• 콘크리트학회논문집
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• 제22권4호
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• pp.535-546
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• 2010

최근 교량구조물의 증가와 더불어 차량 및 선박과 시설물 간의 충돌사고가 발생할 확률이 높아지고 있다. 특히 교량을 구성하는 상부구조와 하부구조 중에서 충돌에 의한 영향은 주로 교각 등의 하부구조가 받을 가능성이 크다. 교각에 차량 혹은 선박이 충돌하게 되면 교량 하부구조에 국부적인 손상을 유발하게 되며, 충돌사고는 훨씬 더 순간적이고 강한 물리적인 질량의 충돌을 동반할 수 있으며, 극단적인 경우 상부구조의 붕괴까지 유발할 수 있다. 그러므로 이 연구에서는 콘크리트 구조물인 교량의 교각과 같은 압축부재에 대한 설계 시 차량 등에 의한 충돌을 고려하고, 차량 충돌하중에 의한 손상지수를 정량적으로 평가하기 위해서 기존의 설계방법을 개선하고 새로운 구조물의 저항성능 평가방법을 정립하기 위하여 동적유한요소해석 프로그램인 LS-DYNA를 이용하여 교각단면, 차량의 충돌각에 따른 충격도, 축력 및 축력비, 콘크리트 강도, 주철근비와 횡방향 철근, 세장비 등을 변화시켜 케이스별 해석을 수행하였다. 이 연구 결과를 통해 콘크리트 구조물의 거동해석 및 설계기법을 Bayesian 통계방법을 이용한 만족도 곡선을 통해 충격하중을 받을 시의 성능 기반형 저항성능 평가방법을 개발하였으며, 이는 실제 충격하중에 의한 구조물의 방호성능 및 설계 시에 적절하게 적용할 수 있을 것으로 판단된다.

• Composites Research
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• 제29권2호
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• pp.73-78
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• 2016

본 연구에서 다루는 탄소섬유 복합재 인라인 휠은 플라스틱 인라인 휠 허브의 기존 재질을 탄소섬유 직물/에폭시 수지로 구성된 디스크 형의 허브로 대체하는 것이다. 지면으로부터의 충격 하중은 탄소섬유 복합재 휠의 충격 성능 평가를 위해 저속 충격 시험이 수행되었고, 기존의 플라스틱 휠의 성능과 비교하여 수행되었다. 본 연구는 시험 조건으로 70 J의 충격 하중을 적용하였다. 충격 에너지는 타격 추의 높이와 무게를 조정하여 조절되었다. 탄소섬유 복합재 디스크 허브의 사용은 무게를 절감하고 실제 운행 조건과 유사한 조건인 낮은 충격에너지에서 우수한 반발력을 나타내는 것으로 확인되었다. 충격 하중에 따라 최대 하중은 비례적으로 증가하지만, 최대 하중의 성장은 20 J 충격 하중에서 감소되었고, 45 J 충격 하중에서부터 감소되는 경향의 결과를 보였다. 탄소섬유 복합재 휠은 5 J, 10 J의 충격 하중에서 전체 충격 에너지의 35.3, 19.1%가 리바운딩 되는 우수한 특성을 보였다. 반면에 20 J 이상의 충격하중에 대해서는 얇은 탄소섬유 복합재 허브의 크랙 생성으로 인해 전체 에너지의 5% 이하로 리바운드 되었다.

• Computers and Concrete
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• 제30권1호
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• pp.19-32
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• 2022

This paper presents an investigation into the failure of RC columns under impact loadings. A numerical simulation of 19 identical RC columns subjected to single and repeated impact loadings was performed. A free-falling hammer was dropped at midspan with the same total kinetic energy input but varying mass and momentum. The specimens under the repeated impact test were struck two times at the same location. The colliding index, defined as the impact energy-momentum ratio, was proposed to explain the different impact responses under equal-energy impacts. The increase of colliding index from low to high indicates the transition of the impact response from static to dynamic and failure mode from flexure to shear. This phenomenon was more evident when the column had a greater axial load and was impacted with a high colliding index. The existence of the axial load had an inhibitory effect on the crack development and increased the shear resistance. The second impact changes the failure mode from flexural to brittle shear as found in the specimen with 20% axial load subjected to high a colliding index. Moreover, a deflection prediction equation based on the impact energy and force was limited to the low colliding index impact.

• Structural Engineering and Mechanics
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• 제76권4호
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• pp.465-477
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• 2020

This paper presents an investigation on the dynamic behavior of SRC columns with built-in cross-shaped steels under impact load. Seven 1/2 scaled SRC specimens were subjected to low-speed impact by a gravity drop hammer test system. Three main parameters, including the lateral impact height, the axial compression ratios and the stirrup spacing, were considered in the response analysis of the specimens. The failure mode, deformation, the absorbed energy of columns, as well as impact loads are discussed. The results are mainly characterized by bending-shear failure, meanwhile specimens can maintain an acceptable integrity. More than 33% of the input impact energy is dissipated, which demonstrates its excellent impact resistance. As the impact height increases, the flexural cracks and shear cracks observed on the surface of specimens were denser and wider. The recorded time-history of impact force and mid-span displacement confirmed the three stages of relative movement between the hammer and the column. Additionally, the displacements had a notable delay compared to the rapid changes observed in the measured impact load. The deflection of the mid-span did not exceed 5.90mm while the impact load reached peak value. The impact resistance of the specimen can be improved by proper design for stirrup ratios and increasing the axial load. However, the cracking and spalling of the concrete cover at the impact point was obvious with the increasing in stiffness.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.356-360
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• 2006

Recently, for the purpose of improving the isolation performance of impact noise, many resilient materials have been installed in a residential building. As one of the reduction method for improving the performance of light-weight impact noise, this study is focused on the load condition of floating layer over resilient material. We studied the correlation between the mass or load of the floating layer and the reduction of light-weight impact noise by experiments in reverberation chamber for testing the impact noise. The results show that the reduction of impact noise is improved by increasing the mass per unit area of floating layer until about $140kg/m^2$. But the reduction is not obvious by adding extra mass on the floating layer.

• 화약ㆍ발파
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• 제27권2호
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• pp.26-32
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• 2009

산업의 발달로 인해 도심지에서의 건물해체 및 발파공사가 증가하여 왔지만, 인접 구조물에 대한 영향 평가는 미미한 실정이었다. 본 연구에서는 탄성파속도 실험과 반발경도 실험으로 콘크리트 재료의 물성을 파악 하였고, 인접 구조물 부재의 내부 손상을 모사하기 위하여 콘크리트 재료에 충격 하중을 가하여 충격 전후의 탄성파속도를 도식화하였다. 결과적으로, 콘크리트 재료는 충격 하중에 따라 탄성파속도가 감소하는 경향을 보였고, 압축강도가 크고 탄성파속도가 빠른 재료일수록 충격 하중에 따른 손상이 작은 것으로 나타났다.

• 오토저널
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• 제13권5호
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• pp.51-64
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• 1991

In this paper, an attempt is made to analyze the impulsive stress directly underneath the concentrated impact point for a supported square plate by using the three-dimensional dynamic theory of elasticity and the potential theory of displacement (stress function) on the supposition that the load, F$_{*}$0 sin .omega.t, acted on the central part of it. The results obtained from this study are as follows: 1. The impulsive stress cannot be analyzed directly underneath the acting point of concenrated impact load in privious theories, but can be analyzed by using the three-dimensional dynamic theory of elasticity and the potential theory of displacement. 2. Theorically, with increasing the pulse width of applied load, it was possible to clarify that the amount of stress in the point of concentrated impact load was increased and that of stress per unit impulse was decreased. 3. The numerical inversion of laplace transformation by the use of the F.F.T algorithm contributes the reduction of C.P.U time and the improvement of the accuracy or results. 4. In this paper recommended, it is found that the approximate equation of impact load function P (.tau.) = A.tau. exp (-B.tau.), and P (.tau.) =0.85A exp (-B.tau.) sinC.tau. could actually apply to all impact problem. In compared with the experimental results, the propriety of the analytical method is reasonable.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.101-106
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• 2003

In order to investigate the mechanical behavior of newly developed materials, the evaluation of mechanical properties using small-size specimen is essential. For those purposes, an instrumented impact testing apparatus, which provides the load-displacement curve under impact loading without oscillations, was devised. To develop the test procedure with the setup, the impact behaviors of various kinds of structural materials such as S45C, SCM4, Ti alloys (Ti-6V-4Al) and Zr-based bulk amorphous metal, were investigated through the instrumented Charpy V-notch impact tests. The calibrations of the dynamic load and displacement that was calculated based on the Newton' second law were carried out through the quasi-static load test and the comparison of a directly measured value using a laser displacement meter. Satisfactory results could be obtained. The crack initiation and propagation processes during impact fracture could be well divided on the curve, depending on the intrinsic characteristic of specimen tested; ductile or brittle. The absorbed impact energy in Zr-basd BAM was largely used for crack initiation not for crack propagation process. The fracture surfaces under impact loading showed different feature when compared with the static cases.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.129-134
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• 2003

The importance of understanding the response of structural composites to impact and CAI cannot be overstated to develop analytical models for impact damage and CAI strength predictions. This paper presents experimental findings observed from quasi-static lateral load tests, low velocity impact tests, CAI strength and open hole compressive strength tests using 3mm thick composite plates ($[45/-45/0/90]_{3s}$ - IM7/8552). The conclusion is drawn that damage areas for both quasi-static lateral load and impact tests are similar and the curves of several drop weight impacts with varying energy levels (between 5.4 J and 18.7 J) fallow the static curve well. In addition, at a given energy the peak force is in good agreement between the static and impact cases. From the CAI strength and open hole compressive strength tests, it is identified that the failure behaviour of the specimens was very similar to that observed in laminated plates with open holes under compression loading. The residual strengths are in good agreement with the measured open hole compressive strengths, considering the impact damage site as an equivalent hole. The experimental findings suggest that simple analytical models for the prediction of impact damage area and CAI strength can be developed on the basis of the failure mechanism observed from the experimental tests.

• Journal of Advanced Marine Engineering and Technology
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• 제20권1호
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• pp.56-66
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• 1996

In this study, the characteristics of generation and propagarion of transient wave induced in the assembly of four collecting plate upon the propagation of waves are analyzed. Also double exposure holographic inteferometry using ruby pulse laser is built in order to investigate the propagation of transient waves generated by impact load. When impact load was applied at edge of connecting band, the vibration of collecting plates was generated from the contact points between collecting plate and band which connects four collecting plates. Waves generated from the lower part and those reflected from the upper part were mixed as time went on and then formed very complex shapes. Also, when impact load was aplied at center of collecting plate, the waves propagating across the convexo-concave plane were reflected partly at curved section. Therefore the vibration amplitude was decreased as the transiet waves were propagated through the convexo-concave plane.