• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.329-334
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• 2005

The use of Polymer Concrete (PC) is growing very rapidly in many structural and construction applications such as box culverts, hazardous waste containers, trench lines, floor drains and the repair and overlay of damaged cement concrete surfaces in pavements, bridges, etc. However, PC has a defect economically because resin which be used for binder is expensive. Therefore the latest research is being progressed to replace existing resin with new resin which can reduce the high cost. Here, Polymer concrete using the recycled PET(polyethylene terephthalate) has some merits such as decrease of environmental destruction, decrease of environmental pollution and development of new construction materials. The variables of this study are amount of resin, curing condition and maximum size of coarse aggregate to find out mechanic properties of this. Stress-strain curve was obtained using MTS equipment by strain control. The results indicated that modulus of elasticity was increased gradually in an ascending branch of curve, as an increase of resin content. Compressive strength was the highest for resin content of $13\%$. And Compressive strength was increased as maximum size of coarse aggregate increases. The strain at maximum stress increases with an increase of resin content and size of coarse aggregate. For the descending branch of stress-strain curve the brittle fracture was decreased when it was cured at the room temperature compared to high temperature.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.29-35
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• 2015

Recent studies to develop Very Large Floating Structure(VLFS) has shown that the construction procedure of the structure needs to acquire precast concrete module connection system using prestressing. However, the loads occurring on water are complex combinations of various condition, so the safe and stable performance of the module joints and bonding materials are key to the success of the construction. Therefore, micro-silica mixed aqua-epoxy development was introduced in Part 1 using a bonding material developed in this study. The performance of the micro-silica mixed aqua-epoxy(MSAE) applied joint of concrete module specimens connected by prestressing tendon was evaluated to verify the usability and safety of the material. RC beam, spliced beam connected by prestressing tendon and MSAE, and continuous prestressed concrete beam were tested for their initial cracking and maximum loads as well as cracking procedure and pattern. The results showed that the MSAE can control the stress concentration effect of the shear key and the crack propagation, and the maximum load capacity of MSAE joint specimens are only 5% less than that of continuous RC specimen. The details of the study are discussed in detail in the paper.

• Journal of Korea Soil Environment Society
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• v.1 no.1
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• pp.67-79
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• 1996

Clay soils typically have low hydraulic conductivities in the presence of high polarity pore fluid, such as water. Low polarity fluids, such as hydrocarbon fuels and halogenated organic solvents, typically cannot migrate into clay pores because they cannot displace the pore water. Oxygenated additives in gasoline, such as alcohols and methyl-tert-butyl ether, are increasingly used to control air pollution emissions. These relatively polar and highly water-soluble compounds may facilitate displacement of pore water and enhance migration of fuels and solvents through clay-rich soil strata. In the reported research, the migration of gasoline-alcohol fuel mixtures (gasohol) through consolidated clay was examined. Prepared kaolinite clay samples were consolidated from slurry, and various combinations of gasoline, alcohol, and water were applied to the clays under 152 Pa gauge pressure. Movement of the fluids into the clay samples was monitored by measur ing displaced pore fluid and by magnetic resonance imaging of the samples. The structures of selected samples were examined using environmental scanning electron microscopy. Results of the research suggest that alcohol added to hydrocarbon fuels can enhance migration through some clays significantly. Gasoline did not migrate appreciably into water saturated clay, even after 14 days under pressure. The gasohol mixture migrated readily into the clay in only 20 minutes. Increased hydraulic conductivity of the clay in the presence of gasohol is hypothesized to be due to the collapse of the clays pore structure when ethanol is present, creating larger pores. Increasing pore diameter decreases the capillary pressure needed for the gasohol to replace water and allows gasohol to migrate through the clay.

• Journal of Korea Water Resources Association
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• v.48 no.3
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• pp.221-231
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• 2015

This is a continuous study on the dam effects for the spatial extension of flood data. In this study, flood reduction rates of dams and their influences on downstream using the spatially extended flood data were implemented. Nam-Han River was selected for measuring the impacts of ChoongJu and HoangSung dams. In the evaluations of flood reduction rate at dams, the larger flood events have the lower flood reduction rates for both dams. At the YeoJoo water level station, the analyses of the relations between flood reduction rates and the sizes of watersheds dams located were performed. the sizes of watersheds having a functional dam have highly influenced on the reduction rates of flood. The average of flood reduction rates was smaller than the area rate. For instances, area rates of HoangSung (0.02) and ChoongJu dams (0.6) are larger than the average flood reduction rates for HoangSung (0.01) and ChoongJu dams (0.51), respectively. However, the water level station follows the dam flood reduction characteristics of dams themselves. The spatial effects of dam flood reductions are analyzed based on the three water level stations (GangChun, YeoJoo, YangPyung). The distance of flood reduction rates lower than 0.1 as average flood reduction rate was the area 7 times of watershed having a dam with 0.02 as a minimum reduction rate.

• Korean Journal of Construction Engineering and Management
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• v.11 no.3
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• pp.43-54
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• 2010

As Urban Regeneration is being carried out, stakeholders are most likely to have disagreements on their interests. Besides, dispersion of numerous communication routes and obscure decision processes aggravate the situation. Eventually, fragmented decision-making processes and complex structure lead to inefficient outcome and delay of projects. This paper is a study on decision-making support not only helps the program manager have more efficient and optimum decision, but also provides alternatives for Urban Regeneration. This study is conducted as follows. Firstly, the project process and the decision-making structure among stakeholders in Urban Regeneration are analyzed, and then the current status of decision-making in Urban Regeneration project is classified. Secondly, with literature study on "Gateway Review", the decision-making gateway review process in Urban Regeneration is defined, and then the "Gateway Review Elements" are listed. Thirdly, to establish gateway review process, this paper presents a check points, namely gate which supports a program manager to monitor and to control the program management in Urban Regeneration. Each gate has several supporting tools such as diagram of critical decision points relation, scheme of stakeholder, checklist. Fourthly, the proposed concept is verified by experts who have been carefully selected to provide their respective reviews. Finally, decision-making support gateway review system is modified based on their critiques and suggestions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.3
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• pp.194-204
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• 2007

A numerical analysis and hydraulic experiments were undertaken to investigate the head loss occurring when a flow passes through vertical perforated walls. The numerical analysis applied continuity, momentum and energy equations to the control volumes that were set near the perforated wall. Non-dimensional equations were then derived to calculate both upstream depth and head loss for the given values of downstream depth and velocity. The hydraulic experiments were performed with several single and triple perforated plates varying their opening ratios and intervals. The numerical results with the single plates were compared with the experimental results, and it was shown that the contraction coefficient of the vertical line jet formed after the perforated plates relies on downstream Froude number as well as opening ratio. Based on the experimental results, empirical formulas were formulated. Finally, the formulas were applied to the triple plates sequentially from downstream side to upstream side, and it was found that in general the predicted values nicely agreed with the experimental results.

• Design & Manufacturing
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• v.12 no.2
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• pp.40-45
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• 2018

Recently, in construction equipment machinery production, development has focused on environmentally-friendly functions to improve existing production capacity. For excavators as well, emphasis has been placed on response to environmental regulations, miniaturization, and noise reduction, while technology is being developed considering cost reduction and safety.Accordingly, the front support, an inner reinforcement part of the excavator, as well as high-strength steel plates to improve safety and reduce weight, are being applied.However, in the case of high-strength materials, Springback occurs in the final formed part due to high residual stress during product forming. Derivation of a forming or product shaping process to reduce springback is needed. Accordingly, regarding the front support, an inner reinforcement part of the excavator, this study derived a method to improve springback and secure shape stiffness through analysis of the springback occurrence rate and springback causes through a forming analysis.As for the results of analyzing the springback occurrence rate of existing products through forming analysis, springback of -22.6 mm < z < 27.35 mm occurred on the z-axis, and it was confirmed that springback occurred due to the stiffness reinforcing bead of the upper and middle parts of the product.To control product residual stress and springback, we confirmed a tendency of springback reduction through local pre-cutting and stiffness reinforcement bead relocation.In the local pre-cutting model, springback was slightly reduced by 5.3% compared with the existing model, an insignificant reduction effect. In the stiffness reinforcement bead relocation model, when an X-shaped stiffness reinforcement bead was added to each corner portion of the product, springback was reduced by at least 80%.The X-shaped bead addition model was selected as the springback reduction model, and the level of stiffness compared to the existing model was confirmed through a structural analysis.The X-shaped bead additional model showed a stress springback of 90% and springback reduction of 7.4% compared with the existing model, indicating that springback and stiffness will be reinforced.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.211-219
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• 2009

The purpose of the study described in this paper was to experimentally investigate branch squared T joints with cold formed hollow structural sections under the in plane moment in a Vierendeel Truss. The branch in the T joints was welded to the upper flange of the chord. The main experimental parameters were the ratio of the width to the thickness of the chord ($2{\gamma}$), with ${16.7{\leq}2{\gamma}{\leq}33.3}$, and the width ratio of the branch to the chord ($\beta$), with ${0.40{\leq}{\beta}{\leq}0.71}$. Nine specimens were tested and manufactured in joints under the in plane bending moment. Based on the results of the test, the in plane moment strength of the branch squared T joints was determined according to the bending deformation of the chord flange yielding, regardless of the ratio of the width to the thickness of the chord and the ratio of the width of the branch to the width of the chord. Also, the in plane moment strength of the branch squared T joints in the hollow structural sections can be defined as 1.5 times the moment load at M1%B the strength of the joints that governed the serviceability in the control group. Finally, the experimental results with the branch squared T joints show that the in lane moment strength of the joint increased as $2{\gamma}$ decreased and $\beta$ increased.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.945-950
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• 2007

The stormwater runoff from paved area are highly polluted because of particulate materials as well as metals from various vehicular activities. The Division of Road Maintenance in Ministry of Construction and Transportation was recently developed the Guidelines of Environment-kindly Road Maintenance. It is actually requiring the BMP construction to control the nonpoint source pollution as based on the TMDL program. This research is carried out in order to define the characteristics of stormwater runoff from the toll-gate of highways since 2006, which is actually one of the main pollutant sources of paved areas. This monitoring is the first phase work for establishing the treatment facilities in the toll-gates. The one of the main characteristics from toll-gate runoff is the first flush phenomenon containing lots of sediments and metal compounds at the beginning of a storm event. Usually it is used to determine the size of treatment facilities and to calculate the reduced pollutant mass in the facility. The research results shows that the mean EMC vaules for heavy metals are determined to $274.3{\mu}g/L$ for Cd, $1,273.4{\mu}g/L$ for Cr, $1,822.0{\mu}g/L$ for Cu, $6,504.9{\mu}g/L$ for Fe, $14,930.3{\mu}g/L$ for Pb, and $714.1{\mu}g/L$ for Zn. Also the metal mass loadings from the toll-gates are calculated using EMC, watershed area and storm duration.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.171-178
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• 2008

Compressive strength of concrete has been regarded as a very important parameter of the quality control both in new and existing concrete pavement. It has been used a lot as the concrete strength evaluation both in the various-mixture-using laboratory and construction field using the same mixture. An error usually occurs in the test experiments of the strength, even in the test experiments with evenly mixed and compacted specimens of the compressive strength. It is caused by the 'manually operated' compressing testing, or by the specimens preparation with eccentricity. When compressive strength of evenly mixed concrete is investigated by the curing ages at the construction field, there have to be lots of specimens. And it needs much labor and cost. To substitute the endlessly repeated test experiments of compressive strength, presumption of compressive strength, by nondestructive tests, is needed. In this study, elastic waves were used among various nondestructive tests. Compressive strength of concrete was presumed according to the curing ages, by using the shear wave velocity which is not affected by restricted conditions. In the result, shear wave velocity is very closely related to the compressive strength at the evenly mixed concrete.