• 한국운동역학회지
• /
• 제17권2호
• /
• pp.31-40
• /
• 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.

• Wind and Structures
• /
• 제11권2호
• /
• pp.153-178
• /
• 2008

Based on the empirical formulas for power spectra of generalized modal forces and local fluctuating wind forces in across-wind and torsional directions, the wind-induced lateral-torsional coupled response analysis of a representative rectangular tall building was conducted by setting various parameters such as eccentricities in centers of mass and/or rigidity and considering different torsional to lateral stiffness ratios. The eccentricity effects on the lateral-torsional coupled responses of the tall building were studied comprehensively by structural dynamic analysis. Extensive computational results indicated that the torsional responses at the geometric center of the building may be significantly affected by the eccentricities in the centers of mass and/or rigidity. Covariance responses were found to be in the same order of magnitude as the along-wind or across-wind responses in many eccentricity cases, suggesting that the lateral-torsional coupled effects on the overall wind-induced responses can not be neglected for such situations. The calculated results also demonstrated that the torsional motion contributed significantly to the total responses of rectangular tall buildings with mass and/or rigidity eccentricities. It was shown through this study that the framework presented in this paper provides a useful tool to evaluate the wind-induced lateral-torsional coupled responses of rectangular buildings, which will enable structural engineers in the preliminary design stages to assess the serviceability of tall buildings, potential structural vibration problems and the need for a detailed wind tunnel test.

• Tribology and Lubricants
• /
• 제28권5호
• /
• pp.203-211
• /
• 2012

Atomic force microscopy (AFM) has been used as a tool, not only for imaging surfaces, but also for measuring surface forces and mechanical properties at the nano-scale. Force calibration is crucial for quantitatively measuring the forces that act between the AFM probe of a force sensing cantilever and a sample. In this work, the lateral force calibrations of a V-shaped cantilever were performed using the finite element method, multiple pivot loading, and thermal noise methods. As a result, it was shown that the multiple pivot loading method was appropriate for the lateral force calibration of a V-shaped cantilever. Further, through crosschecking of the abovementioned methods, it was concluded that the thermal noise method could be used for determining the lateral spring constants as long as the lateral deflection sensitivity was accurately determined. To obtain the lateral deflection sensitivity from the sticking portion of the friction loop, the contact stiffness should be taken into account.

• 한국강구조학회 논문집
• /
• 제24권2호
• /
• pp.175-188
• /
• 2012

본 연구에서는 개구제형 트윈 거더 교량의 곡률에 따른 상부수평브레이싱 부재력 산정식의 적절성 및 적용성을 검토하였다. 이를 위해 3경간 연속교를 대상으로 곡률반경을 50m에서 1,200m로 변화시켜 상부수평브레이싱의 부재력 산정식과 3차원 유한요소해석을 통한 부재력을 비교하였다. 그리하여 상부수평브레이싱의 공칭부재력을 계산할 수 있는 보정계수를 제안하였다. 특히 상부수평브레이싱 수직재 부재력 산정식은 3차원 유한요소해석결과와 잘 부합하지 않는 것으로 나타났는데, 이는 가로보의 유무에 따른 교축직각방향 강성의 영향이라 판단된다. 그리고 사재와 수직재의 휨, 비틀림, 뒤틀림 및 수평분력의 영향을 곡률별로 도식화하여 나타내었다.

• 한국운동역학회지
• /
• 제26권2호
• /
• pp.191-195
• /
• 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.

• Structural Engineering and Mechanics
• /
• 제5권4호
• /
• pp.399-414
• /
• 1997

This paper presents an investigation into the seismic response characteristics of a proposed ligh-weight pedestrian cable-stayed bridge made entirely from Glass Fiber Reinforced Plastics(GFRP). The study employs three dimensional finite element models to study and compare the dynamic characteristics and the seismic response of the GFRP bridge to a conventional Steel-Concrete (SC) cable-stayed bridge alternative. The two bridges were subjected to three synthetic earthquakes that differ in the frequency content characteristics. The performance of the GFRP bridge was compared to that of the SC bridge by normalizing the live load and the seismic internal forces with respect to the dead load internal forces. The normalized seismically induced internal forces were compared to the normalized live load internal forces for each design alternative. The study shows that the design alternatives have different dynamic characteristics. The light GFRP alternative has more flexible deck motion in the lateral direction than the heavier SC alternative. While the SC alternative has more vertical deck modes than the GFRP alternative, it has less lateral deck modes than the GFRP alternative in the studied frequency range. The GFRP towers are more flexible in the lateral direction than the SC towers. The GFRP bridge tower attracted less normalized base shear force than the SC bridge towers. However, earthquakes, with peak acceleration of only 0.1 g, and with a variety of frequency content could induce high enough seismic internal forces at the tower bases of the GFRP cable-stayed bridge to govern the structural design of such bridge. Careful seismic analysis, design, and detailing of the tower connections are required to achieve satisfactory seismic performance of GFRP long span bridges.

• 조명전기설비학회논문지
• /
• 제23권5호
• /
• pp.42-49
• /
• 2009

배전용 콘크리트 전주에 작용하는 힘들이 지반의 변위에 미치는 영향을 유한요소법을 이용하여 분석하였다. 지반의 종류, 풍하중, 근가의 위치, 매입길이, 경간의 길이를 변화시키며 단전주와 겹전주의 경우에 지반의 변위를 분석하였다. 근가의 위치는 매입길이의 1/4지점에서 변위가 최소로 나타났다. 지반의 종류는 지반의 강성이 클수록 변위가 작아서 연약한 점토나 느슨한 모래지반 또는 실트 지반은 변위가 크다. 겹전주는 굴착면적이 커서 변위가 다소 큰 것으로 판단되며 시공시에는 콘크리트보강이 필요하다. 지표면에 가까울수록 횡방향 변위는 매입길이비가 작은 전주가 더 크게 나타났다. 횡방향 변위를 줄이기 위해서는 매입길이를 크게 하는 것이 좋다. 경간길이는 횡방향 변위에 영향이 별로 없는 것으로 나타났다.

• 제어로봇시스템학회논문지
• /
• 제21권7호
• /
• pp.595-601
• /
• 2015

This paper presents an unified chassis control with electronic stability control (ESC) and active front steering (AFS) under lateral force constraint on AFS. When generating the control yaw moment, an optimization problem is formulated in order to determine the tire forces, generated by ESC and AFS. With Karush-Kuhn-Tucker optimality condition, the optimum tire forces can be algebraically calculated. On low friction road, the lateral force in front wheels is easily saturation. When saturated, AFS cannot generate the required control yaw moment. To cope with this problem, new constraint on the lateral tire force is added into the original optimization problem. To check the effectiveness of the propose method, simulation is performed on the vehicle simulation package, CarSim.

• Tribology and Lubricants
• /
• 제29권5호
• /
• pp.275-285
• /
• 2013

The Reynolds equation is commonly used to investigate the lubrication characteristics of a spool valve. However, the applicability of the Reynolds equation is questionable for analyzing a spool valve because cavitation often occurs in the grooves of the valve and the depth of a groove is much higher than the clearance in most cases. In this study, the validity of the Reynolds equation in the spool valve analysis is investigated by comparing the results obtained from the Reynolds equation and those obtained from the Navier-Stokes equation. The results are compared in terms of the lateral forces, friction forces, and volume flow rates (leakages). A significant difference of more than 20% is found in the lateral forces in cases where cavitation occurs and there are many grooves. Therefore, the Navier-Stokes equation should be used to investigate the lubrication characteristics of a spool valve when cavitation occurs and when the spool valve contains many grooves.

• Earthquakes and Structures
• /
• 제20권4호
• /
• pp.405-415
• /
• 2021

Following the dynamic property analysis and elaboration, linear response spectrum analysis (RSA) and response history analysis (RHA) were conducted on a representative hyperbolic cooling towers (HCT) in present study. The seismic responses in tower shell were illustrated in detail, including the internal force amplitude, modal contribution, influence from damping ratio, comparison of results got from RSA and RHA and especially the latitude distributions of internal forces. The results show that the eigenmodes could be classified in a new method into four types according to their mode shapes and only the lateral bending modes and vertical stretching modes are meaningful for horizontal and vertical earthquake correspondingly. The bending modes and seismic deformation display the same feature which is global lateral bending accompanied by minute circular flow displacement of section. This feature also decides the latitude distributions of internal forces as sine or cosine. Moreover, the following method is also proposed for approximate estimation of internal force amplitudes without time-consuming response history analysis: getting the response spectrums of the selected ground accelerations and then comparing values of response spectrums at the natural period of first lateral bending mode because it is always prime dominant for horizontal seismic responses.