• 콘크리트학회논문집
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• 제24권3호
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• pp.249-258
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• 2012

교대 일체식 교량과 강합성 라멘교는 유지보수의 주된 원인이 되는 신축이음 및 받침이 생략되어 유지관리 및 구조적인 장점을 얻을 수 있는 교량 형식이다. 하지만, 통상적으로 거더를 교대에 매립하는 형태로 시공되는 접합부는 시공상세가 복잡하고 접합부의 시공상세를 간략화하여 시공효율을 향상시킨 새로운 교량 형식을 제안하였다. 제안된 형식의 교량은 PS 강봉에 긴장력을 도입하여 강재로 제작된 거더와 교대를 일체화하는 형태의 교량이다. 이 연구에서는 PS 강봉으로 일체화된 접합부의 피로 성능을 평가하기 위하여 접합부에 대한 유한요소해석 및 피로실험을 실시하였다. 유한요소해석 결과, 제안된 교량의 접합부는 기본적으로 피로에 의한 손상의 가능성이 매우 낮은 것으로 나타났으며, 피로시험 결과로부터 2,000,000회의 피로반복하중이 재하된 상태에서도 접합부의 일체화 성능을 유지하고 있는 것을 확인할 수 있었다.

• Structural Monitoring and Maintenance
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• 제5권3호
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• pp.417-428
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• 2018

In this paper, various model reduction methods were assessed using a shear frame, plane and space truss structures. Each of the structures is one-dimensional, two-dimensional and three-dimensional, respectively. Three scenarios of poor, better, and the best were considered for each of the structures in which 25%, 40%, and 60% of the total degrees of freedom (DOFs) were measured in each of them, respectively. Natural frequencies of the full and reduced order structures were compared in each of the numerical examples to assess the performance of model reduction methods. Generally, it was found that system equivalent reduction expansion process (SEREP) provides full accuracy in the model reduction in all of the numerical examples and scenarios. Iterated improved reduced system (IIRS) was the second-best, providing acceptable results and lower error in higher modes in comparison to the improved reduced system (IRS) method. Although the Guyan's method has very low levels of accuracy. Structures were classified with the excitation frequency. High-frequency structures compared to low-frequency structures have been poor performance in the model reduction methods (Guyan, IRS, and IIRS).

• 전력전자학회논문지
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• 제3권2호
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• pp.156-164
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• 1998

3상 전압원 PWM 컨버터의 동작 영역을 동기 좌표계의 전류 벡터 평면에서 구분하고 그 특징을 설명하였다. 그 중 감역률 영역에서는 주어진 부하에 해당하는 입력 전류를 단위 역률로 제어하는 경우, 입력 전류는 왜곡되고 DC 링크 전압에는 맥동과 제어 오차가 발생하게 되어 주어진 부하 조건에서는 좋은 제어 성과를 얻을 수 없다. 본 논문에서는 이러한 문제점을 해결하는 최적 전류 벡터를 선정하는 방법을 제안하였다. 최적 전류 벡터의 선정으로 입력 전류를 가능한 최대 역률로서 정현적으로 제어하는 동시에 안정한 DC 링크 전압을 제어할 수 있게 하여 3상 전압원 PWM 컨버터의 동작 영역을 확장시킬 수 있다. 제안된 제어 방법을 실험을 통하여 증명하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1380-1383
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• 2004

The scanning type XY stage is frequently used these days as precision positioning system in equipment for semiconductor or display element. It is requested higher velocity and more precise accuracy for higher productivity and measuring performance. The position accuracy of general stage is primarily affected by the geometric errors caused by parasitic motion of stage, misalignments such as perpendicular error, and thermal expansion of structure. In the case of scanning type stage, H type frame is usually used as base stage which is driven by two actuators such as linear motor. In the point view of scanning process, the stage is used in moving motion. Therefore, dynamic variation is added as significant position error source with other parasitic motion error. Because the scanning axis is driven by two actuators with two position detectors, 2 dimensional position errors have different characteristic compared to general tacked type XY stage. In this study 2D position error of scanning stage is analyzed by 1D heterodyne interferometer calibrator, which can measure 1D linear position error, straightness error, yaw error and pitch error, and perpendicular error. The 2D position error is evaluated by diagonal measurement (ISO230-6). The yaw error and perpendicular error are compensated on the base stage of scanning axis. And, the horizontal straightness error is compensated by cross axis compensation. And, dynamic motion error in scanning motion is analyzed.

• 한국실내디자인학회논문집
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• 제38호
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• pp.65-74
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• 2003

The purpose of this study Is to find out the design guideline for women's hospital focusing on the patient needs. The results of research are as follows: 1) As a basic frame of evaluation model, the quality of service of medical facilities and patients' reaction to the physical environment are fixed as a variable called' satisfaction degree'. This study analyzes the influence on space efficiency evaluation according to the difference of types through basic model (Model I-1,2) as verification model to identify the difference between satisfaction degree of outpatients and that of inpatients. 2) The difference of satisfaction degree about the hospital facilities by space evaluation matrix is according to the types of inpatients and to space importance. 3) The control of importance degree about the interior facilities of the hospital according to the specific character of the hospital is necessary. Maintenance of the status quo, or reduction, or expansion is needed according to the satisfaction degree corresponding to the importance degree. Finally, the model is used to for the planning & design for the future women's hospital.

• Structural Engineering and Mechanics
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• 제46권1호
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• pp.19-37
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• 2013

The optimum design of base isolation system considering model parameter uncertainty is usually performed by using the unconditional response of structure obtained by the total probability theory, as the performance index. Though, the probabilistic approach is powerful, it cannot be applied when the maximum possible ranges of variations are known and can be only modelled as uncertain but bounded type. In such cases, the interval analysis method is a viable alternative. The present study focuses on the bounded optimization of base isolation system to mitigate the seismic vibration effect of structures characterized by bounded type system parameters. With this intention in view, the conditional stochastic response quantities are obtained in random vibration framework using the state space formulation. Subsequently, with the aid of matrix perturbation theory using first order Taylor series expansion of dynamic response function and its interval extension, the vibration control problem is transformed to appropriate deterministic optimization problems correspond to a lower bound and upper bound optimum solutions. A lead rubber bearing isolating a multi-storeyed building frame is considered for numerical study to elucidate the proposed bounded optimization procedure and the optimum performance of the isolation system.

• 한국자동차공학회논문집
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• 제17권4호
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• pp.118-125
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• 2009

Bumper is designed to protect the automotive frame without damage at low velocity. Expanded polypropylene (EPP) foam is used in the bumper as an energy absorbing material. In order to exactly predict the energy absorbing performance of the foam material under impact loading condition, it is important to use high strain rate material properties. In this study, a new apparatus for dynamic compression tests was developed to investigate the high strain rate behavior of EPP foams. Three kinds of EPP foams which have different expansion ratios were tested to investigate the quasi-static and dynamic compression behavior. Quasi-static compressions were performed at low strain rates of 0.001/s, 0.1/s and 1/s. The dynamic compressions were carried out at high strain rates of 50/s and 100/s with the developed apparatus. It was observed that the EPP foam has significant strain rate effect as compared to quasi-static behavior.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.694-699
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• 2002

In autobody assembly, thin-wall, tubular connections have been used for the frame structure. Recent interest in light materials, such as aluminum or magnesium alloys, has been rapidly growing for weight reduction and fuel efficiency. Due to higher thermal expansion coefficient, low stiffness/strength, and low softening temperature of aluminum and magnesium alloys, control of welding-induced distortion in these connections becomes a critical issue. In this study, the material sensitivity to welding distortion was investigated using a T-tubular connection of three types materials; low carbon steel (A500 Gr. A), aluminum alloy (5456-H116) and magnesium alloy (AZ91C-T6). An uncoupled thermal and mechanical finite element analysis scheme using the ABAQUS software program was developed to model and simulate the welding process, welding procedure and material behaviors. The predicted angular distortions were correlated to the cumulative plastic strains. A unique relationship between distortion and plastic strains exists for all three materials studied. The amount of distortion is proportional to the magnitude and distribution of the cumulative plastic strains in the weldment. The magnesium alloy has the highest distortion sensitivity, followed by the other two materials with the steel connection having the least distortion. Results from studies of thin-aluminum plates show that welding distortion can be minimized by reducing the cumulative plastic strains by preventing heat diffusion into the base metal using a strong heat sink placed directly beneath the weld. A rapid cooling method is recommended to reduce welding distortion of magnesium tubular connections.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2008년도 춘계 학술발표회 논문집
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• pp.43-48
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• 2008

본 논문은 유닛 모듈러를 구성하는 주구조체인 각형강관 기둥과 냉간성형 LEB C-형강 보가 볼트 접합된 접합부를 가진 모듈러 건물의 접합부 구조성능 및 시공성을 평가하는 것이 연구의 목적이다. 모듈러 건축의 장점은 공사기간 단축, 경량성, 이동가능성 등으로 볼 수 있다. 반면에 유닛 또는 모듈의 운송비용이 공사비 절감 비용을 반감시킬 수 있고 많은 공장들이 외부 지역에 있으므로 이들을 도심지나 원하는 지역으로 이동하기 위해서는 비용이 추가된다. 그리고 유닛이나 모듈 설치에 크레인 등의 장비 사용으로 인해 시공비용이 증가될 수 있는 단점들이 존재한다. 본 연구에서는 해체조립이 용이한 볼트접합부 구조성능 및 모듈러 건축물의 시공사례를 통하여 공기, 비용 등 측면에서 기존 연구와 비교분석을 진행하고자 한다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 제5회 박판성형 SYMPOSIUM
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• pp.93-98
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• 2006

Warm forming technology was classified into hot gas forming of using compressible fluid as a nitrogen gas and warm hydroforming of using the incompressible fluid as a thermal oil by using medium fluid. In this study, the aluminum side-rail part was developed with warm hydroforming technology. For the warm hydroforming system, top and bottom die was designed to insert heating cartridge in die cavity and special indirect fluid heating system was designed to heat the thermal oil. As increase the temperature, hydroformability was increased linearly. Aluminum side-rail center part was formed 90% at the internal pressure of 100bar and perfectly formed at 300bar within a moderate temperature. The tube material used for warm hydroforming was a aluminum 6000 series alloy with the diameter of 120mm, thickness of 5mm, length of 1,300mm. Warm hydroformed side-rail center part had 20% of maximum expansion ratio and below 20% of maximum thinning ratio at corner radius. This results were provided to show warm hydroforming possibility for aluminum automotive components.