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Ground motion response spectra (GMRS) at rock/soil sites in regions where earthquake ground motions have dominant contents at high frequencies of 10 Hz or more are evaluated and the effects of soil amplification on the GMRS are studied. The seismic hazard levels at the soil sites are estimated from soil amplification functions and hazard curves for rock outcrop motions. The soil amplification functions are obtained using modified earthquake ground motions which match the uniform hazard response spectra (UHRS) for rock outcrop motions with various mean annual frequencies of exceedance in order to consider the effects of earthquake ground motions consistently in a site response analysis. UHRS at soil sites are determined from the calculated seismic hazard curves. Subsequently, design factors, which will be applied to UHRS, and the corresponding GMRS are evaluated such that the seismic risk for the structures, systems, and components of nuclear facilities would be equal to a target seismic risk. It can be observed from example applications that the UHRS and GMRS at soil sites have peaks at the natural frequencies of the soil, where the soil responses are amplified. Amplification at soil sites depends on the frequency contents of rock outcrop motions.
Jin Ho Lee; Hieu Van Nguyen; In-Kil Choi; Jung Han Kim. Effects of Soil Amplification on Ground Motion Response Spectra with High-Frequency Contents at Generic Soil Sites for Nuclear Facilities in Korea. KSCE Journal of Civil Engineering 2021, 25, 2394 -2410.
AMA StyleJin Ho Lee, Hieu Van Nguyen, In-Kil Choi, Jung Han Kim. Effects of Soil Amplification on Ground Motion Response Spectra with High-Frequency Contents at Generic Soil Sites for Nuclear Facilities in Korea. KSCE Journal of Civil Engineering. 2021; 25 (7):2394-2410.
Chicago/Turabian StyleJin Ho Lee; Hieu Van Nguyen; In-Kil Choi; Jung Han Kim. 2021. "Effects of Soil Amplification on Ground Motion Response Spectra with High-Frequency Contents at Generic Soil Sites for Nuclear Facilities in Korea." KSCE Journal of Civil Engineering 25, no. 7: 2394-2410.
When a seismic force acts on bridges, the pier can be damaged by the horizontal inertia force of the superstructure. To prevent this failure, criteria for seismic reinforcement details have been developed in many design codes. However, in moderate seismicity regions, many existing bridges were constructed without considering seismic detail because the detailed seismic design code was only applied recently. These existing structures should be retrofitted by evaluating their seismic performance. Even if the seismic design criteria are not applied, it cannot be concluded that the structure does not have adequate seismic performance. In particular, the performance of a lap-spliced reinforcement bar at a construction joint applied by past practices cannot be easily evaluated analytically. Therefore, experimental tests on the bridge piers considering a non-seismic detail of existing structures need to be performed to evaluate the seismic performance. For this reason, six small scale specimens according to existing bridge piers were constructed and seismic performances were evaluated experimentally. The three types of reinforcement detail were adjusted, including a lap-splice for construction joints. Quasi-static loading tests were performed for three types of scale model with two-column piers in both the longitudinal and transverse directions. From the test results, the effect on the failure mechanism of the lap-splice and transverse reinforcement ratio were investigated. The difference in failure characteristics according to the loading direction was investigated by the location of plastic hinges. Finally, the seismic capacity related to the displacement ductility factor and the absorbed energy by hysteresis behavior for each test were obtained and discussed.
Jung Kim; Ick-Hyun Kim; Jin Lee. Experimental Study on the Behavior of Existing Reinforced Concrete Multi-Column Piers under Earthquake Loading. Applied Sciences 2021, 11, 2652 .
AMA StyleJung Kim, Ick-Hyun Kim, Jin Lee. Experimental Study on the Behavior of Existing Reinforced Concrete Multi-Column Piers under Earthquake Loading. Applied Sciences. 2021; 11 (6):2652.
Chicago/Turabian StyleJung Kim; Ick-Hyun Kim; Jin Lee. 2021. "Experimental Study on the Behavior of Existing Reinforced Concrete Multi-Column Piers under Earthquake Loading." Applied Sciences 11, no. 6: 2652.
Probabilistic safety assessment (PSA) of nuclear facilities on external multi-hazards has become a major issue after the Fukushima accident in 2011. However, the existing external hazard PSA methodology is for single hazard events and cannot cover the impact of multi-hazards. Therefore, this study proposes a methodology for quantifying multi-hazard risks for nuclear energy plants. Specifically, we developed an efficient multi-hazard PSA methodology based on the probability distribution-based Boolean algebraic approach and sampling-based method, which are currently single-hazard PSA methodologies. The limitations of the probability distribution-based Boolean algebraic approach not being able to handle partial dependencies between the components are solved through this sampling-based method. In addition, we devised an algorithm that was more efficient than the existing algorithm for improving the limits of the current sampling-based method, as it required a significant computational time. The proposed methodology was applied from simple examples to single- and multi-hazard PSA examples of actual nuclear power plants. The results showed that the proposed methodology was verified in terms of accuracy and efficiency perspectives. Regarding the sampling-based method, it was confirmed that the proposed algorithm yielded fragility and risk results that have similar degrees of accuracy, even though it extracted a smaller number of samples than the existing algorithm.
ShinYoung Kwag; Jeong Gon Ha; Min Kyu Kim; Jung Han Kim. Development of Efficient External Multi-Hazard Risk Quantification Methodology for Nuclear Facilities. Energies 2019, 12, 3925 .
AMA StyleShinYoung Kwag, Jeong Gon Ha, Min Kyu Kim, Jung Han Kim. Development of Efficient External Multi-Hazard Risk Quantification Methodology for Nuclear Facilities. Energies. 2019; 12 (20):3925.
Chicago/Turabian StyleShinYoung Kwag; Jeong Gon Ha; Min Kyu Kim; Jung Han Kim. 2019. "Development of Efficient External Multi-Hazard Risk Quantification Methodology for Nuclear Facilities." Energies 12, no. 20: 3925.
Full-scale lead rubber bearings were tested by 2-D horizontal input motions. 2-D test motion with isolation frequency should be applied for rubber type isolator. The failure strain level by 2-D test decreased 20% lower compared to 1-D test.
Jung Han Kim; Min Kyu Kim; In-Kil Choi. Experimental study on seismic behavior of lead-rubber bearing considering bi-directional horizontal input motions. Engineering Structures 2019, 198, 109529 .
AMA StyleJung Han Kim, Min Kyu Kim, In-Kil Choi. Experimental study on seismic behavior of lead-rubber bearing considering bi-directional horizontal input motions. Engineering Structures. 2019; 198 ():109529.
Chicago/Turabian StyleJung Han Kim; Min Kyu Kim; In-Kil Choi. 2019. "Experimental study on seismic behavior of lead-rubber bearing considering bi-directional horizontal input motions." Engineering Structures 198, no. : 109529.
The seismic performance of nuclear power plants can be improved by installing the proposed seismic isolation system. Due to the characteristics of this system, while acceleration seismic response and base shear can be reduced, the displacement seismic response of the isolated structure increases. Therefore, the restriction of excessive displacement responses becomes critical to the design and safety assessment of isolated structures. Such seismic design and safety assessment requires a seismic response distribution, which itself necessitates a large number of nonlinear dynamic analyses. However, the stochastic response database can directly estimate the maximum seismic response distribution of an isolated structure without nonlinear dynamic analyses. In this study, a sensitivity analysis was performed using the stochastic response database for the isolated structures that affect the maximum seismic response distribution. First, the important seismic isolation parameters were selected, followed by an investigation into the effects these parameters have on the mean and standard deviation of the maximum seismic response distribution of the isolated structure. It is believed that this information will be useful in the seismic design and safety assessment of nuclear power plants with seismic isolation systems.
Seunghyun Eem; Jung Han Kim. Sensitivity analysis for the distribution of maximum responses by seismic isolation system parameters using the stochastic response database. Nuclear Engineering and Design 2019, 347, 53 -58.
AMA StyleSeunghyun Eem, Jung Han Kim. Sensitivity analysis for the distribution of maximum responses by seismic isolation system parameters using the stochastic response database. Nuclear Engineering and Design. 2019; 347 ():53-58.
Chicago/Turabian StyleSeunghyun Eem; Jung Han Kim. 2019. "Sensitivity analysis for the distribution of maximum responses by seismic isolation system parameters using the stochastic response database." Nuclear Engineering and Design 347, no. : 53-58.
Following a surge of interest in multi-unit risk in the last few years, many recent studies have suggested methods for multi-unit probabilistic safety assessment (MUPSA) and addressed several related aspects. Most of the existing studies though focused on two-unit nuclear power plant (NPP) sites or used rather simplified PSA models to demonstrate the proposed approaches. When considering an NPP site with three or more units, some approaches are inapplicable or yield very conservative results. Since the number of such sites is increasing, there is a strong need to develop and validate practical approaches to the related MUPSA. This paper provides several detailed approaches that are applicable to multi-unit Level 1 PSA for sites with up to six or more reactor units. To validate the approaches, a multi-unit Level 1 PSA model is developed and the site core damage frequency (CDF) is estimated for each of four representative multi-unit initiators, as well as for the case of a simultaneous occurrence of independent single-unit initiators in multiple units. For this purpose, an NPP site with six identical OPR-1000 units is considered, with full-scale Level 1 PSA models for a specific OPR-1000 plant used as the base single-unit models.
Dong-San Kim; Sang Hoon Han; Jin Hee Park; Ho-Gon Lim; Jung Han Kim. Multi-unit Level 1 probabilistic safety assessment: Approaches and their application to a six-unit nuclear power plant site. Nuclear Engineering and Technology 2018, 50, 1217 -1233.
AMA StyleDong-San Kim, Sang Hoon Han, Jin Hee Park, Ho-Gon Lim, Jung Han Kim. Multi-unit Level 1 probabilistic safety assessment: Approaches and their application to a six-unit nuclear power plant site. Nuclear Engineering and Technology. 2018; 50 (8):1217-1233.
Chicago/Turabian StyleDong-San Kim; Sang Hoon Han; Jin Hee Park; Ho-Gon Lim; Jung Han Kim. 2018. "Multi-unit Level 1 probabilistic safety assessment: Approaches and their application to a six-unit nuclear power plant site." Nuclear Engineering and Technology 50, no. 8: 1217-1233.