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주부석,손호영 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.9
Reactor containment buildings serve as the last barrier to prevent radioactive leakage due to accidents and their safety is crucial in overpressurization conditions. Thus, the Regulatory Guide (RG) 1.216 has mentioned the global strain as one of failure criteria in the free-field for cylindrical prestressed concrete containment vessels (PCCV) subject to internal pressure. However, there is a limit that RG 1.216 shows the free-field without the specific locations of failure criteria and also the global strain corresponding to only azimuth 135 has been mentioned in NUREG/CR-6685, regardless of the elevations of the structure. Therefore, in order to reevaluate the failure criteria of the 1:4 scaled PCCV, the high fidelity simulation model based on the experimental test was significantly validated in this study, and it was interesting to find that the experimental and numerical result was very close to each other. In addition, for the consideration of the material uncertainties, the Latin hypercube method was used as a statistical approach. Consequently, it was revealed that the radial displacements of various azimuth area such as 120, 135, 150, 180 and 210 at elevations 4680 mm and 6,200 mm can represent as the global deformation at the free-field, obtained from the statistical approach.
Seismic Fragility of Steel Piping System Based on Pipe Size, Coupling Type, and Wall Thickness
주부석,Abhinav Gupta,류용희 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.4
In this study, a probabilistic framework of the damage assessment of pipelines subjected to extreme hazard scenario was developed to mitigate the risk and enhance design reliability. Nonlinear 3D fi nite element models of T-joint systems were developed based on experimental tests with respect to leakage detection of black iron piping systems, and a damage assessment analysis of the vulnerability of their components according to nominal pipe size, coupling type, and wall thickness under seismic wave propagations was performed. The analysis results showed the 2-inch schedule 40 threaded T-joint system to be more fragile than the others with respect to the nominal pipe sizes. As for the coupling types, the data indicated that the probability of failure of the threaded T-joint coupling was signifi cantly higher than that of the grooved type. Finally, the seismic capacity of the schedule 40 wall thickness was weaker than that of schedule 10 in the 4-inch grooved coupling, due to the diff erence in the prohibition of energy dissipation. Therefore, this assessment can contribute to the damage detection and fi nancial losses due to failure of the joint piping system in a liquid pipeline, prior to the decision-making.
주부석,전법규,남준석,류용희,손호영 한국재난정보학회 2017 한국재난정보학회 학술대회 Vol.2017 No.11
최근 세계적으로 많은 지진이 발생하고 있으며 기상이변으로 인한 자연재해로 인해 주요 시설물들의 안 전성에 관한 관심이 증가하고 있는 추세이다. 특히 비구조 요소의 경우 구조 요소보다 건설 초기 투자비용 이 높아 지진이 발생하였을 때 많은 피해가 발생할 가능성이 있으며 비구조 요소의 파괴는 심각한 2차피 해로 발전 될 수 있으므로 내진안전성 평가는 반드시 이루어져야 한다고 볼 수 있다. 따라서 본 연구에서 는 압착식 조인트의 접촉을 고려한 수계소화설비 파이프라인의 내진성능 평가를 위한 비선형 유한요소 모 델을 구축하였다.
Performance-based drift prediction of reinforced concrete shear wall using bagging ensemble method
주부석,곽신영,이상우 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8
Reinforced Concrete (RC) shear walls are one of the civil structures in nuclear power plants to resist lateral loads such as earthquakes and wind loads effectively. Risk-informed and performance-based regulation in the nuclear industry requires considering possible accidents and determining desirable performance on structures. As a result, rather than predicting only the ultimate capacity of structures, the prediction of performances on structures depending on different damage states or various accident scenarios have increasingly needed. This study aims to develop machine-learning models predicting drifts of the RC shear walls according to the damage limit states. The damage limit states are divided into four categories: the onset of cracking, yielding of rebars, crushing of concrete, and structural failure. The data on the drift of shear walls at each damage state are collected from the existing studies, and four regression machine-learning models are used to train the datasets. In addition, the bagging ensemble method is applied to improve the accuracy of the individual machine-learning models. The developed models are to predict the drifts of shear walls consisting of various cross-sections based on designated damage limit states in advance and help to determine the repairing methods according to damage levels to shear walls
Seismic fragility evaluation of piping system installed in critical structures
주부석,정우영,Yong Hee Ryu 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.3
Seismic performance of critical facilities has been focused on the structural components over the past decade. However, most earthquake damages were observed to the nonstructural components during and after the earthquakes. The primary objective of this research was to develop the seismic fragility of the piping system incorporating the nonlinear Tee-joint finite element model in the full scale piping configuration installed in critical facilities. The procedure for evaluating fragility curves corresponding to the first damage state was considered the effects of the top floor acceleration sensitivities for 5, 10, 15, and 20 story linear RC and steel building systems subjected to 22 selected ground motions as a function of ground motion uncertainties. The result of this study revealed that the conditional probability of failure of the piping system on the top floor in critical facilities did not increase with increased level of story height and in fact, story level in buildings can tune the fragilities between the building and the piping system.