• Nuclear Engineering and Technology
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• 제51권3호
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• pp.894-903
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• 2019

An approach for collapse risk assessment is proposed to evaluate the vulnerability of electric cabinet in nuclear power plants. The lognormal approaches, namely maximum likelihood estimation and linear regression, are introduced to establish the fragility curves. These two fragility analyses are applied for the numerical models of cabinets considering various boundary conditions, which are expressed by representing restrained and anchored models at the base. The models have been built and verified using the system identification (SI) technique. The fundamental frequency of the electric cabinet is sensitive because of many attached devices. To bypass this complex problem, the average spectral acceleration $S_{\bar{a}}$ in the range of period that cover the first mode period is chosen as an intensity measure on the fragility function. The nonlinear time history analyses for cabinet are conducted using a suite of 40 ground motions. The obtained curves with different approaches are compared, and the variability of risk assessment is evaluated for restrained and anchored models. The fragility curves obtained for anchored model are found to be closer each other, compared to the fragility curves for restrained model. It is also found that the support boundary conditions played a significant role in acceleration response of cabinet.

• Structural Engineering and Mechanics
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• 제91권4호
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• pp.369-382
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• 2024

The earthquake loss assessment framework of ductile reinforced concrete (or RC) frame using component-performance -based methodology was studied in this paper. The elasto-plastic rotation angle was used as the damage indicator of structural component, and the damage-to-loss model was proposed on the basis of the deformation indicator of structural component. Dynamic instability during incremental dynamic analysis was taken as collapse criterion, and column failure was taken as criterion that structure has to be demolished. Expected earthquake losses of low-rise, mid-rise and high-rise RC frames were discussed. The expected earthquake loss encompassed collapse loss, demolition loss and repair loss. Furthermore, component groups of RC frame were divided into structural components, nonstructural components and rugged components. The results indicate that ductile RC frame is more likely to be demolished than collapse, especially in low-rise and mid-rise RC frames. Furthermore, the less collapse margin ratio the structure has, the more demolition probability the structure will suffer under rare earthquake. The demolition share of total earthquake loss might be more prominent than repair share and collapse share in ductile RC frame.

• 대한토목학회논문집
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• 제38권3호
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• pp.439-448
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• 2018

지진 조기경보 시스템(EEWS)은 상대적으로 빠른 속도로 전파되는 P파를 관측하여 잇따라 도달하는 S파에 의한 피해 위험을 미리 경보하고, 시민의 즉각적인 대피를 유도하는 것을 목표로 한다. 현재 대한민국의 지진 조기경보 시스템은 최초 P파 관측 후 50초 이내에 지진 경보 발령이 가능한 상태이며 2020년까지 지진 경보 발령 시간을 P파 관측 후 10초 이내로 단축하겠다고 공표한 상태이다. 이를 위해서는 지진 발생 시 P파의 관측이 5초 내에 이루어져야 한다. 2016년 리히터 규모 5.8의 경주 지진 이후 국내 지진 재난 대응체계에 대한 개선의 요구에 힘입어 재난 및 안전관리 기본법 내 재난관리책임기관의 기능 연속성 계획 수립에 관한 항이 신설되었다. 국립공원 관리공단 역시 재난으로부터의 탐방객 안전확보의 의무를 지닌 바, 보다 능동적인 대응체계를 위해 유관기관과의 협력체계 구축을 추진하고 있다. 이에 따라, 본 연구에서는 통합지진관측망의 분포 및 국립공원의 공간적 분포를 정량화하여 국립공원의 지진 조기경보 서비스 제공의 잠재적인 취약성을 분석하였다. 분석 결과, 중부지방에 위치하는 속리산, 계룡산, 가야산, 덕유산 및 동남부 지방의 경주 국립공원은 자체적으로 지진파를 감지하여 분석하는 현장시스템의 보강이 필요할 것으로 나타났으며 북한산 국립공원은 통합지진관측망 중심의 전방탐지시스템의 개선이 필요할 것으로 나타났다.

• Steel and Composite Structures
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• 제34권6호
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• pp.891-907
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• 2020

Many studies reveal that during destructive earthquakes, most of the structures enter the inelastic phase. The amount of hysteretic energy in a structure is considered as an important criterion in structure design and an important indicator for the degree of its damage or vulnerability. The hysteretic energy value wasted after the structure yields is the most important component of the energy equation that affects the structures system damage thereof. Controlling this value of energy leads to controlling the structure behavior. Here, for the first time, the hysteretic behavior and energy dissipation capacity are assessed at presence of elliptical braced resisting frames (ELBRFs), through an experimental study and numerical analysis of FEM. The ELBRFs are of lateral load systems, when located in the middle bay of the frame and connected properly to the beams and columns, in addition to improving the structural behavior, do not have the problem of architectural space in the bracing systems. The energy dissipation capacity is assessed in four frames of small single-story single-bay ELBRFs at ½ scale with different accessories, and compared with SMRF and X-bracing systems. The frames are analyzed through a nonlinear FEM and a quasi-static cyclic loading. The performance features here consist of hysteresis behavior, plasticity factor, energy dissipation, resistance and stiffness variation, shear strength and Von-Mises stress distribution. The test results indicate that the good behavior of the elliptical bracing resisting frame improves strength, stiffness, ductility and dissipated energy capacity in a significant manner.

• Steel and Composite Structures
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• 제53권1호
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• pp.103-114
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• 2024

This study proposes a new hybrid approach that utilizes post-earthquake survey data and numerical analysis results from an evolving finite element routing model to capture vulnerability processes. In order to achieve cost-effective evaluation and optimization, this study introduced an online data evolution data platform. The proposed method consists of four stages: 1) development of diagnostic sensitivity curve; 2) determination of probability distribution parameters of throughput threshold through optimization; 3) update of distribution parameters using smart evolution method; 4) derivation of updated diffusion parameters. Produce a blending curve. The analytical curves were initially obtained based on a finite element model used to represent a similar RC building with an estimated (previous) capacity height in the damaged area. The previous data are updated based on the estimated empirical failure probabilities from the post-earthquake survey data, and the mixed sensitivity curve is constructed using the update (subsequent) that best describes the empirical failure probabilities. The results show that the earthquake rupture estimate is close to the empirical rupture probability and corresponds very accurately to the real engineering online practical analysis. The objectives of this paper are to obtain adequate, safe and affordable housing and basic services, promote inclusive and sustainable urbanization and participation, implement sustainable and disaster-resilient buildings, sustainable human settlement planning and management. Therefore, with the continuous development of artificial intelligence and management strategy, this goal is expected to be achieved in the near future.

• 한국산림과학회지
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• 제112권3호
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• pp.382-392
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• 2023

최근 기후변화와 지질환경변화로 인해 산지토사재해의 발생 빈도가 급증하는 경향이 보고되고 있다. 최근 국내에서 땅밀림이 빈번하게 발생하고 있는 만큼, 땅밀림지의 체계적이고 효율적인 복구 및 관리가 필요하다. 본 연구는 경기도 양평군 개군면 자연리 산 4-1에 발생한 땅밀림에 대하여 물리탐사기법을 통해 재해취약성을 파악하고, 파괴 지반의 전반적 지질구조를 규명하여 안정성을 검토하는 것이 목적이다. 또한, 시추조사도 함께 실시하여 측정한 데이터의 신뢰성을 검증하였다. 연구 결과, 토사층과 풍화대의 상부에 저비저항 이상대가 분포하며, 이 구간은 탐사측선 50-120 m 구간으로 땅밀림현상의 주요 지시자인 인장균열이 관찰되는 연경도가 낮은 땅밀림구역으로 확인되며, 토사층 내에 불연속면 잔존 가능성을 추정한 후, 활동연약대를 안정시키는 복구방법을 강구하였다. 따라서 국내 현실에서 땅밀림 위험지를 파악하여 땅밀림 발생 징후에 대한 지속적인 모니터링을 통해 경제적, 사회적 피해를 줄일 수 있는 대책마련을 위한 연구가 필요하다고 사료된다.