• 한국전자파학회논문지
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• 제30권2호
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• pp.160-168
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• 2019

본 논문에서는 근전계 빔 집속(near-field beam focusing: NFBF) 시험을 활용한 평면위상배열레이다 시스템의 성능 검증 방안을 제시하고 결과의 유효성을 확인하였다. 제시한 시험 기법은 안테나 개구면 크기 두 배 거리의 근전계 영역에서 레이다 시스템을 검증하는 방안으로 야외가 아닌 전자파 무반향실 내에서 원전계 성능 시험과 동일하게 레이다 시스템을 검증할 수 있었다. 이를 위해 근전계 에너지를 사용한 빔 집속 시험의 시험 구성도 및 검증 절차에 대하여 기술하였다. 또한 빔 조향된 근전계 빔 집속 시험에 대한 수학적인 검증을 통해 개별채널의 추가적인 위상 보상값을 수치화하였다. 이론적인 검증에 기반하여 실제 근전계 빔 집속 시험을 수행하였고 이상적인 결과와의 비교를 통해 시험 방법의 유효성을 확인하였다.

• Journal of Welding and Joining
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• 제15권3호
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• pp.79-87
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• 1997

This study was performed to evaluate basic characteristics of electron beam welding process for a 9% Ni steel plate. The principal welding process parameters, such as working distance, accelerating voltage, beam current and welding speed were investigated. The AB (Arata Beam) test method was also applied to characterize beam size and energy density of the electron beam welding process. The electron beam size was found to decrease with the increase of accelerating voltage and the decrease of working distance. So, in case of high voltage (150kV), spot size and energy density of electron beam were revealed to be 0.9mm and $6.5\times10^5W/\textrm{cm}^2$ respectively. The accelerating voltage among the welding parameters was found to be the most important factor governing the penetration depth. When the accelerating voltage of electron beam was low ($\leq$90kV), beam current and welding speed did not affect on the penetration depth significantly. However, in case of high voltage ($\geq$120kV), the depth of penetration increased very sensitively with the increase of beam current and the decrease of welding speed.

• 한국강구조학회 논문집
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• 제14권1호
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• pp.79-85
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• 2002

본 연구에서는 기존에 사용된 H-Beam 교량을 편향부와 외부 긴장력을 도입하여 보강효과에 의하여 지간을 증가시킬 수 있고 단면을 축소할 수 있다는 근거를 제시하였고, 유연도법을 이용하여 편향부의 효과에 의한 추가 긴장량을 산정하였다. 또한, 실험변수(긴장량, Tendon의 개수, 편향부의 유 무)에 의해서 표준실험체(기존 H-Beam)와 외부 긴장된 H-Beam 등 5개의 실험체를 제작하여 휨 실험을 실시하여 외부 긴장된 H-Beam의 역학적 거동을 연구하였다. 특히, 보강효과 및 편향부의 효과를 실험적으로 검증하였다.

• Steel and Composite Structures
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• 제46권4호
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• pp.539-551
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• 2023

In order to study the fire resistance of castellated composite beams with ortho-hexagonal holes and different beam-end restraints, temperature rise tests with constant load were conducted on full-scale castellated composite beams with ortho-hexagonal holes and hinge or rigid joint constraints to investigate the temperature distribution, displacement changes and failure patterns of castellated composite beams with two different beam-end constraints during the whole course of fire. The results show that (1) During the fire, the axial pressure and horizontal expansion deformation generated in the rigid joint constrained composite beam were larger than those in the hinge joint constrained castellated composite beam, and their maximum horizontal expansion displacements were 30.2 mm and 17.8 mm, respectively. (2) After the fire, the cracks on the slab surface of the castellated composite beam with rigid joint constraint were more complicated than hinge restraint, and the failure more serious; the lower flange and web at the ends of the castellated steal beams with hinge and rigid joint constraint produced serious local buckling, and the angles of the ortho-hexagonal holes at the support cracked; the welds at both ends of the castellated composite beam with rigid joint constraint cracked. (3) Based on the simplified calculation method of solid-web composite beam, considering the effect of holes on the web, this paper calculated the axial force and displacement of the beam-end constrained castellated composite beams under fire. The calculation results agreed well with the test results.

• 한국유체기계학회 논문집
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• 제17권5호
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• pp.11-18
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• 2014

Chilled Beam system is the kind of water-air system which reduces the conveyance energy for air conditioning as well as allows efficient installation and comfortable indoor environment, and has been increasingly popular mainly in Europe. To effectively install such Chilled Beam system domestically, it is necessary to develop the product considering domestic climatic condition and the requirements for air conditioning system, and particularly the way to deal with condensation during operation of cooling system in summer shall be provided. In this study, the optimal design on induction structure of Chilled Beam unit was carried out through a numerical method, and the performance test for the prototype of unit was conducted in a real-scale experiment facilities of Chilled Beam unit. While the flowrate of 1st air is 101.3 CMH, the pressure in pressure chamber is 158.7 Pa and the cooling capacities of 1st air side and 2nd air side are 498.1 W and 709.5 W respectively.

• 한국강구조학회 논문집
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• 제19권6호
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• pp.655-661
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• 2007

강재의 접합형식으로 쐐기의 원리를 이용한 새로운 접합장치인 쐐기형 접합장치(wedge connectors)가 개발되었다. 본 연구에서는 새로운 접합장치를 적용한 철골 보-기둥 접합부의 내진성능에 대한 실험연구를 수행하였다. 새로운 접합장치를 적용한 2개의 보-기둥 접합부 시험체에 대해 반복하중 실험을 수행하였다. 2개의 시험체는 켄티레버형이며 동일한 상세를 갖도록 제작되었다. 반복하중 실험의 결과 2개의 시험체 모두 특수모멘트골조에 대해 요구되는 총회전각인 0.04 라디안보다 큰 0.06라디안의 총회전각을 발휘할 수 있었으며 기존의 보-기둥 접합형식에 비해 에너지 소산능력이 크게 우수한 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제32권4호
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• pp.531-547
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• 2009

This paper presents the experimental results on the strength behavior and failure modes of box beam-to-circular column connections in steel piers. Previous research introduced parameters such as joint central angles, extension of horizontal stiffeners, and use of equivalent web depth, which ignored strength behavior and failure modes of box beam-to-circular column connections. The use of equivalent web depth $d_2$ is not reasonable when central angle ${\alpha}$ is closer to $90^{\circ}$; therefore, a monotonic loading test has been performed for eight connection specimens. From the test, it is identified that the connection with the circular column is stronger than the connection with the box-sectioned substitution column. Also, the strength of the beam-to-column connections with horizontal stiffeners is higher than the one of the no column stiffeners. The concrete-filled effect of box beam-to-circular column connection is also investigated, and the experimental yield strength of the connection is compared with the theoretical one. Also, more a reasonable equivalent web depth is suggested. The failure modes of connection are clearly defined.

• 대한기계학회논문집A
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• 제21권12호
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• pp.2008-2018
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• 1997

In this study, free vibration analysis of double through-the-width split beam is studied based on the author's earlier work. Each segment which constructs double through-the-width split beam is considered as Timoshenko beam. The effect of coupling between longitudinal and transverse vibration on the natural frequencies of split beams is considered. Data acquisition and modal test of double split beam for clamped-free boundary condition are carried out. Experimental and numerical results obtained by ANSYS were compared with the calculated data by present theory and their comparisons give good agreement with one another. The influences of the size and location of double split, shear deformation, and boundary conditions on the natural frequencies are demonstrated for illustrative purpose. Effects of double split on the dynamic characteristics of beams can be used to detect the size and the location of damages in structures.

• 소성∙가공
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• 제24권2호
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• pp.130-137
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• 2015

This paper presents the development process of automotive side door impact beam for passenger cars. Weight reduction while maintaining functional requirements is one of the major goals in the automotive industry. In this study, thin-walled side door beam using quenchable boron steel was designed to reduce the weight of conventional side door tubular one. In order to estimate design for the proposed side door beams, the static side impact protection tests(FMVSS 214) were conducted using the finite element method. Based on the simulation results, geometry modification of the side door beam has been performed via creating new reinforcing ribs. Furthermore, the manufactured frontal impact beam was mounted on the real side door of a passenger car, and then static impact protection test carried out. It is concluded that the presented test results can provide significant contribution to the stiffness of side door impact beams and light-weighting door research.

• 한국공간구조학회논문집
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• 제15권1호
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• pp.57-64
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• 2015

This paper shows the test results of continuous reinforced concrete beams with external post-tensioning rods. Six three-span beams were prepared and tested to fail. Three beams were designed to have flexure-dominating behavior and the others to have shear-critical behavior. In each group, one beam without external post-tensioning rods was designated as a control beam and two beams had the external post-tensioning rods of 18 mm or 22 mm diameter. External post-tensioning rods were installed within an interior span of 6000 mm. They show V-shaped configuration because two anchorages were located at the top of interior supports and a saddle pin at mid-span was installed at the bottom of the beam. Test results show that the load and shear capacities of strengthened beams were increased when compared with the control beam. Additionally, the measured shear strength was compared with the strength predicted by ACI 318-11 code equations. The detailed ACI 318-11 equation predicted the measured shear strength and failure location of the continuous beam reasonably well.