https://doi.org/10.12652/Ksce.2024.44.3.0271

이헌우(Lee, Heon-Woo) ; 아시프 라비아(Asif, Rabea) ; 허종완(Hu, Jong-Wan)

Traditional oil, a depleting resource, accounts for only one-third of the world's oil reserves, so research and cases of utilizing non-traditional oil as a resource are continuously increasing. However, unconventional oil contains bitumen containing solid particles such as sand, and because it is exposed to a high temperature and high pressure environment, deformation can frequently occur in oil pipelines. Therefore, variables such as material, thickness, and angle that can affect the deformation of the oil pipeline were derived and applied to the oil pipeline, and finite element analysis was performed using the Ansys program. As a result of finite element analysis, deformation and maximum load capacity were derived. Afterwards, the same analysis was performed by modeling an optimized oil pipeline by combining the factors with the best deformation resistance and maximum load capacity. As a result of the analysis, the effect of reducing deformation and increasing the maximum load capacity by about 30 % was confirmed, and factors for suppressing deformation when analyzing oil pipelines were derived.

https://doi.org/10.12652/Ksce.2024.44.3.0277

김건규(Kim, Gungyu) ; 곽신영(Kwag, Shinyoung) ; 임승현(Eem, Seunghyun) ; 진승섭(Jin, Seung-Seop)

Recently, the intensity and frequency of typhoons have been increasing due to climate change, and typhoons can cause a loss of offsite power (LOOP) at nuclear power plants (NPPs). Therefore, it is necessary to prepare for typhoon-induced high winds through the probabilistic safety assessment (PSA) of offsite power systems. However, research on PSA for offsite power system in NPPs under typhoon-induced high winds is still lacking. In this study, PSA was performed for offsite power systems subjected to typhoon-induced high winds at the Kori NPP site, which has experienced frequent damages to its offsite power system among NPP sites in Korea. In order to perform PSA for typhoon-induced high winds in offsite power systems, the typhoon hazard at Kori NPP site was derived using logic tree and Monte Carlo simulation. Utilizing the fragility of components constituting the power system, performed a fragility analysis of the power system. Lastly, the probability that offsite power system will not be able to supply power to the NPP was derived.

https://doi.org/10.12652/Ksce.2024.44.3.0283

신민건(Shin, Mingun) ; 부상필(Boo, Sangpil) ; 박상렬(Park, Sangyeol) ; 문경태(Moon, Kyoungtae)

Currently, the quality standards for recycled aggregates in Korea are very high, at almost the same level as natural aggregates, so recycled aggregates cannot be widely used for concrete. In particular, it is necessary to evaluate how the moisture conditions and curing conditions of recycled aggregates with high absorption rates and wearing rates affect the compressive strength of concrete. Therefore, in this study, we wanted to investigate the effects on compressive strength through experiments using the moisture conditions and curing conditions of recycled coarse aggregate as variables, and compare the compressive strength characteristics of natural coarse aggregate concrete. As a result of this experimental study, the effect of compressive strength on concrete using recycled coarse aggregates according to curing conditions was similar to that of natural aggregate concrete, and the compressive strength showed a low strength of about 13 to 17 %. The effect of the moisture conditions of recycled coarse aggregates was that in the case of wet curing, concrete using wet aggregate showed slightly higher compressive strength than concrete using dry aggregate, but in the case of air curing, on the contrary, dry recycled aggregate concrete was relatively higher than wet aggregate concrete.

https://doi.org/10.12652/Ksce.2024.44.3.0291

김지은(Kim, Ji Eun) ; 손호준(Son, Ho-Jun) ; 김태식(Kim, Taesik) ; 김원범(Kim, Won-Beom) ; 김태웅(Kim, Tae-Woong)

Sustained meteorological drought can lead to hydrological drought, known as drought propagation. The propagated droughts cause more damage to the region than the non-propagated droughts. Recent studies on drought propagation have focused on identifying the lag time using correlation analysis. There is a lack of studies comparing damage patterns between propagated and non-propagated droughts. In this study, the overlap and pooling propagation between meteorological and hydrological droughts were analyzed using drought indices in Chungcheong Province to identify drought propagation, and the propagation characteristics such as pooling, attenuation, lag and extension were analyzed. The results showed that although Chungju-si experienced a meteorological drought in 2010, no damage was caused by the drought. However, a meteorological drought in 2017 and 2018 propagated into a hydrological drought of longer duration but less severity, resulting in drought-affected damage. Similarly, Cheongyang-gun experienced a meteorological drought in 2017, but no damage was reported from the drought. However, in the neighboring county of Buyeo-gun, a meteorological drought with a similar magnitude propagated to a hydrological drought during the same period, resulting in drought-affected damage. The overall results indicated that the damage from propagated drought events was more severe than the non-propagated drought events, and these results can be used as basic data for establishing drought response policies suitable for the region.

https://doi.org/10.12652/Ksce.2024.44.3.0303

정연지(Chung, Yeon-Ji) ; 김민기(Kim, Min-ki) ; 엄명진(Um, Myoung-Jin)

Precipitation data are an integral part of water management planning, especially the design of hydroelectric structures and the study of floods and droughts. However, it is difficult to obtain accurate data due to space-time constraints. The recent increase in hydrological variability due to climate change has further emphasized the importance of precipitation simulation techniques. Therefore, in this study, the Modified Bartlett-Lewis Rectangular Pulse model was utilized to apply the parameters necessary to predict daily precipitation. The effect of this parameter on the daily precipitation prediction was analyzed by applying exponential distribution, Gamma distribution, and Weibull distribution to evaluate the suitability of daily precipitation prediction according to each distribution type. As a result, it is judged that parameters should be selected in consideration of regional and seasonal characteristics when simulating precipitation using the MBLRP model.

https://doi.org/10.12652/Ksce.2024.44.3.0315

홍다희(Hong, Dahee) ; 김석우(Kim, Soukwoo) ; 조현선(Cho, Hyeonseon) ; 유지영(Yoo, Jiyoung) ; 김태웅(Kim, Tae-Woong)

Precipitation is a crucial meteorological variable widely used as essential input data in most hydrological models. However, due to climate change, there is an escalating precipitation variability. Trend analysis plays an important role in planning and operating water resources systems. As recently developed, Innovative Polygon Trend Analysis (IPTA) is useful in identifying and and analyzing the trends of hydrologic variables. In this study, the IPTA was applied to monthly precipitation data obtained from 13 meteorological observatories in Jeolla province, along with synthesized precipitation data according to Shared Socioeconomic Pathways (SSP) scenarios. The trend results were compared those obtained from the Mann-Kendall test and the Sen’s slope estimation which are generally used in practice. The results revealed monthly precipitations from February to July and November had increasing trends, and monthly precipitation in October had a decreasing trend. IPTA, Mann-Kendall test, and Sen’s slope estimation detected trends in 75.00 %, 5.13 %, and 5.13 % of 156(13 stations × 12 months) time series of monthly precipitation, respectively, which indicates that the IPTA is more sensitive in trend detection compared to the Mann-Kendall test and Sen’s slope estimation.

https://doi.org/10.12652/Ksce.2024.44.3.0329

최성욱(Choi, Seongwook)

In the case of multi-function weirs installed in Korea, the free hydraulic jump or the submerged hydraulic jump is occurred depending on the height of the gate opening and the tailwater level when the sluice gate of the movable weir is partially opened. In this study, the submerged hydraulic jump for the flows under the sluice gate were simulated and the mean flow, turbulence statistics, and relative water depth are investigated using numerical simulation. For numerical simulation, the unsteady Reynolds-averaged Navier-Stokes equation, volume of fluid method, and k-ωSST turbulence model were used. The numerical model was validated using the results of other researchers' previously performed experiments, and it was investigated that the numerical model appropriately simulates the two-phase flow in the hydraulic jump. In addition, the distribution of mean flow, turbulence statistics, and the length of recirculation region was investigated.

https://doi.org/10.12652/Ksce.2024.44.3.0337

윤대호(Yun, Dae-Ho) ; 임병권(Lim, Byeong-Gwon) ; 이지성(Lee, Ji-Sung) ; 김윤태(Kim, Yun-Tae)

Artificial reef often experiences a functional loss due to scour, even though serveral surveys of a seabed were performed prior to installation. Particularly in the east and west coasts in Korea, where the artificial reefs are installed, there are clear differences in the geotechnical characteristics of the seabed. Therefore, in this study, both field surveys and laboratory experiments were conducted to investigate the scouring characteristics of artificial reefs installed on the east and west coasts of Korea. The laboratory experiments were performed with different velocities and soil types. The field survey results of artificial reef revealed that artificial reef-installed seabeds in the east and west coasts are more vulnerable to scour than settlement. Particularly in the west coast, the loss ratio caused by scour was found to exceed 50 % in most cases. The experimental results showed that scouring occurred faster and more severely on the west coast seabed, which has a smaller particle size compared to the east coast. Additionally when the scour depth exceeded approximately 10 % of the height of the artificial reef, the artificial reef tilted forward and further scouring was induced.

https://doi.org/10.12652/Ksce.2024.44.3.0349

도명식(Do, Myungsik) ; 정유미(Jeong, Yumi)

The purpose of this study is to analyze the performance of the road network according to the penetration rate of autonomous vehicles (AV) of Level 4 or higher and the change in traffic volume. First, prior studies related to vehicle control variables of AV were reviewed, and future traffic demand in 2040, which is predicted to have a 50 % market share of AVs, was reflected in the simulation analysis. In addition, the change in traffic flow of continuous and intermittent flows was analyzed by increasing the AV market penetration rate and traffic volume of passenger cars, trucks, and buses by 25 % step by step from 0 to 100 %. As a result of the analysis, it was confirmed that the travel time increased as the traffic increased, and the pattern of decreasing the travel time due to the increase in the share of AVs, that is, the development of technology, can also be confirmed. Furthermore, it was also confirmed that the traffic speed showed a trend of increasing as the share of AVs increased. In this study, it was confirmed that the law of diminishing marginal rate of substitution (MRS) was satisfied by calculating the MRS according to the combination of traffic volume and speed while increasing the market penetration rate of AVs. Furthermore, it was confirmed that the convexity of the indifference curve was also satisfied in both intermittent and continuous traffic flow environments.

https://doi.org/10.12652/Ksce.2024.44.3.0361

임광균(Lim, Kwangk-kyun)

Advertising on the exterior of buses was initiated in 1985 with the aim of generating operational funds for the 1988 Seoul Olympics. However, despite numerous technological advancements, the regulations governing the method (sheet attachment), area, and placement of exterior advertising on buses have remained unchanged to date. This has constrained the potential for profitability and efficiency in bus exterior advertising. According to Seoul Metropolitan Government, metro usage increased by 23 % in 2019 (prior to the COVID-19) compared to 2006, while bus usage decreased by 10 %. Consequently, financial subsidy for buses surged significantly over the past five years (2018-2022), averaging around KRW 450 billion, which is approximately 1.27 times the average for the preceding decade (2013-2022). The majority of revenue for bus transportation agencies is derived from passenger fares (81.1 %) and subsidies from Seoul City (17.5 %). Hence, it is imperative to enhance the share of revenue from sources other than fares. This study proposes an expansion of the role of bus exterior advertising by increasing the advertising area as a means to increase non-fare revenue. Two alternatives were proposed to expand the advertising area by 17 % and 94 %, respectively, compared to the current level, and their potential impacts were analyzed. The findings indicate that advertising revenue could increase from a minimum of KRW 3.2 billion to a maximum of KRW 53.9 billion, and public subsidies could be reduced by as much as 11.9 %. The bus exterior advertising can serve as an effective approach to diversify transportation revenue and decrease public subsidies.

https://doi.org/10.12652/Ksce.2024.44.3.0375

박희성(Park, Heesung) ; 김태영(Kim, Tae Yeong)

The size of the construction industry is increasing, and its impact on the entire national industry is also significant. However, construction cost increases, construction period delays, safety accidents, and quality problems occur during the construction process. This paper analyzed the construction cost, construction period, and change order performance for civil infrastructures for which post evaluation was performed. The analysis was conducted by dividing civil engineering facilities by type, construction nature, construction cost, contract nature, and delivery method. Planned and actual construction cost and period were compared during the planning, design, and construction process of civil engineering facilities. There is a possibility of input errors in project performance data, this paper proposes to the post-evaluation center should perform post-evaluation. Also, post-evaluation implementation guidelines for change orders should be revised. Additionally, further analysis of each facility was proposed through continuous data collection.

https://doi.org/10.12652/Ksce.2024.44.3.0385

박영훈(Park, Younghoon)

To enhance the accuracy of sinkhole detection using GPR, this study derived a convolutional neural network that can optimally extract sinkhole characteristics from GPR B-scan grayscale images. The pre-trained convolutional neural network is evaluated to be more than twice as effective as the vanilla convolutional neural network. In pre-trained convolutional neural networks, fast feature extraction is found to cause less overfitting than feature extraction. It is analyzed that the top-1 verification accuracy and computation time are different depending on the type of architecture and simulation conditions. Among the pre-trained convolutional neural networks, InceptionV3 are evaluated as most robust for sinkhole detection in GPR B-scan grayscale images. When considering both top-1 verification accuracy and architecture efficiency index, VGG19 and VGG16 are analyzed to have high efficiency as the backbone for extracting sinkhole feature from GPR B-scan grayscale images. MobileNetV3-Large backbone is found to be suitable when mounted on GPR equipment to extract sinkhole feature in real time.

https://doi.org/10.12652/Ksce.2024.44.3.0397

정지헌(Jung, Ji Heon) ; 조수민(Jo, Su Min) ; 어양담(Eo, Yang Dam) ; 박진혁(Park, Jinhyeok) ; 최연오(Choi, Yeon Oh)

In order to improve the visibility of nighttime thermal infrared images, a simulation method with daytime color images was proposed. As a simulation method consisting of two steps, the daytime thermal infrared image was simulated by learning the unpaired nighttime thermal infrared image and daytime thermal infrared image, then the result was translated into a daytime color image. A temperature change regression equation was constructed and applied to reflect the systematic characteristics of temperature changes in daytime and nighttime images, and day and night simulation and colorization were trained and modeled by CycleGAN. For the experimental area, 100 images were captured and used for training. As a result, the simulation showed an average SSIM of 0.2449 and a PSNR of 51.2254. It was confirmed that the method could simulate complex and detailed features such as vegetation.

https://doi.org/10.12652/Ksce.2024.44.3.0407

정지원(Jeong, Ji Won) ; 안승준(Ahn, Seungjun) ; 유민택(Yoo, Min-Taek)

Over the past 20 years, there has been a rapid increase in the number and size of subway stations and underground structures worldwide, and the importance of safety for subway users has also continuously grown. Subway stations, due to their structural characteristics, have limited visibility and escape routes in disaster situations, posing a high risk of human casualties and economic losses. Therefore, an analysis of disaster vulnerabilities is essential not only for existing subway systems but also for deep underground facilities like GTX. This paper presents a case study applying a betweenness centrality-based disaster vulnerability analysis framework to the case of Gwanggyo Central Station. The analysis of Gwanggyo Central Station's base model and various disaster scenarios revealed that the betweenness centrality distribution is symmetrical, following the symmetrical spatial structure of the station, with high centrality concentrated in the central areas of basement levels one and two. These areas exhibited values more than 220 % above the average, indicating a high likelihood of bottleneck phenomena during evacuation in disaster situations. To mitigate this vulnerability, scenarios were proposed to distribute evacuation flows concentrated in the central areas, enhancing the usability of peripheral areas as evacuation routes by connecting staircases continuously. This modification, when considered, showed a decrease in centrality concentration, confirming that the proposed addition of evacuation paths could effectively contribute to dispersing the flow of evacuation in Gwanggyo Central Station. This case study demonstrates the effectiveness of the proposed framework for assessing evacuation vulnerability in enhancing subway station user safety and can be effectively applied in disaster response and management plans for major underground facilities.

https://doi.org/10.12652/Ksce.2024.44.3.0417

(Chae, Yun Seok) ; (Kim, Sigon)

This study compared and analyzed the importance of command priority between railway traffic controllers through pairwise comparison of AHP analysis. 27 railway traffic controllers working on metropolitan railway control center, urban railway control center, and unmanned driving control center responded. As a result of the analysis, all the railway traffic controllers generally recognized the train driving control and train signal control as the most important priorities. For the controller in the manned driving system, a train driving control was the highest at 0.375. On the other hand, the controller based on unmanned driving recognized train signal control as the highest priority at 0.469. In the result of the AHP analysis considering all the variables, the braking system was the highest priority at 0.19 based on manned train driving. On the other hand, the controller based on unmanned train driving recognized wired and wireless network systems and SCADA as the highest priority at 0.267.