• Title/Summary/Keyword: tension reinforcement

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Effect of Bond Action of Longitudinal Bars on Shear Transfer Mechanism in RC Beams (RC 보에서의 전단저항기구와 주철근의 부착 작용과의 관계)

  • Kim Kil-Hee
    • Journal of the Korea Concrete Institute
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    • v.17 no.4 s.88
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    • pp.513-520
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    • 2005
  • The uniform truss mechanism is widely accepted as a shear transfer mechanism in reinforced concrete members. However, the uniform truss action cannot be expected when the bond stress distribution is not constant along longitudinal bars. A test method in which only the truss action takes place is developed and conducted to investigate the truss actions under various bond contributions. Based on the experimental results and analysis, the following findings can be obtained: 1) The bond stress distribution depends on the axial compression force, the amount of shear reinforcement and loading conditions. 2) The analysis using the combined truss model consisting of uniform and fan-shape trusses can predict the experimental results

The Strength Characteristics of PVA Fiber Reinforced CSG Materials (PVA섬유 보강 CSG 재료의 강도특성)

  • Jin, Guang-Ri;Kim, Ki-Young;Quan, He-Chun;Kim, Kyu-Won
    • Journal of the Korean Geotechnical Society
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    • v.29 no.12
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    • pp.95-104
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    • 2013
  • Recently, application of CSG is increasing in various design construction projects. At the initial stage of cementation CSG materials show the same mechanical characteristics as soil, however, as the cementation process develops, CSG materials gradually reveal material characteristics of concrete. The hardened CSG manifests elastic behavior such as maximum strength at small strain range and rapid brittle failure. In this research, PVA fiber stiffeners were used in order to: (1) reduce such brittle behavioral characteristics; (2) improve the relatively weak tension performance of CSG materials. The binding strength between the bed materials and fiber prevents rapid brittle failure and increases tensional strength of fiber reinforced CSG materials.Test results show that fiber reinforcement alone could induce the stress-strain characteristics of CSG materials from brittle failure to ductile failure and also increase the residual strength.

Sensory evaluation of a body lotion formulated with hot spring water from Deokgu, Korea (덕구온천수로 제조된 바디로션의 관능평가)

  • Kim, So Jung;Kang, Mingyeong;Lee, Taek-Kyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.4
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    • pp.420-427
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    • 2019
  • The purpose of this study was to evaluate hot spring water (HSW) from Deokgu as a cosmetic ingredient in the preparation of a body lotion. The HSW was tested for its suitability as an aqueous-phase main component. Microbiological and chemical stability tests of the HSW were carried out. Microorganisms including E. coli were not detected or detected below the detection limits, and no harmful heavy metals were found. The cytotoxicity of the HSW was also considered, and its pH determined over a period of three months. Further, sensory characteristics were assessed for consumer acceptance by performing sensory tests on body lotions formulated using either Deokgu HSW or distilled water. Skin moisturization, irritation and tension reinforcement were found to be enhanced when using the HSW lotion rather than that formulated with distilled water. Taken together, the results of this study show that the use of HSW in cosmetic formulations contributes to the efficacy of these products.

Solubility Study of Graphene-oxide with Various Solvents (산화그래핀(Graphene oxide)의 솔벤트(solvent)별 Solubility에 대한 연구)

  • Jung, Su-Yeon;Choi, Sung-Woong
    • Composites Research
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    • v.35 no.1
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    • pp.18-22
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    • 2022
  • Dispersion is one of the most important factors in the manufacture of composite materials. In the manufacture of composite materials, solvents are used to better disperse the reinforcement, nano-filler in the matrix. Since dispersion is affected with solvents, it is necessary to study which solvent is adopted to get good dispersion. In this study, the dispersion behavior and solubility of graphene oxide(GO) were examined under various solvents (DMF, NMP, ethylene glycol, Acetone, DI water) to identify dispersion. As a result of UV-Vis spectroscopy absorbance measurement, it was found that DMF and ethylene glycol had the best dispersibility, whereas DI water showed the lowest dispersibility. In addition, as a result of visually observing the dispersion according to the surface tension and time, it was found that the dispersibility was excellent in the order of DI water, ethylene glycol, NMP, DMF, and acetone, which was consistent with the Hansen solubility parameter value.

Life Experiences of Middle School Students from Broken Homes (결손가정 중학생의 생활경험)

  • Choe, Gee-Hyun;Chung, Yeon-Kang;Yeoum, Soon-Gyo
    • Journal of the Korean Society of School Health
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    • v.10 no.2
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    • pp.271-283
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    • 1997
  • This study is designed for the school health education, contributing experience of life from middle school students from broken homes by describing specifically what they go through. And on this basis this study works out a grounded theory on the experience of life for middle school students from broken homes. The data was collected through a series of interviews with nine subjects singled out at each stage of research. With the permission of the subjects, the interviews were recorded and transcribed. The interviews lasted from 30 minutes up to one hour and 20 minutes. The in-depth interviewing methods and observations was used for data collection. The data was analyzed in the framework of grounded theory as mapped out by Strauss & Corbin (1990). By analyzing the materials eighty-three concepts were extracted, and they were united into 21 subordinate categories through the course of analysis. These were classified into nine precedence categories. The core category was found to be the adaptation of 'Wichookdem" or "Shrinkage". "Shrinkage" widows experienced was showed as the results "Self-reliance" and "Overcoming" through the course of generation and reaction, confrontation, and adaptation. According to the analysis findings of materials, the central phenomenon was showed as "shrinkage", the causal condition as "surprise", "Darkness", "Grudge", "Desolate", "Empty". The veins as presence of those around people and existence of support, and the meditate situation as self-support. For the strategy in solving "shrinkage", preparations of countermeasure and self-reinforcement were showed. And self-reliance and overcoming were the results. Through the contrast to the cases of ground materials, relation statements as follows were induced; (1) The weaker the suffering is, the weaker the "shrinkage" tends to be. (2) The stronger the suffering is, the stronger the "shrinkage" tends to be. (3) The more frequent and serious the suffering, the stronger the "shrinkage" tend to be. (4) The more infrequent and not serious the suffering is, the weaker the "shrinkage" tends to be. (5) The weaker the "shrinkage" is, the more self-control1ed the responses tends to be. (6) The stronger the "shrinkage" is, the more impulsive the responses tends to be. (7) The more satisfying the support is, the more self-controlled the responses to the "shrinkage" tends to be. (8) The more dissatisfying the support is, the more impulsive the responses to the "shrinkage" tends to be. (9) The more concrete the type of support is, the more self-controlled the responses to the "shrinkage" tends to be. (10) The more superficial the type of support is, the more impulsive the responses to the "shrinkage" tends to be. (11) The more self-controlled the responses are, the more self-reliant the subjects tends to be. (12) The more impulsive the responses are, the more conflict and wandering the subjects tends to be. (13) Whether the responses to the "shrinkage" express themselves in self-control or an impulse, it will be resulted in the form of either tension or pain. The following two were confirmed on the basis of repetitive relations; (1) If a subject's suffering is weak, infrequent and not serious, the "shrinkage" is weak. Also the subject's support is highly satisfying, and the support type is concrete. The responses to the "shrinkage" result in self-control which consequence is self-reliance with part. of it resulting in tension and pain. (2) If a subject's suffering is strong, frequent and serious, the "shrinkage" is strong. Also the subject's support is dissatisfying, and the support type is superficial. The responses to the "shrinkage" result in an impulsion whose consequence is wandering with part of it resulting in tension and pain. Through the results in this study, the following is to be suggested; O This research is basically aimed at analyzing the experience of the middle school students living in broken homes, for the more inclusive approach, the study for them is made systematically according to the type of their problems.

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An Experimental Study on the Seismic Performance of Shear Connections and Rib Plate H Beam to Column Connections (전단접합 및 리브 플레이트로 보강한 H형 보-기둥 접합부의 내진성능에 관한 실험적 연구)

  • Oh, Kyung Hyun;Seo, Seong Yeon;Kim, Sung Yong;Yang, Young Sung;Kim, Kyu Suk
    • Journal of Korean Society of Steel Construction
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    • v.17 no.5 s.78
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    • pp.569-580
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    • 2005
  • The postbeam joint connection of the existing steel structure moment flexible frame system did not produce sufficient seismic resistance during the earthquakes in Northridge and Kobe, and it sustained brittle fracturing on the joint connection. This study was performed to execute the high-tensile bolt share connection of H-beams web and the full-scale experiment as a parameter of the existing reinforcement of H-flange rib, by making the shape of the existing joint connection. This experiment was performed to determine the extent of the decrease of the number of high-tensile bolts and how to improve workability of the two-phase shear connection of web beam. In addition, this study was performed to enhance the seismic resistant capacity through the enforcement of rib plates. As a result of the experiment of two-phase shear connection of H-beam web and of joint connection to be reinforced by rib plates, the results of this study showed that the initial stiffness, energy-dissipation capacity, and rotational capacity of plasticity was higher than the existing joint connection. As to the rate of increasing the strength and deformation capacity, there were differences between the tension side and compression side because of the position of shear tap. However, as a whole, they have shown excellent seismic resistant capacity. Also, all the test subjects exceeded 4% (rate of delamination), about 0.029 rad (total plastic capacity), and about 130% (maximum strength of joint connection) of fully plastic moment for the original section. Accordingly, this study was considered as it would be available in the design more than the intermediate-level of moment flexible frame.

Cyclic Loading Tests of Concrete-Filled Composite Beam-Column Connections with Hybrid Moment Connections (복합모멘트접합을 갖는 콘크리트 충전 보-기둥 합성접합부의 반복하중 실험)

  • Lim, Jong Jin;Kim, Dong Gwan;Lee, Sang Hyun;Lee, Chang Nam;Eom, Tae Sung
    • Journal of Korean Society of Steel Construction
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    • v.28 no.5
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    • pp.345-354
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    • 2016
  • In the present study, hybrid moment connections of welding and bar reinforcement for composite beam-column connections were proposed. Concrete-filled octagonal tube and U-section were used for the column and beam, respectively. In the beam-column connection, the top flange and web of the beam U-section were connected to the column plate by welding. However, to reduce stress concentration at the weld joints, the bottom flange of the beam was not welded to the column plate. Instead, to transfer the tension force of the beam flange, reinforcing bars passing through the column plate were used. Four exterior connections with conventional welded and hybrid moment connections were tested under cyclic loading and their cyclic behaviors were investigated. The test results showed that the hybrid moment connections successfully transferred the beam moment to the column. The strength and ductility of the hybrid moment connections were comparable to the conventional welded moment connection with exterior diaphragm; however, the connection performance was significantly affected by the details of the hybrid moment connection.

Failure Prediction for Weak Rock Slopes in a Large Open-pit Mine by GPS Measurements and Assessment of Landslide Susceptibility (대규모 노천광 연약암반 사면에서의 GPS 계측과 위험도평가에 의한 파괴예측)

  • SunWoo, Choon;Jung, Yong-Bok;Choi, Yo-Soon;Park, Hyeong-Dong
    • The Journal of Engineering Geology
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    • v.20 no.3
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    • pp.243-255
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    • 2010
  • The slope design of an open-pit mine must consider economical efficiency and stability. Thus, the overall slope angle is the principal factor because of limited support or reinforcement options available in such a setting. In this study, slope displacement, as monitored by a GPS system, was analyzed for a coal mine at Pasir, Indonesia. Predictions of failure time by inverse velocity analysis showed good agreement with field observations. Therefore, the failure time of an unstable slope can be roughly estimated prior to failure. A GIS model that combines fuzzy theory and the analytical hierarchy process (AHP) was developed to assess slope instability in open-pit coal mines. This model simultaneously considers seven factors that influence the instability of open-pit slopes (i.e., overall slope gradient, slope height, surface flows, excavation plan, tension cracks, faults, and water body). Application of the proposed method to an open-pit coal mine revealed an enhanced prediction accuracy of failure time and failure site compared with existing methods.

Evaluation of Flexural Strength of Wide Sleepers with Reinforcing Bars for Quick-Hardened Concrete Track (보강철근이 적용된 급속경화궤도용 광폭침목의 보유 휨 내력 평가)

  • Bae, Young-Hoon;Lee, Il-Wha
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.2
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    • pp.702-709
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    • 2018
  • A quick-hardened concrete track was developed to improve the aged ballasted track to a concrete track, and applied to earthworks and tunnels of main and urban railways. Rebars for reinforcement are not generally applied to prestressed concrete sleepers. On the other hand, many cracked sleepers have been observed in railroad sites. A wide sleeper, which is one of the main components of quick-hardened concrete track, should be structurally safe and crack-resistant in a ballasted and concrete track to avoid this problem. In particular, a wide sleeper manufactured by a post-tension method must have reinforcing bars applied to the rail-seat section. In this paper, static tests, dynamic tests, and fatigue tests were carried out to compare the flexural strength and crack resistance performance of a wide sleeper with and without reinforcing bars for a quick-hardened concrete track. As a result of the test, if some reinforcing bars are applied appropriately to the rail-seat section of a wide sleeper, it will be possible to prevent the occurrence of cracks, delay the expansion of the crack width, and the flexural fracture.

A Theoretical Study on the FRP Retrofit of Existing Circular Bridge Piers for Seismic Performance Enhancement (기존 원형교각의 내진성능 향상을 위한 FRP 보강에 대한 이론적 연구)

  • Kwon Tae-Gyu;Choi Young-Min;Hwang Yoon-Knok;Yoon Soon-Jong
    • Journal of the Korea Concrete Institute
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    • v.16 no.1 s.79
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    • pp.61-69
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    • 2004
  • The bridge piers under service suffered a brittle failure due to the deterioration of lap-spliced longitudinal reinforcement without developing its flexural capacity or ductility. The earthquake induced lateral force results in tension which causes bond-slip failure at the lap-spliced region in circular bridge piers. In this case, such a brittle failure can be controlled by the seismic retrofit using FRP laminated circular tube. The retrofitted piers using FRP laminated circular tube showed significant improvement in seismic performance due to FRP's confinement effect. This paper presents the analytical results on the seismic strengthening effect of circular bridge piers with poor lap-splice details and strengthened with FRP laminated circular tube. FRP's confinement effect is predicted by the classical elasticity solution for the laminated circular tube manufactured with several layers. The FRP laminated circular tube induces the flexural failure instead of a bond-slip failure of the circular reinforced concrete piers under seismic induced lateral forces. To investigate the correctness and effectiveness of analytical solution derived in this study, the analytical results were compared with the experimental data and it was confirmed that the results were correlated well each other, The effects on the confinement of FRP laminated circular tube, such as the number of layers, the fiber orientations, and the mechanical properties, were investigated. From the parametric study, it was found that the number of layers, the fiber orientations, and the major Young's modulus (E11) of the FRP laminated circular tube were the dominant parameters affecting the confinement of reinforced concrete circular bridge piers.