• Structural Engineering and Mechanics
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• 제58권2호
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• pp.199-216
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• 2016

A large number of bridges were built several decades ago, and most of which have gradually suffered serious deteriorations or damage due to the increasing traffic loads, environmental effects, and inadequate maintenance. However, very few studies were conducted to investigate the vibration behaviors of a damaged bridge under moving vehicles. In this paper, the vibration behaviors of such vehicle-bridge system are investigated in details, in which the effects of the concrete cracks and bridge surface roughness are particularly considered. Specifically, two vehicle models are introduced, i.e., a simplified four degree-of-freedoms (DOFs) vehicle model and a more complex seven DOFs vehicle model, respectively. The bridges are modeled in two types, including a single-span uniform beam and a full scale reinforced concrete high-pier bridge, respectively. The crack zone in the reinforced concrete bridge is considered by a damage function. The bridge and vehicle coupled equations are established by combining the equations of motion of both the bridge and vehicles using the displacement relationship and interaction force relationship at the contact points between the tires and bridge. The numerical simulations and verifications show that the proposed modeling method can rationally simulate the vibration behaviors of the damaged bridge under moving vehicles; the effect of cracks on the impact factors is very small and can be neglected for the bridge with none roughness, however, the effect of cracks on the impact factors is very significant and cannot be neglected for the bridge with roughness.

• 한국음향학회지
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• 제39권4호
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• pp.351-363
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• 2020

발사체는 비행 중 공기역학적 현상에 기인하는 음향하중의 영향을 받는데, 특별히 천음속 영역에서 그 영향이 증가된다. 음향하중으로 인한 페어링 내부 소음진동은 탑재물의 오작동을 유발할 수 있어 이를 예측하고 저감하는 과정이 필수적이다. 본 연구에서는 발사체 외부에 작용하는 공기역학적 음향하중에 의한 페어링 내부 음향 진동환경을 예측하고, 음향 블랭킷과 헬름홀츠 공명기를 이용하여 소음저감 설계를 구현하는 프로세스를 개발하였다. 음향하중 예측은 Reynolds-Averaged Navier-Stokes(RANS) 유동해석 결과와 난류 경계층 내부 압력섭동에 관한 준 경험식을 이용하였고, 음향진동 연성해석은 ANSYS APDL과 VA One SEA의 Finite Element Statistical Energy Analysis(FE-SEA) 하이브리드 해법을 이용하였다. 개발된 절차를 천음속 해머 헤드형 발사체에 적용하여 음향하중 저감효과를 확인하고 개발된 절차의 유효성을 검증하였다. 본 연구에서 개발된 절차는 타당한 수준의 정확도로 신속한 결과를 얻을 수 있어 발사체 초기설계 단계에 유용하게 쓰일 수 있을 것으로 예상된다.

• International Journal of Automotive Technology
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• 제2권4호
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• pp.157-164
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• 2001

The vehicle electric power system, which consists of two major components: a generator and a battery, which have to provide numerous electrical and electronic systems with enough electrical energy. A detailed understanding of the characteristics of the electric power system, electrical load demands, and the driving environment such as road, season, and vehicle weight is required when the capacities of the generator and the battery are to be determined for a vehicle. An easy-to-use and inexpensive simulation program may be needed to avoid the over/under design problem of the electric power system. A vehicle electric power simulator is developed in this study. The simulator can be utilized to determine the optimal capacities of generators and batteries. To improve the expandability and easy usage of the simulation program, the program is organized in modular structures, and is run on a PC. Empirical electrical models of various generators and batteries, and the structure of the simulation program are presented. For executing the vehicle electric power simulator, data of engine speed profile and electric loads of a vehicle are required, and these data are obtained from real driving conditions. In order to improve the accuracy of the simulator, numerous driving data of a vehicle are logged and analyzed.

• 한국자동차공학회논문집
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• 제25권2호
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• pp.140-148
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• 2017

Accidents involving wheelchair accessible vehicles have been frequently occurring since the introduction of these vehicles in the Korean market. However, detailed regulations, which are required to ensure the safety of the wheel-chair occupants, are unavailable. In this study, both domestic and international vehicle safety regulations are analyzed in order to select the regulations that are similar to the transportation environment of Korea. Sled tests with an actual wheel-chair accessible vehicle were carried out based on the analyzed regulation requirements, as well as the values of the HIC, belt loads, dummy movements, and wheelchair movements. The test results showed that the movements of the dummy and the wheelchair did not meet the criteria of the regulation due to the improper positioning of the restraint systems.

• 콘크리트학회논문집
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• 제15권5호
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• pp.635-642
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• 2003

최근들어 노후화된 교량의 증가에 따라 바닥판의 보강효과에 대한 많은 연구가 이루어지고 있으나 대부분의 연구는 실험실 수준에 국한되어 있으며, 구조물의 피로거동은 이동하중이 아닌 고정반복하중에 의한 연구가 집중적으로 시행되고 있다. 본 연구에서는 이동하중의 영향을 반영하기 위하여 국내에서 실측된 축하중으로 활하중 모델을 제시하였다. 확률론적 해석과 신뢰성 해석을 적용하여 탄소섬유쉬트와 격자형 탄소섬유로 성능향상된 바닥판의 보강효과 및 연장수명을 예측한 결과 성능향상 된 설계 2등급의 교량바닥판은 일반적인 증가 차량하중에 대하여 사용기간동안 충분한 내하력뿐만 아니라 충분한 피로거항성을 갖는 것으로 나타났다.

• 한국자동차공학회논문집
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• 제19권4호
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• pp.47-53
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• 2011

Firstly, FEM model for the body frame of a fuel cell vehicle was built up and design optimization results based on different schemes were exhibited. One scheme was to minimize weight while maintaining the normal mode frequencies and the other was to increase the frequencies without weight change. Next, for a rear frame model, shape parameter study on collapse characteristics such as peak resistance load and absorbed energy was carried out. Also, the stiffness of frame mounting brackets was predicted using inertance calculation and the durability of those mounting brackets for vehicle system loads was evaluated. Finally, for a representative mounting model, the influence on durability due to thickness change was analyzed.

• 자동차안전학회지
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• 제12권3호
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• pp.27-33
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• 2020

In this paper, the process of predicting efficient durability performance for vibration durability test of automobile parts using vibration test load on automobile fuel tank is presented. First of all, the common standard load that can be applied to the initial development process of the automobile was used for the fuel tank and the vulnerability of the fuel tank to the vibration fatigue load was identified through frequency response analysis. In addition, the vulnerability of the fuel tank was re-enacted through vibration durability test results, and the scale factor was applied to the standard load. In order to predict the vibration durability performance required for detailed design, vibration fatigue analysis was performed on the developed vehicle with the frequency of vibration severity equivalent to the durability test, and the vulnerability and life span of the fuel tank were identified through the process of applying weights to these selected standard loads, thereby reducing the test time of the development vehicle.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.281-284
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• 2014

Unlike ordinary vehicle chassis frame, chassis frame of military vehicle is long and that is operated in harsh driving environment in middle of war. Thus, because large dynamic loads is acting on the frame, it is important to secure the durability of the frame based on the structural dynamic characteristic analysis. The purpose of the study is that the chassis frame is optimized to secure durability of the chassis frame of the military vehicle according to the structural dynamic characteristic analysis. Also, structure optimization are performed using parametric optimization and topology optimization methods.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(II)
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• pp.1041-1046
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• 2002

A railway open deck plate girder bridge without ballast should support relatively heavier vehicle loads compared with its self-weight. For such a reason, actual dynamic response of the bridge is considerably differing with normal prediction because additional masses added from vehicle to a bridge have an effect on the dynamic characteristics of the bridge. These differences affect to the estimation of a natural frequency change that adopted for one of the evaluation technique of strength decrease, and these make trouble to the analysis of a natural frequency from the field test data that measured at the bridge subjected to a running vehicle. In this study, classification of mass participation ratio for each component of open deck plate girder bridge without ballast and the comparison according to the change of vibration characteristics for the case of subjected to a running vehicle were accomplished.

• 한국군사과학기술학회지
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• 제16권1호
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• pp.48-55
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• 2013

To obtain the requirements of capability and analyze mission loads for weapon systems which are in process of development, Operational Mode Summary/Mission Profile(OMS/MP) should be documented in advance. In this paper, we have proposed a systematic and practical OMS/MP model processes of a weapon mounted combat vehicle for analyzing power and energy strategy. The wartime and peacetime OMS/MP of a hybrid wheeled combat vehicle which is mounted with an anti-tank guided weapon(ATGW) is also presented as its application.