• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.128-136
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• 2010

In according with concrete structural design standard, it is common designing flexure reinforcement concrete to induce tension failure. So reinforcing ratio is limited to inducing tension failure. And maximum reinforcing ratio is regulated to protecting concrete compression strength caused by over reinforced building. Minimum reinforcing ratio is also limited in designing standard to protecting brittle failure as extremely using less reinforcing bar. But in minimum reinforcing ratio it is extremely conservative or it is sometimes impossible to induce stable tension-failure because they are depending on yield failure and experienced method and concrete designing standard strength. Therefore the purpose of the present paper is to evaluate the flexural behavior of minimum steel ratio of reinforced concrete of beams and to propose the guide-line of equation of minimum steel ratio by performing static flexural test of 16 beams according to size effect, number of steel, yielding stress of steel, and concrete compressive strength which are presumed effective variables. From experimental results, the equation of minimum steel ratio was newly proposed considered size effect.

• Journal of the Korean Society of Safety
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• v.9 no.3
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• pp.13-21
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• 1994

Effects of tensile and compression residual stresses in the welded SS41 and A17075-76 on fatigue crack propagation behavior are investigated when a crack propagates from residual stresses region. We propose the fatigue crack growth equation on tensile and compression residual stresses in welded metal. The results obtained in this experimental study are summarized as follows . 1 ) A fatigue crack growth equation which applied fatigue fracture behavior of the welded metal is proposed. (equation omitted) where, $\alpha$, $\beta$, ${\gamma}$ and $\delta$ are constants, and R$_{eff}$ is effective stress ratio [R$_{eff}$=(Kmin+Kres)/(Kmax+Kres)], Kcf is critical fatigue stress intensity factor. The constants are obtained from nonlinear least square method. The relation between crack length and number of cycles obtained by integrating the fatigue crack growth rate equation is in agreement with the experimental data. 2) The experimental results confirmed that the cause of crack extension and retardation by residual stresses has relation to the phenomenon of crack closure. 3) The relaxing trend of residual stresses by the crack propagation was greater In case of compressive residual stress than that of tensile residual stress in the welded metal.tal.

• Journal of the Korean GEO-environmental Society
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• v.12 no.5
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• pp.21-28
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• 2011

It is important to obtain detailed physical and mechanical properties of the soil for effective and economical plans and constructions of the structures located on deep seabed soft clay layer. This study is to find out the engineering properties of the seabed soft clay such as water content, initial void ratio, liquid and plastic limits, the compression index, etc., to make correlations between soil parameters, and to compare and analyze the findings with that from the previous researchers. Finally a representative correlation among the soil parameters was determined.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.2
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• pp.117-122
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• 2000

The fractal image compression is based on the self-similarity that some area in an image is very similar to others. This compression method offers high compression ratio and fast decompression, but it has very long encoding time. To cut-off the encoding time, most researches give a restriction on domain blocks to be compared with a range block or make an effective search sequence of the domain blocks for a range block. However, most of them take much encoding time yet. In this research, we propose an algorithm that greatly reduces the encoding time by considering the coherence between range blocks. This algorithm first classifies all range blocks into some groups using the coherence between range blocks, and then searches corresponding domain blocks only for the key block of each group. If this scheme is joined in a prior work of the other fractal compression algorithm, it will give a great effectiveness to encoding time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.207-216
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• 2005

External confinement by CFS (Carbon Fiber Sheet) is a very effective retrofit method for the reinforced concrete columns subject to either static or seismic loads. For the reliable and cost-effective design of CFS, an accurate stress-strain model is required for CFS-confined concrete. In this paper, uniaxial compression test on short RC column with square section was performed. To evaluate the effect of confinement on the stress-strain relationship of CFS-confined concrete, CFS area ratio and tie area ratio are considered. Based on the experimental results, a stress-strain model is proposed for concrete confined by CFS wraps. In the development of the model, the method to compute the actual hoop strains in CFS jackets at the rupture was examined and resolved. Overall, the results of the model agree well with test data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11C
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• pp.1067-1075
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• 2009

In this paper, we propose an adaptive companding scheme to effectively reduce PAPR (Peak-to-Average Power Ratio) of the OFDM (Orthogonal Frequency Division Multiplexing) signals, while considering both complexity and BER (Bit Error Rate) performance of systems. The proposed scheme adaptively alters the compression function in the transmitter and the expanding function in the receiver to simultaneously take into account the BER performance and the PAPR reduction. In this paper, we also measure in-band and out-of-band spectra of the proposed scheme, and observe the BER performance after applying the filtering to reduce the out-of-band radiation. As compared to the conventional companding algorithm, simulation results reveal that the proposed scheme achieves more reliable BER performance in all the cases of with and without the filtering, and has a good spectrum characteristic with effective PAPR reduction.

• Journal of Acupuncture Research
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• v.35 no.4
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• pp.219-225
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• 2018

Background: The purpose of this study was to review whether Korean medicine treatment was effective to maintain the spinal stability and to relieve spinal symptom by reviewing medical records of 18 vertebral compression fracture patients. Methods: The subjects were 18 thoracolumbar compression fracture patients who were taken more than two lateral view x-rays of fractured vertebra from Jan, 2010 to June, 2018. They were divided into two groups: the time admitted into Department of Acupuncture & Moxibustion Medicine, Pohang Korean Medical Hospital of Daegu Hanny University from onset (Research 1) and whether or not they have a past history of osteoporosis (Research 2). Then, they were follow-up observed and compared by compression ratio and numerical rating scale (NRS) and so on. Results: The amount of weekly compression rate increase of 18 patients was 1.76% per week. According to the result of Research 1, the patients group (14 patients) who were admitted into the hospital within 1-2 weeks from getting injury was 1.88% per week whereas the patients group(4 patients) who were admitted into the hospital within 3-4 weeks from getting injury was 1.22% per week. By Research 2 result, the patients group (7 patients) who had been diagnosed as an osteoporosis patient was 2.19% per week, and those (11 patients) who had not was 1.49% per week. There was a statistical significance in the change of the amount of compression rate increase in the case of Research 1, but there was not in the case of Research 2. NRS was decreased without significant difference regardless of the time admitted into the hospital and whether or not the patients had the past history of osteoporosis. Conclusion: Considering that there were more amount of compression rate increase at 1-4 weeks from onset, it is necessary to offer treatment more actively on early time from onset. Further research is needed into the increase of compression rate by the patients' having a past history of osteoporosis or not. Given that NRS decreased without significant difference, it is assumed that Korean medicine treatment has a meaningful effect on relieving subjective symptom of patients who are diagnosed as vertebral compression fractures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.4
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• pp.343-351
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• 2010

Bending and axial compressive stresses are distributed across the whole upper flange of a box girder bridge which has the span-to-depth ratio (B/L) of below 0.5, according to Korea Bridge Design Specifications (Minister of Land, Transport and Maritime Affairs, 2005). Shear lag phenomenon, however, can take place in the construction phase of cable-stayed bridge, in which stresses combining bending moment due to dead weight and cable vertical compression are induced. This study aims to analyze the effective width of flange over which composite stresses are given, which should be calculated during the construction phase of stiffening girder of single plane cable-stayed box girder bridge. The study results indicate that the full width of stiffening girder can be regarded as the effective flange width when the span-to-depth ratio for the deck is below 0.38. In other words, the area, where shear lag is taken into consideration, is larger than the width of box girder in single plane cable-stayed box girder bridges. Therefore, the current practice of considering the full width as the effective flange width regardless of changes of the span-to-depth ratio during the construction stage can produce an unsafe bridge. If the effective flange width is determined according to the single span structural system in the early stage of construction when the span-to depth ratio for the deck is high and composite stresses of every part expect each end of the bridge are calculated, it can result in a safe structural design. Since the span-to-depth ratio gradually decreases, however, it is appropriate to determine the effective width of flange on the basis of the full width and the cantilever structural system.

• Journal of ILASS-Korea
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• v.22 no.1
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• pp.22-28
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• 2017

In this study, the effects of intake valve closing timing by using Cam-in-Cam system on combustion and emission characteristics for diesel engine were investigated under GT-POWER simulation environment. As a result, it was found that volumetric efficiency and effective compression ratio were decreased as the intake valve closing(IVC) timing is retarded due to its backflow effect. Also, we found that in-cylinder pressure, heat release rate and NOx emission were decreased as IVC timing was retarded. These show that the LIVC(late intake valve closing) can be effective to control AFR and mixing rate in diffusion combustion of diesel engine.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.239-246
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• 1999

recently there have been many destructive seismic events in Kobe Japan in 1995 and in Northridge California USA in 1994. etc. The Korean Bridge Design Standard Specifications adopted the seismic design requirements in 1992. Comparing the earthquake magnitude in Korea with those in the west coast of the USA it may be said that the current seismic design requirements of the Korean Bridge Design Standard Specifications provides too conservation design results especially for transverse reinforcement details and amount in reinforced concrete columns. This fact usually makes construction problems in concrete casting due to transverse reinforcement congestion. And the effective stiffness Ieff depends on the axial load P(Ag{{{{ {f }_{ck } }}) and the longitudinal reinforcement ratio Ast/Ag and it is conservative to use the effective stiffness Ieff than the gross section moment Ig. Seismic design for transverse reinforcement content of concrete column is considered of extreme-fiber compression strain R-factor axial load and stiffness etc.