• Structural Engineering and Mechanics
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• v.38 no.2
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• pp.141-156
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• 2011

A cable stayed bridge under construction has low structural damping and is not as stable as the completed bridge. Control countermeasures, such as the installation of energy dissipating devices, are thus required. In this study, the general procedure and key issues on adopting an active control device, the active mass damper (AMD), for vibration control of cable stayed bridges under construction were studied. Taking a typical cable stayed bridge as the prototype structure; a lab-scale test structure was designed and fabricated firstly. A baseline FEM model was then setup and updated according to the modal parameters measured from vibration test on the structure. A numerical study to simulate the bridge-AMD control system was conducted and an efficient LQG-based controller was designed. Based on that, an experimental implementation of AMD control of the transverse vibration of the bridge model was performed. The results from numerical simulation and experimental study verified that the AMD-based active control was feasible and efficient for reducing dynamic responses of a complex structural system. Moreover, the discussion made in this study clarified some critical problems which should be addressed for the practical implementation of AMD control on real cable-stayed bridges.

• Steel and Composite Structures
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• v.24 no.2
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• pp.227-237
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• 2017

This paper presents optimization of a long-span portal steel frame under dynamic wind loads using a surrogate-assisted evolutionary algorithm. Long-span portal steel frames are often used in low-rise industrial and commercial buildings. The structure needs be able to resist the wind loads, and at the same time it should be as light as possible in order to be cost-effective. In this work, numerical model of a portal steel frame is constructed using structural analysis program (SAP2000), with the web-heights at five locations of I-sections of the columns and rafters as the decision variables. In order to evaluate the performance of a given design under dynamic wind loading, the equivalent static wind load (ESWL) is obtained from a database of wind pressures measured in wind tunnel tests. A modified formulation of the problem compared to the one available in the literature is also presented, considering additional design constraints for practicality. Evolutionary algorithms (EA) are often used to solve such non-linear, black-box problems, but when each design evaluation is computationally expensive (e.g., in this case a SAP2000 simulation), the time taken for optimization using EAs becomes untenable. To overcome this challenge, we employ a surrogate-assisted evolutionary algorithm (SAEA) to expedite the convergence towards the optimum design. The presented SAEA uses multiple spatially distributed surrogate models to approximate the simulations more accurately in lieu of commonly used single global surrogate models. Through rigorous numerical experiments, improvements in results and time savings obtained using SAEA over EA are demonstrated.

• Geomechanics and Engineering
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• v.24 no.5
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• pp.471-478
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• 2021

Water damage is one of the five disasters that affect the safety of coal mine production. The erosion of rocks by water is a very important link in the process of water inrush induced by fault activation. Through the observation and experiment of fault filling samples, according to the existing rock classification standards, fault sediments are divided into breccia, dynamic metamorphic schist and mudstone. Similar materials are developed with the characteristics of particle size distribution, cementation strength and water rationality, and then relevant tests and analyses are carried out. The experimental results show that the water-rock interaction mainly reduces the compressive strength, mechanical strength, cohesion and friction Angle of similar materials, and cracks or deformations are easy to occur under uniaxial load, which may be an important process of water inrush induced by fault activation. Mechanical experiment of similar material specimen can not only save time and cost of large scale experiment, but also master the direction and method of the experiment. The research provides a new idea for the failure process of rock structure in fault activation water inrush.

• Geomechanics and Engineering
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• v.30 no.3
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• pp.281-291
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• 2022

Complex rock masses include various joint planes, bedding planes and other weak structural planes. The existence of these structural planes affects the mechanical properties, deformation rules and failure modes of jointed rock masses. To study the influence of the parameters of a nonpersistent joint network on the mechanical properties and failure modes of jointed rock masses, synthetic rock mass (SRM) technology based on discrete elements is introduced. The results show that as the size of the joints in the rock mass increases, the compressive strength and the discreteness of the rock mass first increase and then decrease. Among them, the joints that are characterized by "small but many" joints and "large and clustered" joints have the most significant impact on the strength of the rock mass. With the increase in joint density in the rock mass, the compressive strength of rock mass decreases monotonically, but the rate of decrease gradually decreases. With the increase in the joint dip angle in rock mass, the strength of the rock mass first decreases and then increases, forming a U-shaped change rule. In the analysis of the failure mode and deformation of a jointed rock mass, the type of plastic zone formed after rock mass failure is closely related to the macroscopic displacement deformation of the rock mass and the parameters of the joints, which generally shows that the location and density of the joints greatly affect the failure mode and displacement degree of the jointed rock mass. The instability mechanism of jointed surrounding rock is revealed.

• The Korean Journal of Emergency Medical Services
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• v.5 no.1
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• pp.89-97
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• 2001

Recently, natural disasters happened to the Korea frequently. Disaster in the present society has been changed and increased it impacts and extent of danger as the society develops. So, Korean people feel uneasy about the unpredictable disaster. Therefore the capability of administration system, and cooperation and support between related organization become more necessary. This study aims to find out better ways of disaster management system which can protect people's lives and fortune from all sort of national disasters. To research policy reform, it is necessary to analyze disaster response organization(national disaster prevention countermeasures headquarters and so on), interorganizational relationship, law system etc. Especially, in this study, role appreciation of government was analyzed to get the rational policy reform measure. Suggestion : First, it is necessary Establishing a consolidated organization for disaster managing and united response organization is necessary such as Federal Emergency Management Agency(FEMA) which controls an over all aspects of disaster management. And it is necessary to develop Integrated Administrative Control System based on comprehensive plan. When the accidents happen, it needs to be many equipments and various specialized personnel. So, to manage a large scale of disaster, it is necessary to have interorganizational network system which many specialized organization including volunteer group are integrated. Also, as soon as the natural disaster happen, many professionals and volunteers are distributed to the spots of disaster in the right man in the right place. Finally, All the citizens have to keep safety rules, and also to take a safe action in ordinary daily life.

• Journal of the Korea Safety Management & Science
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• v.19 no.1
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• pp.1-8
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• 2017

The current study aims to propose a reorganization plan for the national emergency management system to improve the current organizational structure for responding to national disasters and emergency situations. As a theoretical framework, the current study identified four key elements of successful disaster response systems: responsiveness, controllability, expertise, and devotedness. On the basis of the four key elements of disaster response systems, this study critically reviewed the current state of the organizational structure of the Korean national emergency response system by discussing the issues inherent in the current structure and by doing a comparative analysis of two high-profile national disaster cases-the Sewol ferry disaster in 2014 and the Gwangsan Rescue of buried people in 2013. Then, this study proposed the reorganization plan for the national disaster response system in which the NEMA is under direct control of the Prime Minister of Korea. It coordinates and controls the related government departments, such as the police, maritime police, and military during the national disaster and emergency situation. This study also proposed a reorganizational plan for the regional disaster response system in Korea. Finally, it was suggested that the status of firefighters should be elevated to the national public servant level in order to achieve organizational efficiency and solve existing problems that come from the current separated systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.167-175
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• 2018

To cope with the increasing number of natural disasters in recent years, managers in the National Disaster and Safety Status Control Center, who have considerable experience and skills, are regarded highly important. Although the National Disaster and Safety Status Control Center oversees the disaster-status control tasks in preparation for various natural and social disasters, there is little data due to the frequent replacement of managers. Therefore, this study developed a disaster-safety code system that tracks and manages disaster information, because the current record management and amount of information sharing remains very low. Among 22 natural and social disaster types, this study targeted four types of disasters: heavy snow, strong winds, high seas, and heavy rain. The final disaster-safety data code system was proposed through the following processes: analysis of the code systems of disaster areas in Korea and overseas, setup of the implementation of directions, development of the classification system, and categorization. For the systematic accumulation of data, the four code systems were integrated into one. A prototype system was developed and operated to verify the validity of the proposed code system. The results showed that data were accumulated and services were provided accordingly with respect to the proposed code system. If past data are accumulated and utilized according to the proposed code system in this study, it will be helpful in the decision making process to respond to new types of disasters, based on past experiences.

• Korean Security Journal
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• no.4
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• pp.343-363
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• 2001

Chapter 1 is the introduction part. With the development of modem science and technology, the world has experienced serious disaster. Each occurrence of such disaster has reminded the people all over the world of the importance of coping with the disaster and therefore all the countries have set up the disaster administration system to handle their disasters in efficient way. The principal purpose of this research is to establish ways and means needed to improve the disaster management system in Korea. Chapter 2 introduces the reader to a disaster management theory Chapter 3 dealt with the problems on the disaster administration system, under which the first and second section mention the points at issue in the system of law and administration of our country, respectively, Chapter 4 dealt with the plan to improve the disaster adminstration system under which the first section describes its basic direction while the second section describes the clarification of the role share of the central government and local autonomous body, beefing up the functions of disaster administration of the central government and local autonomous body. establishment of disaster prevention system, activation of support program against disaster, raising the professional personnels, extending the disaster prevention facilities, etc. Chapter 5, the conclusion, describes the difficulties in coping with the disaster under the existing disaster administration system. Therefore, the entire fundamental of disaster administration is in need such as distinct roles of the central government and local autonomous body, improving the systems of law and administration, education and training, and guidance and superintendence, etc. In addition, the control function of the concerned authorities must be reinforced to perform the disaster administration system smoothly while establishing 24 hour emergency system. Also, the financial support from the central government and technical study on the disaster administration should be done continuously on long-term basis.

• Wind and Structures
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• v.10 no.2
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• pp.209-214
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• 2007

• Journal of Korean Society of Forest Science
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• v.94 no.4 s.161
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• pp.252-257
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• 2005

The study on long-term change of natural and sediment disasters such as landslides and debris flows is not thoroughgoing enough in spite of increasing of concern for disaster. Therefore, the change of natural and sediment disasters was investigated with the number of victims caused by both disasters and the ratio of sediment disasters for natural disasters was compared. The number of victims by sediment and natural disasters has apparently been decreasing despite of the change of rainfall pattern. The number of victims was changed to 140 persons/year in the late 1990s from 250 persons/year in the 1970s of natural disaster and that of sediment disaster to 20 persons/year in the late 1990s from 60 persons/year in the late 1970s. Furthermore, the ratio of sediment disaster victims to natural disaster victims has decreased from 2/7 in the 1970s to 2/15 after 1980s. But, the system of sediment disaster management and new soil erosion control works tough introduction of watershed management concept are requested because of increased landslide area in recent years (206ha in 1981 $\rightarrow$ 688ha in 1999).