• Journal of the Korea Society of Computer and Information
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• v.12 no.5
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• pp.29-37
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• 2007

In this paper, we propose a new real-time ground motion monitoring system using MMA data which can be gathered more earlier than generic seismic data transmission method. Proposed system receives maximum, minimum and average data based on 20sps which is sent from station on every second continuously. And it calculates a PGA as a quantity of ground motion then visualizes that data to monitor the ground motion around whole country. To verify PGA data from MMA data, we checked Mu-dan-jang earthquake data of China on 2002/6/29. The proposed system was inspected by using log file of Oh-dae-san earthquake data on 2007/1/20. As results of experiment, the proposed system is proven to detect the event(earthquake) faster then existing method and to produce a useful quantitative information.

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.2
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• pp.207-219
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• 2023

Purpose : This study was conducted to investigate the changes in trunk movement and ground reaction during sit to stand motion using visual feedback. Methods : Fifteen adults (average age: 23.53±1.77 years) participated in this study. An infrared reflective marker was attached to the body each participant for motion analysis, and the participants performed sit to stand motion while wearing a hat attached with a laser pointer, which provided visual feedback. First, the sit to stand action was repeated thrice without obtaining any visual feedback, followed by a three minute break. Next, the laser pointers attached to hats were irradiated on a whiteboard, located at a distance of 5 m in front of the chairs, on which the participants sat; a baseline was set, and the participants performed stand up movements three times under this condition. A visual feedback was provided to the participants to prevent the laser pointers from crossing the set baseline. During each stand-up movement, the position of the reflective marker attached to the subject's body was recorded in real time using an infrared camera for motion analysis. The trunk movement and ground reaction force were extracted through recorded data and analyzed according to the presence or absence of visual feedback. Results : The results indicated that in the presence of a visual feedback during the sit-to-stand movements, the range of motion of the trunk and hip joints decreased, whereas that of the knee and ankle joints increased in the sagittal plane. The rotation angle of the trunk in the horizontal plane decreased. The left and right movement speed of the center of pressure increased, the pressing force decreased, and the forward and backward movement speed of the trunk decreased. Conclusion : The results suggest that the efficiency and stability of the stand up movement of a body increase when a visual feedback is provided.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.293-304
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• 2007

In 2007, Round Robin Test (RRT) on ground response analyses has been conducted by the technical committee of Soil Dynamics and Geotechnical Earthquake Engineering of Korean Geotechnical Society. Total 14 teams have reported 16 different results. This paper discusses the evaluation of ground response dispersion caused by the difference of input ground motions. In order to determine the characteristics of ground response, this study analysed the peak ground acceleration, predominant period, and response spectrum of reported ground surface motions. The results suggest that ground response dispersion due to the difference of input ground motions can be significant.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.132-138
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• 2003

The use of long rails in high-speed railway bridges causes additional stresses due to nonlinear behaviours between the rail and bridge decks in the neighbourhood of the deck joints. In the seismic response analysis of high-speed railway bridges, since structural response is highly sensitive to properties of the ground motion, spatial variation of the ground excitation affects responses of the bridges, which in turn affect stresses in the rails. In addition, it is shown that high-speed trains need very long distances to stop when braking under seismic occurrence corresponding to operational earthquake performance level so that verification of the safe stoppage of the train is also required. In view of such additional stresses due to long rails, sensibility of structural response to the properties of the ground motion and braking distance needed by the train to stop safely, this paper proposes and establishes a time domain nonlinear dynamic analysis method that accounts for braking loads, spatial variation of the ground motion and material nonlinearities of rails to analyze long rail stresses in high-speed railway bridges subjected to seismic event. The accuracy of the proposed method is demonstrated through an application on a typical site of the Korean high-speed railway.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.192-205
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• 2020

Seismic design practices and seismic response analyses of civil structures and nuclear power plants (NPPs) have conventionally used the peak ground acceleration (PGA) or spectral acceleration (S_a) as an intensity measure (IM) of an earthquake. However, there are many other earthquake IMs that were proposed by various researchers. The aim of this study is to investigate the correlation between seismic responses of NPP components and 23 earthquake IMs and identify the best IMs for correlating with damage of NPP structures. Particularly, low- and high-frequency ground motion records are separately accounted in correlation analyses. An advanced power reactor NPP in Korea, APR1400, is selected for numerical analyses where containment and auxiliary buildings are modeled using SAP2000. Floor displacements and accelerations are monitored for the non- and base-isolated NPP structures while shear deformations of the base isolator are additionally monitored for the base-isolated NPP. A series of Pearson's correlation coefficients are calculated to recognize the correlation between each of the 23 earthquake IMs and responses of NPP structures. The numerical results demonstrate that there is a significant difference in the correlation between earthquake IMs and seismic responses of non-isolated NPP structures considering low- and high-frequency ground motion groups. Meanwhile, a trivial discrepancy of the correlation is observed in the case of the base-isolated NPP subjected to the two groups of ground motions. Moreover, a selection of PGA or S_a for seismic response analyses of NPP structures in the high-frequency seismic regions may not be the best option. Additionally, a set of fragility curves are thereafter developed for the base-isolated NPP based on the shear deformation of lead rubber bearing (LRB) with respect to the strongly correlated IMs. The results reveal that the probability of damage to the structure is higher for low-frequency earthquakes compared with that of high-frequency ground motions.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.6
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• pp.293-303
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• 2020

Seismic fragility was assessed for non-seismic reinforced concrete shear walls in Korean high-rise apartment buildings in order to implement an earthquake damage prediction system. Seismic hazard was defined with an earthquake scenario, in which ground motion intensity was varied with respect to prescribed seismic center distances given an earthquake magnitude. Ground motion response spectra were computed using Korean ground motion attenuation equations to match accelerograms. Seismic fragility functions were developed using nonlinear static and dynamic analysis for comparison. Differences in seismic fragility between damage state criteria including inter-story drifts and the performance of individual structural members were investigated. The analyzed building had an exceptionally long period for the fundamental mode in the longitudinal direction and corresponding contribution of higher modes because of a prominently insufficient wall quantity in such direction. The results showed that nonlinear static analyses based on a single mode tend to underestimate structural damage. Moreover, detailed assessments of structural members are recommended for seismic fragility assessment of a relatively low performance level such as collapse prevention. On the other hand, inter-story drift is a more appropriate criterion for a relatively high performance level such as immediate occupancy.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.214-221
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• 2002

This study introduces a method to generate artificial earthquakes in Korean Peninsular using historical earthquake catalogues and point source model. For this purpose, three earthquake catalogues compiled by different researchers are compared to each other. And epicenters and magnitudes of future earthquakes are generated based on those catalogues. In generating ground motion accelertation, point source model proposed by Boore and Atkinson was adopted. Parameters of the model for South-Eastern part of Korean Peninsular was proposed by Noh and kn. From the epicenters, magnitudes, and ground motion models, possible earthquakes for 50,000 years are generated. Using these generated earthquakes ground accelrations and uniform hazard response spectra (UHRS) having 2%, 5%, and 10% exceedance probability in 50 years are proposed.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.133-144
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• 2000

The dynamic walking planning and the inverse dynamics of the biped robot is investigated in this paper. The biped robot is modeled with 14 degrees of freedom rigid bodies considering the walking pattern and kinematic construction of humanoid. The method of the computer aided multibody dynamics is applied to the dynamic analysis. The equations of motion of biped are initially represented as terms of the Cartesian corrdinates then they are converted to the minimum number of equations of motion in terms of the joint coordinates using the velocity transformation matrix. For the consideration of the relationships between the ground and foot the holonomic constraints are added or deleted on the equations of motion. the number of these constraints can be changed by types of walking patterns with three modes. In order for the dynamic walking to be stabilizable optimized trunk positions are iteratively determined by satisfying the system ZMP(Zero Moment Point) and ground conditions.

• Journal of the Korean Society of Safety
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• v.23 no.2
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• pp.7-13
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• 2008

In a long-span bridge which is constructed on soft soil, it is requested to make a plan considering soil-structure interaction, and soil-structure interaction is partially under consideration at the actual bridge plan. Many researches on dynamic behavior of a bridge affected by soil-structure interacting have been accomplished, but it is difficult to estimate dynamic behavior of a bridge on soft soil accurately because of many uncertainties. This paper presents the results about dynamic response of a long-span suspension bridge in the site composed of soft soil considering incident angle of input ground motion. The effect of soft soil was evaluated by the use o computer program SASSI and a long-span suspension bridge was modeled by finite element program MIDAS. The effect of incident angle of input ground motion was investigated on the dynamic response of a long-span bridge.

• Journal of the Korean Geotechnical Society
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• v.22 no.4
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• pp.105-111
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• 2006

Earthquake strong motion recordings from two deeply embedded sites with instrumented structures and free-field accelerographs are used to evaluate variations between foundation-level and free-field ground motions. The foundation free-field ground motion variations are quantified in terms of frequency-dependent transmissibility function amplitude, ${\mid}H\mid$. Comparisons are then performed with an analytical model for the assumed conditions of a rigid base slab and a vertically propagating, coherent incident wave. The limiting assumptions of the model are not strictly satisfactory for actual structures, and the results of the analysis reflect not only incoherence effects, but also possible foundation flexibility and wave inclination effects. Nonetheless, the simple analytical model is in an acceptable agreement with the empirical analysis and appears to be applicable in practice.