• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.87-98
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• 2005

When a tunnel is excavated below groundwater table, the groundwater flows into the excavated wall of tunnel and seepage forces are acting on the tunnel wall. The ground reaction curve is defined as the relationship between internal pressure and radial displacement of tunnel wall. Therefore, the ground reaction curve is significantly affected by seepage forces. In this study, the theoretical solutions of ground reaction curves were derived for both the dry condition and the seepage forces. The theoretical solutions derived were validated by numerical analysis. The ground reaction curves with the support characteristic curve were also analyzed in various conditions of groundwater table. Finally, the theoretical solutions of the ground reaction curve derived in this study can be utilized easily to determine the appropriate time of support systems, the stiffness of support system and so forth for the reasonable design.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.2
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• pp.183-204
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• 2007

When a tunnel is excavated below groundwater table, the groundwater flows into the excavated wall of tunnel and seepage forces are acting on the tunnel wall. Such seepage forces significantly affect the ground reaction curve which is defined as the relationship between internal pressure and radial displacement of tunnel wall. In this paper, seepage forces arising from the ground water flow into a tunnel were estimated quantitatively. Magnitude of seepage forces was decided based on hydraulic gradient distribution around tunnel. Using these results, the theoretical solutions of ground reaction curve with consideration of seepage forces under steady-state flow were derived. A no-support condition and a supported condition with grouted bolts and shotcrete lining were considered, respectively. The theoretical solution derived in this study was validated by numerical analysis. The changes in the ground reaction curve according to various cover depths and groundwater table conditions were investigated. Based on the results, the application limit of theoretical solutions was suggested.

• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.103-111
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• 2005

The purpose of this study was to analysis golf swing in accordance with each club using ground reaction force data. The subject of this study was current professional golf players in Korea. Golf clubs used for this study were driver, iron4, iron7, and pitching. The ground reaction force for left and right foot was collected by one Kistler and one Bertec force platforms. Also collected visual data by NC high speed camera to check the phase which was composed of address, top of backswing, impact and finish. Sampling rate was 600Hz both ground reaction forces data and visual data. The conclusion are as follows. 1. An aspect of change for ground reaction force was that the weight between the left foot and right foot were contrary to each other in general as the phase. 2. Without regard to the type of golf club, the ratio of necessary ground reaction forces for each phase in accordance with address, top of backswing, impact, and finish was comparatively identical. 3. According to the type of golf club, the tendency of Fy was not varied. In terms of Driver, at the moment of impact, the weight of foot-both right and left-was moved to the movement direction of golf because of the rotation force from swing.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.193-204
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• 2002

The purpose of this study was to investigate the effect of martial art type and target height on the ground reaction force factors during Dollyuchagi motion. Data were collected using force plate. Five Taekwondo players and five Hapkido players were tested during Dollyuchagi motion to three different target heights(0.8, 1.2, 1.6 m). After analysis of kinetics using force plate data, maximum vertical ground reaction force was 1.62~2.44 BW, and impulse was $0.66\sim1.01 BW{\cdot}s$. Even though there was no difference for maximum ground reaction forces and impulse between Hapkido and Taekwondo, as target height was higher, impulse increased. Anterior-posterior and vertical ground reaction forces at kicking foot take-off were greater with target height, although there was no difference for medio-lateral force with target height. At impact there was significant difference for anterior-posterior ground reaction force between Hapkido and Taekwondo players. Taekwondo players' force (range, -0.23~-0.26 BW) was greater than Hapkido players's force (range, -0.08~-0.14 BW).

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1259-1266
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• 2005

In a NATM tunnel, fully grouted bolts are widely used as part of supporting system. Grouted bolts play an important role not as to take some parts of load acting on a tunnel lining but as to reinforce the ground adjacent the tunnel. In conjunction with tunnel construction, the presence of groundwater may pose a number of difficulties. With respect to tunnel design, influences of groundwater on tunnel behavior have been considered in many aspects. However, the effect on grouted bolts has been rarely investigated. In this study, the behavior of grouted bolts, which are affected by the seepage forces, was examined. To investigate the effects of seepage forces, the theoretical solutions for a drained condition were also found. Based on the theoretical solutions, ground reaction curves considering seepage forces were obtained. By comparing the ground reaction curves supported by grouted bolts with those for the unsupported cases, the effect of reinforcement was evaluated. Finally, through comparison between supported ground reaction curves in the drained condition and those in the case of groundwater flow, it was found that the grouted bolts are more structurely beneficial when the seepage occurs towards the tunnel than when there is no groundwater flow.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.17 no.2
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• pp.131-143
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• 2007

The purpose of this study was to compare the ground reaction forces and plantar pressure variables among three different safety shoes (Type 1: ergonomically designed and high quality shoes, 2: curved and cushioned safety hoes, and 3: regular safety shoes) and to find the effect of insole during walking. Ten healthy subjects were recruited for this study. The ground reaction force was measured using a 3 dimensional motion analysis system. Plantar pressures were measured Pedar Mobile foot pressure scan system. The ground reaction force variables were not significantly different among three different shoe types and insole conditions. After insertion insole, plantar pressure distributions were improved. These results suggest that the type 1 safety shoes was superior than other safety shoes in the statistics, and applying insole could be a possible method to prevent fatigue of lower extremity and musculoskeletal disorders. Further studies are needed to find the effect of ergonomically designed safety shoes design and insole on practical value prevention of musculoskeletal disorder, fatigue and satisfaction of workers.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.339-342
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• 1996

Vertical ground reaction forces on a treadmill were measured at different walking speeds using two tandem force plates. Comparing vertical ground reaction forces in treadmill walking with those in ground free walking, treadmill walking overestimated the first and second peak forces. With the increase of the walking speed, this phenomenon becomes more significant. In treadmill running, the first peak force reached 210-280% of the body weight. However, the instrumented treadmill showed a great potential to investigate the kinetics for multiple foot-strike measurements.

• Korean Journal of Applied Biomechanics
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• v.17 no.2
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• pp.31-40
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• 2007

Proper weight shifting is essential for a successful shot in golf swing and this could be described by means of the ground forces between the feet and ground. It is assumed that the ground forces would different according to the club used because the length and swing weight of each club is different. But, in present, it is not clear what changes are made by the change of clubs and this affect the swing motion. Therefore this study focused on the investigation of the changes of the ground forces and ground reaction forces (GRF) by the change of club length. The subjects were three professional male golfers. Four swings (driver, iron 3, iron 5, and iron 7) for each subject were taken by two high speed video cameras and two AMTI force platforms were used to measure the GRF simultaneously. Kwon GRF 2.0 and Mathcad 13 software were used to post processing the data. Changes of the three major component of GRF (Vertical, lateral, anterior-posterior force) at 10 predefined events were analyzed including the maximum. Major findings of this study were as follows. 1. Vertical forces; - There were no significant changes until the top of backswing. - Maximum was occurred at the club horizontal position in the downswing for both feet. The shorter club produced more maximum forces than longer ones in the left foot, but reverse were true for the right foot. - Maximum forces at impact shows the same patterns. 2. Lateral forces; Maximum was occurred at the club horizontal position for both feet, but there were no lateral forces because the direction of two forces was different. Maximum force pattern by different clubs was same as the vertical component. 3. Anterior-posterior forces; - This component made a counter-clock wise moment about a vertical axis located between two foot until the club vertical position was reached during the backswing, and reverse moment were produced when the club reached horizontal at the downswing. - Also this component made a forward moment about a horizontal axis located in the CG during the fore half of the downswing, and a reverse moment until the club reached vertical at the follow through phase. Maximum was occurred at the club vertical in the downswing for both feet. The longer club produced more maximum forces than shorter ones for both feet.

• Korean Journal of Applied Biomechanics
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• v.26 no.2
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• pp.191-195
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• 2016

Purpose: The purpose of this study was to analyze the immediate effects of ankle restriction with an elastic band on ground reaction force during a golf swing. Method: There were five subjects who were teaching pros with an average golf score of 75. A force platform (9281B, Switzerland) was used. The independent variable was the presence of an elastic band. The dependent variables were three-dimensional ground reaction forces to analyze the transfer of momentum with the timing, control and coordination of the three forces. A paired t-test within subject repeated measure design was used via an SPSS 20.0. Results: Wearing an elastic band around one's ankles significantly makes shorter time differences between the moment of cross anterior / posterior forces and vertical force and median value of anterior / posterior forces during the backswing, between medial and lateral maximum and anterior / posterior force from the top of the back swing to the mid down swing, and creates an anterior / posterior maximum force. Conclusion: Wearing an elastic band around one's ankles affects control and coordination between three dimensional forces, and anterior force power according to each phase of the golf swing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.431-437
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• 2010

The purpose of this study is to compute the ground reaction forces during gait in the absence of force plates. The difficulties in using force plates for hemiparetic patients inspired us to initiate this study. Level-walking experiments were performed using a three-dimensional motion analysis system with synchronized force plates. Kinematic data were obtained from the three-dimensional trajectories of reflective markers. Gait events were also detected from the kinematic data. The human body was modeled as 13 rigid segments. The mass and the center of mass of each segment were determined from anthropometric data. Vertical ground-reaction forces obtained from the kinematic data were in good agreement with those obtained using the force plate. The computed and measured values of anterior and lateral ground reaction showed similar tendencies. The computation results can be used as the basic data for inverse dynamic analysis.