• Computational Structural Engineering
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• v.17 no.2
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• pp.31-41
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• 2004

몇 일 전 필자는 대전에 위치한 한 연구소에 근무하고 계신 분으로부터 지진취약도 분석에 관한 문의 전화를 받았다. 그분의 대학 후배가 지진취약도에 대한 연구를 하고 싶다는 내용이었다. 최근 필자는 그분 외에도 다른 분들과 함께 지진취약도 분석 및 이를 확장한 바람에 의한, 혹은 홍수에 의한 구조물의 확률적 안전성 분석에 관한 논의를 하곤 하였다. 현재까지 국내에서는 구조물의 취약도 분석에 대한 연구가 그다지 활발하지 않으나, 이에 대한 관심은 지속적으로 증가할 것으로 보여진다. 지진취약도를 한마디로 요약하면, "임의의 크기를 갖는 지진이 발생하였을 때, 구조물에 어느 규모 이상의 손상이 발생할 확률"을 의미하는 것으로, 구조물의 확률적 지진안전성으로 부를 수 있다. 예를 들어, "최대지반가속도가 0.1g인 지진이 발생하였을 때, 해당 구조물에 보수를 요하는 수준 이상의 손상이 발생할 확률이 30%이다"와 같은 정보를 지진취약도 곡선으로부터 읽을 수 있다. (중략)

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.3
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• pp.65-72
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• 2011

Extensive computer simulations to account for the randomness in the process of seismic demand estimation have been a serious obstacle to the adoption of probabilistic performance assessments for the decision of applying seismic intervention schemes. In this study, a method for rapid fragility assessments based on a response database and the fragility contour method are presented. By the comparison of response contours in different formats, it is shown that representing maximum responses in ductility demand is better for the investigation of the effect of structural parameter changes on seismic demands than representations in absolute values. The presented fragility contour enables designers to practically investigate the probabilistic performance level of every possible retrofit option in a convenient manner using visualized data sets. This example demonstrates the extreme efficiency of the proposed approach in performing fragility assessments and successful application to the seismic retrofit strategies based on limit state probabilities.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.5
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• pp.397-404
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• 2012

Fragility curves show the probability of a system reaching a limit state as a function of some measure of seismic intensity. To obtain fragility curves of six and twelve story staggered wall structures with middle corridor, incremental dynamic analyses were carried out using twenty two pairs of earthquake records, and their failure probabilities for various intensity of seismic load were investigated. The performances of staggered wall structures with added columns along the central corridor and the structures with their first story walls replaced by columns were compared with those of the regular staggered wall structures. Based on the analysis results it was concluded that staggered wall structures with central columns have the largest safety margin for the same level of seismic load.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.1
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• pp.57-65
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• 2024

In a fire-resistant structure, uncertainties arise in factors such as ventilation, material elasticity modulus, yield strength, coefficient of thermal expansion, external forces, and fire location. The ventilation uncertainty affects thefactor contributes to uncertainties in fire temperature, subsequently impacting the structural temperature. These temperatures, combined with material properties, give rise to uncertain structural responses. Given the nonlinear behavior of structures under fire conditions, calculating fire fragility traditionally involves time-consuming Monte Carlo simulations. To address this, recent studies have explored leveraging machine learning algorithms to predict fire fragility, aiming to enhance efficiency while maintaining accuracy. This study focuses on predicting the fire fragility of a steel moment frame building, accounting for uncertainties in fire size, location, and structural material properties. The fragility curve, derived from nonlinear structural behavior under fire, follows a log-normal distribution. The results demonstrate that the proposed method accurately and efficiently predicts fire fragility, showcasing its effectiveness in streamlining the analysis process.

• Journal of Digital Convergence
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• v.13 no.10
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• pp.343-351
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• 2015

With the diverse services of the current M2M environment being expanded to the organizations, the corporations, and the daily lives, the possibility of the occurrence of the vulnerabilities of the security of the related technologies have become an issue. In order to solve such a problem of the vulnerability of the security, this thesis proposes the technique for applying the cryptography algorithm for the protection of the device key of the M2M environment. The proposed technique was based on the elliptic curve cryptography Through the key exchange and the signature exchange in the beginning, the security session was created. And the white box cipher was applied to the encryption that creates the white box table using the security session key. Application results cipher algorithm, Elliptic Curve Cryptography provides a lightweight mutual authentication, a session key for protecting the communication session and a conventional white-box cipher algorithm and was guaranteed the session key used to encrypt protected in different ways. The proposed protocol has secure advantages against Data modulation and exposure, MITM(Man-in-the-middle attack), Data forgery and Manipulation attack.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.65-76
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• 2010

In this paper, earthquake fragility analysis has been comparatively performed with regard to a buried gas pipeline of API X65 which has been widely used in Korea. For this purpose, a nonlinear time-history analyses has been carried out for 15 different analytical models of a buried gas pipeline in terms of the selected 12 sets of earthquake ground motions with 0.1g of scaling interval. Following that, earthquake fragility analyses have been conducted using the maximum axial strain of the pipeline obtained from the nonlinear time-history analyses. Parameters under consideration for subsequent earthquake fragility analyses are soil conditions, end-restraint conditions, burial depth and the type of pipeline. Comparative analyses reveal that whereas the first three parameters influence the fragility curves, particularly soil conditions amongst the three parameters, the last parameter has a little effect on the curves. In all, the present study can be considered as a benchmark fragility analysis of a buried gas pipeline in the absence of an earthquake fragility analysis of the pipeline and thus is expected to be a useful source regarding earthquake fragility analyses of a buried gas pipelines.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.91-102
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• 2007

Through lessons in recent earthquakes, the bridge engineering community recognizes the need for new seismic design methodologies based on the inelastic structural performance of RC bridge structures. This study represents results of performance-based fragility analysis of reinforced concrete (RC) bridge. Monte carlo simulation is performed to study nonlinear dynamic responses of RC bridge. Two-parameter log-normal distribution function is used to represent the fragility curves. These two-parameters, referred to as fragility parameters, are estimated by the traditional maximum likelihood procedure, which is treated each event of RC bridge pier damage as a realization of Bernoulli experiment. In order to formulate the fragility curves, five different damage states are described by two practical factors: the displacement and curvature ductility, which are mostly influencing on the seismic behavior of RC bridge piers. Five damage states are quantitatively assessed in terms of these seismic ductilities on the basis of numerous experimental results of RC bridge piers. Thereby, the performance-based fragility curves of RC bridge pier are provided in this paper. This approach can be used in constructing the fragility curves of various bridge structures and be applied to construct the seismic hazard map.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.4
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• pp.445-452
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• 2010

In this paper an assessment of the internal pressure fragility of the CANDU type containment buildings is performed. The uncertainties of the performance of the containment buildings, material properties and tendon characteristics are referred from the in-service reports of Wolsung Unit 1. The containment buildings are modeled as a three-dimensional finite elements with considering the major opening and penetrations. A new method to evaluate the probabilistic fragility of the massive structural system is developed. The fragility curves of the target containment building are presented with repect to the failure modes and reliability levels. The center of wall is reveled as the most weak structural component of the containment building in the sense of the rupture and catastrophic rupture failure modes.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.430-430
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• 2011

최근 지구온난화, 엘리뇨 및 라니냐 등 지구환경 변화에 따른 기후변화의 영향으로 짧은 시간에 매우 높은 강도를 가진 이상호우에 의해 많은 인명과 재산피해가 발생하고 있다. 우리나라의 경우에도 1990년대 후반부터 과거와 달리 국지적 집중호우가 빈번히 발생하고 있으며 집중호우에 의한 홍수는 우리나라의 가장 빈번한 자연재해 중 하나가 되었다. 이러한 성격의 홍수는 소유역 규모의 좁은 지역과 급경사지역에서 짧은 지속시간과 집중적인 강우강도에 의해 발생하고, 빠른 유속과 토사를 동반하는 빠른 수문반응으로 홍수에 대비할 시간이 부족한 것이 특징이기 때문에 기존의 홍수예보모형을 이용하여 발생홍수의 특성을 예측하기에는 많은 어려움이 있다. 유출수문곡선의 특성을 분석하여 홍수의 특성을 분석하는 연구는 Kyiamah (1996)가 유출수문곡선의 기초적인 상승곡선, 지체시간, 첨두홍수량을 이용하여 돌발홍수사상에 대한 크기를 산정하였으며, 이를 바탕으로 Bhaskar 등 (2000)은 유출수문곡선의 상승부 기울기, 첨두 홍수량비, 홍수 반응시간을 이용하여 돌발홍수지수(Flash Flood Index)를 산정하고 이 지수에 의해 돌발홍수를 설명하고자 하였다. 국내에서는 정재철 (2000)이 보청천을 대상으로 단 몇 개의 사상만을 대상으로 Bhaskar 등 (2000)이 제시한 돌발홍수지수를 적용한 바가 있다. 그러나, 이들 연구에서는 소수의 수문사상만을 이용하였기 때문에 상대심도를 산정하는데 있어 문제가 있으며 상대심도를 산정하는데 있어 각 심도계수들의 임의적인 도수분포를 이용하였기 때문에 매우 주관적이라고 할 수 있다. 김병식 등 (2008)은 한강유역의 과거 101개의 홍수사상에 대해 돌발홍수의 상대심도를 파악하기 위하여 돌발홍수지수를 산정하고 2006년 7월의 집중호우에 의해 발행한 홍수사상의 돌발홍수 심도를 시간 및 공간적으로 정량화하였다. 이러한 기존의 연구는 홍수심도 산정시에 필요한 유출수문곡선을 실측된 자료를 이용하여 산정하였으나 국내의 소유역의 경우 실측된 유출수문곡선 자료가 그다지 많지 않은 관계로 인해 홍수심도를 산정하는데 많은 어려움을 내포하고 있다. 따라서 본 연구에서는 미계측 소유역중 시범유역을 선정하고 30년 이상 장기간 실측 강우의 기왕최대 시강우량 자료에 대하여 강우-유출모형을 통한 홍수유출수문곡선을 모의한 후, 빈도별 확률강우량에 대한 수문곡선 특성인자들의 비를 무차원 지수화하여 극한홍수사상에 대한 설계강우의 취약성을 평가하기 위한 홍수위험지수 (Flood Hazard Index) 산정방법을 제시하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.145-151
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• 2019

The fragility analyses for the partially filled horizontal cylindrical tank having a flexible wall were conducted to evaluate seismic performance. An equivalent simplified model with two lumped masses representing to impulsive and convective masses was used to represent the liquid storage system. This simplified model was validated by comparing its time history analysis results with the 3D FSI model results. The horizontal tank was analyzed under bi-directional excitations. Seismic fragility curves for the stability were developed in transverse and longitudinal directions. Fragility curves show that seismic damage for the horizontal storage system is more susceptible in the transverse direction.