• Journal of the Society of Disaster Information
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• v.19 no.4
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• pp.976-983
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• 2023

Purpose: The dynamic behavior of a bridge structure under seismic loading depends on many uncertainties, such as the nature of the seismic waves and the material and geometric properties. However, not all uncertainties have a significant impact on the dynamic behavior of a bridge structure. Since probabilistic seismic performance evaluation considering even low-impact uncertainties is computationally expensive, the uncertainties should be identified by considering their impact on the dynamic behavior of the bridge. Therefore, in this study, a global sensitivity analysis was performed to identify the main parameters affecting the dynamic behavior of bridges with I-curved girders. Method: Considering the uncertainty of the earthquake and the material and geometric uncertainty of the curved bridge, a finite element analysis was performed, and a surrogate model was developed based on the analysis results. The surrogate model was evaluated using performance metrics such as coefficient of determination, and finally, a global sensitivity analysis based on the surrogate model was performed. Result: The uncertainty factors that have the greatest influence on the stress response of the I-curved girder under seismic loading are the peak ground acceleration (PGA), the height of the bridge (h), and the yield stress of the steel (fy). The main effect sensitivity indices of PGA, h, and fy were found to be 0.7096, 0.0839, and 0.0352, respectively, and the total sensitivity indices were found to be 0.9459, 0.1297, and 0.0678, respectively. Conclusion: The stress response of the I-shaped curved girder is dominated by the uncertainty of the input motions and is strongly influenced by the interaction effect between each uncertainty factor. Therefore, additional sensitivity analysis of the uncertainty of the input motions, such as the number of input motions and the intensity measure(IM), and a global sensitivity analysis considering the structural uncertainty, such as the number and curvature of the curved girders, are required.

• Journal of the Society of Disaster Information
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• v.20 no.3
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• pp.705-713
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• 2024

Purpose: Currently, the only routes that enter Yeongjong Island are Yeongjong Bridge and Incheon Bridge, which are private roads. The purpose of this study is to predict and study changes in transportation demand for new routes and two existing routes according to the plan to open the 3rd Bridge, a new route, in December 2025. Method: The basic data for traffic demand forecast were O/D and NETWORK data from 2021.08, KOTI. In order to examine the reliable impact of Yeongjong Bridge and Incheon Bridge on the opening of the 3rd Bridge, it is necessary to correct the traffic distribution of Yeongjong Island and Incheon International Airport to suit reality, and in this study, the trip distribution by region was corrected and applied using Mobile Big Data. Result: As of 2026, the scheduled year of the opening of the 3rd Bridge, two alternatives, Alternative 1 (2,000 won) and Alternative 2 (4,000 won), were established and future transportation demand analysis was conducted, In the case of Alternative 1, which is similar to the existing private road toll restructuring, the traffic volume of the 3rd Bridge was predicted to be 42,836 out of 199,101 veh/day in the Yeongjong area in 2026, and the traffic volume reduction rate of the existing road was analyzed as 21.5%. Conlclusion: As a result of the review (based on Alternative 1), the proportion of convertted traffic on the 3rd Yanji Bridge was estimated to be 70% of Yeongjong Bridge and 30% of Incheon Bridge, and 21.5% of the predicted traffic reduction on the existing road when the 3rd Yanji Bridge was opened is considered appropriate considering the results of the case review and changes in conditions. It is judged that it is a way to secure the reliability of the prediction of traffic demand because communication big data is used to reflect more realistic traffic distribution when predicting future traffic demand.

• Journal of the Korea Society of Computer and Information
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• v.29 no.9
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• pp.125-136
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• 2024

This study presents an automated Python algorithm for analyzing rainfall characteristics to establish critical rainfall thresholds as part of a landslide early warning system. Rainfall data were sourced from the Korea Meteorological Administration's Automatic Weather System (AWS) and the Korea Forest Service's Automatic Mountain Observation System (AMOS), while landslide data from 2020 to 2023 were gathered via the Life Safety Map. The algorithm involves three main steps: 1) processing rainfall data to correct inconsistencies and fill data gaps, 2) identifying the nearest observation station to each landslide location, and 3) conducting statistical analysis of rainfall characteristics. The analysis utilized power law and nonlinear regression, yielding an average R² of 0.45 for the relationships between rainfall intensity-duration, effective rainfall-duration, antecedent rainfall-duration, and maximum hourly rainfall-duration. The critical thresholds identified were 0.9-1.4 mm/hr for rainfall intensity, 68.5-132.5 mm for effective rainfall, 81.6-151.1 mm for antecedent rainfall, and 17.5-26.5 mm for maximum hourly rainfall. Validation using AUC-ROC analysis showed a low AUC value of 0.5, highlighting the limitations of using rainfall data alone to predict landslides. Additionally, the algorithm's speed performance evaluation revealed a total processing time of 30 minutes, further emphasizing the limitations of relying solely on rainfall data for disaster prediction. However, to mitigate loss of life and property damage due to disasters, it is crucial to establish criteria using quantitative and easily interpretable methods. Thus, the algorithm developed in this study is expected to contribute to reducing damage by providing a quantitative evaluation of critical rainfall thresholds that trigger landslides.

• Korean Journal of Remote Sensing
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• v.34 no.6_1
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• pp.869-877
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• 2018

The area of desert in East Asia is increasing every year, and it cause a great cost of social damage. Because desert is widely distributed and it is difficult to approach people, remote sensing using satellites is commonly used. But the study of desert area comparison is insufficient which is calculated by satellite sensor. It is important to recognize the characteristics of the desert area data that are calculated for each sensor because the desert area calculated according to the selection of the sensor may be different and may affect the climate prediction and desertification prevention measures. In this study, the desert area of Northeast Asia in 2001-2013 was calculated and compared using Moderate Resolution Imaging Spectroradiometer (MODIS) and Vegetation. As a result of the comparison, the desert area of Vegetation increased by $3,020km^2/year$, while in the case of MODIS, it decreased by $20,911km^2/year$. We performed indirect validation because It is difficult to obtain actual data. We analyzed the correlation with the occurrence frequency of Asian dust affected by desert area change. As a result, MODIS showed a relatively low correlation with R = 0.2071 and Vegetation had a relatively high correlation with R = 0.4837. It is considered that Vegetation performed more accurate desert area calculation in Northeast Asian desert area.

• Korean Journal of Remote Sensing
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• v.33 no.5_3
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• pp.809-820
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• 2017

Efficient management of large-size wastes generated from disasters etc. is always in demand. Large-size wastes are closely connected to the environment, producing adverse effects on the air quality, water quality, living environment and so on. When large-size wastes are generated, we must be able to estimate the generated amount in order to transfer them to a temporary trans-shipment site, or to properly treat them. Currently, we estimate the amount of generated large-size wastes by using satellite images or unit measure for wastes; however, the accuracy of such estimations have been constantly questioned. Therefore, the present study was performed to establish three-dimensional spatial information based on UAS, to measure the amount of waste, and to evaluate the accuracy of the measurement. A measurement was made at a waste site by using UAS, and the X, Y, Z RMSE values of the three-dimensional spatial information were found to be 0.022 m, 0.023 m, and 0.14 m, all of which show relatively high accuracy. The amount of waste measured using these values was computed to be approximately $4,273,400m^3$. In addition, the amount of waste at the same site was measured by using Terrestrial LiDAR, which is used for the precise measurement of geographical features, cultural properties and the like. The resulting value was $4,274,188m^3$, which is not significantly different from the amount of waste computed by using UAS. Thus, the possibility of measuring the amount of waste using UAS was confirmed, and UAS-based measurement is believed to be useful for environmental control with respect to disaster wastes, large-size wastes, and the like.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.4
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• pp.71-80
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• 2014

This study predicted damage areas due to landslides in Gangwon Province and estimated the scale of damage to roads, buildings, and forests on the local government level. By using old research findings to predict landslides, the study established techniques to make maps for landslide vulnerability, occurrence possibility, and risk. The scale of damage to roads, buildings, and forests was estimated at the local government level by making a landslide risk map for 100mm, 200mm, and 300mm of accumulated rainfall. The scale of damage to roads, buildings, and forests was estimated to be greatest in Hongcheon-gun, Jeongseon-gun, and Hongcheon-gun, respectively, in case of 100mm~200mm accumulated rainfall, in Chuncheon City, Pyeongchang-gun, and Hongcheon-gun, respectively, in case of 200mm~300mm accumulated rainfall, and in Hongcheon-gun in case of 300mm accumulated rainfall or more. Those estimation results of scale of damage by landslides at the local government level will help to set priorities in landslide prevention and provide basic data for budget decisions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2593-2600
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• 2013

The main purpose of this study is to carry out the performance evaluation of Ultra-light Fixed Wing UAV(Unmanned Aerial Vehicle) photogrammetry which is being, currently, applied for various fields such as cultural assets, accident survey, military reconnaissance work, and disaster management at home and abroad. Firstly, RMSE estimation of Aerial Triangulation (AT) are within approximately 0.10 cm in position (X, Y). And through the comparison of parcel's boundary points coordinates by terrestrial surveying and by UAV photogrammetry, the analysis shows that RMSE are shifted approximately 0.174~0.205 m in X-direction, 0.294~0.298 m in Y-direction respectively. Lastly, parcel's area by orthophoto of UAV photogrammetry and by that of cadastre register has been shown the difference by 0.118 m2. The results presented in this study is just one case study of orthophoto accuracy assessment of Ultra-light fixed wing UAV photogrammetry, hereafter various researches such as AT, direct-georeferencing, flight planning, practical applications, etc. should be necessary continuously.

• Fire Science and Engineering
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• v.34 no.2
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• pp.110-119
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• 2020

The National Fire Safety Code (NFSC) sets forth the installation methods and technical standards of firefighting facilities. This information is stipulated in the attached Table 1 of the Enforcement Decree of the Act on Fire Prevention and Installation, Maintenance and Safety Control of Fire-Fighting Systems. The NFSC serves as a foundation for fire prevention and public safety. However, the current version of the NFSC has been under scrutiny due to its delayed enactment and revision process. This is because of its structural inflexibility, time-consuming procedures, and mixed usage of both performance and technical standards. Furthermore, there are difficulties with keeping its unique specialties due to the absence of a specialized, permanent independent entity that enacts, revises, and maintains its standards. Moreover, the NFSC lacks collectivity, openness, and consistency. Therefore, to overcome the aforementioned obstacles, this study investigates the operational and legal status of the NFSC and the problems regarding its enactment and revision process. Further, it presents suggestions for system improvement by analyzing and comparing the information with domestic and foreign counterparts dedicated to managing their similar technical NFSC standards. First, the study recommends that the legal performance and technical standards mixed within the current NFSC should be separated. Second, the enactment and revision of technical standards should be implemented by the private sector and not by the government. Third, technical standards should adopt a user-oriented approach for the code system.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.4
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• pp.176-192
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• 2006

The need for a systematic drought management has increased since last countrywide drought in 2001. Naturally various studies for establishing drought plan and preventing drought disaster have been conducted. MODIS image provided by Terra satellite has effective spatial and temporal resolutions to observe spatial and temporal characteristics of a region. MODIS data products are easy for preprocessing and correcting geometrically and provide various data set in regular which are applicable for drought monitoring. In this study, Ansung river and the upstream of South Han river basin was chosen for case study to identify and assess spring drought. The multi-period MODIS image and accumulated precipitation were used to detect not only the drought year but also the vegetation change of normal year and the result were compared with various spatial data. The result shows NDVI and LSWI with is more appropriate than LST for assesing spring drought in Korea and two month cumulative precipitation has moderate relationship with drought. It is necessary to use MODIS image which has same period and same space for effective drought analysis because drought is also affected by landover and altitude.

• Journal of the Korean Association of Geographic Information Studies
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• v.19 no.4
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• pp.36-51
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• 2016

This study assessed urban flood risk using a Bayesian probability statistical method and GIS incorporating a climate change scenario. Risk is assessed based on a combination of hazard probability and its consequences, the degree of impact. Flood probability was calculated on the basis of a Bayesian model and future flood occurrence likelihoods were estimated using climate change scenario data. The flood impacts include human and property damage. Focusing on Seocho-gu, Seoul, the findings are as follows. Current flood probability is high in areas near rivers, as well as low lying and impervious areas, such as Seocho-dong and Banpo-dong. Flood risk areas are predicted to increase by a multiple of 1.3 from 2030 to 2050. Risk assessment results generally show that human risk is relatively high in high-rise residential zones, whereas property risk is high in commercial zones. The magnitude of property damage risk for 2050 increased by 6.6% compared to 2030. The proposed flood risk assessment method provides detailed spatial results that will contribute to decision making for disaster mitigation.