• Earthquakes and Structures
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• v.14 no.3
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• pp.249-259
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• 2018

This paper aims to assess the seismic risk of a plane moment-resisting frames (MRFs) consisting of concrete-filled double skin steel tube (CFDST) columns and I-section steel beams. Firstly, three typical limit performance levels of CFDST structures are determined in accordance with the cyclic tests of seven CFDST joint specimens with 1/2-scaled and the limits stipulated in FEMA 356. Then, finite element (FE) models of the test specimens are built by considering with material degradation, nonlinear behavior of beam-column connections and panel zones. The mechanical behavior of the concrete material are modeled in compression stressed condition in trip-direction based on unified strength theory, and such numerical model were verified by tests. Besides, numerical models on 3, 6 and 9-story CFDST frames are established. Furthermore, the seismic responses of these models to earthquake excitations are investigated using nonlinear time-history analyses (NTHA), and the limits capacities are determined from incremental dynamic analyses (IDA). In addition, fragility curves are developed for these models associated with 10%/50yr and 2%/50yr events as defined in SAC project for the region on Los Angeles in the Unite State. Lastly, the annual probabilities of each limits and the collapse probabilities in 50 years for these models are calculated and compared. Such results provide risk information for the CFDST-MRFs based on the probabilistic risk assessment method.

• Earthquakes and Structures
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• v.22 no.3
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• pp.245-261
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• 2022

Key questions to researchers interested in nonlinear analysis of skeletal structures are whether the distributed plasticity approach - albeit computationally demanding - is more reliable than the concentrated plasticity to adequately capture the extent and severity of the inelastic response, and whether force-based formulation is more efficient than displacement-based formulation without compromising accuracy. The present research focusing on performance-based seismic response of mid-span concrete bridges provides a pilot holistic investigation opting for some hands-on answers. OpenSees software is considered adopting different modeling techniques, viz. distributed plasticity (through either displacement-based or force-based elements) and concentrated plasticity via beam-with-hinges elements. The pros and cons of each are discussed based on nonlinear pushover analysis results, and fragility curves generated for various performance levels relying on incremental dynamic analyses under real earthquake records. Among prime conclusions, distributed plasticity modeling albeit inherently not relying on prior knowledge of plastic hinge length still somewhat depends on such information to ensure accurate results. For instance, displacement-based and force-based approaches secure optimal accuracy when dividing, for the former, the member into sub-elements, and satisfying, for the latter, a distance between any two consecutive integration points, close to the expected plastic hinge length. On the other hand, using beam-with-hinges elements is computationally more efficient relative to the distributed plasticity, yet with acceptable accuracy provided the user has prior reasonable estimate of the anticipated plastic hinge length. Furthermore, when intrusive performance levels (viz. life safety or collapse) are of concern, concentrated plasticity via beam-with-hinges ensures conservative predicted capacity of investigated bridge systems.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.3
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• pp.121-128
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• 2018

Severe earthquakes can cause damage to society both socially and economically. An appropriate initial response can alleviate damage from severe earthquakes. In order to formulate an appropriate initial response, it is necessary to identify damage situations in societies; however, it is difficult to grasp this information immediately after an earthquake event. In this study, an earthquake damage assessment methodology for buildings is proposed for estimating damage situations immediately after severe earthquakes. A response spectrum database is constructed to provide response spectra at arbitrary locations from earthquake measurements immediately after the event. The fragility curves are used to estimate the damage of the buildings. Earthquake damage assessment is performed from the response spectrum database at the building scale to provide enhanced damage condition information. Earthquake damage assessment for Gyeongju city and Pohang city were conducted using the proposed methodology, when an earthquake occurred on September 12, 2016, and November 15, 2017. Results confirm that the proposed earthquake damage assessment effectively represented the earthquake damage situation in the city to decide on an appropriate initial response by providing detailed information at the building scale.

• Geomechanics and Engineering
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• v.21 no.2
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• pp.143-152
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• 2020

Korean society experienced successive earthquakes exceeding 5.0 magnitude in the past three years resulting in an increasing concern about earthquake stability of urban infrastructures. This study focuses on the significant aspects of earthquake risk assessment for the cut-and-cover underground railway station based on two-dimensional dynamic numerical analysis. Presented are features from a case study performed for the railway station in Seoul, South Korea. The PLAXIS2D was employed for numerical simulation and input of the earthquake ground motion was chosen from Pohang earthquake records (M5.4). The paper shows key aspects of earthquake risk for soil-structure system varying important parameters including embedded depth, supported ground information, and applied seismicity level, and then draws several meaningful conclusions from the analysis results such as seismic risk assessment.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.223-230
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• 1999

The seismic damage assessment to the postulated earthquake is attempted for the buildings in the model district of Seoul City. The capacity spectrum method is employed in which the vulnerability functions are expressed as functions of the spectral displacement. the database of the building stock is constructed and managed using Geographic Information System software. The model district is selected to represent the typical structural and residential characteristics of Seoul City The structural properties were collected from the design documents. The field inspections were carried out to find out the current status of the building. They are classified into 11 structural types. The fragility curves in HazUS are employed, The ground motions from the postulated earthquakes are simulated using the Boor's methods, The surface soil in the district is classified into 3 profiles using the depth as the parameter. The one-dimensional wave propagation method is used to calculate he filtered ground motion through surface soil layer. The average spectrum of this sample time histories is used as the demand curves. The calculated results are expressed in maps using GIS software ArcView 3.0a

• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.4
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• pp.10-27
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• 2014

HAZUS-MH is a GIS-based computer program that estimates potential losses from multi-hazard phenomena: earthquakes, floods and hurricanes. With respect to seismic disaster, characteristics of a hypothetical or actual earthquake are entered into HAZUS. Then HAZUS estimates the intensity of ground shaking and calculates the correspondent losses. In this study, HAZUS was used as a part of the preparations of the future seismic events at a coastal plant facility area. To reliably characterize the target facility area, many geotechnical characteristics data were synthesized from the existing site investigation reports. And the buildings and facilities were sorted by analyzing their material and structural characteristics. In particular, the study area was divided into 17 blocks taking into account the situation of both land development and facility distribution. The ground conditions of blocks were categorized according to the site classification scheme for earthquake-resistant design. Moreover, seismic fragility curves of a main facilities were derived based on the numerical modeling and were incorporated into the database in HAZUS. The results estimated in the study area using HAZUS showed various seismic damage and loss potentials depending on site conditions and structural categories. This case study verified the usefulness of the HAZUS for estimating earthquake losses in coastal facility areas.

• International Commerce and Information Review
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• v.11 no.3
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• pp.339-361
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• 2009

This paper attempts to provide a way to improvement in trade & commerce between Korea and Russia, analyzing the influence of the circumstances of the Russian economy on economic relations between the two countries. The study briefly reviews the current situation of the Russian economy, and tries to examine the strong points to be considered as leverage for cooperation and the weak points to be overcome. Previous studies have determined that the Russian economy has unlimited potential for growth, because it is endowed with abundant resources, and has a government willing to reform for the opening of the economy, as well as high-quality labor. However, the economic structure is vulnerable to impact of the worldwide financial crisis. It is not possible to overlook its institutional fragility and vulnerability such as a corrupt bureaucracy or a relatively large black market. These undesirable factors may not only undermine the basis of Russia economy but also a hindrance to economic cooperation by increasing economic uncertainty. This paper attempts to analyze comprehensively the socio-economic factors that influence the open-economy of Russia, and to illustrate strategies for improvement in trade and commerce through the viewpoint of Korean firms that are already in business or are trying to enter in the near future. Some measures to improve their economic cooperation are suggested at the end.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.16 no.2
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• pp.43-59
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• 2005

Traditional paper records have to be preserved in the original form to ensure the authenticity. On the other hand. electronic records have to be continuously changed in content itself or metadata to be preserved in long-term period, so the proof of the legality of each change made so far and the proof of the protection against all the illegal changes are the essential. to ensure these requirements. We need some functions including the authentication of original captured records. the protection of records against the loss or forgery, the authentication of preserved records, and the treatment of authentication-failed records. This paper explains the fragility of authenticity for electronic records, identifies the functions needed, suggests the implementation idea, and describes the overall management polity for electronic records to ensure the authenticity.

• International Commerce and Information Review
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• v.2 no.1
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• pp.83-103
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• 2009

This paper attempts to provide a way to improvement in trade & commerce between Korea and Russia, analyzing the influence of the circumstances of the Russian economy on economic relations between the two countries. The study briefly reviews the current situation of the Russian economy, and tries to examine the strong points to be considered as leverage for cooperation and the weak points to be overcome. Previous studies have determined that the Russian economy has unlimited potential for growth, because it is endowed with abundant resources, and has a government willing to reform for the opening of the economy, as well as high-quality labor. However, the economic structure is vulnerable to impact of the worldwide financial crisis. It is not possible to overlook its institutional fragility and vulnerability such as a corrupt bureaucracy or a relatively large black market. These undesirable factors may not only undermine the basis of Russia economy but also a hindrance to economic cooperation by increasing economic uncertainty. This paper attempts to analyze comprehensively the socio-economic factors that influence the open-economy of Russia, and to illustrate strategies for improvement in trade and commerce through the viewpoint of Korean firms that are already in business or are trying to enter in the near future. Some measures to improve their economic cooperation are suggested at the end.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.37-38
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• 2006

In this paper, we describe a security problem of IPsec. And we propose a solution for this problem. The problem is a fragility of IPsec Gateway which is used in tunnel mode. The role of IPsec Gateway is encrypting or decrypting IPsec packets. Because of the role of IPsec Gateway, IPsec Gateway suffers overhead for decrypting numerous packets. Adversaries can easily attack IPsec Gateway using a DDoS attack. To solve this problem, we propose the "Priority based Random Packet Drop" method. In this method, the white list which is a list of normal users is created. After that, according to the frequency of uses, the method marks priorities of random drops to the white list. If anomalous traffic appeared, this method will drop many packets which consist of anomalous traffic. In simple experiment, we show our solution is proper to defend IPsec Gateway. For this experiment, we use empirical backbone traffic which includes DoS attacks.