• Smart Structures and Systems
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• 제25권6호
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• pp.679-691
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• 2020

To identify the bridge information from the response of test vehicles passing on it (also known as the indirect approach) has aroused the interest of many researchers thanks to its economy, easy implementation and less disruption to traffic. The surface roughness of bridge remains an obstacle for such method as it contaminates the vehicle response severely and thereby renders many vehicle-response-based bridge identification methods ineffective. This study aims to eliminate such effect with the responses of two different test vehicles. The proposed method can estimate the surface profile of a bridge based on the acceleration data of the vehicles running on the bridge successively, and obtain the normalized contact point response, which proves to be relatively immune to surface roughness. The frequencies and mode shapes of bridge can be further extracted from the normalized contact point acceleration with spectral analysis and Hilbert transform. The effectiveness of the proposed method is verified numerically with a three-span continuous bridge. The influence of measurement noise is also examined.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.440-445
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• 2003

Maglev is the vehicle which can run in levitated condition by the electro-magnets, and propelled by linear induction motors. The Maglev is divided in two parts such as carbody and bogies, and the bogies are the driving device of the vehicle. The frame of the bogie must endure many loads occurred in the operation of the vehicle. So the bogie frame is designed and manufactured in the view of good safety and maintainability. The methods of design of frames are developed in regards of stresses and weights of structures. In this research, the extrusion of bogie frame is re-designed by the process of topology optimization with the ANSYS. By this process, the optimal shape of extrusion is acquired and additional optimization researches would be required in the view of size and shape of the members in the extrusion.

• Steel and Composite Structures
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• 제46권1호
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• pp.133-141
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• 2023

Based on the third-order shear deformation theory, the wave propagations in doubly curved spherical- and cylindrical- panels reinforced by carbon nanotubes (CNTs) are firstly investigated in present work. The coupled equations of wave propagation for the carbon nanotubes reinforced composite (CNTRC) doubly curved panels are established. Then, combined with the harmonic balance method, the eigenvalue technique is adopted to simulate the velocity-wave number curves of the CNTRC doubly curved panels. In the end, numerical results are showed to discuss the effects of the impact of key parameters including the volume fraction, different shell types (including spherical (R₁=R₂=R) and cylindrical (R₁=R, R₂=→∞)), wave number as well as modal number on the sensitivity of elastic waves propagating in CNTRC doubly curved shells.

• Earthquakes and Structures
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• 제27권2호
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• pp.155-164
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• 2024

Studying the propagation characteristics of waves in circular plates has important engineering value. In this paper, graphene sheet reinforced foam (GPLRMF) circular plates are taken as the research object, and the propagation characteristics of shear and bending waves in the structure are analyzed. In the process of research, we assume that the material properties are closely related to temperature, and use the first-order shear deformation theory (FSDT) to establish the dynamic model of GPLRMF circular plates. Considering the simply supported boundary conditions, the relationship between phase velocity/group velocity and wave number was obtained through Laplace transform. Subsequently, the influence of material and geometric parameters on wave propagation characteristics was analyzed, and the results showed that the porosity coefficient and temperature had a significant impact on the characteristics of wave propagation in circular plates.

• 대한기계학회논문집A
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• 제34권5호
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• pp.519-525
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• 2010

승용 차량과 항공기와 같은 대형 구조물에 대한 해석에는 유한요소법이 일반적으로 사용되고 있다. 그러나 대형 구조물을 유한요소로 모델화 하여 해석하는 경우에는 자유도의 수가 수천에서 수만에 이르게 되어 이를 직접 해석하기 위해서는 많은 시간과 노력이 필요하다. 따라서 차량 모델과 같은 대형 복잡 구조물을 효율적으로 해석하기 위해 부분구조 합성법이 많이 사용되고 있다. 본 연구에서는 Craig-Bampton 방법을 이용한 전차량 모델링 방법을 제안하고 전차량 모델의 진동 특성을 분석하였다. 차량 모델을 구성하는 각 부분을 각각 부분구조 모델로 치환한 후 다시 합성하여 전차량 모델을 구성하였다. 또한, 서브프레임 주요 설계변수, 즉 마운트 위치나 프레임 크기의 편차가 전체 시스템의 모드 특성의 통계적 변화에 미치는 영향을 살펴보았다.

• Steel and Composite Structures
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• 제43권2호
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• pp.165-183
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• 2022

Most transportation departments have recognized and developed procedures to address the ever-increasing weights of trucks traveling on bridges in a service today. Transportation agencies also recognize the issues with overheight vehicles' collisions with bridges, but few stakeholders have definitive countermeasures. Bridges are becoming more vulnerable to collisions from overheight vehicles. The exact response under lateral impact force is difficult to predict. In this paper, nonlinear impact analysis shows that the degree of deformation recorded through the modeling of the unprotected vehicle-girder model provides realistic results compared to the observation from the US-61 bridge overheight vehicle impact. The predicted displacements are 0.229 m, 0.161 m, and 0.271 m in the girder bottom flange (lateral), bottom flange (vertical), and web (lateral) deformations, respectively, due to a truck traveling at 112.65 km/h. With such large deformations, the integrity of an impacted bridge becomes jeopardized, which in most cases requires closing the bridge for safety reasons and a need for rehabilitation. We proposed different sacrificial cushion systems to dissipate the energy of an overheight vehicle impact. The goal was to design and tune a suitable energy absorbing system that can protect the bridge and possibly reduce stresses in the overheight vehicle, minimizing the consequences of an impact. A material representing a Sorbothane high impact rubber was chosen and modeled in ANSYS. Out of three sacrificial schemes, a sandwich system is the best in protecting both the bridge and the overheight vehicle. The mitigation system reduced the lateral deflection in the bottom flange by 89%. The system decreased the stresses in the bridge girder and the top portion of the vehicle by 82% and 25%, respectively. The results reveal the capability of the proposed sacrificial system as an effective mitigation system.

• Smart Structures and Systems
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• 제11권1호
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• pp.1-17
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• 2013

This paper intended to investigate the feasibility of bridge health monitoring using a linear system parameter of a time series model identified from traffic-induced vibrations of bridges through a laboratory moving vehicle experiment on scaled model bridges. This study considered the system parameter of the bridge-vehicle interactive system rather than modal ones because signals obtained under a moving vehicle are not the responses of the bridge itself but those of the interactive system. To overcome the shortcomings of modal parameter-based bridge diagnosis using a time series model, this study considered coefficients of Autoregressive model (AR coefficients) as an early indicator of anomaly of bridges. This study also investigated sensitivity of AR coefficients in detecting anomaly of bridges. Observations demonstrated effectiveness of using AR coefficients as an early indicator for anomaly of bridges.

• 한국분말재료학회지
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• 제22권5호
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• pp.362-366
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• 2015

The effect of sublimable vehicle composition in the camphor-naphthalene system on the pore structure of porous Cu-Ni alloy is investigated. The CuO-NiO mixed slurries with hypoeutectic, eutectic and hypereutectic compositions are frozen into a mold at $-25^{\circ}C$. Pores are generated by sublimation of the vehicles at room temperature. After hydrogen reduction at $300^{\circ}C$ and sintering at $850^{\circ}C$ for 1 h, the green body of CuO-NiO is completely converted to porous Cu-Ni alloy with various pore structures. The sintered samples show large pores which are aligned parallel to the sublimable vehicle growth direction. The pore size and porosity decrease with increase in powder content due to the degree of powder rearrangement in slurry. In the hypoeutectic composition slurry, small pores with dendritic morphology are observed in the sintered Cu-Ni, whereas the specimen of hypereutectic composition shows pore structure of plate shape. The change of pore structure is explained by growth behavior of primary camphor and naphthalene crystals during solidification of camphor-naphthalene alloys.

• 대한공간정보학회지
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• 제2권2호
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• pp.89-98
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• 1994

자동차항법장치에 있어서 정확한 위치표현기능, 최적경로안내, 목적지검색, 지형지물정보 제공기능 등을 수행하기 위해서는 수치도로지도가 가장 기본적 요소이다. 그러나, 미국의 TIGER 화일같이 수치도로지도제작에 쉽게 이용될 수 있는 범국가적인 수치지도가 한국에는 마련되어 있지 않으므로, 새로이 제작을 할 수밖에 없는 현실이다. 본 연구에서는 항법용 수치도로지도를 제작함에 있어서 그 호환성과 경제성을 확보하고, 수치도로지도의 질적안정성을 기하기 위한 필요조건을 제시하였으며, 그 결과로 좌표계와 정확도의 기준을 제시하였고, 데이타베이스 항목과 그 구조를 결정하였다.

• 한국항행학회논문지
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• 제13권6호
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• pp.813-819
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• 2009

무인항공기의 에일러론 및 플랩, 엘리베이터 등을 제어하기위한 작동기들은 구조적으로 Time variant한 비선형적인 특성을 가지고 있을 뿐 아니라, 비행 중에 풍향 및 풍량에 따라 모델링하기 힘든 외란이 발생할 경우가 많이 발생하기 때문에 우수한 제어성능을 보이는 제어기 설계에 많은 어려움이 있었다. 본 논문에서는 기존의 PID 제어기의 장점을 그대로 살리면서 실시간으로 변화하는 시스템에 adaptive하게 대응할 수 있고 Auto gain tuning을 이용하여 개발자의 시간과 노력을 현저히 줄일 수 있는 Fuzzy Auto gain tuning PID 제어 알고리즘을 비행체 Actuator 제어에 적용한 연구내용을 기술하였다.