• 한국자동차공학회논문집
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• 제23권1호
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• pp.105-111
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• 2015

Since 2007, Insurance Institute of Highway Safety(IIHS) has conducted the new bumper test using bumper barrier to estimate the repair cost of impacted vehicle. In this study, for the front body FE model of a medium size passenger car analyzes were carried out to optimize the shape of backbeam center reinforcement bracket. First, overlap effect was examined with changing the overlap magnitude and spot welds were added along the backbeam center line for reducing the section shear deformation. Next, for an overlap model design parameter study was performed for the bracket. Thickness effect was examined and an inner reinforcement was added to the bracket. Also, the lower part of bracket was deleted and additionally the bracket length was extended. The results were discussed in terms of backbeam backward deflection, barrier backstop intrusion and weight. Compared with the current design, the final model showed 44.1% bracket weight reduction with 30.0% decrease of backbeam deflection.

• Smart Structures and Systems
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• 제24권5호
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• pp.607-616
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• 2019

The video deflectometer based on digital image correlation is a non-contacting optical measurement method which has become a useful tool for characterization of the vertical deflections of large structures. In this study, a novel imaging model has been established which considers the variations of pitch angles in the full image. The new model allows deflection measurement at a wide working distance with high accuracy. A monocular video deflectometer has been accordingly developed with an inclination sensor, which facilitates dynamic determination of the orientations and rotation of the optical axis of the camera. This layout has advantages over the video deflectometers based on theodolites with respect to convenience. Experiments have been presented to show the accuracy of the new imaging model and the performance of the monocular video deflectometer in outdoor applications. Finally, this equipment has been applied to the measurement of the vertical deflection of Yingwuzhou Yangtze River Bridge in real time at a distance of hundreds of meters. The results show good agreement with the embedded GPS outputs.

• Structural Engineering and Mechanics
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• 제45권3호
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• pp.323-336
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• 2013

With the ongoing development in the computer science areas of artificial intelligence and computational intelligence, researchers are able to apply them successfully in the construction industry. Given the complexities indeep beam behaviour and the difficulties in accurate evaluation of its deflection, the current study has employed the Adaptive Network-based Fuzzy Inference System (ANFIS) as one of the modelling tools to predict deflection for high strength self compacting concrete (HSSCC) deep beams. In this study, about 3668measured data on eight HSSCC deep beams are considered. Effective input data and the corresponding deflection as output data were recorded at all loading stages up to failure load for all tested deep beams. The results of ANFIS modelling and the classical linear regression were compared and concluded that the ANFIS results are highly accurate, precise and satisfactory.

• 한국기계가공학회지
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• 제15권3호
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• pp.115-121
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• 2016

A mackerel grader is a machine for sorting mackerel according to size. In this study, the dynamic deflection and optimal sorting simulation of a mackerel grader was carried out by using multi-body dynamics. To analyze the dynamic deflection of the roller, RecurDyn, a multi-body dynamics analysis program, was used. The dynamic deflection of the roller pipe was analyzed according to the inclination of the roller pipe. When the inclination of the roller pipe was 30 degrees, the roller indicated the maximum deflection of about 6.3 mm at the center of the mass. To simulate the mackerel sorting, the mackerel grader machine was modeled, and the contact simulation between the mackerel model and the rotating roller pipe was carried out. When the inclination of the roller frame was 7 degrees, the mackerel grader indicated optimal sorting performance.

• Structural Engineering and Mechanics
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• 제35권2호
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• pp.191-203
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• 2010

To investigate the critical buckling load and post-buckling behavior of an axially loaded pile entirely embedded in soil, the non-linear large deflection differential equation for a pinned pile, based on the Winkler-model and the discretionary distribution function of the foundation coefficient along pile shaft, was established by energy method. Assuming that the deflection function was a power series of some perturbation parameter according to the boundary condition and load in the pile, the non-linear large deflection differential equation was transformed to a series of linear differential equations by using perturbation approach. By taking the perturbation parameter at middle deflection, the higher-order asymptotic solution of load-deflection was then found. Effect of ratios of soil depth to pile length, and ratios of pile stiffness to soil stiffness on the critical buckling load and performance of piles (entirely embedded and partially embedded) after flexural buckling were analyzed. Results show that the buckling load capacity increases as the ratios of pile stiffness to soil stiffness increasing. The pile performance will be more stable when ratios of soil depth to pile length, and soil stiffness to pile stiffness decrease.

• 한국구조물진단유지관리공학회 논문집
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• 제12권3호
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• pp.93-100
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• 2008

혹독한 자연환경하에서의 구조물의 내구성이 주요한 관심사도 대두되면서 건설분야에서 섬유강화폴리머의 사용이 점차 증가하고 있는 추세이다. 본 연구에서는 FRP bar를 휨부재의 휨보강근으로서의 적용가능성을 평가하기 위하여 휨실험을 수행하였다. 탄소섬유, 유리섬유 및 탄소와 유리섬유를 혼합한 hybrid 섬유 보강근을 사용하여 보강량을 변화시킨 12개의 실험체를 제작하여 실험을 수행하였으며, 그결과는 파괴형태, 모멘트-변위, 휨강도, 연성지수 및 단면에서의 변형율분포 등에 대하여 분석하였다. 실험결과는 ACI 기준에 제시된 모델과 비교하였으며, 전체적으로 보의 휨강도는 강도설계이론에 의한 결과와 거의 유사한 것으로 나타났다. 그러나 처짐의 경우에는 유리섬유의 경우는 이론이 과대평가 되었으며, 탄소섬유는 과소평가되는 것으로 나타났다.

• 한국전산구조공학회논문집
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• 제27권6호
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• pp.543-549
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• 2014

불확실성을 가지는 콘크리트의 특성으로 인해 철근 콘크리트 부재의 처짐에는 높은 변동성이 발생할 수 있다. 그러나 현행 설계규준은 이를 고려하지 않고 경험적인 데이터에 바탕을 두고 있으며, 부재의 최소 두께 또는 최대 허용 처짐만을 제시하고 있다. 본 논문에서는 철근 콘크리트 플랫 플레이트의 처짐 예측이 가능한 유한요소해석 모델에 확률해석 모델을 적용하여 철근 콘크리트 플랫 플레이트 처짐의 변동성을 평가하고자 하였다. 이를 위해 콘크리트, 철근, 부재치수, 인장강성에 관련된 8개 요소를 변수로 한 몬테카를로 시뮬레이션을 수행하였다. 해석결과, 스팬의 크기가 증가할수록 하중으로 인한 처짐에 더 민감하게 반응하는 것으로 나타났으며, 재하되는 활하중의 크기가 클수록, 슬래브의 두께가 작을수록 처짐의 변동성이 큰 것으로 나타났다.

• Coupled systems mechanics
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• 제4권4호
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• pp.279-295
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• 2015

The article presents a theoretical-experimental approach developed for modeling the coefficient of sliding friction in the dynamic system tool-workpiece in slide diamond burnishing of low-alloy unhardened steels. The experimental setup, implemented on conventional lathe, includes a specially designed device, with a straight cantilever beam as body. The beam is simultaneously loaded by bending (from transverse slide friction force) and compression (from longitudinal burnishing force), which is a reason for geometrical nonlinearity. A method, based on the idea of separation of the variables (time and metric) before establishing the differential equation of motion, has been applied for dynamic modeling of the beam elastic curve. Between the longitudinal (burnishing force) and transverse (slide friction force) forces exists a correlation defined by Coulomb's law of sliding friction. On this basis, an analytical relationship between the beam deflection and the sought friction coefficient has been obtained. In order to measure the deflection of the beam, strain gauges connected in a "full bridge" type of circuit are used. A flexible adhesive is selected, which provides an opportunity for dynamic measurements through the constructed measuring system. The signal is proportional to the beam deflection and is fed to the analog input of USB DAQ board, from where the signal enters in a purposely created virtual instrument which is developed by means of Labview. The basic characteristic of the virtual instrument is the ability to record and visualize in a real time the measured deflection. The signal sampling frequency is chosen in accordance with Nyquist-Shannon sampling theorem. In order to obtain a regression model of the friction coefficient with the participation of the diamond burnishing process parameters, an experimental design with 55 experimental points is synthesized. A regression analysis and analysis of variance have been carried out. The influence of the factors on the friction coefficient is established using sections of the hyper-surface of the friction coefficient model with the hyper-planes.

• 콘크리트학회논문집
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• 제23권4호
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• pp.413-420
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• 2011

휨 보강근의 종류 및 조합, 섬유 혼입을 변수로 하는 고강도 콘크리트 보의 구조 실험 결과를 균열 모멘트, 극한 모멘트, 처짐 등에 대해 각종 설계기준 및 가이드라인, 여러 연구자들에 의한 예측식과 비교 검토하였다. 섬유를 혼입하지 않은 FRP 보강근 보강 보의 극한 모멘트 이론값은 실험값을 과소평가하였다. 강섬유가 혼입된 FRP 보강근보강보에 대한 ACI 544.4R, Campione의 모델은 섬유 보강 콘크리트의 증가된 극한 압축 변형률을 고려하지 않고 있어 극한 모멘트를 부정확하게 예측하였다. 섬유가 혼입되지 않은 부재에 대해 Bischoff의 처짐 모델은 섬유가 혼입되지 않은 부재들의 사용 하중 하에서의 처짐을 정확하게 예측한 반면, ACI 440 위원회 모델은 사용 하중 하에서의 처짐을 비보수적으로 예측하였다. 이질 보강근이 동시에 적용된 부재에 대해 Bischoff 모델과는 달리 ACI 440 위원회의 처짐 모델은 직접적인 적용이 불가능하기 때문에 ACI 440 위원회 식을 이용하여 이질 보강근이 동시에 적용된 부재의 처짐을 예측하는 방법을 제안하였다. 또한 철근과 FRP 보강근이 동시에 보강된 보에서 철근이 항복한 이후의 처짐을 예측할 수 있는 방법을 제안하였다.

• 콘크리트학회논문집
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• 제11권5호
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• pp.131-137
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• 1999

The use of higher strength materials with the strength methed of design has resulted in more slender member and shallower sections. For this reason, it is necessary to satisfy the requirements of serviceability even though the structural safety is the most important limit state. This paper is only concerned with the control of deflections in the serviceability. In this study, an analytical model is presented to predict the deflections of reinforced concrete beams to given loading and environmental conditions. This model is based on the finite element approach in which a finite element is generally divided into a number of stiffening effect due to cracking, creep and shrinkage. Comparisons are made with available measured deflections reported by others to assess the capability of the layered beam model. The calculated values of instantaneous and long-term deflection show good agreement with experimental results in the range of tension stiffening parameter $\beta$ between 2.5 and 3.0.