• Smart Structures and Systems
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• 제15권3호
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• pp.717-733
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• 2015

Modal parameters of a structure are commonly used quantities for system identification and damage detection. With a limited number of studies on the statistics assessment of modal parameters, this paper presents procedures to properly account for the uncertainties present in the process of extracting modal parameters. Particularly, this paper focuses on how to deal with the measurement error in an ambient vibration test and the modeling error resulting from a modal parameter extraction process. A bootstrap approach is adopted, when an ensemble of a limited number of noised time-history response recordings is available. To estimate the modeling error associated with the extraction process, a model prediction expansion approach is adopted where the modeling error is considered as an "adjustment" to the prediction obtained from the extraction process. The proposed procedures can be further incorporated into the probabilistic analysis of applications where the modal parameters are used. This study considers the effects of the measurement and modeling errors and can provide guidance in allocating resources to improve the estimation accuracy of the modal data. As an illustration, the proposed procedures are applied to extract the modal data of a damaged beam, and the extracted modal data are used to detect potential damage locations using a damage detection method. It is shown that the variability in the modal parameters can be considered to be quite low due to the measurement and modeling errors; however, this low variability has a significant impact on the damage detection results for the studied beam.

• 한국해양공학회지
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• 제22권3호
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• pp.47-57
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• 2008

Many accidents occur on the oceans. Accidents involving ships can cause enormous damage. When an accident occurs, the cost of environmental restoration can bankrupt even a top-ranked international company. The potential damages resulting from ship accidents have resulted in many international agreements such as MARPOL, SOLAS, ISM Code, etc. The viability of damaged ships has become more and more important. A damaged ship's viability and cargo safety can be improved by a safety assessment design procedure. We consider th￡ shipbuilding industry's distributed characteristics to define a safety assessment system with software engineering-based requirements analysis. We used a distributed network-based simulation method (HLA - High level architecture), because of ease of reuse and expansion of existing components to other situations, and because it is a military standard. HLA is the standard for distributed network-based simulation in many countries including the United States, Canada, Israel, and Korea. The paper describes research to develop a prototype of a network-based safety assessment simulation system by software engineering based analysis.

• 조명전기설비학회논문지
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• 제28권12호
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• pp.38-44
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• 2014

The photovoltaic power system is performing power generation by being installed in outdoors. Therefore it has the characteristics affected by environmental factors. In particular, if the solar power generation facility connected to the grid, the power can be generated continuously in a state of being secured operating voltage of the inverter and solar irradiation. In that case, if an abnormal situation such as flooding or heavy rains has occur, the possibility of electric shock or damage of facilities due to current leakage or a floating matters is present. In this paper, we performed electrical safety assessment about the connection part, junction box and cable of the solar module when the solar power system was flooded. we also assessed whether or not the leakage current is occurred in case of the cable was damaged. As a result, in case of the leakage current is large, we can be known that it is the risk of electric shock as well as cause of inverter damage.

• 기술사
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• 제37권6호
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• pp.37-40
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• 2004

This year's main theme of Japan-Korea Joint Symposium of Professional Engineering is 'Conservation of the earth environment and risk management' As a keynote speaker. I a going to discuss the strategies to make appropriate future environment of our countries. In particular, following items are discussed in the speech. 1. The Desert greening with peat at Uighur area 2. Anoter viewpoint of the environmental problem 3. Review of the Earth Warming 4. Review of the environment of the Earth 5. Corresponding of Emission Trading scheme of carbon dioxide to the atmosphere 6. Un-precious present from continent to Japan 7. Corresponding of asbestos damage 8. Risk assessment and Risk management

• 환경정책연구
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• 제5권4호
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• pp.1-18
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• 2006

최근 들어 강원도 및 경상북도 지역에서의 홍수 피해가 증가하고 있다. 우리나라의 강수 패턴이 변화하는 현실에서 적극적인 홍수 대책의 수립이 요구되고 있다. 본 연구는 환경 방재의 정책적 기반이 될 정확하고 정량적인 취약성 산정 근거를 제시하고자 한다. 본 연구는 과거 20년간 한반도에서 발생한 홍수의 피해액에 근거하여 홍수에 대한 취약성을 분석하였다. 1980년대에는 남부지방(경상남도, 전라남도)에서 침수와 범람으로 농경지 유실과 선박 부문에서 가장 큰 피해가 발생하였다. 이후에는 전체 피해액에서 남부지방에서의 피해가 차지하는 비율이 감소하고 중부지방(충청남도)은 점차 피해율이 증가하지만 전체 피해규모는 유지되는 경향을 보인다. 남부지방의 피해가 감소하는 것에 비해 북부지방(강원도, 경기도)과 산간지역(경상북도)의 홍수 피해율은 상대적으로 증가해 왔으며, 피해규모는 20년간 꾸준히 지속되고 있다. 남부지방의 과거 피해 발생요인이 침수인 것에 반해 경상북도와 강원도 지역의 피해는 침수면적과의 상관관계가 적어 침수보다는 다른 요인에 의한 공공시설물의 피해가 크다. 홍수 피해액이 홍수 피해의 영향과 이에 대한 대응조치가 동시에 작용하여 나오는 결과물이라고 할 때, 본 연구의 피해액을 이용한 취약성 평가는 향후 기후환경변화에 따른 간접적인 지표로 사용될 수 있다.

• 환경생물
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• 제18권1호
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• pp.163-198
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• 2000

본 연구는 현행 환경영향평가의 식물상 항목에서 내제되어 있는 여러 문제점의 대안으로써 환경평가를 위한 식물군을 제시하였다. 이들은 어느 특정한 지역공간의 자연환경 우수성의 정도와 종보존 우선순위를 파악하고 결정하는 데 이용될 수 있다. 구계분석을 통하여 선택된 식물군은 그들의 분포범위에 따라 5개의 등급으로 구분하였다. 제V등급은 고립하거나 혹은 불연속적으로 분포하는 식물로 41과 76속으로 83분류군이 이에 해당한다. 제 IV등급은 1개의 아구에만 분포하는 식물로 78과 217속으로 314분류군이 해당되며, 제III등급은 2개의 아구에 나타나는 식물로 93과 223속으로 307분류군이 이에 딸린다. 제II등급은 비교적 국내의 전 아구에 분포하지만 일반적으로 1,000m이상의 높은 산지에 나타나는 식물로 43과 92속으로 109분류군이 이에 속하고, 제I등급은 3개의 아구에 나타나는 식물로 91과 207속으로 258분류군의 집합체로 환경평가를 위한 식물군은 142과 559속으로 도합 1,071분류군으로 집계되었다. 결론적으로 제V등급 식물군은 분포하는 면적이 가장 협소하기 때문에 다른 등급 식물군에 비해 구조적으로 환경 변화에 도태될 가능성이 가장 크다.

• 한국지진공학회논문집
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• 제22권5호
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• pp.271-280
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• 2018

This paper presents a framework for developing aftershock fragility curves for reinforced concrete bridges initially damaged by mainshocks. The presented aftershock fragility is a damage-dependent fragility function, which is conditioned on an initial damage state resulting from mainshocks. The presented framework can capture the cumulative damage of as-built bridges due to mainshock-aftershock sequences as well as the reduced vulnerability of bridges repaired with CFRP pier jackets. To achieve this goal, the numerical model of column jackets is firstly presented and then validated using existing experimental data available in literature. A four-span concrete box-girder bridge is selected as a case study to examine the application of the presented framework. The aftershock fragility curves are derived using response data from back-to-back nonlinear dynamic analyses under mainshock-aftershock sequences. The aftershock fragility curves for as-built bridge columns are firstly compared with different levels of initial damage state, and then the post-repair effect of FRP pier jacket is examined through the comparison of aftershock fragility curves for as-built and repaired piers.

• 대한원격탐사학회지
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• 제35권1호
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• pp.163-177
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• 2019

As inter-Korean relations progress, the issue of natural disasters which could directly affect the lives of the people in both Koreas, has not yet been discussed. Considering the current status of inter-Korean relations and the ongoing disaster-related damage in North Korea, it is imperative to establish a technical plan at the pan-governmental level to reduce the damage from natural disasters. The purpose of this study is to secure the Korea Peninsula against natural disasters by organizing South Korea's science and technologies related to natural disasters in order to reduce the damage, and to evaluate the applicability of said technologies. The situation of natural disasters in North Korea for 17 years has been summarized and reclassified based on eight types of natural disasters. Technologies related to natural disasters in South Korea were also investigated and reclassified. Based on the data, a priority evaluation was performed and the prioritization of technology application for each natural disaster type in North Korea was calculated through a quadrant analysis. As a result, the three major categories of high-priority technologies were classified as natural disaster monitoring with remote sensing and spatial information technology, construction of research basis and database based on geographic information system (GIS) and integrated management of complex natural disasters.

• Computers and Concrete
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• 제29권1호
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• pp.1-14
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• 2022

Several aspects influence corrosive processes in reinforced concrete (RC) structures such as environmental conditions, structural geometry and mechanical properties. Since these aspects present large randomnesses, probabilistic models allow a more accurate description of the corrosive phenomena. Besides, the definition of limit states in the reliability assessment requires a proper mechanical model. In this context, this study proposes a straightforward methodology for the mechanical-probabilistic modelling of RC structures subjected to reinforcements' corrosion. An improved damage approach is proposed to define the limit states for the probabilistic modelling, considering three main degradation phenomena: concrete cracking, rebar yielding and rebar corrosion caused either by chloride or carbonation mechanisms. The stochastic analysis is evaluated by the Monte Carlo simulation method due to the computational efficiency of the Lumped Damage Model for Corrosion (LDMC). The proposed mechanical-probabilistic methodology is implemented in a computational framework and applied to the analysis of a simply supported RC beam and a 2D RC frame. Curves illustrate the probability of failure evolution over a service life of 50 years. Moreover, the proposed model allows drawing the probability of failure map and then identifying the critical failure path for progressive collapse analysis. Collapse path changes caused by the corrosion phenomena are observed.

• 한국환경보건학회지
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• 제40권1호
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• pp.27-37
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• 2014

Objectives: On September 27, 2012, leakage of anhydrous hydrofluoric acid occurred in a chemical plant in the Gumi National Industrial Complex. Following the accident, local factory workers and residents complained of abnormal health conditions. In addition, visual discolorations were widely observed in crops and trees in surrounding areas. The main objectives of the present study were to identify the area that was affected by the spill using data obtained from plants, soil, and water samples after the accident. Methods: Fluoride concentrations were analyzed in pine tree needles, soil, nearby streams, ponds and reservoirs collected from an area within a radius of three kilometers from the plant where the leak occurred. Fluoride concentrations in the air at the time of leakage were then estimated from fluoride concentrations that were measured in the pine tree needles. A Kriged map was developed to describe the spatial distribution of hydrofluoric acid at the time of the leakage and was compared with the area designated as a Special Disaster Zone by the government. Results: The Special Disaster Zone did not include all the affected area that was estimated by the Kriged map. Analytical results of the environmental samples also supported this discrepancy. Conclusion: Using plants, atmospheric concentrations of fluoride at the time of the leakage could be estimated. For the area that was identified as affected, further public health risk assessment and environmental risk assessment should be considered. Also, in the absence of air monitoring at the time of leakage, studies employing plants may be conducted in order to better understand the spatial extent and severity of the contamination.