• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.3
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• pp.29-38
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• 2009

n the event of an earthquake, additional stresses can occur in the continuous welded rails (CWR) of High-speed railway (HSR) bridges due to relative displacements at expansion joints, and this stress can cause derailment. The amplification of ground motion occurs as a result of site effects, and this is pronounced at the site of a soft surface soil layer and of a rigid surface soil layer over a soft one. As a result, the amplified ground motion leads to an amplified seismic response in HSR bridges. A change in bridge pier height affects the seismic behavior of the bridge. A HSR bridge with gravel ballast tracks will show different dynamic behavior during an earthquake than one with concrete ballast tracks. The seismic responses of HSR bridges and their CWR are analyzed considering the derailment-inducing factors.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.270-283
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• 2024

Purpose: Considering the rising frequency of earthquakes in Korea, it is crucial to revise the rainfall thresholds for landslide triggering following earthquake events. This study was conducted to provide scientific justification and preliminary data for adjusting rainfall thresholds for landslide early warnings after earthquakes through soil physical experiments. Method: The study analyzed the change in soil shear strength by direct shear tests on disturbed and undisturbed samples collected from cut slopes. Also, The study analyzed the soil strength parameters of remolded soil samples subjected to drying and wetting conditions, focusing on the relationship between the degree of saturation after submergence and the strength parameters. Result: Compaction water content variation in direct shear tests showed that higher water content and saturation in disturbed samples led to a significant decrease in cohesion (over 50%) and a reduction in shear resistance angle (1~2°). Additionally, during the ring shear tests, the shear strength was observed to gradually decrease once water was supplied to the shear plane. The maximum shear strength decreased by approximately 65-75%, while the residual shear strength decreased by approximately 53-60%. Conclusion: Seismic activity amplifies landslide risk during subsequent rainfall, necessitating proactive mitigation strategies in earthquake-prone areas. This research is anticipated to provide scientific justification and preliminary data for reducing the rainfall threshold for landslide initiation in earthquake-susceptible regions.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.5
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• pp.1-17
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• 2002

Prognostic characteristics of hypothetical tsunamis in the East Sea are further discussed based on numerical simulations using linear long wave theory than the last paper(Choi et al). As for choice of source zones, we used 28 cases based on fault parameters of hypothetical earthquakes and 76 cases based on simple initial surface shapes of tsunamigenic earthquakes selected by the seismic gap theory. As a result, the wave heights along the whole coastline adjacent to the East See of tsunamis due to these hypothetical earthquake are presented. Analyses also lead us to conclude that the selection of geographical zones with low risk of tsunamis can be used as a tool for coastal disaster mitigation planning.

• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.254-260
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• 2011

We studied magnitude determination method using high-frequency energy radiation duration to calculate rapidly magnitude of large earthquakes that occurred around Japan. Fourteen earthquakes were analyzed using Korea Meteorological Administration (KMA) data. We calculated duration of high-frequency energy radiation with 2~4 Hz band pass filter at each data and estimated magnitude. As a result, duration becomes longer as magnitude becomes larger and the magnitude estimated using regional earthquake data are similar to that using teleseismic data. Therefore when an earthquake occurs around Japan we will be able to estimate the magnitude in a relatively short time using KMA data and it may be possible to determine if the earthquake is large enough to produce tsunami.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.55-64
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• 2002

In the present study, in order to apply a cyclic viscoelastic-viscoplastic constitutive model to multi-layered ground conditions during large earthquake, the numerical simulations of the 1995 Hyogoken Nanbu Earthquake at Port Island, Kobe, Japan, were performed by the seismic response analysis. From the seismic response analysis, it was found that the acceleration calculated from the cyclic elasto-viscoplastic model and cyclic viscoelastic-viscoplastic models for clay was in close agreement with the recorded accelerations at the Port Island down-hole array, and the cyclic elastic-viscoplastic and viscoelastic-viscoplastic constitutive models showed little different behavior characteristics near clay layer. Thus, the propriety of viscoplastic model for clay was convinced. Therefore, it can be concluded that a cyclic viscoelastic-viscoplastic constitutive model can give a good description of the amplification and also it showed accurate damping characteristics of clay during large event which induces plastic deformation in large strain range.

• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.5-19
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• 2009

Most of earthquake-induced geotechnical hazards have been caused by the site effects relating to the amplification of ground motion, which is strongly influenced by the local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated GIS-based information system for geotechnical data, called geotechnical information system (GTIS), was constructed to establish a regional counterplan against earthquake-induced hazards at an urban area of Daejeon, which is represented as a hub of research and development in Korea. To build the GTIS for the area concerned, pre-existing geotechnical data collections were performed across the extended area including the study area and site visits were additionally carried out to acquire surface geo-knowledge data. For practical application of the GTIS used to estimate the site effects at the area concerned, seismic zoning map of the site period was created and presented as regional synthetic strategy for earthquake-induced hazards prediction. In addition, seismic zonation for site classification according to the spatial distribution of the site period was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site in the study area. Based on this case study on seismic zonations in Daejeon, it was verified that the GIS-based GTIS was very useful for the regional prediction of seismic hazards and also the decision support for seismic hazard mitigation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.11-20
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• 1992

In general, the cross-section of a girder of a bridge has only one axis of symmetry. Therefore, lateral forces such as earthquake and wind may cause torsion coupled with lateral bending in the gider. This induces additional stresses especially in cables arranged in double-planes. Since this effect cannot be considered by using the conventional frame elements, the stiffness and the mass matrices of the geometrically nonlinear thin-walled frame element have to be used in order to model the girder. Theoretical development and verification of the frame element used in this study were made through a-previously presented paper. In this paper, seismic analysis of a three dimensional cable-stayed bridge considering the unsymmetry of the girder cross-section is performed to investigate the coupled flexural-torsional behaviors.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.3
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• pp.205-216
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• 2024

Recently, seismic Probabilistic Safety Assessment (PSA) methods have been developed for process plants, such as gas plants, oil refineries, and chemical plants. The framework originated from the PSA of nuclear power plants, which aims to assess the risk of reactor core damage. The original PSA method was modified to adopt the characteristics of a process plant whose purpose is continuous operation without shutdown. Therefore, a fault tree, whose top event is shut down, was constructed and transformed into a Bayesian Network (BN), a probabilistic graph model, for efficient risk-informed decision-making. In this research, the fault tree-based BN from the previous research is further developed to consider the multi-hazard of earthquake-induced fire and explosion (EQ-induced F&E). For this purpose, an event tree describing the occurrence of fire and explosion from a release is first constructed and transformed into a BN. And then, this BN is connected to the previous BN model developed for seismic PSA. A virtual plot plan of a gas plant is introduced as a basis for the construction of the specific EQ-induced F&E BN to test the proposed BN framework. The paper demonstrates the method through two examples of risk-informed decision-making. In particular, the second example verifies how the proposed method can establish a repair and retrofit strategy when a shutdown occurs in a process plant.

• Journal of the Society of Disaster Information
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• v.17 no.4
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• pp.694-709
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• 2021

Purpose: In this study, earthquake-induced landslide risk assessment was conducted to provide basic data for efficient and preemptive damage prevention by selecting the erosion control work before the earthquake and the prediction and restoration priorities of the damaged area after the earthquake. Method: The study analyzed the previous studies abroad to examine the evaluation methodology and to derive the evaluation factors, and examine the utilization of the landslide hazard map currently used in Korea. In addition, the earthquake-induced landslide hazard map was also established on a pilot basis based on the fault zone and epicenter of Pohang using seismic attenuation. Result: The earthquake-induced landslide risk assessment study showed that China ranked 44%, Italy 16%, the U.S. 15%, Japan 10%, and Taiwan 8%. As for the evaluation method, the statistical model was the most common at 59%, and the physical model was found at 23%. The factors frequently used in the statistical model were altitude, distance from the fault, gradient, slope aspect, country rock, and topographic curvature. Since Korea's landslide hazard map reflects topography, geology, and forest floor conditions, it has been shown that it is reasonable to evaluate the risk of earthquake-induced landslides using it. As a result of evaluating the risk of landslides based on the fault zone and epicenter in the Pohang area, the risk grade was changed to reflect the impact of the earthquake. Conclusion: It is effective to use the landslide hazard map to evaluate the risk of earthquake-induced landslides at the regional scale. The risk map based on the fault zone is effective when used in the selection of a target site for preventive erosion control work to prevent damage from earthquake-induced landslides. In addition, the risk map based on the epicenter can be used for efficient follow-up management in order to prioritize damage prevention measures, such as to investigate the current status of landslide damage after an earthquake, or to restore the damaged area.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.15-25
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• 2001

본 고에서는 블록식 보강토 옹벽의 지진시 거동에 관한 유한요소해석 결과를 다루었다. 보강토 옹벽의 지진시 변위거동을 검토한 결과 벽체저부를 지점으로 하는 캔틸레버형태의 변위 거동을 보였으며 따라서 옹벽 상단부에서의 보강재 인장력 증가가 현저하게 나타나 벽체전반에 걸친 분포양상은 균등한 경향을 보였다. 한편, 지진하중으로 인한 증분유발인장력에 관하여 검토한 결과 기존의 보강토 옹벽 내진설계기준과 비교하여 정성.정량적인 측면에서 상당한 차이를 보였으며 내진설계기준이 전반적으로 과소평가 하는 것으로 나타났다. 아울러서, 내진설계측면에서 변위억제 방안에 관한 매개변수 연구결과 임의 조건에 있어서 최대의 보강효과를 나타내는 보강재 임계 강성과 포설길이가 존재하며 최적의 보강효과를 얻기 위해서는 이에 대한 종합적인 검토가 요구되는 것으로 나타났다. 본 고에서는 연구결과를 종합적으로 고찰하여 실무 적용관점에서의 주안점을 언급하였다.