• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.107-112
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• 2005

In this study, the dynamic analysis is performed fur predicting the transmitted force to flexible human body induced by prototype HIF(High Impulsive force) device operation, which is partially assembled by major parts. A beam-mass model and a shear-structure model are used for the flexible mount structure and their dynamic behavior are investigated by experimental results under rigid/flexible mount conditions using a general purpose device. From the test result of prototype device in rigid mount condition, the transmitted force to human body which can not be measured directly, is estimated based on the proved mount structure model.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.247-258
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• 2007

This paper describes the results of an experimental study on the new type of encased composite beams that use deep deck plates, which could reduce the story height of buildings by controlling the bottom flange of steel beams. The profiled steel beam was thus developed. It was advantageous to the long span of the buildings. Seven full-scale specimens were constructed, and simply supported bending tests were conducted on the encased composite beams with different steel plate thicknesses, with and without shear studs, reinforcing bars, and web openings. The test results showed that the encased composite beams that were developed in this study had sufficient composite action without additional shear connectors due to their inherent shear-bond effects between the steel beams and concrete.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.59-69
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• 2005

Employing the classical beam theory for the design of welded steel moment connections has been brought into question by several researchers since the 1994 Northridge earthquake. In this study, the load transfer mechanism in various welded steel moment connections is comprehensively reviewed mainly based on recent studies conducted by the writer. Available analytical and experimental results showed that the load path in almost all the welded steel moment connections is completely different from that as predicted by the classical beam theory. Vertical plates near the connection such as the beam web, the web of the straight haunch, and the rib act as a strut rather than following the classical beam theory. The shear force transfer in the RBS connection is essentially the same as that in PN type connection. Some simplified analytical models that can be used as the basis of a practical design procedure are also presented.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.83-90
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• 2007

The present study reports a simple unbonded-type shear strengthening technique for reinforced concrete beams using wire rope units. Fifteen beams failed in shear were repaired and strengthened with wire rope units, and then retested to failure. Influence of the prestressing force, orientation and spacing of wire rope units on the shear behavior of strengthened beams having shear span-to-depth ratios of 1.5, 2.5, or 3.25 were investigated. Test results showed that beams strengthened with wire rope units exhibited a higher shear strength and a larger post-failure deformation than the corresponding original beams. Inclined wire rope units was more effective for shear strength enhancement than vertical wire rope units. The increase of the prestressing force in wire rope units causes the decrease of the principal tensile stress in concrete, as a result, the diagonal tensile cracking strength of strengthened beams was higher than that of the corresponding original beams. Shear capacity of strengthened beams is compared with predictions obtained from ACI 318-05 and EC 2. Shear capacity of strengthened beams having shear span-to-depth ratio below 2.5 is reasonably predicted using ACI 318-05 formula. On the other hand, EC 2 overestimates the shear transfer capacity of wire rope units for beams having shear span-to-depth ratio above 2.5.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.555-562
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• 2016

The objective of the present study is to evaluate the shear transfer capacity of transverse reinforcement at the concrete interfaces with smooth construction joint. The transverse reinforcing bars were classified into two groups: V-type for the arrangement perpendicular to the interface and X-type for inclined-crossing arrangement. The transverse reinforcement ratio at the interface varied from 0.0045 to 0.0135 for V-type and 0.0064 to 0.0045 for X-type. The mechanism analysis proposed for monolithic concrete interface, derived based on the upper-bound theorem of concrete plasticity, was modified to evaluate the shear friction capacity of concrete interfaces with smooth construction joint. Test results showed that the specimens with X-type reinforcement had lower amount of relative slippage at the interface and higher shear friction capacity than the companion specimens with V-type reinforcement. This observation was independent of the unit weight of concrete. The mean and standard deviation of the ratios between the experimental shear friction strength of smooth construction joints and predictions obtained from the proposed model are 1.07 and 0.14, respectively.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.493-504
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• 2008

This paper deals with the experimental analysis of the flexural behaviour of encased composite beams with hollow core slabs and channels. The shear force between steel beams and hollow core slabs are transferred by channels. Three full-scale specimens were constructed and tested with different steel beam heights, which were compared with those of previous studies. Based on observation of the experiments, the encased composite beams exhibited full shear connection behaviour without any other shear connectors due to their inherent mechanical and chemical bond stress. Experimental results show a behaviour similar to steel-concrete composite beams with classical connectors: elastic and yield domains, great ductility, flexural failure mode (plastic hinge), low relative movement at steel-concrete interface and all specimens failed in a very ductile manner. Consequently, this study enables the validation of the proposed connection device under static loading and shows that it meets modern structural requirements.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.185-186
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• 2009

In the present study, the deformation capacity of slender shear walls with thin web was studied. As reported by other researchers, web-crushing and rebar-fracture, developing by inelastic deformation after flexural yielding, were considered as the governing failure modes of walls. To address the effect of the longitudinal elongation on web-crushing and rebar-fracture, the longitudinal elongation was predicted by using truss model analysis. The failure criteria by web-crushing and rebar-fracture were defined as a function of the longitudinal elongation. The proposed method was applied to 17 shear wall specimens with boundary columns, and the prediction results were compared with the test results. The results showed that proposed method predicted the maximum deformations and failure modes of the wall specimens with reasonable precision.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.169-172
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• 2008

Longitudinal elongation develops in reinforced concrete beams that exhibit flexural yielding during cyclic loading. The longitudinal elongation can decrease the shear strength and deformation capacity of the beams. In the present study, nonlinear truss model analysis was performed to study the elongation mechanism of reinforced concrete beams. The results showed that residual tensile plastic strain of the longitudinal reinforcing bar in the plastic hinge is the primary factor causing the member elongation, and that the shear-force transfer mechanism of diagonal concrete struts has a substantial effect on the magnitude of the elongation. Based on the analysis results, a simplified method for evaluating member elongation was developed. The proposed method was applied to test specimens with various design parameters and loading conditions..

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.91-95
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• 1992

현재 대부분의 공작기계에서는 모터의 동력을 주축으로 전달하기 위해서 커플링, 밸트,기어 등을 사용하고 있지 만 주축이 고속회전할 수록 커플링 구동방법에서는 주축과 모터의 미스얼라인먼트에 의한 진동과 소음이 커지고 벨트 구동방법에서는 원심력에 의한 벨트 장력의 증가 및 벨트의 파손현상, 벨트와 풀리간의 미끄럼현상 등이 발생하며, 기거 구동방법에서는 기어간의 금속접촉에 의한 진동과 소음이 증대하게 된다. 본 연구에서는 모터내장형 주축의 동특성을 체계적으로 해석하기 위해서 유한요소모델을 도입하였다. 특히 공작기계 주축은 세장비가 비교적 작기 때문에 Timoshenko보 이론으로 모델화하였고, 여러장의 얇은 철심용 강판들도 적층된 내장형 모터의 회전부(rotor)는 굽힘변형 및 전단변형에 대해서 상당 수준의 강성효과를 나타내기 때문에 질량효과 외에도 그 강성효과를 수학적 모델에서 고려하였다, 또한 진동실험 결과로 부터 모터회전부의 강성특성을 규명하는 방법을 제시하였으며, 제안된 규명방법의 유용성은 모터내장형 주축에 대한 모드매개변수의 이론값과 실험값을 비교함으로써 입증하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.2
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• pp.13-22
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• 2001

지진하중을 받는 다경간 단순형교의 낙교방지대책으로 적용되는 cable restrainer를 적절하게 설계하기 위해서는 restrainer의 보강효과에 대한 분석이 우선적으로 이루어져야한다. 본 연구에서는 단순지지 다경간 교량시스템을 중심으로 restrainer로 보강된 교량의 보강효과와 다양한 교량의 영향 요소를 고려할 수 있는 단순화된 해석모형을 개발하였으며, 이를 바탕으로 대상교량의 인접 진동계간의 상대거리, 충돌력, 하부교각으로 전달되는 전단역과 휨모멘트의 변화 등의 동적거동특성을 조사하여 restrainer의 보강효과를 분석하였다. 또한, restrainer의 여유길이 변화, 강성변화, 그리고 restrainer 길이변화에 따른 응답특성을 분석하였다.