• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.2
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• pp.23-32
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• 2023

Probabilistic and deterministic analyses are implemented for the armor units of rubble foundation mound of composite breakwaters which is needed to protect the upright section against the scour of foundation mounds. By a little modification and incorporation of the previous empirical formulas that has commonly been applied to design the armor units of foundation mound, a new type formula of stability number has been suggested which is capable of taking into account slopes of foundation mounds, damage ratios of armor units, and incident wave numbers. The new proposed formula becomes mathematically identical with the previous empirical formula under the same conditions used in the developing process. Deterministic design have first been carried out to evaluate the minimum weights of armor units for several conditions associated with a typical section of composite breakwater. When the slopes of foundation mound become steepening and the incident wave numbers are increasing, the bigger armor units more than those from the previous empirical formula should be required. The opposite trends however are shown if the damage ratios is much more allowed. Meanwhile, the reliability analysis, which is one of probabilistic models, has been performed in order to quantitatively verify how the armor unit resulted from the deterministic design is stable. It has been confirmed that 1.2% of annual encounter probability of failure has been evaluated under the condition of 1% damage ratio of armor units for the design wave of 50 years return period. By additionally calculating the influence factors of the related random variables on the failure probability due to those uncertainties, it has been found that Hudson's stability coefficient, significant wave height, and water depth above foundation mound have sequentially been given the impacts on failure regardless of the incident wave angles. Finally, sensitivity analysis has been interpreted with respect to the variations of random variables which are implicitly involved in the formula of stability number for armor units of foundation mound. Then, the probability of failure have been rapidly decreased as the water depth above foundation mound are deepening. However, it has been shown that the probability of failure have been increased according as the berm width of foundation mound are widening and wave periods become shortening.

• Korean Journal of Remote Sensing
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• v.39 no.2
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• pp.233-246
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• 2023

In terms of understanding the water cycle and efficient water resource management, the importance of soil moisture has been highlighted. However, in Korea, the lack of qualified in-situ soil moisture data results in very limited utility. Even if satellite-based data are applied, the absence of ground reference data makes objective evaluation and correction difficult. The cosmic-ray neutron probe (CRNP) can play a key role in producing data for satellite data calibration. The installation of CRNP is non-invasive, minimizing damage to the soil and vegetation environment, and has the advantage of having a spatial representative for the intermediate scale. These characteristics are advantageous to establish an observation network in Korea which has lots of mountainous areas with dense vegetation. Therefore, this study was conducted to evaluate the applicability of the CRNP soil moisture observatory in Korea as part of the establishment of a Korean cOsmic-ray Soil Moisture Observing System (KOSMOS). The CRNP observation station was installed with the Gunup-ri observation station, considering the ease of securing power and installation sites and the efficient use of other hydro-meteorological factors. In order to evaluate the CRNP soil moisture data, 12 additional in-situ soil moisture sensors were installed, and spatial representativeness was evaluated through a temporal stability analysis. The neutrons generated by CRNP were found to be about 1,087 counts per hour on average, which was lower than that of the Solmacheon observation station, indicating that the Hongcheon observation station has a more humid environment. Soil moisture was estimated through neutron correction and early-stage calibration of the observed neutron data. The CRNP soil moisture data showed a high correlation with r=0.82 and high accuracy with root mean square error=0.02 m³/m³ in validation with in-situ data, even in a short calibration period. It is expected that higher quality soil moisture data production with greater accuracy will be possible after recalibration with the accumulation of annual data reflecting seasonal patterns. These results, together with previous studies that verified the excellence of CRNP soil moisture data, suggest that high-quality soil moisture data can be produced when constructing KOSMOS.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.94-101
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• 2023

In this study, the development performance of the head bars, which is SD700, was experimentally evaluated at the RC (reinforced concrete) or SFRC (steel fiber reinforced concrete external beam-column joint. A total of 10 specimens were tested, and variables such as steel fibers, length of settlement, effective depth of the beam, and stirrups of the column were planned. As a result of the experiment, the specimens showed side-face blowout, concrete breakout, and shear failure depending on the experimental variables. In the RC series experiments with development length as a variable, it was confirmed that the development strength increased by 26.5~42.2% as the development length increased by 25-80%, which was not proportional to the development length. JD-based experiments with twice the effective depth of beams showed concrete breakout failure, reducing the maximum strength by 31.5% to 62% compared to the reference experiment. The S-series experiment, in which the spacing of the shear reinforcement around the enlarged head reinforcement was 1/2 times that of the reference experiment, increased the maximum strength by 8.4 to 9.7%. The concrete compressive strength of SFRC was evaluated to be 29.3% smaller than the concrete compressive strength of RC, but the development strength of SFRC specimens increased by 7.3% to 12.2%. Accordingly it was confirmed that the development performance of the head bar was greatly improved by reinforcing the steel fiber. Considering the results of 92% and 99% of the experimental maximum strength of the experiment arranged with 92% and 110% of the KDS-based settlement length, it is judged that the safety rate needs to be considered even more. In addition, it is required to present a design formula that considers the effective depth of the beam compared to the development length.

• Journal of the Society of Disaster Information
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• v.19 no.4
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• pp.869-881
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• 2023

Purpose: This study aims to come up with improvement measures to improve the effectiveness of child safety measures. Method: The current status of child safety accidents was investigated and implications were deduced by analyzing major child safety measures by government department in the past. In addition, a perception survey was conducted on 1,000 people including children, guardians, and children's facility workers who are subject to child safety policies. Result: Regarding the safety of children's living space(environment), 35.3% of guardians answered that more than 1/3 of them were not safe. Both guardians(95.3%) and children's facility workers(89%) answered that there was the highest risk of 'traffic accidents', and the second risk factor was parents(carelessness of workers at children's facilities) and children's facility workers(careless of guardians at home). Looking at the risks by place, "road and sidewalk" was the most dangerous place and for child safety, guardians(64.3%) and workers (78.3%) both said that the role of "parent" is the most important. For improvements to prevent child safety accidents, the response rate of "strengthening safety management of road traffic facilities" is the most necessary with 75.8% for guardians and 65% for child use facilities. Conclusion: The reinforcement measures to strengthen the effectiveness of child safety measures are as follows. First, in order to ensure the continuity of child safety measures, it should be operated effectively so that those subject to the establishment of the Comprehensive Plan for Child Safety, which took effect in August 2022, can feel it. Second, in order to improve the sensitivity of children's policy targets, promotion measures that take into account the characteristics of each child safety field should be continuously strengthened. Third, it is necessary to expand safety infrastructure for each field to secure child safety. Fourth, it is necessary to strengthen safety education that can ensure safety for children themselves and to come up with detailed measures to make safety education for parents(guardians) mandatory.

• Journal of the Korea Institute of Building Construction
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• v.24 no.2
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• pp.273-284
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• 2024

This study investigates the impact of international oil price fluctuations on overseas construction orders secured by domestic and foreign companies. The analysis employs statistical data spanning the past 20 years, encompassing international oil prices, overseas construction orders from domestic firms, and new overseas construction orders from the top 250 global construction companies. The correlation between these variables is assessed using correlation coefficients(R), determination coefficients(R²), and p-values. The results indicate a strong positive correlation between international oil prices and overseas construction orders. The correlation coefficient between domestic overseas construction orders and oil prices is found to be 0.8 or higher, signifying a significant influence. Similarly, a high correlation coefficient of 0.76 is observed between oil prices and new orders from leading global construction companies. Further analysis reveals a particularly strong correlation between oil prices and overseas construction orders in Asia and the Middle East, potentially due to the prevalence of oil-related projects in these regions. Additionally, a high correlation is observed between oil prices and orders for industrial facilities compared to architectural projects. This suggests an increase in plant construction volumes driven by fluctuations in oil prices. Based on these findings, the study proposes an entry strategy for navigating oil price volatility and maintaining competitiveness in the overseas construction market. Key recommendations include diversifying project locations and supplier bases; utilizing hedging techniques for exchange rate risk management, adapting to local infrastructure and market conditions, establishing local partnerships and securing skilled local labor, implementing technological innovations and digitization at construction sites to enhance productivity and cost reduction The insights gained from this study, coupled with the proposed overseas expansion strategies, offer valuable guidance for mitigating risks in the global construction market and fostering resilience in response to international oil price fluctuations. This approach is expected to strengthen the competitiveness of domestic and foreign construction firms seeking success in the international arena.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.1
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• pp.8-16
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• 2024

Limestone (CaCO₃, calcium carbonate), which is used as a raw material in the portland cement and steel industry, emits CO₂ through decarbonation by high temperatures in the manufacturing process. To reduce CO₂ emissions by the use of raw materials like limestone, it has been proposed to replace limestone with various industrial by-products that contain CaO but less or none of the carbonated minerals, that cause CO₂ emissions. Loss of Ignition (LOI), Thermogravimetric analysis (TG), and Infrared Spectroscopy (IR) are used to quantitative the amount of CO₂ emission by using these industrial by-products, but CO₂ emissions can be either over or underestimated depending on the characteristics of by-product materials. In this study, we estimated CO₂ contents by LOI, TG, IR and DTG(Differential Thermogravimetric analysis) of calcite(CaCO₃) and samples that contain CO₂ in the form of carbonate and whose weight increases by oxidation at high temperatures. The test results showed for CaCO₃ samples, all test methods have a sufficient level of reliability. On the other hand, for the CO₂ content of the sample whose weight increases at high temperature, LOI and TG did not properly estimate the CO₂ content of the sample, and IR tended to overestimate compared to the predicted value, but the estimated result by DTG was close to the predicted valu e. From these resu lts, in the case of samples that contain less than a few percent of CO₂ and whose weight increases during the temperature that carbonate minerals decompose, estimating the CO₂ content using DTG is a more reasonable way than LOI, TG, and IR.