• Structural Engineering and Mechanics
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• v.35 no.6
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• pp.735-758
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• 2010

The paper proposes two methodologies for damage identification from measured natural frequencies of a contiguously damaged reinforced concrete beam, idealised with distributed damage model. The first method identifies damage from Iso-Eigen-Value-Change contours, plotted between pairs of different frequencies. The performance of the method is checked for a wide variation of damage positions and extents. The method is also extended to a discrete structure in the form of a five-storied shear building and the simplicity of the method is demonstrated. The second method is through smeared damage model, where the damage is assumed constant for different segments of the beam and the lengths and centres of these segments are the known inputs. First-order perturbation method is used to derive the relevant expressions. Both these methods are based on distributed damage models and have been checked with experimental program on simply supported reinforced concrete beams, subjected to different stages of symmetric and un-symmetric damages. The results of the experiments are encouraging and show that both the methods can be adopted together in a damage identification scenario.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.37-46
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• 2006

The principal objective of this study is to assess the hierarchical effects of defects on the elastic stiffness properties at different levels of observation. In particular, quantitative damage measures which characterize the fundamental mode of degradation in the form of elastic damage provide quite insightful meanings at the level of constitutive relations and at the level of structures. For illustration, a total of three model problems of increasing complexity, a 1-D bar structure, a 2-D stress concentration problem, and a heterogeneous composite material made of a matrix with particle inclusions. Considering a damage scenario for the particle inclusions the material system degrades from a composite with very stiff inclusions to a porous material with an intact matrix skeleton. In other damage scenario for the matrix, the material system degrades from a composite made of a very stiff skeleton to a disconnected assembly of particles because of progressive matrix erosion. The trace-back and forth of tight bounds in terms of the reduction of the lowest eigenvalues are extensively discussed at different levels of observation.

• Journal of the Korea Safety Management & Science
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• v.26 no.3
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• pp.51-57
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• 2024

The purpose of this study is to compare and analyze the impact range of explosion damage due to gas leaks at LPG filling stations, focusing on propane and butane, which are components of vehicle LPG. The scenarios were designed based on the explosion incident at an LPG filling station in Gangwon-do, where an actual gas leak accident occurred, resulting in Scenario I and Scenario II. The ALOHA program, developed by the U.S. National Oceanic and Atmospheric Administration (NOAA), was used as the tool to analyze the impact range of the explosion damage for both substances. The results of the study indicated that, under identical conditions, propane had a wider impact range of damage than butane. This is presumed to be due to the greater explosion energy of propane, attributable to its physicochemical properties. Therefore, when preparing for LPG leak accidents, measures for propane need to be prioritized. As safety measures for propane, two suggestions were made to minimize human casualties. First, from a preventive perspective, it is suggested to educate workers about propane. Second, from the perspective of response measures and damage minimization, it is suggested to thoroughly prepare emergency evacuation and rescue plans, evacuation routes, designated shelters, and emergency response teams. This study compares and analyzes the impact range of radiative heat damage based on LPG components. However, hazardous accidents are critically influenced by the type of leaking substance, the form of the leak, and meteorological factors affecting the diffusion pattern of the substance. Therefore, for future research, it is proposed to model various leakage scenarios for the same substance to conduct a comprehensive risk assessment.

• Journal of the Korean Institute of Gas
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• v.11 no.2 s.35
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• pp.15-24
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• 2007

For consequence analysis at a gas explosion by vessel release, release rates, demage areas of facilities, and fatality areas were estimated and analyzed at various conditions(release materials, temperatures, pressures, and vessel types) by using the release scenario of API-581 BRD. Simulation results showed that release rates and consequences in the vessel release were higher than those in the pipe release, and the order of release rates and damage areas was as follows; tank>reactor>drum> column.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.355-358
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• 2010

The objective of this study is to predict and minimize annual damage by flood. We approached this problem by implementing simple algorithm instead of using commercial programs. The biggest weak area was selected as the simulated damage range per rainfall scenario.

• International journal of advanced smart convergence
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• v.13 no.3
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• pp.345-357
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• 2024

High rise hotels are densely populated and have complex ignition sources. Once a fire occurs, it can cause serious casualties and property damage. The impact of a fire is greater on special groups such as the elderly and children who move slowly. At present, research mainly focuses on the impact of high-rise building structures on evacuation consequences, but there is little research on the safety evacuation consequences of elderly and children in high-rise hotels, as well as the behavior of people in groups during the safety evacuation process. Therefore, we propose to use Pathfinder software to simulate three scenarios for the elderly and children in high-rise hotels. Scenario 1 involves arranging the elderly and children on higher floors, Scenario 2 involves arranging them on middle floors, and Scenario 2 involves arranging them on lower floors. We further provide three types of personnel pairing schemes for each scenario, namely: no one pairing, two people pairing, and three people pairing. Through simulation analysis, we found that placing elderly and children with lower mobility on lower floors resulted in the shortest safe evacuation time; The evacuation time for solo actions without companionship is the shortest, followed by two people in groups, and the safety evacuation time for three people in groups is the longest. Our research findings have significant implications for improving the evacuation efficiency of personnel in fire scenarios.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.189-189
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• 2016

To generate information that contributes to climate change risk management, it is important to perform a precise assessment on the impact in diverse aspects. Considering this academic necessity, Japanese government launched continuous research project for the climate change impact assessment, and one of the representative project is Program for Risk Information on Climate Change (Sousei Program), Theme D; Precise Impact Assessment on Climate Change (FY2012 ~ FY2016). In this research program, quantitative impact assessments have been doing from a variety of perspectives including natural hazards, water resources, and ecosystems and biodiversity. Especially for the natural hazards aspect, a comprehensive impact assessment has been carried out with the worst-case scenario of typhoons, which cause the most serious weather-related damage in Japan, concerning the frequency and scale of the typhoons as well as accompanying disasters by heavy rainfall, strong winds, high tides, high waves, and landslides. In this presentation, a framework of comprehensive impact assessment with the worst-case scenario under the climate change condition is introduced based on a case study of Theme D in Sousei program There are approx. 25 typhoons annually and around 10 of those approach or make landfall in Japan. The number of typhoons may not change increase in the future, but it is known that a small alteration in the path of a typhoon can have an extremely large impact on the amount of rain and wind Japan receives, and as a result, cause immense damage. Specifically, it is important to assess the impact of a complex disaster including precipitation, strong winds, river overflows, and high tide inundation, simulating how different the damage of Isewan Typhoon (T5915) in 1959 would have been if the typhoon had taken a different path, or how powerful or how much damage it would cause if Isewan Typhoon occurs again in the future when the sea surface water temperature has risen due to climate changes (Pseudo global warming experiment). The research group also predict and assess how the frequency of "100-years return period" disasters and worst-case damage will change in the coming century. As a final goal in this research activity, the natural disaster impact assessment will extend not only Japan but also major rivers in Southeast Asia, with a special focus on floods and inundations.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.2
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• pp.1-15
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• 2020

In this study, the characteristics of crop damage area by flooding for 113 middle range watersheds during 2000-2016 were analyzed and future crop damage area by flooding were analyzed using 13 GCM outputs such as hourly maximum rainfall, 10-min maximum rainfall, number of days of 80 mm/day, daily rainfall maximum, annual rainfall amount associated with RCP 4.5 and RCP 8.5 scenarios and watershed characteristic data such as DEM, urbanization ratio, population density, asset density, road improvement ratio, river improvement ratio, drainage system improvement ratio, pumping capacity, detention basin capacity, and crop damage area by flooding. A constrained multiple linear regression model was used to construct the relationships between the crop damage area by flooding and other variables. Future flood index related to crop damage may mainly increase in the Mankyung watershed, Southwest part of Youngsan and Sumjin river basin and Southern part of Nackdong river basin. Results are useful to identify watersheds which need to establish strategies for responding to future flood damage.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.122-128
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• 2009

In this study, damage detection method using harmony search method and frequency response is proposed. In order to verify this method, the following approaches are implemented. Firstly, damage detection method using harmony search was developed. To detect damage, objective functions that minimize difference with natural frequency and modal strain energy from undamaged and damaged model are used. Secondly, efficiency of developed damage detection method was verified by damage detection of beam structure. And results of harmony search and micro genetic algorithm are compared and evaluated. Thirdly, numerical model was implemented for harbor caisson structure and damage scenario was determined. Lastly, damage detection was performed by proposed method and utility of proposed method is verified.

• Structural Engineering and Mechanics
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• v.19 no.1
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• pp.21-42
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• 2005

A method is presented to detect and assess the structural damage from changes in natural frequencies using Genetic Algorithm (GA). Using the natural frequencies of the structure, it is possible to formulate the inverse problem in optimization terms and then to utilize a solution procedure employing GA to assess the damages. The technique has been applied to a cantilever beam and a plane frame, each one with different damage scenario to study the efficiency of the developed algorithm. A laboratory tested data has been used to verify the proposed algorithm. The study indicates the potentiality of the developed code to solve a wide range of inverse identification problems in a systematic way. The outcomes show that this method can detect and estimate the amount of damages with satisfactory precision.