• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.199-208
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• 2010

A friction damper installed at a building shows nonlinear behavior since its stick and slip states are occurred repeatedly depending on the amplitude of external loadings to dissipate input energy. Friction damping is existed for the building with a friction damper. In additionally viscous one is inherently included. Therefore, the building installed in such combined damping is quite involved to find the analytical solution. In this study, first, displacement and acceleration characteristics are identified based on the exact solution for a single-degree-freedom building with a friction damper having both friction and viscous damping. Second, in free vibration, the equivalent viscous damping ratio is obtained by the energy dissipation. Third, numerical analysis is carried out to find response configuration with various friction force ratios. Fourth, corresponding equivalent viscous damping ratio is derived with the finding that the response reaches into steady-state for both friction and viscous damped structure. It is deduced using balance of input external energy and output dissipation energy for steady-state response. Finally, the equivalent viscous damping ratios of free or harmonic vibration are verified through nonlinear analysis.

• Journal of The Korean Association For Science Education
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• v.38 no.4
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• pp.481-494
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• 2018

This study investigated elementary students' understanding of Earth revolution and its accompanied apparent motion of constellation in terms of spatial reasoning. We designed a set of multi-tiered constructed response items in which students described their own idea about the reason of consecutive movement of constellations for three months and drew a diagram about relative locations of the Sun, the Earth, and the constellations. Sixty-five sixth grade students from four elementary schools participated in the tests both before and after science classes on the relative movement of Earth and Moon. Their answers to the items were categorized inductively in terms of transforming frames of reference which are observed on the Earth and designed from the Space-based perspective. We analyzed those categories by the levels of spatial reasoning and depicted the change of students' levels between pre/post-tests so that we could get an idea on the preliminary developmental pathway of students' understanding of this topic. The lower anchor description was that constellations move around the Earth with geocentric perspective. Intermediate level descriptions were planar understanding of Earth movement, intuitive idea on constellation movement along with the Earth. Students with intermediate levels did not reach understanding of the apparent motion of constellations. As the upper anchor description students understood the apparent motion of constellations according to the Earth revolution and could transform their frames of reference between Earth-based view and Space-based view. The features as the case of evolutionary learning progressions and critical points of students' development for this topic were discussed.

• Journal of Industrial Convergence
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• v.20 no.12
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• pp.213-217
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• 2022

The purpose of this study was to investigate the relationship between age, physical activity (walking, strength exercise), subjective body shape recognition, and weight change with subjective health status in the population aged 30 years or older among the data of the National Health and Nutrition Examination Survey (2018) of Koreans. The subject and method of this study was a secondary analysis study using the 7th 3rd year National Health and Nutrition Examination Survey (2018). Age, walking days per week, strength training days per week, subjective health status, subjective body shape recognition, and weight change during the year were used the SPSS (p<.01). The response rate of walking for 7 days (every day) was 21.9% for those aged 30-45, 27.2% for those aged 50-64, and 26.6% for those aged 65 or older. aged 8.4% and over 65 years old 7.9% (p<.001). The subjective health status was positively correlated with age (.091), number of walking days per week (.739), number of days of strength exercise per week (.530), subjective perception of body shape (.256), and weight change over one year (.303). There was a relationship (p<.01). In this study, the age group that answered 'bad' in subjective health status was the highest at 21.4% of those aged 65 or older, followed by 15.7% of those aged 50-64 and 11.0% of those aged 30-45. This could be expected to improve subjective health status by walking and strength training. Based on these results, it was intended to provide basic data for preparing health-related programs to improve subjective health status of individuals according to age.

• Journal of Korea Entertainment Industry Association
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• v.13 no.7
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• pp.347-360
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• 2019

The purpose of this study was to examine how the fitness participation was influenced on exercise enthusiasm, exercise commitment and exercise satisfaction by female fitness participants, Subjects were selected among the female fitness center users living in Sunchon, Yeosu, Gwangyang. A total of 223 questionnaires were used in the actual analysis via convenience sampling method out of 250 questionnaires. Data analysis wad processed by SPSS 25.0 program with frequency analysis, exploratory factor analysis, reliability analysis, correlation analysis and multiple regression analysis and the following results were made. First, as a result of analyzing the effects of exercise enthusiasm on exercise commitment, it was found that harmony enthusiasm had positive (+) influence on cognitive commitment and behavioral commitment. Second, as a result of analyzing the effects of exercise enthusiasm on exercise satisfaction, it was found that harmony enthusiasm had positive (+) influence on exercise ability improvement, social relationship promotion and psychological benefits, and harmony enthusiasm and compulsive enthusiasm had positive (+) influence on physical function improvement. Third, as a result of analyzing the effects of commitment on exercise satisfaction, it was found that behavioral commitment had positive (+) influence on exercise ability improvement, physical function improvement and social relationship promotion and harmony enthusiasm and compulsive enthusiasm had positive(+) influence on psychological benefits.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.75-86
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• 1999

An analysis model is developed to evaluate the dynamic responses of a bridge system under seismic excitations, in which pounding actions between girders are considered in addition to other phenomena such as nonlinear pier motion, rotational and translational motions of foundations. The model also considers the abutment and restrainers connecting adjacent girders to prevent the unseating failures. Using the developed model, the longitudinal dynamic behaviors of a bridge system are examined for various peak ground accelerations, and the effects of the applied restrainers are investigated. It is found that the restrainers reduce the relative displacement with the shorter clearance length as well as the higher stiffness of the restrainers for moderate excitations. However, in the region with strong excitations the restrainers may yield due to the large relative displacement. Therefore, the extension of support length in addition to restrainers may need to prevent the unseating failure more effectively.

• Journal of the Korean Applied Science and Technology
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• v.37 no.4
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• pp.807-819
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• 2020

The purpose of this study is to investigate the relationship between the motivation to participate in sports for elderly, the factors for fun, leisure satisfaction, and exercise persistence. In order to analyze the data, a total of 200 questionnaires were distributed to senior citizens participating in sports programs at the Senior Citizen Welfare Center in Seoul, and a total of 183 copies (91.5%) of data were used as valid samples excluding 17 unfaithful responses. For data processing, frequency analysis, confirmatory factor analysis, Cronbach's α, concentration validity, discriminant validity, concept reliability, correlation analysis, and structural equation model verification were performed using IBM AMOS 21.First, the motivation to participate in sports for the elderly influenced the fun factor. Second, the motivation to participate in sports for the elderly influenced leisure satisfaction. Third, the motivation to participate in sports for the elderly influenced the exercise continuation. Fourth, the fun factor of sports for the elderly influenced leisure satisfaction. Fifth, the fun factor of elderly sports influenced the exercise continuation. Sixth, the satisfaction of sports for the elderly affected the exercise continuation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3C
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• pp.187-196
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• 2008

An earthquake of magnitude 5.0 occurred at Ssang-gye-sa, a Buddhist temple in Jirisan, located near the southern border of the Korean peninsula on 4 July 1936. It resulted in severe damage of several buildings and structures in Ssang-gye-sa. Particularly, the top component of a five-story stone pagoda in the temple was tipped over and fell down during the earthquake. This earthquake damage case would be usefully applied to estimating the intensity of ground motion in the Korean peninsula, a moderate seismicity region, where strong motion has never been recorded with the exception of historic seismic events. In order to estimate the local site effects and the corresponding ground motion at Ssang-gye-sa site, intensive site investigations including borehole drilling and in-situ seismic tests such as crosshole and SASW tests were performed in the temple area. Based on the site characteristics, site-specific seismic response analyses using various input motions were conducted for a representative Ssang-gye-sa site by means of both one-dimensional equivalent-linear and nonlinear methods with six input rock outcrop acceleration levels ranging from 0.044g to 0.220g. The resultant site-specific seismic responses indicated the amplified ground motions in the short-period range near the site period of Ssang-gye-sa. Furthermore, the intensity on rock outcrop of the 1936 Jirisan earthquake was estimated by making a comparison between the site responses analysis results in this study and the full-scaled seismic test of pagoda model in the prior study.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.3
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• pp.151-162
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• 2024

As the incidence direction of ground motion (or seismic wave) changes, the seismic response of the structure will also change according to that direction. In order to analyze the effect of the seismic response of the example bridge according to the direction of incidence of ground motion, the acceleration response spectra (S_a-T1) corresponding to the 1-second period obtained for various angles of incidence were obtained. Using S_a-T1, 40 sets of orthogonal pairs of horizontal component seismic waves corresponding to 5 types of percentiles were generated. Seismic vulnerability analysis of the bridge piers was performed by obtaining the seismic response of an example bridge according to the direction of incidence of ground motion. By analyzing the seismic vulnerability analysis of seismic waves corresponding to five types of percentiles, it was found that the median value of the seismic vulnerability curve differs by about 1.2 to 2.6 times depending on the incident direction of the seismic wave. In other words, depending on the incidence direction of seismic waves, the degree of damage to the bridge structure can vary by about 1.2 to 2.6 times.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.82-89
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• 2016

In this study, we proposed a pier of pontoon-type, "Very Large Floating Structure" (VLFS), with the length of 500m, breadth of 200 m and height of 2 m in Yeosu domestic port. Since this structure ought to endure wave loads for long periods at sea, it is essential to analyze the wave response characteristics. Direct-method is used to analyze the fluid-structure problem and the coupled motion of equation is used to obtain response results. The structural part is calculated by using finite element method (FEM) and the fluid part is analyzed by using boundary element method (BEM). Dynamic responses caused by the elastic deformation and rigid motion of structure are analyzed by numerical calculation. To investigate response characteristics of the pier in regular waves, several factors such as the wavelength, water depth, wave direction and flexural rigidity of structure are considered. As a result, wave response of pier changed at the point of $L/{\lambda}$ 1.5 and represented the torsional phenomenon according to the various incident waves. And the responses showed increasing tendency as the water depths increase at the incident point in case of $L/{\lambda}=8.0$ and peak point of vertical displacement amplitude moved from side to side as the flexural rigidity of structure changes.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.117-122
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• 2001

The shock test of shipboard equipments is performed for the evaluation of the shock-resistant. capability by analyzing the maximum acceleration, the effective time duration and the shock response spectrum, etc. But some measured signals have impulsive noise and gaussian white noise because of the ambient noise, the acquisition equipment error and the transient movement of cables during the shock test. The improved transient signal analysis method which removes the noise of measured signal using the threshold policy of the median filter and the orthogonal wavelet coefficients is proposed. It was verified that the signal-to-noise ratio was improved about 30dB by the numerical simulation. And the shock response spectrum was extracted using the denoised shock response signal which was applied by this proposed method.