• Journal of the Society of Disaster Information
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• v.7 no.3
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• pp.171-180
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• 2011

As a great earthquake hit east Japan recently, the interests for the necessity of earthquake resistant design and earthquake resistance ability of existent structures are much increased. The damage or collapse of a bridge, as a social overhead capital structure affects socially and economically. Thus the evaluation of earthquake resistance ability of these structures is very important. The reviewing methods for earthquake resistance ability are mostly deterministic. Although the deterministic methods are fit for the evaluation of safety of each member, they are not practical for the whole structure. For the evaluation of structural safety for earthquake, the method for the evaluation of fragility or damage is needed for some stages of damage. In this paper, fragility curves of steel box bridge using RFPB bearing for PGA, PGV, SA, SV, SI are constructed, and these are compared with the cases of FPB.

• Journal of the Society of Disaster Information
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• v.18 no.4
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• pp.899-907
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• 2022

Purpose: Although many studies on seismic fragility analysis of general bridges have been conducted using machine learning methods, studies on curved bridge structures are insignificant. Therefore, the purpose of this study is to analyze the seismic fragility of bridges with I-shaped curved girders based on the machine learning method considering the material property and geometric uncertainties. Method: Material properties and pier height were considered as uncertainty parameters. Parameters were sampled using the Latin hypercube technique and time history analysis was performed considering the seismic uncertainty. Machine learning data was created by applying artificial neural network and response surface analysis method to the original data. Finally, earthquake fragility analysis was performed using original data and learning data. Result: Parameters were sampled using the Latin hypercube technique, and a total of 160 time history analyzes were performed considering the uncertainty of the earthquake. The analysis result and the predicted value obtained through machine learning were compared, and the coefficient of determination was compared to compare the similarity between the two values. The coefficient of determination of the response surface method was 0.737, which was relatively similar to the observed value. The seismic fragility curve also showed that the predicted value through the response surface method was similar to the observed value. Conclusion: In this study, when the observed value through the finite element analysis and the predicted value through the machine learning method were compared, it was found that the response surface method predicted a result similar to the observed value. However, both machine learning methods were found to underestimate the observed values.

• Computational Structural Engineering
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• v.11 no.3
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• pp.253-262
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• 1998

본 연구에서는 경부고속철도의 주요 교량형식인 PSC 박스교량을 3차원 뼈대요소를 사용하여 모형화하였으며, 궤도불규칙성의 형상은 지수 스펙트럴 밀도함수를 사용하여 생성시켰다. 경부고속철도차량(K-TGV)중 동력차는 17자유도의 3차원 주행열차로 모형화하였고, 이러한 교량, 궤도불규칙성 및 차량 모형을 이용하여 교량과 차량의 상호작용을 해석할 수 있는 프로그램을 개발하였다. 동적해석을 위한 교량과 차량의 운동방정식은 Lagrange 방정식을 사용하여 유도하였으며, 운동방정식의 수치해석에는 Newmark-β법을 사용하였다. 개발된 프로그램을 이용하여 동력차의 주행에 의한 교량의 시간이력곡선을 구하였으며, 궤도불규칙성의 영향을 분석하였다. 또한 도상의 유무에 따른 교량동적거동의 특성과 함께 열하중의 편심의 영향도 분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.325-331
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• 2016

This research developed a flood fragility curve of bridges considering the debris impacts. Damage and failures of civil infrastructure due to natural disasters can cause casualties as well as social and economic losses. Fragility analysis is an effective tool to help better understand the vulnerability of a structure to possible extreme events, such as earthquakes and floods. In particular, flood-induced failures of bridges are relatively common in Korea, because of the mountainous regions and summer concentrated rainfall. The main failure reasons during floods are reported to be debris impact and scour; however, research regarding debris impacts is considered challenging due to various uncertainties that affect the failure probability. This study introduces a fragility analysis methodology for evaluating the structural vulnerability due to debris impacts during floods. The proposed method describes how the essential components in fragility analysis are considered, including limit-state function, intensity measure of the debris impact, and finite element model. A numerical example of the proposed fragility analysis is presented using a bridge pier system under a debris impact.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.738-741
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• 2010

최근 국내에서 해상교량 건설이 증가하면서 교량에 충돌하는 선박의 충돌력에 대한 관심도 증가하지만 선박충돌력에 대한 국내 기준은 AASHTO LRFD에 근거를 두고 있는 실정이다. AASHTO LRFD에 의한 선박충돌력은 Woisin의 평균충돌력 개념에 바탕을 두고 있으며, 충돌속도가 증가함에 따라 AASHTO LRFD에서 제시하는 충돌력의 변화곡선을 따르고 있다. 하지만 AASHTO에서 제시된 충돌력 변화곡선은 선박의 최대충돌력 변화곡선과 같이 선형적 변화를 보이는 반면, 본 선박 충돌해석 결과의 평균충돌력은 최대충돌력의 선형적 변화거동과 일치하지 않는 것으로 나타났다. 따라서 본 논문에서는 선박의 비선형 충돌해석을 통하여 AASHTO LRFD에 의해 산정되는 선박충돌력의 부적절성을 거론하였다.

• Journal of Korean Society of Steel Construction
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• v.14 no.3
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• pp.395-402
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• 2002

This study proposed a muti-objective optimum design method for rational optimizing of orthotropic steel deck bridges. This multi-objective optimum design method was found to be effective in optimizing multi-objective problems, considering cost and deflection functions. It may ve difficult to optimize orthotropic steel deck bridges using a conventional optimization, since the bridges have several parts and show complex structural behaviors. Therefore, the Pareto curve can be obtained by performing the multi-objective optimization for real orthotropic steel deck bridges, using the multi-level technique with excellent efficiency. A reasonable and economical design can be attained using the Parato curve in the cost and deflection functions of the bridge. Thus, more reasonable design values can be determined based on a comparison with those using a conventional design procedure.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.267-275
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• 2014

Recently, the construction of curved bridge has increased, thus researchers perform the analytic studies on PSC curved bridge. However, the grid analysis method that are mostly used in the construction industry is not adequate to acquire the precise behavior evaluation of curved PSC briges. Therefore, the precise finite element analysis considering the effective variables were performed to establish the basis for the design method of curved PSC bridge by using 3D elements and bar element. The evaluated variables in this analysis were the number of girders, loading point, section figure, change of prestressing force. The results show the load carrying capacity of the 3 girder type bridge is 200% of that of the 2 girder type, and that applying load on outer girder makes the load resistance capacity and the deflection deviation of 2 girders smaller. The structural capacity of the bridge is improved when the section size is increased, but the efficiency of it is not sufficient enough compare to that of the change of prestressing forces. The change of prestressing forces shows that the camber and the load carrying capacity are linearly increased as PS force is increased. Moreover, when the PS force applied on outer girder is increased than that of inner girder, the deviation of deflection the girders decreases, thereby the stability of the bridge is enhanced.

• 한국방재학회:학술대회논문집
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• 2009.02b
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• pp.106.1-106.1
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• 2009

• Journal of the Society of Disaster Information
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• v.19 no.4
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• pp.976-983
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• 2023

Purpose: The dynamic behavior of a bridge structure under seismic loading depends on many uncertainties, such as the nature of the seismic waves and the material and geometric properties. However, not all uncertainties have a significant impact on the dynamic behavior of a bridge structure. Since probabilistic seismic performance evaluation considering even low-impact uncertainties is computationally expensive, the uncertainties should be identified by considering their impact on the dynamic behavior of the bridge. Therefore, in this study, a global sensitivity analysis was performed to identify the main parameters affecting the dynamic behavior of bridges with I-curved girders. Method: Considering the uncertainty of the earthquake and the material and geometric uncertainty of the curved bridge, a finite element analysis was performed, and a surrogate model was developed based on the analysis results. The surrogate model was evaluated using performance metrics such as coefficient of determination, and finally, a global sensitivity analysis based on the surrogate model was performed. Result: The uncertainty factors that have the greatest influence on the stress response of the I-curved girder under seismic loading are the peak ground acceleration (PGA), the height of the bridge (h), and the yield stress of the steel (fy). The main effect sensitivity indices of PGA, h, and fy were found to be 0.7096, 0.0839, and 0.0352, respectively, and the total sensitivity indices were found to be 0.9459, 0.1297, and 0.0678, respectively. Conclusion: The stress response of the I-shaped curved girder is dominated by the uncertainty of the input motions and is strongly influenced by the interaction effect between each uncertainty factor. Therefore, additional sensitivity analysis of the uncertainty of the input motions, such as the number of input motions and the intensity measure(IM), and a global sensitivity analysis considering the structural uncertainty, such as the number and curvature of the curved girders, are required.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2005.04a
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• pp.510-515
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• 2005