• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.345-352
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• 1989

Upsetting of non-circular blocks is characterized by the three-dimensional deformation with lateral sidewise spread as well as axial bulging along thickness. A kinematically admissible velocity field for the upsetting of prismatic or non-prismatic blocks is proposed which considers the different frictional conditions at the top and bottom surfaces of a billet. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to some chosen parameters. Experiments are carried out with annealed SM 15C steel billets at room temperature for different billet shapes and frictional conditions. The theoretical predictions both in the forging load and the deformed configurations are shown to be in good agreement with the experimental observations. Therefore, the velocity field proposed in this work can be used for the prediction of forging load and deformation in upsetting of prismatic or non-prismatic blocks, considering the different frictional conditions at two flat dies.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.199-211
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• 2008

This study deals with the side right-angle collisions of 4-legged signalized intersections in Cheongju. The goals are to analyze the characteristics of accidents and to find out the accident factors that affect severity using ordered probit model. In pursuing the above, the study uses the data of 580 side right-angle collisions occurred at the 181 intersections(2004-2005). The analyses show that more accidents were occurred in the nighttime and in going straight. The main cause was analyzed to be the red-light violation. Also, the main results of modeling are the following, First, the likelihood ratio index is 0.094 and t-ratio values that explain goodness of fit are significant. Second, minor road traffic volumes, minor road lanes, major road left-turn lanes, major road left-turn signal, major road yellow signal time, cross angle, major and minor road speed limits are significant factors affecting crash severities at signalized intersections.

• Proceedings of the Costume Culture Conference
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• 2004.04a
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• pp.113-115
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• 2004

리브조직은 위편성물의 기본 조직으로 앞코와 뒤코의 직각 혹은 그것에 가까운 각도의 조합에 의해 겉뜨기와 안뜨기가 교대로 편성되어 코스방향으로 골을 형성하는 조직으로 주로 단이나 몸판에 사용된다. 주로 단에는 1×1, 2×1 rib을 사용하고 몸판에는 3바늘 이상 골을 형성하는 리브조직을 주로 사용하지만 2×2 , 3×3 rib등 여러 가지가 사용된다 앞코와 앞코끼리, 뒤코와 뒤코끼리 서로 붙어 있어 단면을 보면 뱀 껍질과 같은 모양처럼 보이는 데 이러한 형상은 다른 조직에 비해 편폭이 좁게 되고 신축성을 좋게 하는 중요한 성질이 된다. (중략)

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.207-213
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• 1990

Natural convection heat transfer in rectangular air enclosure was studied interferometrically and numerically for the use of adiabatic and constant temperature horizontal boundary conditions. In the isothermal horizontal boundary case with the temperature difference ratio, .DELTA. $T_{v/}$.DELTA. $T_{H}$ .simeq. 1 temperature distribution in the enclosure is strongly stratified and the average Nusselt Number is higher than that of adiabatic horizontal boundary case.ase.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2016.11a
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• pp.259-260
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• 2016

어린이의 경우 다른 연령층에 비해 신체적, 정신적으로 완성되지 못하여 교통사고의 가능성이 높으며, 특히 전국의 어린이 교통사고는 점진적으로 감소 추세이나 인천의 어린이 교통사고는 감소하다가 다시 증가 추세에 들어선 실정이다. 따라서 본 연구의 목적은 어린이 교통사고 심각도에 영향을 미치는 주요 요인들을 발견하고 제시하고자 하였다. 순서형 로지스틱 회귀분석을 활용하여 순서척도인 반응변수에 대한 설명변수의 오즈(Odds)를 확인하고자 하였으며 안전운전불이행, 차대사람(횡단중), 차대차(측면직각충돌)사고가 유의한 결과로 나타났다. 안전운전불이행으로 인한 사망사고와 기타사고의 오즈차이는 1.35배, 측면직각충돌로 인한 사망사고와 기타사고의 오즈차이는 1.76배 증가하는 것으로 나타났고, 횡단중인 경우에는 오히려 사망 위험도의 오즈값이 0.58배로 감소하는 것으로 나타났다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.133-141
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• 2005

The behavior of the ground in crossed zone due to the excavation of new lower tunnel rectangularly crossed to that was studied by model tests and numerical analysis in shallow cover. Results of the model tests show that earth pressure of the ground in crossed zone were redistributed due to the longitudinal arching effect by the excavation of lower tunnel. By the numerical analysis, minimum principal stress in crown of single tunnel has more decrease than parallel tunnel or crossed tunnel. Vertical stress at rectangularly crossed tunnel decrease more than single tunnel by stress shadow.

• Composites Research
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• v.23 no.1
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• pp.17-22
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• 2010

The compressive and dynamic properties of magnetorheological elastomers were investigated as functions of magnetizable particle volume fraction, alignment of the embedded particle and magnetic force. The specimens consisted of pure and filled silicons with randomly dispersed, longitudinal and transverse aligned magnetizable particle chains. To align the embedded particles in the elastomer, the cross-linking of the elastomer composites took place in a magnetic field. The compression and dynamic tests in the absence and the presence of different magnetic forces were carried out. The modulus and loss factor of the elastomer composites increase with increasing volume fraction at the same magnetic force. The case of longitudinal alignment shows a high modulus and loss factor when compared to the case of transverse alignment or random dispersion.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.4
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• pp.26-37
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• 2020

This study intends to present a fragility analysis method suitable for concrete cable-stayed bridges by performing an analysis reflecting design criteria and material characteristics from the results of inelastic time-history analysis. In order to obtain the fragility curve of the cable-stayed bridge, the limit state of the main component of the cable-stayed bridge is determined, and the damage state is classified by comparing it with the response value based on inelastic time history analysis. The seismic fragility curve of the cable-stayed bridge was made by obtaining the probability of damage to PGA that the dynamic response of the vulnerable parts to input ground motion would exceed the limit state of each structural member. According to the pylon's fragility curve, the probability of moderate damage at 0.5g is 32% for the longitudinal direction, while 7% for the transversal direction, indicating that the probability of damage in the longitudinal direction is higher in the same PGA than in the transversal direction. The seismic fragility curve of the connections showed a very high probability of damage, meaning that damage to the connections caused by earthquakes is very sensitive compared to damage to the pylon and cables. The cable's seismic fragility curve also showed that the probability of complete damage state after moderate damage state gradually decreased, resulting in less than 30% probability of complete damage at 2.0g.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.47-55
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• 2006

Seismic performance and retrofit of reinforced concrete (RC) two-column piers widely used at roadway bridges in Korea was experimentally evaluated. Ten two-column piers that were 400 mm in diameter and 2,000 mm in height were constructed. These piers were subjected to hi-directional cyclic loadings under a constant axial load of $0.1f_{ck}A_g$. Test parameters were the confinement steel ratio, loading pattern, lap splice of longitudinal reinforcing bars, and retrofitting method. Specimens with lap-spliced longitudinal bars were retrofitted with steel jacket, pre-stressing steel wire, and steel band. Test result showed that while the specimens subjected to bi-directional lateral cyclic loadings which consisted of two main amplitudes in the transverse axis and two sub amplitudes in longitudinal axis, referred to as a T-series cyclic loadings, exhibited plastic hinges both at the top and bottom parts of the column, the specimens subjected to bi-directional lateral cyclic loadings in an opposite way, referred to as a L-series cyclic loadings, exhibited a plastic hinge only at the bottom of the column. The displacement ductility of the specimen under the T-series loadings was bigger than that of the specimen under the L-series loadings. Specimen retrofitted with pre-stressing steel wires exhibited poor ductility due to the upward shift of the plastic hinge region because of over-reinforcement, but specimens retrofitted with steel jacket and steel band showed the required displacement ductility. Steel band can be an effective retrofitting scheme to improve the seimsic performance of RC bridge piers, considering its practical construction.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.3
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• pp.173-184
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• 2023

Presently, the general seismic fragility evaluation method for a bridge system composed of member elements with different nonlinear behaviors against strong earthquakes has been to evaluate at the element-level. This study aims to develop a system-level seismic fragility evaluation method that represents a structural system. Because the seismic behavior of bridges is generally divided into transverse and longitudinal directions, this study evaluated the system-level seismic fragility in both directions separately. The element-level seismic fragility evaluation in the longitudinal direction was performed for piers, bridge bearings, pounding, abutments, and unseating. Because pounding, abutment, and unseating do not affect the transverse directional damages, the element-level seismic fragility evaluation was limited to piers and bridge bearings. Seismic analysis using nonlinear models of various structural members was performed using the OpenSEES program. System-level seismic fragility was evaluated assuming that damage between element-levels was serially connected. Pier damage was identified to have a dominant effect on system-level seismic fragility than other element-level damages. In other words, the most vulnerable element-level seismic fragility has the most dominant effect on the system-level seismic fragility.