• Journal of the Korean GEO-environmental Society
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• v.19 no.11
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• pp.31-37
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• 2018

Most of tall building systems are composed of above-ground structure and underground structure used for parking and stores. The underground structure may have a pronounced influence on tall building response, but its influence is still not well understood. In a widely referred report on seismic design of tall buildings, it is recommended to model the underground structure ignoring the surrounding ground and to impose input ground motion calculated considering the underground structure-soil kinematic interaction between at its base. In this study, dynamic analyses are performed on 1B and 5B basements. The motions at the base are calculated to free field responses. The motions are further compared to two procedures outlined in the report to account for the kinematic interaction. It is shown that one of the procedure fits well for the 1B model, whereas both procedures provide poor fit with 5B model analysis result.

• Korean Journal of Applied Biomechanics
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• v.24 no.1
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• pp.51-57
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• 2014

The purpose of this study was to compare and analyze kinetic variables of lower limbs according to types of ankle taping in drop landing. For this, targeting seven male basketball players (average age: $20.8{\pm}0.74yrs$, average height: $187.4{\pm}3.92cm$, average weight: $79.8{\pm}7.62kg$) with no instability of ankle joints, the drop landing motion was conducted according to three types of inelastic taping (C-type), elastic taping (K-type), and no treatment (N-taping). Based on the result, the next conclusion was reached. First, the effect of taping for the players with stable ankles was minimal and the high load on ankle joints offset the fixing effect of inelastic taping. Thus the inelastic taping for the players with stable ankles did not have an effect on the control of dorsal flexion during one-foot landing. Second, increasing angular velocity by increasing the movable range of knee joints disperses impact forces, yet inelastic taping restricted the range of knee joint motion and at the same time increased angular velocity, adding to a negative effect on knee joints. Third, inelastic taping induced inefficient motion of Lower limbs and unstable impact force control of ankle joints at the moment of landing and produced maximum vertical ground reaction force, which led to an increase of load. Therefore, inelastic ankle taping of players whose jump actions occur very often should be reconsidered. Also, it is thought that this study has a great meaning in proving the problem of inelastic taping related to knee pain with unknown causes.

• Korean Journal of Applied Biomechanics
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• v.18 no.2
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• pp.41-48
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• 2008

The purpose of this study was to analyze the lower extremities joint moment pattern by two types of service motion in tennis pinpoint and platform stance. Seven skilled high school tennis players participated, and the kinematics were recorded by the Vicon motion analysis system. For the gathering and analysis of the data Workstation, Bodybuilder and polygon were used. joint moments and Ground Reaction Forces for the phases involved were analyzed with the following results. There was a different moment pattern for the lower extremities between the two serve motions. For the platform stance there was only a large dorsal flexion moment but for the pinpoint stance there were other large moments. The flexion and maximum moment of the lower extremities occurred at the point of change from back swing and to the forward swing motion. Therefore, this data provides evidence that there is a high risk of injury at this point.

• Korean Journal of Applied Biomechanics
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• v.21 no.2
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• pp.223-230
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• 2011

The purpose of this study was to analysis the effect of form and hardness of outsoles on the motion of the lower extremity joints and on foot pressure during gait. The subjects were 15 women(mean age, $48.5{\pm}2.4$ years), who had no serious musculoskeletal, coordination, balance or joint/ligament problems within 1 year prior to the study. The pelvic tilt, joint angles at the lower extremities and the vertical ground reaction force(GRF) were compared during gait with 3 types of shoes (A, B, C) by using one-way repeated ANOVA(p<.05). During gait, the peak tilt angle and the range of motion(ROM) of the ankle and knee joints were found to be significantly different among the 3 types of shoes. The type C shoes showed a significantly lower mean second maximum vertical GRF than types A and B. The curved outsoles of type C shoes, which had a form and hardness different from those of A and B, was designed strategically for walking shoes to provide stability to the Additionally, type C induced the dispersion of eccentric pressure and made the center of pressure roll over to the center line of the foot.

• Korean Journal of Applied Biomechanics
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• v.26 no.4
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• pp.433-441
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• 2016

Objective: The purpose of this study was to understand the injury mechanism and to provide quantitative data to use in prevention or posture correction training by conducting kinematic and kinetic analyses of risk factors of lower extremity joint injury depending on the change of direction at different angles after a landing motion. Method: This study included 11 men in their twenties (age: $24.6{\pm}1.7years$, height: $176.6{\pm}4.4cm$, weight: $71.3{\pm}8.0kg$) who were right-leg dominant. By using seven infrared cameras (Oqus 300, Qualisys, Sweden), one force platform (AMTI, USA), and an accelerometer (Noraxon, USA), single-leg drop landing was performed at a height of 30 cm. The joint range of motion (ROM) of the lower extremity, peak joint moment, peak joint power, peak vertical ground reaction force (GRF), and peak vertical acceleration were measured. For statistical analysis, one-way repeated-measures analysis of variance was conducted at a significance level of ${\alpha}$ <.05. Results: Ankle and knee joint ROM in the sagittal plane significantly differed, respectively (F = 3.145, p = .024; F = 14.183, p = .000), depending on the change of direction. However, no significant differences were observed in the ROM of ankle and knee joint in the transverse plane. Significant differences in peak joint moment were also observed but no statistically significant differences were found in negative joint power between the conditions. Peak vertical GRF was high in landing (LAD) and after landing, left $45^{\circ}$ cutting (LLC), with a significant difference (F = 9.363, p = .000). The peak vertical acceleration was relatively high in LAD and LLC compared with other conditions, but the difference was not significant. Conclusion: We conclude that moving in the left direction may expose athletes to greater injury risk in terms of joint kinetics than moving in the right direction. However, further investigation of joint injury mechanisms in sports would be required to confirm these findings.

• Journal of Korean Association for Spatial Structures
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• v.20 no.2
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• pp.51-58
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• 2020

Recently, deep learning that is the most popular and effective class of machine learning algorithms is widely applied to various industrial areas. A number of research on various topics about structural engineering was performed by using artificial neural networks, such as structural design optimization, vibration control and system identification etc. When nonlinear semi-active structural control devices are applied to building structure, a lot of computational effort is required to predict dynamic structural responses of finite element method (FEM) model for development of control algorithm. To solve this problem, an artificial neural network model was developed in this study. Among various deep learning algorithms, a recurrent neural network (RNN) was used to make the time history response prediction model. An RNN can retain state from one iteration to the next by using its own output as input for the next step. An eleven-story building structure with semi-active tuned mass damper (TMD) was used as an example structure. The semi-active TMD was composed of magnetorheological damper. Five historical earthquakes and five artificial ground motions were used as ground excitations for training of an RNN model. Another artificial ground motion that was not used for training was used for verification of the developed RNN model. Parametric studies on various hyper-parameters including number of hidden layers, sequence length, number of LSTM cells, etc. After appropriate training iteration of the RNN model with proper hyper-parameters, the RNN model for prediction of seismic responses of the building structure with semi-active TMD was developed. The developed RNN model can effectively provide very accurate seismic responses compared to the FEM model.

• Publications of The Korean Astronomical Society
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• v.15 no.1
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• pp.15-19
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• 2000

The lens mass determined from the photometrically obtained Einstein time scale suffers from large uncertainty due to the lens parameter degeneracy. The uncertainty can be substantially reduced if the mass is determined from the lens proper motion obtained from astrometric measurements of the source image centroid shifts, ${\delta}{\theta}_c$, by using high precision interferometers from space-based platform such as the Space Interferometry Mission (SIM), and ground-based interferometers soon available on several 8-10m class telescopes. However, for the complete resolution of the lens parameter degeneracy it is required to determine the lens parallax by measuring the parallax-induced deviations in the centroid shifts trajectory, ${\Delta}{\delta}{\theta}_c$ aloe. In this paper, we investigate the detectabilities of ${\delta}{\theta}_c$ and ${\Delta}{\delta}{\theta}_c$ by determining the distributions of the maximum centroid shifts, $f({\delta}{\theta}_{c,max})$, and the average maximum deviations, $(<{\Delta}{\delta}_{c,max}>)$, for different types of Galactic microlensing events caused by various masses. From this investigation, we find that as long as source stars are bright enough for astrometric observations it is expected that $f({\delta}{\theta}_c)$ for most events caused by lenses with masses greater than 0.1 $M_\bigodot$ regardless of the event types can be easily detected from observations by using not only the SIM (with a detection threshold but also the ${\delta}{\theta}_{th}\;\~3{\mu}as)$ but also the ground-based interferometers $(with\;{\delta}{\theta}_{th}\;\~3{\mu}as)$. However, from ground-based observations, it will be difficult to detect ${\Delta}{\delta}{\theta}_c$ for most Galactic bulge self-lensing events, and the detection will be restricted only for small fractions of disk-bulge and halo-LMC events for which the deviations are relatively large. From observations by using the SIM, on the other hand, detecting ${\Delta}{\delta}{\theta}_c$ will be possible for majority of disk and halo events and for a substantial fraction of bulge self-lensing events. For the complete resolution of the lens parameter degeneracy, therefore, SIM observations will be essential.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.297-302
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• 2007

Vibrating test of vehicle component can be possible in lab-based simulators instead of field testing owing to the development of technology in control algorithm as well as computational process. Currently, Multi-Axial Simulation Table(MAST) is recommended as a vibrating equipment, which excites a target component for 3-directional translation and rotation motion simultaneously and hence, vibrational condition can be fully approximated to that of real road test. But, the vibration-free performance of target component is not guaranteed with MAST system, which is only simulator subjective to the operator. Rather, the reliability of multi-axial vibration test is dependent on the quality of input profile which should cover the required severity of vibrating condition on target component. In this paper, multi-axial vibration testing methodology of vehicle component is presented here, from data acquisition of vehicle accelerations to the obtaining the input profile of MAST using severe data at proving ground. To compare the severity of vibration condition, between real road test and proving ground one, energy principle of equivalent damage is proposed to calculate energy matrices of acceleration data and then, it is determined the optimal combination of special events on proving ground which is equivalent to real road test at the aspects of vibration fatigue using sequential searching optimal algorithm. To explain the vibration methodology clearly, seat and door component of vehicle are selected as a example.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.7
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• pp.391-399
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• 2018

The site coefficients in the common requirements for seismic design codes, which were promulgated in 2017, were reevaluated and the standard design spectrum for soil sites were newly proposed in order to ensure the consistency of the standard design spectra for rock and soil sites specified in the common requirements. Using the 55 ground motions from domestic and overseas intraplate earthquakes, which were used to derive the standard design spectrum for rock sites, as rock outcropping motions, site response analyses of Korean soil were performed and its ground-motion-amplification was characterized. Then, the site coefficients for soil sites were reevaluated. Compared with the existing site coefficients, the newly proposed short-period site coefficient $F_a$ increased and the long-period site coefficient $F_v$ decreased overall. A new standard design spectrum for soil sites was proposed using the reevaluated site coefficients. When compared with the existing design spectrum, it could be seen that the proposed site coefficients and the standard design spectrum for soil sites were reasonably derived. They reflected the short-period characteristics of earthquake and soil in Korea.

• Journal of the Korean Geotechnical Society
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• v.28 no.5
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• pp.55-65
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• 2012

The purpose of this study is to estimate seismic damage for harbor site considering dynamic amplification characteristics. First of all, a series of ground response analysis is performed and then correlation equations between rock outcrop accelerations and peak ground accelerations (PGAs) are determined. These equations are saved into DB and when an earthquake occurs, PGAs are determined by them as soon as possible. For earthquake events, seismic damage grades of harbor structures are determined by using the correlated PGAs and fragility curves of harbor structures in real time. In this study, seismic damage was estimated and classified into several grades by applying two hypothetical earthquakes.