• Structural Engineering and Mechanics
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• 제77권6호
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• pp.809-817
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• 2021

In this study, the dynamic behavior of a three-span hybrid continuous arch bridge under vehicle loading is investigated. The natural vibration characteristics of the bridge were analyzed through pulsation test. In the dynamic loading test, the vibrations of the bridge under different truck speeds and different pavement conditions were tested, and time histories of deflection and acceleration of the bridge were measured. Based on the dynamic loading test, the impact coefficient was analyzed. The results indicate that the pavement smoothness had more impacts on the vibration of the bridge than the truck's speed. The vertical damping of the bridge under the excitation of the trucks is larger than the transverse damping. Resonance occurs at the side span of the bridge under a truck at 10 km/h.

• Structural Engineering and Mechanics
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• 제84권5호
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• pp.619-632
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• 2022

Reinforced concrete (RC) structures may be subjected to sudden dynamic impact loads such as explosions occurring for different reasons, the collision of masses driven by rockfall, flood, landslide, and avalanche effect structural members, the crash of vehicles to the highway and seaway structures. Many analytical, numerical, and experimental studies focused on the behavior of RC structural elements such as columns, beams, and slabs under sudden dynamic impact loads. However, there is no comprehensive study on the behavior of the RC column-beam connections under the effect of sudden dynamic impact loads. For this purpose, an experimental study was performed to investigate the behavior of RC column-beam connections under the effect of low-velocity impact loads. Sixteen RC beam-column connections with a scale of 1/3 were manufactured and tested under impact load using the drop-weight test setup. The concrete compressive strength, shear reinforcement spacing in the beam, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, and displacements measured from the test specimens were recorded in experiments. Besides, shear and bending crack widths were measured. The effect of experimental variables on the impact behavior of RC beam-column connections has been determined and interpreted in detail. Besides, a finite element model has been established for verification and comparison of the experimental results by using ABAQUS software. It has been demonstrated that concrete strength, shear reinforcement ratio, and impact energy significantly affect the impact behavior of RC column-beam connections.

• 한국도로학회논문집
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• 제15권3호
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• pp.53-63
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• 2013

PURPOSES : This study is to evaluate moisture susceptibility of asphalt mixtures by using non-destructive impact wave and to determine durability so as to decrease the gap between before and after freezing in the future. METHODS : Using non-destructive impact wave, this study is to determine the dynamic modulus of asphalt specimen. Furthermore, the results obtained from two experiment accelerometers are used for the dynamic modulus determination. The dynamic moduli of specimens are compared with those of the freezing-thawing specimens. RESULTS : Test results showed that the dynamic modulus before freezing and thawing environment loads at each temperature dropped about 3.7% after the environmental loads. Furthermore, correlation analysis indicates that transition of dynamic modulus at each point is about 89.59%. CONCLUSIONS: Evaluation of asphalt mixtures using non-destructive impact wave has excellent repeatability and simple equipment for the test. Consequently, the method in the study will be useful for evaluating the characteristics of a various asphalt mixtures.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.254-260
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• 2000

The spacer grid is one of the main structural components in fuel assembly, which supports the fuel rods, guides cooling water, and protects the fuel assembly from the external impact load such as earthquakes. The nonlinear dynamic impact analysis is conducted by using the finite element code ABAQUS/Explicit. Boundary condition for dynamic analysis is well applied to the test condition. Simulation results also similarly predict the local buckling phenomena. In addition to the buckling parameter, the local buckling cause is examined by both simulation and test method. It is found to correspond well with the test results. Impact tests are also carried out for some specimens of the spacer grid in order to compare the results between the test and the simulation. This test is accomplished by a free fall dummy weight onto the specimen. From this test, only the uppermost and lowermost layers of the multi-cell are buckled, which implies the local buckling at the weakest point of the grid structure.

• 한국정밀공학회지
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• 제23권12호
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• pp.88-94
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• 2006

In this study, the dynamic impact analysis for the passenger air-bag(PAB) module has been carried out by using FEM to predict the dynamic characteristics of vehicle ride safety against head impact. The impact performance of vehicle air-bag is directly related to the design parameters of passenger air-bag module assembly, such as the tie bar bracket's width and thickness, respectively, However, the product's design of PAB module parameters are estimated through experimental trial and error according to the designer's experience, generally. Therefore, the dynamic analysis of head impact test of the passenger air-bag module assembly of automobile is needed to construct the analytical methodology At first, the FE models, which are consist of instrument panel, PAB Module, and head part, are combined to the whole module system. Then, impact analysis is carried out by the explicit solution procedure with assembled FE model. And the dynamic characteristics of the head impact are observed to prove the effectiveness of the proposed method by comparing with the experimental results. The better optimized impact performance characteristics is proposed by changing the tie bracket's width md thickness of module. The proposed approach of impact analysis will provides an efficient vehicle to improve the design quality and reduce the design period and cost. The results reported herein will provide a better understanding of the vehicle dynamic characteristics against head impact.

• Computers and Concrete
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• 제28권5호
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• pp.479-486
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• 2021

Reinforced concrete (RC) slabs are exposed to several static and dynamic effects during their period of service. Accordingly, there are many studies focused on the behavior of RC slabs under these effects in the literature. However, impact loading which can be more effective than other loads is not considered in the design phase of RC slabs. This study aims to investigate the dynamic behavior of two-way RC slabs under sudden impact loading. For this purpose, 3 different simply supported slab specimens are manufactured. These specimens are tested under impact loading by using the drop test setup and necessary measurement devices such as accelerometers, dynamic load cell, LVDT and data-logger. Mass and drop height of the hammer are taken constant during experimental study. It is seen that rigidity of the specimens effect experimental results. While acceleration values increase, displacement values decrease as the sizes of the specimens have bigger values. In the numerical part of the study, artificial neural networks (ANN) analysis is utilized. ANN analysis is used to model different physical dynamic processes depending upon the experimental variables. Maximum acceleration and displacement values are predicted by ANN analysis. Experimental and numerical values are compared and it is found out that proposed ANN model has yielded consistent results in the estimation of experimental values of the test specimens.

• Elastomers and Composites
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• 제41권1호
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• pp.40-48
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• 2006

고무는 금속 및 플라스틱 재료와 달리 작은 하중에서도 큰 변형이 발생되며, 높은 변형 구간에서 탄성특성을 보이는 특징이 있다. 특히 충격흡수 특성이 금속 및 플라스틱보다 우수하므로 제진 및 충격 완충구조물로 널리 활용되고 있다. 충격하중을 받는 고무 구조물의 특성을 평가하기 위하여 자유 낙하형 충격시험기를 이용하여 충격실험을 실시하였으며, ABAQUS/Explicit를 이용하여 유한요소 해석을 수행하였다. 고무의 동강성은 충격펄스의 최대변형량과 충격지속시간으로부터 얻어진 진폭과 주파수를 적용하여 동특성 시험을 수행하고 WLF모델을 적용하여 높은 주파수 대역의 동강성을 예측하였다. 실험을 실시한 $0.3{\sim}l.5J$의 충격에너지 영역에서는 고무의 경도가 증가되면 충격흡수율이 감소되며, 충격에너지가 커질수록 충격흡수율은 감소하는 경향을 나타내었다.

• Computers and Concrete
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• 제14권5호
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• pp.563-575
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• 2014

Concrete which is a composite material is frequently used in construction works. Properties and behavior of concrete are significant under the effect of different loading cases. Impact loading which is a sudden dynamic one may have destructive effects on structures. Testing apparatuses are designed to investigate the impact effect on test members. Artificial Neural Network (ANN) is a computational model that is inspired by the structure or functional aspects of biological neural networks. It can be defined as an emulation of biological neural system. In this study, impact parameters as acceleration and impact force values of a reinforced concrete slab are obtained by using a testing apparatus and essential test devices. Afterwards, ANN analysis which is used to model different physical dynamic processes depending on several variables is performed in the numerical part of the study. Finally, test and predicted results are compared and it's seen that ANN analysis is an alternative way to predict the results successfully.

• 유통과학연구
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• 제22권1호
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• pp.61-67
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• 2024

Purpose: The study has identified factors affecting dynamic capabilities and the distribution of competitive advantage under the impact of dynamic capabilities of Vietnamese fintech businesses. Research design, data, and methods: The method used in this study is a survey analysis of 120 Vietnamese fintech businesses to test the hypothesized relationships of the research model as well as evaluate its effectiveness. The study uses the Cronbach alpha analysis, factor analyses, and structural equation modeling to assess the research's measurement and structural models. Results: Research results show that 3 critical success factors: "Capacity to develop financial service ideas," "Ability to develop a platform," and "Business capacity" have a positive impact on "Dynamic capabilities." In addition, the study also evaluates the effect of "dynamic capabilities" on the "competitive advantage" of fintech businesses. Conclusion: Theoretically, this result contributes to discovering new, specific factors affecting the dynamic capabilities of fintech businesses. In practice, the research results are empirical evidence of the distribution of competitive advantages of Vietnamese Fintech businesses and their impact on dynamic capabilities.

• Journal of Welding and Joining
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• 제7권3호
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• pp.19-27
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• 1989

Both the SS41 steel and the M.E.F(martensite encapsulated islands of frrite) dual phase steel made of SS41 steel by heat treatment were welded by friction welding, and then manufactured machinemade Vnotch standard Charpy impact specimens and precracked with a fatigue system at BM(base metal), HAZ(heat affected zone) and WZ(weld interface Zone). The impact test of them was performed with an instrumented impact test machine at a number of temperatures in constant loading velocity and the dynamic fracture characteristics were studied on bases of the absorbed energy, dynamic fracture toughness and fractography from the test. The results obtained are as follows; At the room temperature, the absorbed energy is HAZ.geq.WZ.geq.BM in case of the M.E.F. dual phase steel: BM.geq.HAZ.geq.WZ in case of the SS41 steel, HAZ.geq.BM.geq.WZ at the low temperature. The absorbed energy is decreased markedly with the temperature lowering; it is highly dependent on the temperature. The dynamic fracture toughness of the M.E.F. dual phase steel is HAZ.geq.WZ.geq.BM at the room temperature; BM.geq.WZ.geq.HAZ below-60.deg. C. Therefore the reliability of friction welding is uncertain at the low temperature(below-60.deg. C). The dynamic fracture toughness of the SS41 steel; HZA.geq.WZ.geq.BM at overall temperature region. The flaw formed by rotational upsetting pressure was shown y SEM; in this region. The absorbed energy per unit area and dynamic fracture toughness were low relative to other region.