• Journal of Korean Neurosurgical Society
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• v.45 no.6
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• pp.378-380
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• 2009

Osteoporotic patients who undergo percutaneous vertebroplasty (PVP) have the risk of a repeated collapse of their adjacent vertebral body due to alteration of load transfer into the adjacent vertebral body. The authors have experienced a rare case of repeated osteoporotic vertebral compression fractures (VCF) resulting in extreme multi-level PVP. A 74-year-old female developed severe back pain after slipping down one month ago. Her X-ray and MR images indicated a T11 VCF. She underwent successful PVP with polymethylmethacrylate (PMMA). Two weeks later, she returned to our hospital due to a similar back pain. Repeated X-ray and MR images showed an adjacent VCF on T12. A retrial of PVP was performed on T12, which provided immediate pain relief. Since then, repeated collapses of the vertebral body occurred 12 times in 13 levels within a 24-month period. Each time the woman was admitted to our hospital, she was diagnosed of newly developed VCFs and underwent repeated PVPs with PMMA, which finally eased back pain. Based on our experience with this patient, repeated multiple PVP is not dangerous because its few and minor complications. Therefore, repeated PVP can serve as an effective treatment modality for extreme-multi level VCFs.

• Earthquakes and Structures
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• v.16 no.4
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• pp.391-399
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• 2019

Residual deformation of high-speed railway bridge piers is cumulative under repeated earthquakes, and influences the safety and ride comfort of high-speed trains. This paper investigates the effects of the peak ground acceleration, longitudinal reinforcement ratio, and axial compression ratio on the cumulative deformation through finite element analysis. A simply-supported beam bridge pier model is established using nonlinear beam-column elements in OpenSees, and validated against a shaking table test. Repeated earthquakes were input in the model. The results show that the cumulative deformation of the bridge piers under repeated earthquakes increases with the peak ground acceleration and the axial compression ratio, and decreases with the longitudinal reinforcement ratio.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.85-97
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• 2005

Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exist concerns over long-term residual deformation when subjected to repeated and/or cyclic loads, especially when used as part of permanent structures. In view of these concerns, in this paper time-dependent deformation characteristics of geosynthetic reinforced soil under sustained and/or repeated loads were investigated using a series of plane strain compression tests on geogrid reinforced weathered granite soil specimens. The results indicate that sustained or repeated loads can yield appreciable magnitudes of residual deformations, and that the residual deformations are influenced not only by the loading characteristics but by the mechanical properties of geogrid. It is also found that the preloading technique can be effectively used in controlling residual deformations of reinforced soils subjected to sustained and/or repeated loads.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.552-557
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• 1997

In this study, a quantitative analysis technique for the damage process of reinforced concrete beams under repeated shear loading is proposed, which can express the progressively increasing strain and stiffness reduction. The analysis technique is mainly based on the modified compression field theory and scalar damage concept. which describe the strain and stress configuration in the shear zone by considering the 2-dimensional effect, and express the degradation of principal compressive strut by cyclic strain increment, secant modulus decrement, and modifying the parabolic stress strain relationship. The analysis of the response of RC beams under repeated shear-flexure loading has been carried out and compared with the experimental results. The present theory may efficiently be used to evaluate the deflection and strain accumulation under repeated loadings.

• Journal of the Korea Society of Computer and Information
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• v.25 no.2
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• pp.157-162
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• 2020

In this paper, we propose an analyze the effects of CPR education for kindergarten students, to determine their role as first responders, and to use them as basic data for the development and activation of CPR education programs for future kindergarten students. Five CPR training sessions were repeated for 10 weeks for children aged 6 and 7 years in kindergarten in J city, and objective data was collected using feedback equipment. The data were analyzed by t-test and paired t-test using SPSS 23.0 for win statistics program. The results showed that chest compression depth, chest compression velocity, and chest compression hand position increased significantly after repeated training. In conclusion, the cardiopulmonary resuscitation training for kindergarten students was effective, and the kindergarten students could play the role of first responders.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.1 s.20
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• pp.39-48
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• 2006

A laboratory investigation was performed to estimate the moduli values of asphalt concrete mixture due to various sinusoidal loadings in compression and tension. Total five modes of loading were used under five testing temperatures of 32, 50, 68, 86, and $104^{\circ}F$ (0, 10, 20, 30, and $40^{\circ}C$); repeated compressive haversine loading with rest period, repeated tensile haversine loading with rest period, cyclic compressive loading, cyclic tensile loading, and alternate tensile-compressive loadings. The test results showed that, due to the repeated haversine loading with rest period, asphalt concrete demonstrated similar moduli in tension and compression at low temperatures,(0 and $10^{\circ}C$) while those moduli were different at high temperatures (20, 30, and $40^{\circ}C$). At high temperatures the compressive moduli were always higher than the tensile moduli. The uniaxial tensile moduli were higher than indirect tensile moduli at low temperatures. However, those moduli were similar at high temperatures. In uniaxial cyclic tension, compression, and alternate tension-compression tests, compressive moduli were higher than tensile and alternate tensile-compressive moduli throughout the temperatures. Generally, the moduli from the repeated haversine loading with rest period were always lower than those from the cyclic sinusoidal loading. The difference in moduli from the repeated haversine loading with rest period and cyclic sinusoidal loading becomes more significant as the temperature decreases.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.493-506
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• 2021

Liquefaction refers to a phenomenon in which excessive pore water pressure occurs when a dynamic load such as an earthquake rapidly acts on a loose sandy soil saturated with soil, and the ground loses effective stress and becomes liquefied. The indoor repeated test for liquefaction evaluation can be confirmed through the repeated triaxial compression test and the repeated shear test. In this regard, this study tried to confirm the liquefaction resistance strength according to the relative density and particle size distribution of sand using the repeated triaxial compression test. As a result of the experiment, it was confirmed that the liquefaction resistance strength increased as the relative density increased regardless of the soil classification, and the liquefaction resistance strength according to the particle size distribution of the sand was confirmed that the liquefaction resistance strength of the SP sample close to SW was significantly higher. In addition, as a result of analyzing 30% of fine powder compared to 0% of fine powder, as the relative density increased to 40~70%, the liquefaction resistance strength decreased by 5~20%, and the domestic weathered soil ground had a fine liquefaction resistance strength compared to Jumunjin standard sand. When the minute was 10%, it was measured to be 30% or more, and when the fine particle was 30%, it was measured to be less than 50%.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.3
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• pp.69-81
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• 1988

The Repeated Load Triaxial and Oedometer Tests to the weathered granite & silty clay soil have been fulfilled to investigate their dynarnic characteristics. The results obtained are summarized as follows ; 1. In the relation between the repeated triaxial compression and the oedometer test, the recoverable strain of weathered granite soil showed a tendency to decrease by the increase of the repeated loads number(N), and that of silty clay showed approximately constant values while the total strain increased continuously. 2. The changes of plastic strain was dependent to the level of deviator stress which is the most important element in the calculation of soil deformation under repeated load condition. And there was a significance of 10% between the level of stress and plastic strain. 3. When the soil was aimost dried or saturated to 100%, the deformation by the repeated loads was small. However the deformation showed peak around the saturation of 50%. 4. When the deformation was predicted by the repeated triaxial load tests of a laboratory, it is desirable to introduce the threshold stress concept in the calculation of deformation of subgrade of the pavement. 5. The improved design equation (Eq. 16) introducing the modulus of conversion(Fo), which is based on the Boussineq' s theory, is considered to be rational in the design of flexible pavement. From the above results, the deformation to the repeated traffic loads could be predicted by the repeated triaxial tests on the pavement materials or undisturbed soil layers, therefore it is think that the durable and econornic pavement could be constructed by reflecting that to the design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.125-134
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• 1990

In order to utilize coal ash, which we go to great expense to scrap, as subba se course material, this study attempts to examine the deformation characteristics of coal ash with the addition of some cement when repeated loads are applied. The material of coal ash is obtained from Young dong and Youngwol thermal power plant. The results are : Unconfined compression strength shows rectilineal increase in propotion to the cement addition ratio. Within the scope of repeated loads of experimental condition, modulus of elasticity tends to decrease while compression strength shows about 21% increase.

• Journal of the Korea Society of Computer and Information
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• v.18 no.10
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• pp.55-61
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• 2013

The important issue in header compression would be how to compress the dynamic field increasing constantly between consecutive packets in the head of IP wireless networks. Existent header compression scheme that can eliminated repeated field in header are RFC2507, RFC3095 and E-ROHC scheme. In this paper, I propose a new method of compressing TS fields, which are the Dynamic fields of the RTP packet, into BCB (Basic Compression Bits) basic bits or NCB (Negotiation Compression Bits, BCB + additional bits) bits. In order to verify the proposed header compression method, I have simulation about proposed video packets of IP wireless networks. using Visual SLAM.