Based on 13 existing test results compiled, the relationship between web slenderness and story drift capacity was obtained. From this relationship, a 1900mm-deep mega beam, fabricated with 25mm-thick plate was expected to experience the web local buckling at 2% story drift and eventually reach a story drift over 3%, thus much exceeding the requirements of C-OMFs. The limiting width to thickness ratio according to the 2010 AISC Specification was shown to be conservative for U section webs of this study. The test-validated supplemental nonlinear finite element analysis was also conducted to further investigate the effects of the horizontal stiffeners (used to tie two webs of a U section) on web local buckling and flexural strength. First, it is shown that the nominal plastic moment under negative bending can be developed without using the horizontal stiffeners, although the presence of the stiffeners can delay the occurrence of web local buckling and restrain its propagation. Considering all these, it is concluded that the 1900mm-deep concrete-filled U-shaped composite beam investigated can be conservatively applied to C-OMFs. Finally, some useful recommendations for the arrangement and design of the horizontal stiffeners are also recommended based on the numerical results.

• Archives of design research
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• v.17 no.4
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• pp.223-232
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• 2004

The pedestrian space on the roads shows virtually different images, depending on the local uniqueness that exists in the roadsides, to the one walking. This sort of characteristics of the region originated from the physical special structures of the roadside building the form of the place. Thus, because of the structural difference of the roadside, Pedestrian sense the difference of regions through other images. Research focused on issues of the local roadside sidewalk spaces as what roadside structure is the type that brings out the unique images of the region, and what facets are pursued additionally here, is needed. A roadside of a prosperous region filled with many Pedestrians is selected as the range for the experiment in order to analyze the structure and image of the pedestrian space. Among the roads of the selected region, the structure of the pedestrian space on the roads with more than four lanes was evaluated. As result of the analysis, the images of 10 pedestrian space could be classified into two groups by the difference in proportions of the Df/H(the width of the sidewalk and the height of the roadside building) and the D/H(the width of the road and the height of the roadside building). In order to observe the images of the pedestrian space classified into two groups, the adjectives used to describe the image of scenery were researched, enabling one to induce the images of the two groups form them. One of the images is the image of prosperities, and the other is the image of pleasantness. In addition, as result to the evaluation focused on the characteristic of the roadside buildings in the selected area, it could be divided into two groups, i.e., the commercial region and the business region. The image of prosperities was sensed on the sidewalks of the commercial region, while the image of pleasantness was seen on that of the business region. This study enabled the acknowledgment that in a pedestrian space on a road structure with more than four lanes, the Pedestrian sense different images, depending on the proportional difference in the width of the sidewalk & the height of the roadside building, and the width of the road & the height of the roadside building. This result is expected to be a good reference when a road structure reflecting the uniqueness of its region is to be designed, and especially when the structure of a pedestrian space is to be created.

• Tunnel and Underground Space
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• v.23 no.2
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• pp.150-159
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• 2013

It is generally well known that the stratification of thermal energy in heat stores can be improved by increasing the aspect ratio (the height-to-width ratio) of the stores. Accordingly, it will be desirable to apply a high aspect ratio so as to demonstrate the good thermal performance of heat stores. However, as the aspect ratio of a store increases, the height of the store become larger compared to its width, which may be unfavorable for the structural stability of the store. Therefore, to determine an optimum aspect ratio of heat stores, a quantitative mechanical stability assessment should be performed in addition to thermal performance evaluations. In the present study, we numerically investigated the mechanical stability of silo-shaped rock caverns for underground thermal energy storage at different aspect ratios. The applied aspect ratios ranged from 1 to 6 and the mechanical stability was examined based on factor of safety using a shear strength reduction method. The results from the present study showed that the factor of safety of rock caverns tended to decrease with the increase in aspect ratio and the stress ratio of the surrounding rock mass was influential to the stability of the caverns. In addition, the numerical results demonstrated that under the same conditions of rock mass properties and aspect ratio, mechanical stability could be improved by the reduction in cavern size (storage volume), which indicates that one can design high-aspect-ratio rock caverns by dividing a single large cavern into multiple small caverns.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.43-51
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• 2020

The main purpose of protective facility for small military unit is to provide the protection of not all the weapons system but the near-miss bullet in Korean army. In particular about the small caliber bullets, especially KM80 in Korea, there were many studies that both of the experiential and structural design methods dose not reflect enough the military threat. For that reason, a new equation to calculate effective anti-piercing depths for RC slabs against small caliber bullets is proposed in earlier research with actual shooting test. But, the test only considers the strength of concrete without the thickness of concrete, types of aggregate, the angle of yaw of bullet, high-strength concrete, etc. Therefore, this study evaluated the ballistic resistance performance by thickness and proportion of magnetic aggregate of concrete. As a result, we identified two major statistical estimations that the error of piercing depth by the angle of yaw of bullet could be cancelled by barrage and the thickness and proportion of magnetic aggregate of concrete dose not effect on the protection ability of concrete structure.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.1
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• pp.49-64
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• 2014

Seabed beneath and near the coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. If the liquefaction occurs in the seabed, the structure may sink, overturn, and eventually fail. Especially, the seabed liquefaction behavior beneath a gravity-based structure under wave loading should be evaluated and considered for design purpose. In this study, to evaluate the liquefaction potential on the seabed, numerical analysis was conducted using 2-dimensional numerical wave tank. The 2-dimensional numerical wave tank was expanded to account for irregular wave fields, and to calculate the dynamic wave pressure and water particle velocity acting on the seabed and the surface boundary of the structure. The simulation results of the wave pressure and the shear stress induced by water particle velocity were used as inputs to a FLIP(Finite element analysis LIquefaction Program). Then, the FLIP evaluated the time and spatial variations in excess pore water pressure, effective stress and liquefaction potential in the seabed. Additionally, the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated. From the analysis, when the shear stress was considered, the liquefaction at the seabed in front of the structure was identified. Since the liquefied seabed particles have no resistance force, scour can possibly occur on the seabed. Therefore, the strength decrease of the seabed at the front of the structure due to high wave loading for the longer period of time such as a storm can increase the structural motion and consequently influence the stability of the structure.

• Journal of Bio-Environment Control
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• v.29 no.1
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• pp.36-42
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• 2020

The objectives of this study were to investigate the standard and roof vent type of multi-span greenhouse and to analyze the characteristics of natural ventilation of multi-span greenhouse with different roof vent using computational fluid dynamics (CFD) code. The vent area proportion of surveyed farms averaged 10%, it was analyzed that the vent design for natural ventilation is insufficient. The results of natural ventilation efficiency of multi-span greenhouse according to roof vent type showed that the temperature of the position in which the crops grew was the lowest in the conical roof vent type and the highest in the half conical roof vent type. For the natural ventilation effect, the conical roof vent type was the best one, but the structural stability should be evaluated in light of wind load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.269-278
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• 2011

Recently, methods on minimizing environmental effect caused from human-made goods have been studied in various research fields. Such issue has been also spotlighted into the civil engineering field; however, application of environmental performance assessment on civil structures is very complicated, since they handles vast ranges of materials and has comparatively long life span with various construction stages. Thus, this study intended to apply environmental performance assessment into an ordinary type of steel box girder bridge, using most popular Life cycle assessment (LCA) procedures, which are called Survey-based method and Indirect method. For better comparison of two methods, greenhouse effect of the example bridge is considered. As result of analysis, total $CO_2$ emission is evaluated as 241.27 ton with Survey-based method while it is evaluated as 221.03 ton with Indirect method. It is also revealed that most $CO_2$ is generated from the process of manufacturing and producing construction materials. Such result indicates that the efficient design which secures certain level of structural safety with minimized input materials. It is considered that the specific LCA on civil structure performed in this study could be utilized to other civil structures for reasonable environmental performance assessment.

• Journal of Korean Society of Steel Construction
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• v.26 no.4
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• pp.361-373
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• 2014

As the height and beam span of buildings built in the construction market increase, increasingly higher quality is being required of the construction materials. In response to this trend, 800MPa tensile strength class steel was developed in domestic company. Currently, experiments applying flexural member, compression member, and connections are continuously conducted, but a design guideline for high strength steel has yet to be established. Among those construction materials, for the high strength steel beam-to-column connections, the evaluation of implementing ductile connections for the high strength steel beam-to-column connections is producing pessimistic results and the number of related researches is inadequate because of the high yield ratio, which is the characteristic of high strength steel. This study on implementation of ductile connections made of high strength steel was conducted using the connection detail as the variable, for the purpose of enhancing the deformation capacity of high strength steel beam-to-column connections. Cyclic loading test and nonlinear finite element analysis were conducted with full-scale mock-up connection models with the applied connection details. As a result, the structural performance of high-strength steel beam-to-column connection with presented detail was contented with demand of Special Moment Frames of KBC standard.