• Computers and Concrete
• /
• v.30 no.1
• /
• pp.19-32
• /
• 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.

• Fashion & Textile Research Journal
• /
• v.24 no.1
• /
• pp.156-163
• /
• 2022

Loss of leg muscle and muscle weakness, which are caused by aging, affect muscle function and sense of balance. As a way of preventing seniors from falling, we developed the idea of wearing functional supporters based on graduated compression technique and in the form of a taping supporter. Their impact on power, sense of balance, overcoming fatigue, and subjective wearing sensation was investigated. The following results were obtained. After wearing functional compression supporters, body temperature increased from 24.5 ± 0.5℃ to 26.3 ± 0.6℃. Calf size, which assesses the level of edema, decreased from 26.1 ± 1.8cm to 25.7 ± 1.8cm. The result of dynamic balance test, which helps estimate the fall prevention effect, increased from 6.4 ± 0.9sec to 7.1 ± 0.6sec. Lactate level, which indicates the level of fatigue, decreased from 8.1 ± 0.6mmol/L to 7.3 ± 0.8mmol/L. Standing long jump record, which assesses power, increased from 110.1 ± 3.1cm to 112.0 ± 2.8cm. Standing on one leg with eyes closed, which assesses sense of balance, increased from 4.2 ± 1.1sec to 6.5 ± 0.8sec. Ankle angle, which assesses joint stability, increased from 75.3 ± 4.0° to 80.1 ± 1.7°. In metabolism and physical performance testing, which assesses keep, the score increased from 26.3 ± 1.7 to 28.8 ± 1.2. Muscle supporting score, which assesses joint stability, increased from 7.3 ± 0.6 to 7.8 ± 0.4. In the category of body type, which assesses wearing sensation and body shaping function, the score increased from 5.7 ± 1.4 to 6.4 ± 1.2

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2005.05a
• /
• pp.173-178
• /
• 2005

The tile construction methods for existing have been used materials within limit which adhesion by wet method in masonry wall and concrete structure. These existing adhesive tech can caused many problems in construction of large and reform tile, after that it can be happened loose scale, peel off, falling off tile by heat and vibration or impact. In according to, this study is to test tile for bond stability, adhesive property by impact, vibration. low property by heat and then, we have the results as below; (1) The tile adhesive stability can be effected as adhesive area between bond agent and tile, adhesive area can more wide and press enough to ensure property. (2) Existing adhesive strength and standard relative tile construction is limited to adjust performance tile on the concrete and masonry wall. In summary, It is necessary to establish standard of performance and test method to ensure tile adhesive salability in dry wall.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.18 no.2
• /
• pp.146-153
• /
• 2015

An unmanned aerial photography method by using an unmanned helicopter is useful method for measuring of the water-entry traces of small falling objects into the sea. Pixel sizes on the aerial photograph may be too large due to a limit of camcorder resolution and a wide shooting area. If the pixel size is too large, identification of water-entry trace is impossible. Thus an accurate prediction of water-entry trace size is required. The traces of water-entry could be classified into three types such as splash, water column, and bubble. Diameters of each trace are predicted by water-entry impact pressure theories, cavity theories, and trial test results. The results are verified by drop tests using an unmanned helicopter at two water-entry speeds. As a result, prediction and test results showed sufficient similarity to evaluate the identifiability of water-entry trace.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2008.04a
• /
• pp.490-494
• /
• 2008

U-Channel Bridge is effective bridge type, because its edge beam performs role of barrier and enables to reduce additional dead loads. Although it is effective to reduce additional dead loads, there is possibility of bridge collapse under impact load due to car crash. Also, edge beam must have ability to induce safe driving and prevent falling accidents. Therefore, it requires behavior analysis and property investigation through the vehicle impact crashing edge beam. This study presents method of structural analysis of U-channel bridge and investigates design specifications for the effect of the edge beam under the vehicle impact. Also, it carries out stability investigation of behavior of edge beam and slab, based on Korean Highway Bridge Design Specifications and AASHTO LRFD Bridge Design Specification.

• 한국방재학회:학술대회논문집
• /
• 2008.02a
• /
• pp.333-336
• /
• 2008

U-Channel Bridge is effective bridge type, because its edge beam performs role of barrier and enables to reduce additional dead loads. Nevertheless, there is possibility of bridge collapse under impact load due to car crash. Also, edge beam must have ability to induce safe driving and prevent falling accidents. Therefore, this study carries out analysis of behavior of edge beam and slab and evaluation of structural stability under impact loads, based on Korean Highway Bridge Design Specifications and AASHTO LRFD Bridge Design Specification. According to analysis result, the maximum stress of edge beam and slab satisfies specification of allowable stress.

• Nuclear Engineering and Technology
• /
• v.46 no.4
• /
• pp.529-540
• /
• 2014

In this research, a drop impact analysis of a fuel assembly in a research reactor is carried out to determine whether the fuel plate integrity is maintained in a drop accident. A fuel assembly drop accident is classified based on where the accident occurs, i.e., inside or outside the reactor, since each occasion results in a different impact load on the fuel assembly. An analysis procedure suitable for each drop situation is systematically established. For an accident occurring outside the reactor, the direct impact of a fuel assembly on the pool bottom is analyzed using implicit and explicit approaches. The effects of the key parameters, such as the impact velocity and structural damping ratios, are also studied. For an accident occurring inside the reactor, the falling fuel assembly may first hit the fixing bar at the upper part of the standing fuel assembly. To confirm the fuel plate integrity, a fracture of the fixing bar should be investigated, since the fixing bar plays a role in protecting the fuel plate from the external impact force. Through such an analysis, the suitability of an impact analysis procedure associated with the drop situation in the research reactor is shown.

• Journal of Yeungnam Medical Science
• /
• v.27 no.2
• /
• pp.122-126
• /
• 2010

It is common m childhood that children suffer intracavity or head injury, falling down backward, having chopsticks in their mouth. But most of them have paralysis of upper and lower extremity because of secondary damage by penetrating injury of brainstem and spine. We could not find this case which have shown infaction of medulla oblangata on MRI and paralysis by impact only without clear penetrating evidence. So the authors report this case with study of literature because we experience one case that have high signal density in brainstem on MRI, Loss of consciousness, and left hemiplegia without clear penetrating evidence after falling down backward, having chopsticks in her mouth and regard it rare case.

• The Journal of Korea Robotics Society
• /
• v.13 no.4
• /
• pp.248-255
• /
• 2018

In this paper, a design for a vehicle body of an armored robot for complex disasters is described. The proposed design considers various requirements in complex disaster situations. Fire, explosion, and poisonous gas may occur simultaneously under those sites. Therefore, the armored robot needs a vehicle body that can protect people from falling objects, high temperature, and poisonous gas. In addition, it should provide intuitive control devices and realistic surrounding views to help the operator respond to emergent situations. To fulfill these requirements of the vehicle body, firstly, the frame was designed to withstand the impact of falling objects. Secondly, the positive pressure device and the cooling device were applied. Thirdly, a panoramic view was implemented that enables real-time observation of surroundings through a number of image sensors. Finally, the cockpit in the vehicle body was designed focused on the manipulability of the armored robot in disaster sites.

• The Journal of Industrial Distribution & Business
• /
• v.9 no.10
• /
• pp.83-89
• /
• 2018

Purpose - The purpose of this study examines when the optimism impact on financial asset price forecasting and the boundary condition of optimism in the financial asset price forecasting. People generally tend to optimistically forecast their future. Optimism is a nature of human beings and optimistic forecasting observed in daily life. But is it always observed in financial asset price forecasting? In this study, two factors were focused on considering whether the optimism that people have applied to predicting future performance of financial investment products (e.g., mutual fund). First, this study examined whether the degree of optimism varied depending on the direction of the prior price trend. Second, this study examined whether the degree of optimism varied according to the forecast period by dividing the future forecasted by people into three time horizon based on forecast period. Research design, data, and methodology - 2 (prior price trend: rising-up trend vs falling-down trend) × 3 (forecast time horizon: short term vs medium term vs long term) experimental design was used. Prior price trend was used between subject and forecast time horizon was used within subject design. 169 undergraduate students participated in the experiment. χ² analysis was used. In this study, prior price trend divided into two types: rising-up trend versus falling-down trend. Forecast time horizon divided into three types: short term (after one month), medium term (after one year), and long term (after five years). Results - Optimistic price forecasting and boundary condition was found. Participants who were exposed to falling-down trend did not make optimistic predictions in the short term, but over time they tended to be more optimistic about the future in the medium term and long term. However, participants who were exposed to rising-up trend were over-optimistic in the short term, but over time, less optimistic in the medium and long term. Optimistic price forecasting was found when participants forecasted in the long term. Exposure to prior price trends (rising-up trend vs falling-down trend) was a boundary condition of optimistic price forecasting. Conclusions - The results indicated that individuals were more likely to be impacted by prior price tends in the short term time horizon, while being optimistic in the long term time horizon.