• Steel and Composite Structures
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• 제22권5호
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• pp.1001-1018
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• 2016

The purpose of this paper is to compare the structural responses obtained from the stochastic analysis of a suspension bridge subjected to uniform and partially correlated seismic ground motions, using different spatial correlation functions commonly used in the earthquake engineering. The spatial correlation function employed in this study consists of a term that characterizes the loss of coherency. To account for the spatial variability of ground motions, the widely used four loss of coherency models in the literature has been taken into account in this study. Because each of these models has its own characteristics, it is intended to determine the sensitivity of a suspension bridge due to these losses of coherency models which represent the spatial variability of ground motions. Bosporus Suspension Bridge connects Europe to Asia in Istanbul is selected as a numerical example. The bridge has steel towers that are flexible, inclined hangers and a steel box-deck of 1074 m main span, with side spans of 231 and 255 m on the European and Asian sides, respectively. For the ground motion the filtered white noise model is considered and applied in the vertical direction, the intensity parameter of this model is obtained by using the S16E component of Pacoima Dam record of 1971 San Fernando earthquake. An analytically simple model called as filtered white noise ground motion model is chosen to represent the earthquake ground motion. When compared with the uniform ground motion case, the results obtained from the spatial variability models with partial correlation outline the necessity to include the spatial variability of ground motions in the stochastic dynamic analysis of suspension bridges. It is observed that while the largest response values are obtained for the model proposed by Harichandran and Vanmarcke, the model proposed by Uscinski produces the smallest responses among the considered partially correlated ground motion models. The response values obtained from the uniform ground motion case are usually smaller than those of the responses obtained from the partially correlated ground motion cases. While the response values at the flexible parts of the bridge are totally dominated by the dynamic component, the pseudo-static component also has significant contributions for the response values at the rigid parts of the bridge. The results also show the consistency of the spatial variability models, which have different characteristics, considered in this study.

• 항공우주시스템공학회지
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• 제11권6호
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• pp.17-25
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• 2017

항공기가 지상에서 주행할 때 지면과 타이어 사이에 걸리는 수직하중 정보는 마찰력, 횡력 계산 시 사용되는 등 항공기 거동에 있어서 주요한 변수이다. 그러나 실제 항공기 주행 시 실시간으로 수직하중 정보를 얻기 힘들고, 실제 시험에서 발생 가능한 비정상적 활주 상황을 방지하기 위하여 사전 해석을 통해 타이어 수직하중 및 항공기 지상 거동 특성을 예측해 볼 필요가 있다. 본 논문에서는 VI-Aircraft S/W를 이용하여 착륙장치 및 Full-Aircraft 모델을 구성하였고 조향 해석 및 활주시험 상황 모사 해석을 통하여 항공기 지상 거동 특성에 대하여 분석하였다.

• 한국운동역학회지
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• 제29권3호
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• pp.173-183
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• 2019

Objective: The aim of this study was to investigate the correlation coefficients between anthropometric parameters of the foot and kinetic variables during running. Method: This study was conducted on 21 healthy young adults (age: $24.8{\pm}2.1yes$, height: $177.2{\pm}5.8cm$, body mass: $73.3{\pm}7.3kg$, foot length: $256.5{\pm}12.3mm$) with normal foot type and heel strike running. To measure the anthropometric parameters, radiographs were taken on the frontal and sagittal planes, and determined the length and width of each segment and the navicular height. Barefoot running was performed at a preferred velocity ($3.0{\pm}0.2m/s$) and a fixed velocity (4.0 m/s) on treadmill (Bertec, USA) in order to measure the kinetic variables. The vertical impact peak force, the vertical active peak force, the braking peak force, the propulsion peak force, the vertical force at mid-stance (vertical ground reaction when the foot is fully landed in mid-stance or at the point where the weight was uniformly distributed on the foot) and the impact loading rate were calculated. Pearson's correlation coefficient was used to investigate the relationship between anthropometric variables and kinetical variables. The significance level was set to ${\alpha}=.05$. Results: At the preferred velocity running, the runner with longer forefoot had lower active force (r=-.448, p=.041) than the runner with short forefoot. At the fixed velocity, as the navicular height increases, the vertical force at full landing moment increases (r= .671, p= .001) and as the rearfoot length increases, the impact loading rate decreases (r=- .469, p= .032). Conclusion: There was a statistically significant difference in the length of fore-foot and rearfoot, and navicular height. Therefore it was conclude that anthropometric properties need to be considered in the foot study. It was expected that the relationship between anthropometric parameters and kinetical variables of foot during running can be used as scientific criteria and data in various fields including performance, injury and equipment development.

• 한국운동역학회지
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• 제17권2호
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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.

• Earthquakes and Structures
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• 제9권5호
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• pp.983-997
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• 2015

This research evaluates the soil conditions for seismic stations situated in Romania using the horizontal-to-vertical spectral ratio (HVSR). The strong ground motion database assembled for this study consists of 179 analogue and digital strong ground motion recordings from four intermediate-depth Vrancea seismic events with $M_w{\geq}6.0$. In the first step of the analysis, the influence of the earthquake magnitude and source-to-site distance on the H/V curves is evaluated. Significant influences from both the earthquake magnitude and hypocentral distance are found especially for soil class A sites. Next, a site classification method proposed in the literature is applied for each seismic station and the soil classes are compared with those obtained from borehole data and from the topographic slope method. In addition, the success and error rates of this method are computed and compared with other studies from the literature. A more in-depth analysis of the H/V results is performed using data from seismic stations in Bucharest and a comparison of the free-field and borehole H/V curves is done for three seismic stations. The results show large differences between the free-field and the borehole curves. As a conclusion, the results from this study represent an intermediary step in the evaluation of the soil conditions for seismic stations in Romania and the need to perform more detailed soil classification analysis is highly emphasized.

• Structural Engineering and Mechanics
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• 제43권5호
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• pp.637-655
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• 2012

In this study, stochastic responses of a cable-stayed bridge subjected to the spatially varying earthquake ground motion are investigated by the finite element method taking into account soil-structure interaction (SSI) effects. The considered bridge in the analysis is Quincy Bay-view Bridge built on the Mississippi River in between 1983-1987 in Illinois, USA. The bridge is composed of two H-shaped concrete towers, double plane fan type cables and a composite concrete-steel girder deck. In order to determine the stochastic response of the bridge, a two-dimensional lumped masses model is considered. Incoherence, wave-passage and site response effects are taken into account for the spatially varying earthquake ground motion. Depending on variation in the earthquake motion, the response values of the cable-stayed bridge supported on firm, medium and soft foundation soil are obtained, separately. The effects of SSI on the stochastic response of the cable-stayed bridge are also investigated including foundation as a rigidly capped vertical pile groups. In this approach, piles closely grouped together beneath the towers are viewed as a single equivalent upright beam. The soil-pile interaction is linearly idealized as an upright beam on Winkler foundation model which is commonly used to study the response of single piles. A sufficient number of springs on the beam should be used along the length of the piles. The springs near the surface are usually the most important to characterize the response of the piles surrounded by the soil; thus a closer spacing may be used in that region. However, in generally springs are evenly spaced at about half the diameter of the pile. The results of the stochastic analysis with and without the SSI are compared each other while the bridge is under the sway of the spatially varying earthquake ground motion. Specifically, in case of rigid towers and soft soil condition, it is pointed out that the SSI should be significantly taken into account for the design of such bridges.

• Physical Therapy Rehabilitation Science
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• 제10권2호
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• pp.98-105
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• 2021

Objective: The purpose of this study was to examined the kinematic relationship and differences through the range of motion (ROM), muscle activity, and vertical ground reaction force (VGRF) during forward and backward lunge movements, which are effective in improving muscle strength and balance ability of the lower extremities, and to provide clinical information on more efficient lunge movements. Design: Cross-sectional study Methods: Fifteen adult males who met the selection criteria were tested for their dominant feet.Forward and backward lunges were then performed, and the ROM, muscle activity, and VGRF were measured for kinematic analysis during the lunge movement.The differences betweenthe forward lunge and backward lunge intervention were examined using a paired t-test. Results: A significant increase in the ROM of the knee and ankle was observed during the forward and backward lunges (p<0.05). In addition, in terms of the muscle activity, the peak values of the vastus medialis oblique (VMO) and VGRF also showed a significant increase in the forward lunge compared to the backward lunge (p<0.05). Conclusions: This study showed an increase in VGRF peak value, knee and ankle ROM, and VMO muscle activity during forward lunge. Based on these results, it is considered necessary to apply differently depending on the direction of progress in consideration of the musculoskeletal situation and physical ability during the lunge movement.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권2호
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• pp.209-217
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• 2016

Unlike conventional airplane, a WIG craft experiences righting moment and adverse yaw moment in banked turning in ground effect. Numerical simulations are carried out to study the aerodynamics of banked wing in ground effect. Configurations of rectangular wing and delta wing are considered, and performance of endplates and ailerons during banking are also studied. The study shows that righting moment increase nonlinearly with heeling angle, and endplates enhance the righting. The asymmetric aerodynamic distribution along span of wing with heeling angle introduces adverse yaw moment. Heeling in ground effect with small ground clearance increases the vertical aerodynamic force and makes WIG craft climb. Deflections of ailerons introduce lift decrease and a light pitching motion. Delta wing shows advantage in banked turning for smaller righting moment and adverse yaw moment during banking.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.407-412
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• 1998

Amplification factor spectrum, using the observed strong ground motions database, has been obtained and compared with Standard Response Spectrum, which were suggested by US NRC. The observed ground motions from the Yongwol and the Kyoungju Earthquake, respectively, which are suppose to represent domestic seismotectonic characteristics such as seismic source, attenuation, and site effect, are used for the analysis of amplification factor spectrum. Amplification factors have been calculated by comparing the observed peak ground motions with results from responses to the observed horizontal and vertical ground motions. The comparison shows that the amplification factors resultant from this study exceeds those of Standard Response Spectum at relatively higher frequencies. The results suggest that the characteristics of the seismic strong ground motion, which are supposed to represent the domestic seismotectonic characteristics, differs from those of Standard Response Spectrum, especially at hither frequencies

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.767-772
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• 2002

Free-field ground motion during earthquake is significantly affected by the local site conditions and it is essential in the seismic design to perform the accurate site-specific ground response analysis. In this paper, one-dimensional seismic characteristics of waste landfill are studied based on the vertical propagation of horizontal shear waves through the column of soil/waste. Seismic response analysis is peformed for short-period, long-period and artificial earthquake ground motions using a computer program for seismic response analysis of horizontally layered soil deposits. The computed peak ground accelerations are compared with the values calculated according to Korean seismic design guidelines. The analysis result shows that the long-period earthquake causes the largest peak ground acceleration while the artificial earthquake results in the smallest one.