• Korean Journal of Construction Engineering and Management
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• v.22 no.6
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• pp.87-95
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• 2021

This study analyzed economic feasibility using the real options theory of the eco-environment area project in Saemangeum. I defined the main factors affecting project sales during the 30 years operation period. The real option-based analysis is proposed through the managerial flexibility by estimating the volatility of project sales using scenarios analysis method. The number of visitors, admission fee, leisure program fee, and O&M costs required for economic analysis of eco-environment park were analyzed by reviewing cases of similar eco-environment parks in Korea. The option value is calculated by assuming that the developers have an option right that can be abandoned. B/C is less than 1 and NPV is negative, so it is impossible to proceed with the project using the traditional economic analysis. The project value difference between NPV (-46.6 billion Won) and option value (28.1 billion Won) increased by 74.7 billion Won. Through this study, decision-makers of public institutions and private developers who plan eco-environment area projects will be able to use the real option technique proposed in this study.

• Journal of the Korean Geotechnical Society
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• v.37 no.4
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• pp.5-17
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• 2021

In this paper, three-dimensional analysis of the curved levee was performed according to curvature angle, and radius of curvature to investigate the property of seepage. The hydraulic gradients in the curved parts of levees decreased in the outer levee and increased in the inner levee, compared to the two-dimensional analysis. The smaller the curvature angle and the radius of curvature, the larger the change of the hydraulic gradient, compared to the two-dimensional analysis. The effect of curvature radius on the hydraulic gradient was greater than the curvature angle. As a result of evaluating the piping safety factor for the critical hydraulic gradient, the safety factor was increased by 2~5% in the outer levee and decreased by 4~12% in the inner levee, compared to the two-dimensional analysis. Considering this reduction, if the two-dimensional analysis is performed on the curved part of the levee, and if designed the safety factor for piping is 0.1~0.3 greater than allowable FS=2.0, the safety factor of the curved part is slightly reduced, but there is no difficulty in securing stability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.143-151
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• 2021

Flexural test of reinforced concrete beam with corroded reinforcement were performed to measure the deflection, curvature and cracking moment for various bar diameter and amounts of corrosion. The amounts of corrosion are varied from 0% to 10% by weight and the bar diameters are chosen as 10mm, 13mm, and 19mm. The changes in reinforcement diameter do not affect the flexural behaviors significantly according to this experiment. If the amounts of corrosion is greater than 2%, the deflection and curvature of the beam increased and the cracking moment decreased. It means that the lower amounts of corrosion does not result structural damage in flexural member significantly as in direct tensile test. A modification factor considering an effect of amounts of corrosion is proposed based on the experiment, which can be used to determine the deflection of reinforced concrete beam with corroded reinforcement.

• Journal of the Korean Association of Geographic Information Studies
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• v.22 no.2
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• pp.97-106
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• 2019

Today, many smart sensor's measurement instruments are used to check the safety situation of various medium and large bridge structures that should be maintained in the construction facilities, but most of them use the method of measuring and confirming the displacement behavior of the bridge at regular intervals. In order to continuously check the safety situation, various measuring instruments are used, but most of them are not able to measure and measure the displacement and behavior of main construction structures at regular intervals. In this study, GNSS and environment smart sensors and drone's image data are transmitted to wireless network so that risk of many bridge's structures can be detected beforehand. As a result, by diagnosing the fine displacement of the bridge in real time and its condition, reinforcement, repair and disaster prevention measures for the structural parts of the bridges, which are expected to be dangerous, and various disasters and accidents can be prevented, and disaster can be prevented could suggest a new alternative.

• Journal of Climate Change Research
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• v.6 no.4
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• pp.311-318
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• 2015

Emission characteristics from charbroiling of four different meats (beef, port, duck and chicken) in a pilot-scale cooking facility were investigated in this study. The analyzed air pollutants include gaseous species (CO, NO, $SO_2$, $NH_3$ and PAHs) as well as particulate matters (TSP, $PM_{10}$, $PM_{2.5}$ and black carbon). The emission factors of $PM_{10}$ and PAHs were in the range of 3~47 g-PM/kg-meat and 0.6~11.41 mg-PAHs/kg-meat, respectively, depending on the type of a meat. In addition, the results also revealed that the high ratio of $PM_{2.5}$ to TSP in a meat charbroiling should be considered to design and to operate air pollution control devices.

• Journal of Digital Convergence
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• v.17 no.3
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• pp.205-213
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• 2019

In a construction site, excavation work has a close relation with temporary earth retaining structure. In order to build the underground structure most effectively in a narrow space, prevent soil relaxation of the external behind ground in excavation work, and maintain a ground water level, it is required to install a temporary earth retaining structure that secures safety. To prevent soil washoff in underground excavation work, the conventional method of temporary earth retaining structure is to make a temporary wall and build the internal support with the use of earth anchor, raker, and struct for excavation work. RSB method that improves the problem of the conventional method is to remove the internal support, make use of two-row soldier piles and bracing, and thereby to resist earth pressure independently for underground excavation. This study revealed that through the field application cases of RSB method and the measurement result, the applicability of the method for installing a temporary earth retaining structure, the assessment result, and displacement all met allowable values of measurement, and that the RSB method, compared to the conventional method, improved constructability and economy.

• Journal of agriculture & life science
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• v.52 no.6
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• pp.111-125
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• 2018

In this study, we evaluated the uniformity of deposition rate and particle size distributions of the variable rate application technique using the unmanned rotorcraft by measuring the spray pattern according to path location in the range of spraying flight. The coefficient of variation (CV) of the lateral coverage rate for the overlapped distribution with the spray swath of 3.6 m in both guidance and auto-pilot flight modes maintaining constant flight speed was about 30% and the CV of the coverage rate by the flight path location was extremely small. Therefore, it was assessed that the variable rate application technology compensating for the variation of ground speed was superior in terms of spray uniformity. In addition, the droplet size distributions in both volume median diameter(VMD) and number median diameter(NMD) were adequate for aerial application and uniform in terms of lateral distribution. Thereafter, we intend to contribute to a precise application on small-scaled fields using the unmanned agricultural rotorcraft by the variable rate application.

• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.107-119
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• 2018

PHC piles, extension-plate attached PHC piles, and steel pipe attached PHC piles were installed in field test site. Axial compressive static load tests including load distribution test and Pile Driving Analyzer (after driving) were done on the tip-transformed PHC piles and the grouted tip-transformed PHC piles. Load-displacement curves of three different type of PHC piles, which are PHC pile (TP-1), extension plate attached PHC pile (TP-2) and steel pipe attached PHC pile (TP-3), showed almost the same behavior. Thus bearing capacity increase effect of the tip-transformed PHC piles was negligible. Share ratio of side resistance and end bearing resistance for PHC pile, extension plate attached PHC pile, and steel pipe attached PHC pile were 95.8% vs. 4.2%, 95.6% vs. 4.4%, and 97.8% vs. 2.2% respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.68-74
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• 2019

In this study, the mechanical property and durability of improved bond performance mortar shotcrete was investigated. Mortar shotcrete was prepared by replacing coarse aggregate with 100% fine aggregate in the shotcrete mixture proportion proposed in the road construction standard specification. OPC, GGBFS and anhydrite were used as binders, and polymer powder was substituted for 1% and 2% of binder for improving bond property. From the experimental results, it was found that the compressive strength decreased with increasing polymer addition, but the bond strength increased. The addition of polymer to mortar shotcrete also reduced the drying shrinkage and improved the resistance to carbonation. Initial hydration heat of mortar shotcrete decreased with the addition of polymer, and it was judged that the initial compressive strength decreased.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.45-53
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• 2019

Slump flow, compressive strength, flexural strength and drying shrinkage were measured to evaluate workability and mechanical performance of geopolymer. Experimental parameters include the addition of gypsum, blending ratio of blast furnace slag and fly ash and addition of shrinkage reducing agent. Geopolymer using blast furnace slag mixed with gypsum showed larger slump flow than blast furnace slag without gypsum. The slump flow when blending ratio of blast furnace slag and fly ash is 5:5 tended to be larger than the slump flow when blending ratio is 8:2. Geopolymer using blast furnace slag without gypsum showed higher compressive strength and flexural strength than blast furnace slag mixed with gypsum. Compressive strength and flexural strength tended to be higher when blending ratio of blast furnace slag and fly ash was 8:2 than when blending ratio was 5:5. Drying shrinkage decreased with increasing fly ash and blast furnace slag without gypsum, and it was found that shrinkage reducing agent is effective to reduce drying shrinkage of geopolymer.