• 제목/요약/키워드: Seismic fragility curve

검색결과 134건 처리시간 0.036초

A new methodology development for flood fragility curve derivation considering structural deterioration for bridges

  • Lee, Jaebeom;Lee, Young-Joo;Kim, Hyunjun;Sim, Sung-Han;Kim, Jin-Man
    • Smart Structures and Systems
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    • 제17권1호
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    • pp.149-165
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    • 2016
  • Floods have been known to be one of the main causes of bridge collapse. Contrary to earthquakes, flood events tend to occur repeatedly and more frequently in rainfall areas; flood-induced damage and collapse account for a significant portion of disasters in many countries. Nevertheless, in contrast to extensive research on the seismic fragility analysis for civil infrastructure, relatively little attention has been devoted to the flood-related fragility. The present study proposes a novel methodology for deriving flood fragility curves for bridges. Fragility curves are generally derived by means of structural reliability analysis, and structural failure modes are defined as excessive demands of the displacement ductility of a bridge under increased water pressure resulting from debris accumulation and structural deterioration, which are known to be the primary causes of bridge failures during flood events. Since these bridge failure modes need to be analyzed through sophisticated structural analysis, flood fragility curve derivation that would require repeated finite element analyses may take a long time. To calculate the probability of flood-induced failure of bridges efficiently, in the proposed framework, the first order reliability method (FORM) is employed for reducing the required number of finite element analyses. In addition, two software packages specialized for reliability analysis and finite element analysis, FERUM (Finite Element Reliability Using MATLAB) and ABAQUS, are coupled so that they can exchange their inputs and outputs during structural reliability analysis, and a Python-based interface for FERUM and ABAQUS is newly developed to effectively coordinate the fragility analysis. The proposed framework of flood fragility analysis is applied to an actual reinforced concrete bridge in South Korea to demonstrate the detailed procedure of the approach.

Seismic vulnerability assessment of confined masonry buildings based on ESDOF

  • Ranjbaran, Fariman;Kiyani, Amir Reza
    • Earthquakes and Structures
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    • 제12권5호
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    • pp.489-499
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    • 2017
  • The effects of past earthquakes have demonstrated the seismic vulnerability of confined masonry structures (CMSs) to earthquakes. The results of experimental analysis indicate that damage to these structures depends on lateral displacement applied to the walls. Seismic evaluation lacks an analytical approach because of the complexity of the behavior of this type of structure; an empirical approach is often used for this purpose. Seismic assessment and risk analysis of CMSs, especially in area have a large number of such buildings is difficult and could be riddled with error. The present study used analytical and numerical models to develop a simplified nonlinear displacement-based approach for seismic assessment of a CMS. The methodology is based on the concept of ESDOF and displacement demand and is compared with displacement capacity at the characteristic period of vibration according to performance level. Displacement demand was identified using the nonlinear displacement spectrum for a specified limit state. This approach is based on a macro model and nonlinear incremental dynamic analysis of a 3D prototype structure taking into account uncertainty of the mechanical properties and results in a simple, precise method for seismic assessment of a CMS. To validate the approach, a case study was considered in the form of an analytical fragility curve which was then compared with the precise method.

Performance-based evaluation of strap-braced cold-formed steel frames using incremental dynamic analysis

  • Davani, M.R.;Hatami, S.;Zare, A.
    • Steel and Composite Structures
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    • 제21권6호
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    • pp.1369-1388
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    • 2016
  • This study is an effort to clearly recognize the seismic damages occurred in strap-braced cold formed steel frames. In order to serve this purpose, a detailed investigation was conducted on 9 full scale strap-braced CFS walls and the required data were derived from the results of the experiments. As a consequence, quantitative and qualitative damage indices have been proposed in three seismic performance levels. Moreover, in order to assess seismic performance of the strap-braced CFS frames, a total of 8 models categorized into three types are utilized. Based on the experimental results, structural characteristics are calculated and all frames have been modeled as single degree of freedom systems. Incremental dynamic analysis using OPENSEES software is utilized to calculate seismic demand of the strap-braced CFS walls. Finally, fragility curves are calculated based on three damage limit states proposed by this paper. The results showed that the use of cladding and other elements, which contribute positively to the lateral stiffness and strength, increase the efficiency of strap-braced CFS walls in seismic events.

지진취약도 곡선의 응답변수에 대한 상관계수 평가 및 변수별 조합 (Evaluation and Combination of Correlation Coefficient for Response Variable of Seismic Fragility Curve)

  • 김시영;김정한
    • 한국전산구조공학회논문집
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    • 제33권6호
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    • pp.401-409
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    • 2020
  • 확률론적 지진취약도 평가는 구조물 혹은 기기의 손상확률을 각 취약도 변수별 조합을 통해 이루어진다. 지진취약도로부터 구해지는 2개 이상 기기의 동시손상확률 계산은 기존에는 각 기기의 손상확률을 독립으로 가정해 왔다. 하지만 기기별 손상확률에 상관성이 있으며, 이를 평가한 결과 상관성에 따라 동시손상확률이 변화할 수 있는 결과를 보였다. 이 지진상관성을 무시하면 비보수적인 결과가 나오고 따라서 이를 고려해서 계산되어야 한다. 이 연구에서는 지진상관계수를 해석적으로 평가하기 위해 몇 가지 확률 변수를 선정하여 각 변수별로 혹은 통합하여 평가하고 그 차이를 비교했다. 그리고 단순화된 모델과, 복잡한 모델에 대한 상관계수 차이도 비교하였다. 이들 방법에 따른 상관계수의 결과와 차이를 분석했다. 그 결과 각 변수별로 평가하는 것과 통합하여 평가할 때 변수별 영향의 차이에 따라 상관성이 변화함을 확인하였고, 모델이 단순할수록 상관성이 높아짐을 확인하였다.

Derivation of analytical fragility curves using SDOF models of masonry structures in Erzincan (Turkey)

  • Karimzadeh, Shaghayegh;Kadas, Koray;Askan, Aysegul;Erberik, M. Altug;Yakut, Ahmet
    • Earthquakes and Structures
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    • 제18권2호
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    • pp.249-261
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    • 2020
  • Seismic loss estimation studies require fragility curves which are usually derived using ground motion datasets. Ground motion records can be either in the form of recorded or simulated time histories compatible with regional seismicity. The main purpose of this study is to investigate the use of alternative ground motion datasets (simulated and real) on the fragility curves. Simulated dataset is prepared considering regional seismicity parameters corresponding to Erzincan using the stochastic finite-fault technique. In addition, regionally compatible records are chosen from the NGA-West2 ground motion database to form the real dataset. The paper additionally studies the effects of hazard variability and two different fragility curve derivation approaches on the generated fragility curves. As the final step for verification purposes, damage states estimated for the fragility curves derived using alternative approaches are compared with the observed damage levels from the 1992 Erzincan (Turkey) earthquake (Mw=6.6). In order to accomplish all these steps, a set of representative masonry buildings from Erzincan region are analyzed using simplified structural models. The results reveal that regionally simulated ground motions can be used alternatively in fragility analyses and damage estimation studies.

지진 손상 상관성이 플랜트의 확률론적 지진 안전성 평가에 미치는 영향 (The Effects of Seismic Failure Correlations on the Probabilistic Seismic Safety Assessments of Nuclear Power Plants)

  • 임승현;곽신영;최인길;전법규;박동욱
    • 한국지진공학회논문집
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    • 제25권2호
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    • pp.53-58
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    • 2021
  • Nuclear power plant's safety against seismic events is evaluated as risk values by probabilistic seismic safety assessment. The risk values vary by the seismic failure correlation between the structures, systems, and components (SSCs). However, most probabilistic seismic safety assessments idealized the seismic failure correlation between the SSCs as entirely dependent or independent. Such a consideration results in an inaccurate assessment result not reflecting real physical phenomenon. A nuclear power plant's seismic risk should be calculated with the appropriate seismic failure correlation coefficient between the SSCs for a reasonable outcome. An accident scenario that has an enormous impact on a nuclear power plant's seismic risk was selected. Moreover, the probabilistic seismic response analyses of a nuclear power plant were performed to derive appropriate seismic failure correlations between SSCs. Based on the analysis results, the seismic failure correlation coefficient between SSCs was derived, and the seismic fragility curve and core damage frequency of the loss of essential power event were calculated. Results were compared with the seismic fragility and core damage frequency of assuming the seismic failure correlations between SSCs were independent and entirely dependent.

머신러닝 기반 I형 곡선 거더 단경간 교량 지진 취약도 분석 (Seismic Fragility of I-Shape Curved Steel Girder Bridge using Machine Learning Method)

  • 전준태;주부석;손호영
    • 한국재난정보학회 논문집
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    • 제18권4호
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    • pp.899-907
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    • 2022
  • 연구목적: 기계학습법을 이용하여 일반적인 직선 교량의 지진 취약도 분석 연구는 다수 수행되었으나 곡선 교량 구조물에 대한 연구 사례는 미미하다. 따라서 본 연구의 목적은 기계학습법 기반 I형 곡선 거더를 갖는 교량의 재료 특성 및 기하학적 불확실성을 고려한 지진 취약도 분석하는 것이다. 연구방법: 강재 및 콘크리트의 재료 특성과 교각의 높이를 불확실성 매개변수로 고려하였다. 라틴하이퍼큐브 기법을 이용하여 매개변수를 샘플링하였으며 지진파의 불확실성을 고려하여 시간이력해석을 수행하였다. 해석결과를 원본데이터로 인공신경망, 반응표면분석법을 적용하여 학습 데이터를 생성하였다. 최종적으로 원본 데이터 및 학습데이터를 이용하여 지진 취약도 분석을 수행하였다. 연구결과: 라틴하이퍼큐브 기법을 이용하여 매개변수를 샘플링하였으며 지진파의 불확실성을 고려하여 총 160회의 시간 이력해석을 수행하였다. 해석결과와 기계학습을 통해 얻어진 예측 값을 비교하였으며 두 값의 유사도를 비교하기 위해 결정계수를 비교하였다. 반응표변분석법의 결정계수가 0.737로 비교적 관측 값과 유사한 것으로 나타났다. 지진 취약도 곡선도 반응표면 분석법을 통해 예측된 값이 관측 값과 유사한 것으로 나타났다. 결론: 본 연구에서 유한요소 해석을 통해 관측된 값과 기계학습법을 통해 예측된 값을 비교하였을 때 반응표면 분석법이 관측값과 유사한 결과를 예측하는 것으로 나타났다. 하지만 두 가지 기계학습법 모두 관측 값에 비해 과소평가되는 것으로 나타났다.

3차원 해석 모델을 이용한 RC 프레임 구조물의 지진 취약도 평가 (Seismic Vulnerability Assessment of RC Frame Structures Using 3D Analytical Models)

  • 문도수;이영주;이상목
    • 한국산학기술학회논문지
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    • 제17권9호
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    • pp.724-731
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    • 2016
  • 지진으로 인한 구조물의 피해가 지속적으로 증가하면서, 구조물의 취약성을 평가하는 일은 지진 대비에 필수적으로 여겨지고 있다. 지진 취약도 곡선은 지진에 대한 구조물의 안전도에 대한 확률 지표로써 널리 이용되고 있으며, 많은 연구자들에 의해 보다 정확하고 효율적인 취약도 곡선 도출을 위한 노력이 계속되고 있다. 하지만 기존의 대부분의 연구에서는 취약도 곡선 도출시 수치해석 시간 절약을 위해 단순화된 2차원 해석모델을 사용해 왔는데, 많은 경우에 있어 2차원 모델은 정확한 구조물의 내진 거동 및 지진 취약성을 평가하기에 적당하지 않을 수 있다. 이에 본 연구에서는 3차원 해석 모델을 사용하여 더욱 정확하면서도 여전히 효과적으로 지진 취약도 곡선을 도출할 수 있는 방법을 제시한다. 이 방법은 신뢰성 해석 소프트웨어인 FERUM과 구조해석 소프트웨어인 ZEUS-NL을 서로 연동시켜 상호 자동적인 데이터 교환이 가능하게 하고, 샘플링 기법이 아닌 FORM 해석 기법을 통해 구조물의 파괴확률을 구한다. 이는 3차원 모델을 사용의 경우에도 효율적으로 구조 신뢰성 해석이 가능하게 해준다. 이를 이용해 RC 프레임 구조물의 3차원 해석 모델을 사용하여 지진 취약성 평가를 수행하였다.

Fragility assessment for electric cabinet in nuclear power plant using response surface methodology

  • Tran, Thanh-Tuan;Cao, Anh-Tuan;Nguyen, Thi-Hong-Xuyen;Kim, Dookie
    • 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.