• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.58-62
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• 2017

In this paper, we studied the structural design for safety improvement of the winch mount of the armored recovery vehicle. From the finite element analysis using the safety factor of the original winch mount, the results determined that the safety factor was very low, namely 1.14 at $-15^{\circ}$ when towing the maximum force. For considering the usage and safety, the safety factor needs to increase to between 1.4 and 1.6. To improve the safety factor, a re-design, such as shape modification and strengthening the welded zone, was performed. After the improvement of the structural design, the safety factor of the improved mount was calculated at 1.78, an increase of about 56.1% from that of the original mount.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.39-44
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• 2016

Recently, there has been increasing concern regarding the collapse of hydraulic structures due to abnormal climate conditions. Therefore, numerous studies of the collapse of hydraulic structures have been carried out. In particular, the velocity of the propagation of a flood wave-front is important for predicting the inundation safety and establishing an EAP (Emergency Action Plan). Although many hydraulic tests have been conducted for precise predictions of a flood wave-front, the scale effect from downsizing has not considered. In this study, the relationships between surface tension and the concentration of surfactant, between surface tension and the velocity of flood wave propagation, and between surface tension and the Weber Number were derived through hydraulic tests using a surfactant and image analysis equipment. Based on these relations, the modification factor for the scale effect of the front of flood wave propagation was suggested. The results highlight the necessity of a modification factor when the Weber Number is lower than 12.2, but the scale effect can be ignored when the Weber Number over 12.2.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.5
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• pp.53-58
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• 2002

A recent development, a concrete-filled steel(CFS) pier is an alternative to a reinforced concrete bridge pier in an urban area, because of its fast construction and excellent ductility against earthquakes. The capacity of CFS piers has not been used to a practical design, because there is no guide of a seismic design for CFS piers. Therefore, the guide of a seismic design value is derived from tests of CFS piers in order to apply it to a practical seismic design. Steel piers and concrete-filled steel piers are tested with constant axial load using quasi-static cyclic lateral load to check ductile capacity and using the real Kobe ground motion of pseudo-dynamic test to verify seismic performance. The results prove that CFS piers have more satisfactory ductility and strength than steel piers and relatively large hysteretic damping in dynamic behaviors. The seismic performance of steel and CFS piers is quantified on the basis of the test results. These results are evaluated through comparison of both the response modification factor method by elastic response spectrum and the performance-based design method by capacity spectrum and demand spectrum using effective viscous damping. The response modification factor of CFS piers is presented to apply in seismic design on a basis of this evaluation for a seismic performance.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.669-677
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• 2009

Twenty-four beam specimens were tested to examine the effect of the maximum aggregate size on the shear behavior of lightweight concrete continuous beams. The maximum aggregate size varied from 4 mm to 19 mm and shear span-to-depth ratio was 2.5 and 0.6 in each all-lightweight, sand-lightweight and normal weight concrete groups. The ratio of the normalized shear capacity of lightweight concrete beams to that of the company normal weight concrete beams was also compared with the modification factor specified in ACI 318-05 for lightweight concrete. The microphotograph showed that some unsplitted aggregates were observed in the failure planes of lightweight concrete beams, which contributed to the enhancement of the shear capacity of lightweight concrete beams. As a result, the normalized shear capacity of lightweight concrete continuous beams increased with the increase of the maximum aggregate size, though the increasing rate was lower than that of normal weight concrete continuous beams. The modification factor specified in ACI 318-05 was generally unconservative in the continuous lightweight concrete beams, showing an increase of the unconservatism with the increase of the maximum aggregate size. In addition, the conservatism of the shear provisions of ACI 318-05 was lower in lightweight concrete beams than in normal weight concrete beams.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.5
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• pp.47-56
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• 2008

This study was performed to evaluate the effect of Response modification factors (R-factor) in 3-, 9- and 20- story steel Moment Resisting Frame (MRF) buildings. Each structure was designed using a R-factor of 8, as tabulated in the 2000 International Building Code provision (IBC 2000) and Korea Building Code (KBC) 2008. In order to evaluate the maximum and minimum performance expected for such structures, an upper bound and lower bound design were adopted for each model. Next, each analytical model was designed using different R-factors (8, 9, 10, 11, 12) and four different structural periods with the original fundamental period. For a detailed case study, a total of 150 analytical models were subjected to 20 ground motions representing a hazard level with a 2% probability of being exceeded in 50 years. In order to evaluate the performance of the structures, static push-over and non-linear time history analysis (NTHA) were performed, and displacement ductility demand was investigated to consider the ductility capacity of the structures. The results show that the dynamic behaviors for the 3- and 9-story buildings are relatively stable and conservative, while the 20-story buildings show a large displacement ductility demand due to dynamic instability factors. (e.g. P-delta effect and high mode effect)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.5
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• pp.837-844
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• 2017

Generally, V/C ratio in uninterrupted traffic flow and average travel speed in interrupted traffic flow are utilized as measure of effect for assessing operational situation of roads. The set of road conditions and traffic conditions are considered to be major variables for assessing operational situation in the traffic flow. However, weather conditions such as rainfall also affect the operational situation of roads. The studies reflected by the rainy situation are conducted in the uninterrupted flow, but the related studies are insufficient in the interrupted flow. In this study, the modification factors during rainfall in the interrupted flow were suggested, and the factors could be used when calculating the average travel speed during rainfall in the interrupted flow. By utilizing the data that were investigated in the same road and traffic conditions and the different weather conditions (rainy day or clear day), the modification factors were founded on regression analysis of the travel speed during rainfall as a dependent variable. Modification factors was suggested in dividing peak time, non-peak time, and whole period. Based on this study, the modification factors can be used to complementing the average travel speed model for assessing the operational situation of urban streets during rainfall.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.259-266
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• 2000

This study was conducted to investigate the seismic behavior assessment of circular reinforcement concrete bridge piers particularly with regard to assessing the displacement ductility curvature ductility response modification factor(R) and plastic hinge region etc, The experimental variables of bridge piers test consisted of transverse steel details amount and spacing different axial load levels etc. The test results indicated that reinforcement concrete bridge piers with confinement steel by the code specification exhibited suffcient ductile behavior and seismic performance. Also it is found that current seismic design code specification of confinement steel requirements may be revised.

• 전기의세계
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• v.27 no.1
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• pp.45-48
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• 1978

A pressure dependence in the value of Es/p at a constant pd is observed in sulphur hexafluoride at pressures in excess of about one bar. This is explained in terms of the non-idealgas behavior of SF$_{6}$ which has a significant influence on the interpretation of electrical breakdown of this gas. The criterions for breakdown at low pressures and in the presence of rough electrodes are modified to allow this phenomeneon.n.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.354.1-354
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• 2002

Pitch is a perception related to frequency, one of the psychological aspects or attributes of tones, and an important factor to determine sound quality of sound together with loudness and timber. while a study on pitch has been actively achieved In the part of speech recognition and speech separation, that for analysis and improvement of product sound quality is not yet enough. (omitted)

• 대한예방의학회:학술대회논문집
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• 2004.10a
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• pp.81.2-81.2
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• 2004