• Earthquakes and Structures
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• v.26 no.2
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• pp.131-147
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• 2024

Damage caused by an earthquake depends on not just the intensity of an earthquake but also the region-specific construction practices. Past earthquakes in Asian countries have highlighted inadequate construction practices, which caused huge life and property losses, indicating the severe need to strengthen existing structures. Strengthening activities shall be proposed as per the proposed weighting factors, first at the higher weighted members to increase the capacity of the building immediately and thereafter, the other members. Through this study on gravity load-designed (GLD) buildings, relative weights are assigned to each storey and exterior and interior columns within a storey based on their contribution to the energy dissipation capacity of the building. The numerical study is conducted on mid-rise archetype GLD buildings, i.e., 4, 6, 8, and 10 stories with variable storey heights, in the high seismic zones. Non-linear static analysis is performed to compute weights based on energy dissipation capacities. The results obtained are verified with the non-linear time history analysis of 4 GLD buildings. It was observed that exterior columns have higher weightage in the energy dissipation capacity of the building than interior columns up to a certain building height. The damage in stories is distributed in a convex to concave parabolic shape from bottom to top as building height increases, and the maxima location of the parabola shifts from bottom to middle stories. Relative weighting factors are assigned as per the damage contribution. And the sequence for strengthening activities is proposed as per the computed weighting factors in descending order for regular RCC buildings. Therefore, proposals made in the study would increase the efficacy of strengthening activities.

• Journal of the Korean earth science society
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• v.43 no.1
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• pp.165-175
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• 2022

Earthquakes have occurred owing to movements on a fault since several billion years ago. Research on the relationship between earthquakes and groundwater began in the 1960s in the United States, but related works, including hydrogeochemistry research, only began in the 2010s in South Korea. In this study, domestic studies on the relationship between earthquakes and groundwater until 2021 were collected from the Web of Science and characterized by subject area (groundwater level, hydrogeochemistry, combination of the two, and others). The results showed that the number of published articles per year was positively correlated with the 2011 Tohoku earthquake, 2016 Gyeongju earthquake, and 2017 Pohang earthquake, with the maximum numbers observed in 2011, 2018, 2019, and 2020. Most studies on the relationship between earthquakes and groundwater level addressed groundwater level fluctuations in the duration of the subject earthquake, with little consideration of the precursors. Groundwater level monitoring data, as well as hydrogeochemical information and microbial communities, may contribute to a more detailed understanding of groundwater flow and chemical reactions in bedrock caused by earthquakes. Therefore, the establishment of a national groundwater monitoring network for seismic monitoring and prediction is required.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.1
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• pp.126-137
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• 2021

Recently, the number of damages on social infrastructure has increased due to natural disasters and the frequency of earthquake events that are higher than magnitude 3 has increased in South Korea. Liquefaction was found near the epicenter of a 5.4 magnitude earthquake that occurred in Pohang, South Korea, in 2017. To explore increases in soil moisture index due to soil liquefaction, changes in the remote exploration index by the land cover before and post-earthquake occurrence were analyzed using liquefaction feasibility index and multi-cyclical Landsat-8 satellite images. We found that the soil moisture index(SMI) in the liquefaction region immediately after the earthquake event increased significantly using the Normal Vegetation Index(NDVI) and Surface Temperature(LST).

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.515-529
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• 2018

Multiple hazards (multihazard) conditions may cause significant risk to structures that are originally designed for individual hazard scenarios. Such a multihazard condition arises when an earthquake strikes to a bridge pre-exposed to scour at foundations due to flood events. This study estimates the impact spectrum of flood-induced scour on seismic vulnerability of bridges. Characteristic river-crossing highway bridges are formed based on the information obtained from bridge inventories. These bridges are analyzed under earthquake-only and the abovementioned multihazard conditions, and bridge fragility curves are developed at component and system levels. Research outcome shows that bridges having pile shafts as foundation elements are protected from any additional seismic vulnerability due to the presence of scour. However, occurrence of floods can increase seismic fragility of bridges at lower damage states due to the adverse impact of scour on bridge components at superstructure level. These findings facilitate bridge design under the stated multihazard condition.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.839-851
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• 1997

Closed-form solutions are analytically derived for stochastic properties of earthquake ground motion fields, which are conditioned by an observed time series at certain observation sites and are characterized by spectra with uncertainties. The theoretical framework presented here can estimate not only the expectations of such simulated earthquake ground motions, but also the prediction errors which offer important information for the field of engineering. Before these derivations are made, the theory of conditional random fields is summarized for convenience in this study. Furthermore, a method for stochastic interpolation of power spectra is explained.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.112-122
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• 2006

Is the high speed train with 300km/h running speed safe from derailment when it meets the mid or small-size earthquakes? In the present step, it is not so easy to judge whether it'll be derailed or not during an earthquake. However, we could elevate the running safety of high speed train as making it slow or even stop. The main objective of this study is to make the domestic running regulation and the re-running manual for high speed train with reference to the standards of France, Japan etc. To do so, numerical analysis and experiment will be performed from the next year. In addition, we'll evaluate possible places of derailment during an earthquake and make a database based on the Geographic Information System to effectively manage them.

• Architectural research
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• v.20 no.1
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• pp.17-25
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• 2018

Countermeasures against earthquake disasters such as the seismic capacity evaluation and/or retrofit schemes of buildings, especially existing low-rise reinforced concrete buildings, have not been fully performed since Korea had not experienced many destructive earthquakes in the past. However, due to more than 1200 earthquakes with low or moderate intensity in the off-coastal and inland of Korea during the past 20 years, and due to the recent moderate earthquakes in Korea, such as the 2016 Gyeongju Earthquake with M=5.8 and the 2017 Pohang Earthquake with M=5.4, the importance of the future earthquake preparedness measures is highly recognized in Korea. The main objective of this study is to provide the basic information regarding seismic capacities of existing low-rise reinforced concrete buildings in Korea. In this paper, seismic capacities of 14 existing low-rise reinforced concrete public buildings in Korea are evaluated based on the Japanese Standard for Evaluation of Seismic Capacity of Existing Reinforced Concrete Buildings. Seismic capacities between existing buildings in Korea and those in Japan is compared, and the relationship of seismic vulnerability of Korean buildings and Japanese buildings damaged due to severe earthquakes are also discussed. Results indicated that Korean existing low-rise reinforced concrete buildings have a narrow distribution of seismic capacities and they are relatively lower than Japanese buildings, and are also expected to have severe damage under the earthquake intensity level experienced in Japan. It should be noted from the research results that the high ductility in Korean existing low-rise buildings obtained from the Japanese Standard may be overestimated, because most buildings investigated herein have the hoop spacing wider than 30 cm. In the future, the modification of strength and ductility indices in the Japanese Standard to propose the seismic capacity evaluation method of Korean buildings is most needed.

• Asian Journal of Business Environment
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• v.4 no.1
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• pp.25-35
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• 2014

Purpose - Appropriate project management knowledge as well as its effective application in the construction industry increase construction quality and, therefore, reduce fatalities and destruction. Research design, data, and methodology - This study was conducted through a comparative analysis of earthquake fatalities in Iran, Turkey, Pakistan, Indonesia, China, Haiti, Japan, and the United States of America. The data was analyzed using a frequency study. The analysis contrasts the fatalities of some of the strongest earthquakes around the world between 1960 and 2010. Results - Poor quality construction practices and a lack of effective application of project management knowledge play a major role in the vast destruction, high death toll, and dismal tragedies that are associated with earthquakes, especially in Iran. Conclusions - Despite the history of tragic earthquakes and their continuing recurrence, this study attempts to make governments, companies, and disaster management personnel aware of the dangers of poor quality construction and the deficient application of project management knowledge and, further, accentuates effective ways to prevent the probability of serious damage in future. This study contains valuable information on the effects of project management application towards reducing earthquake fatalities and destruction.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.317-320
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• 2007

This research focuses on a network based data distribution and visualization system of Multi-functional Tran-port SATellite (MTSAT). Institute of Industrial Science (IIS) and Institute of Earthquake Research Institute (ERI) both at University of Tokyo have been receiving, processing, archiving and distributing of MTSAT imagery with a direct receiving of High Rate Information Transmit (HRIT) since October 2006. A software package, mtsatgeo, is developed including radiometric correction, geometric correction and spatial subset, and they are available on a web-based data distribution and processing service accessed at http://webgms.iis.u-tokyo.ac.jp/.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.439-446
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• 1998

One of the most important roles in the nonlinear dynamic structural analysis is to select a proper ground excitation, which dominates the response of a structure. Because of the lack of recorded accelerograms in Korea, a stochastic model of ground excitation with various dynamic properties rather than recorded accelerograms is necessarily required. If all information is not available at site, the information from other sites with similar features can be used by the procedure of seismic hazard analysis. Eliopoulos and Wen identified the parameters of the ground motion model by the empirical relations or expressions developed by Trifunac and Lee. Because the relations used in the parameter identification are largely empirical, it is required to apply the artificial neural networks instead of the empirical model. Additionally, neural networks have the advantage of the empirical model that it can continuously re-train the new recorded data, so that it can adapt to the change of the enormous data. Based on the redefined traditional processes, three neural-networks-based models (FAS_NN, PSD_NN and INT_NN) are proposed to individually substitute the Fourier amplitude spectrum, the parameter identification of power spectral density function and intensity function. The paper describes the first half of the research for the development of Neural-Networks-based model for the generation of an Artificial earthquake and a Response Spectrum(NNARS).