• 대한안전경영과학회지
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• 제23권4호
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• pp.67-72
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• 2021

To ensure the safety and functionality of a railroad bridge, maintaining the integrity of the bridge via continuous structural health monitoring is important. However, most structural integrity monitoring methods proposed to date are based on modal responses which require the extracting process and have limited availability. In this paper, the applicability of the existing damage identification method based on free-vibration reponses to time-domain deflection shapes due to moving train load is investigated. Since the proposed method directly utilizes the time-domain responses of the structure due to the moving vehicles, the extracting process for modal responses can be avoided, and the applicability of structural health evaluation can be enhanced. The feasibility of the presented method is verified via a numerical example of a simple plate girder bridge.

• 대한안전경영과학회지
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• 제23권1호
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• pp.57-64
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• 2021

Recently, advanced countries assessment the risk of fire to prevent large-scale damage to high-rise buildings, In addition, performance-Based design, which is a fire risk assessment, is being conducted in Korea to prevent massive damage to high-rise buildings. However, unlike advanced countries, fire risk assessment in Korea is subject to fire risk assessment only for objects subject to consent from fire-fighting facilities such as building permits, When building engineers and fire-fighting engineers assessment the risk of fire, It has always been discussed because the results vary depending on which part of the evaluation is focused between economic feasibility and safety. Therefore, in this study, we would like to propose a fire risk assessment process suitable for domestic conditions by comparing the process of performance-based design, which is a domestic fire risk assessment, and the process of Iso/TC 16732 which is an overseas fire risk assessment.

• Wind and Structures
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• 제9권4호
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• pp.255-270
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• 2006

Several analytical procedures available in literature, for the evaluation of wind induced fatigue damage of structures, either assume the wide band random stress variations as narrow band random process or use correction factors along with narrow band assumption. This paper compares the correction factors obtained using the Rainflow Cycle (RFC) counting of the measured stress time histories on a lamp mast and a lattice tower, with those evaluated using different frequency domain methods available in literature. A Bi-modal spectral method has been formulated by idealising the single spectral moment method into two modes of background and resonant components, as considered in the gust response factor, for the evaluation of fatigue of slender structures subjected to "along-wind vibrations". A closed form approximation for the effective frequency of the background component has been developed. The simplicity and the accuracy of the new method have been illustrated through a case study by simulating stress time histories at the base of an urban light pole for different mean wind speeds. The correction factors obtained by the Bi-modal spectral method have been compared with those obtained from the simulated stress time histories using RFC counting method. The developed Bi-modal method is observed to be a simple and easy to use alternative to detailed time and frequency domain fatigue analyses without considerable computational and experimental efforts.

• 한국공간구조학회논문집
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• 제16권3호
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• pp.67-78
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• 2016

Determining of the shape in the process of design for natural draught cooling tower is very important, because the shape of hyperbolic shell is respond sensitively to dynamic behavior of the whole cooling tower against wind load. In engineering practice, the geometric parameters have been determining based on the natural frequency. This study analyses influence of the tower shell geometric parameters on the structural behavior. For three representative models were selected, they were analyzed based on evaluation of damage by means of nonlinear FE-method. As a result, a hyperbolic rotational shell with the small radius overall was the lowest damage index induced by sufficient capacity of the stress redistribution and thus a wind-insensitive structure.

• 한국방재학회 논문집
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• 제5권4호
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• pp.95-105
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• 2005

우리나라는 비교적 안정된 판 내부에 존재한다. 하지만, 1976년 안전지대로 평가된 중국 탕산지역의 대규모 지진이 발생한 것처럼 우리나라도 지진에 대해 안전한 지역이라고 단언할 수는 없다. 게다가, 지진학자들도 국내에서 중규모 이상의 지진발생 가능성이 높다고 지적하고 있다. 이러한, 지진은 자체를 예방할 수 없기 때문에 내진설계에 대한 연구와 지진재해 관리체계에 대한 연구가 전반적으로 이루어지고 있다. 그러나, 지진발생 시 초기 대응이나 수습과정에 대한 연구는 미비한 상태이며, 지진피해 평가시스템 구축을 위한 극소수의 연구가 진행되고 있는 실정이다. 따라서, 본 연구는 국내실정을 고려한 지진피해 평가시스템 구축을 위한 기초자료를 제시함을 목적으로 한다. 이를 위하여 강남구 비내진 철근콘크리트 아파트를 표준형 건축물로 선정하여 지진피해를 예측하고, 취약도 함수의 도출과 층간변위에 따른 피해평가를 행하여 HAZUS 프로그램 취약도 함수 적용결과와 비교 분석한다.

• 반도체디스플레이기술학회지
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• 제11권3호
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• pp.7-11
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• 2012

Among various wet cleaning methods, megasonic and jet spray gained their popularity in single wafer cleaning process for the efficient removal of particulate contaminants from the wafer surface. In the present study, we evaluated these two cleaning methods for particle removal efficiency (PRE) and pattern damage on the aluminum layered wafer surface. Also the effect of $CO_2$ dissolved water in jet spray cleaning is assessed by measuring PRE. It is observed that the jet spray cleaning process is more effective in terms of PRE and pattern damage compared to megasonic cleaning and the mixing of $CO_2$ in the water during jet sprays further increases the PRE. We believe that the outcome of the present study is useful for the semiconductor cleaning process engineers and researchers.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 사면안정학술발표회
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• pp.3.1-11
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• 2003

Recently the problems related to the failure of the retaining wall structure has become great concern since the damage to the properties and human losses have occurred in the rainy season. However, a detail guideline on safety inspection and appropriate diagnosis on the retaining wall structure have not yet proposed and therefore, the inspection process and results are mainly dependant upon the engineers. The objective of this study is to propose objective and quantitative evaluation method for the condition based on the damage shapes and material types. In this purpose, composing materials of retaining wall are divided Into concrete, gabion, stone and reinforced earth, and then the evaluation items and method are suggested on the basis of the materials and structural characteristics of the retaining wall.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제4권1호
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• pp.31-37
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• 2001

In this paper, an integrated damage identification system (IDIS) is proposed to locate and size damage in real structures. The application of the IDIS to real structures includes the measurement of modal responses, the construction of damage-detection models, and the implementation of measurements and models into the damage-detection process. Firstly, the theory of the damage identification method is outlined. Secondly, the schematic and each component of the IDIS are described. Finally, the practicality of the IDIS is verified from experiments on two different bridge-models, a model plate-grider and a model truss.

• Earthquakes and Structures
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• 제17권6호
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• pp.577-590
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• 2019

The seismic response of structures to strong ground motions is a complex problem that has been studied for decades. However, most of current seismic regulations do not assess the potential level of damage that a structure may undergo during a strong earthquake. This will happen in spite that the design objectives for any structural system are formulated in terms of acceptable levels of damage. In this article, we analyze the expected damage in single-degree-of-freedom systems subjected to long-duration ground motions generated in soft soil sites, such as those located in the lakebed of Mexico City. An energy-based methodology is formulated, under the consideration of input energy as the basis for the evaluation process, to estimate expected damage. The results of the proposed methodology are validated with damage curves established directly with nonlinear dynamic analyses.

• Steel and Composite Structures
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• 제47권1호
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• pp.121-134
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• 2023

This paper tested 11 concrete-encased concrete-filled steel tube (CFST) composite columns and one reinforced concrete column under combined axial compression and lateral loads. The primary parameters, including the loading system, axial compression ratio, volume stirrup ratio, diameter-to-thickness ratio of the steel tube, and stirrup form, were varied. The influence of the parameters on the failure mode, strength, ductility, energy dissipation, strength degradation, and damage evolution of the composite columns were revealed. Moreover, a two-parameter nonlinear seismic damage model for composite columns was established, which can reflect the degree and development process of the seismic damage. In addition, the relationships among the inter-story drift ratio, damage index and seismic performance level of composite columns were established to provide a theoretical basis for seismic performance design and damage assessments.