• Title/Summary/Keyword: 인발에너지

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Influence of Number of Twist on Tensile Behavior of High Performance Fiber Reinforced Cementitious Composites with Twisted Steel Fibers (비틀림 강섬유의 비틀림 횟수가 고성능 섬유보강 시멘트 복합재료의 인장거동에 미치는 영향)

  • Kim, Dong-Joo
    • Journal of the Korea Concrete Institute
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    • v.22 no.4
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    • pp.575-583
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    • 2010
  • This research investigated the influence of the number of twist on single fiber pullout behavior of Twisted steel (T-) fiber and tensile behavior of high performance cementitious composites reinforced with the (T-) fibers (HPFRCC). Micromechanical pullout model for T- fibers has been applied to analytically investigate the influence of various fiber parameters including the number of twist on single fiber pullout behavior; and, to optimize the number of twist to generate larger pullout energy during fiber pullout without fiber breakage. In addition, an experimental program including single fiber pullout and tensile tests has been performed to investigate the influence of twist ratio experimentally. Two types of T- fiber with different twisted ratios, T(L)- fiber (6ribs/30 mm) and T(H)- fiber (18ribs/30 mm), were tested. T(L)- fiber produced higher equivalent bond strength (larger pullout energy) although T(H)- fiber produced higher pullout stress during pullout since T(H)- fiber showed fiber breakage during pullout. Tensile test results confirmed that T(L)- fiber in high strength mortar generates better tensile performance of HPFRCC, e.g., load carrying capacity, strain capacity and multiple micro-cracking behavior.

Experimental study on pullout performance of structural fiber embedded in cement composites according to fineness modulus of fine aggregate (시멘트 복합체에 근입된 숏크리트용 구조 섬유의 잔골재 조립률에 따른 인발성능 비교)

  • Choi, Chang-Soon;Lee, Sang-Don;Song, Ki-Il
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.24 no.4
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    • pp.317-326
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    • 2022
  • This research performed single fiber pull-out test to evaluate the effect between fineness modulus of cement composites and the fiber bond performance (bond strength and pull-out energy). A synthetic fiber (polypropylene) and a steel fiber (hooked ends type) were inserted in the middle of dog bone shape specimens which were designed with fine aggregates of F. M. 1.96, 2.69, 3.43. The experiment results showed bond strength and pullout energy of synthetic fiber are improved as fineness modulus of cement composites increases. It is considered that the frictional resistance between synthetic fiber and cement composite increases as fineness modulus of cement composite increases and consume more energy while pull out the fiber from cement composite. However bond performance of steel fiber which resist pull out by mechanical behavior is less effected on fineness modulus of cement composite. It is considered that the mechanical fixedness of hooked ends exerts a greater effect on the pullout resistance than the frictional resistance between the cement composite and the steel fiber so F. M. of fine aggregate has a relatively small effect on the pullout resistance with the steel fiber.

Bond Strength of Steel Fiber Incorporated in Ultra High Performance Fiber-Reinforced Concrete (초고성능 섬유보강 콘크리트에 혼입된 강섬유의 부착강도 평가)

  • Kang, Su-Tae
    • Journal of the Korea Concrete Institute
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    • v.25 no.5
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    • pp.547-554
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    • 2013
  • This study was intended to estimate the bond strength of steel fiber in UHPFRC through pullout test. The pullout test was carried out with the double-sided pullout specimens with multiple fibers. First, the effect of fiber density on the bond strength was investigated, and the experimental result presented that the density range considered in this study was proved not to produce fiber-to-fiber interaction. The bond strength was estimated from several methods, which are based on the pullout load or energy at peak load, and the total energy absorbed until fibers are pulled out completely. the estimated bond strength obtained from the total energy was shown to be under the influence of the embedded length of fiber. the bond strengths obtained from peak load condition was 6.64 MPa in average, which had little difference compared to 6.46 MPa calculated by peak load only. Considering simplicity of test and analysis, it may be no matter to estimate the bond strength from peak load in pullout test.

Study on Pullout Behavior and Determination of Ultimate Uplift Capacity of Pile Driven in Small Pressured Chamber (소형 압력 토조내에 타입된 말뚝의 인발 거동과 극한 인발 지지력 결정에 관한 연구)

  • 최용규
    • Geotechnical Engineering
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    • v.11 no.2
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    • pp.19-28
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    • 1995
  • Based on the various test data acquired in the field, the large pressure chamber and the small pressure chamber, uplift behaviors and method of determining the ultimate uplift capacity of pile driven in small pressure chamber were studied. After uplift pile experienced 2 or 3 sudden slip due to increase of uplift load, complete pullout failure was occurred. Thus, it appears that the ultimate uplift capacity could be identified as the load at displacement where first slip occurs. The ultimate uplift capacity might be determined in every test and the disturbance after first uplift test could be recovered by adding one blow of the drop hammer, which had to depend on the model pile capacity.

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Pullout and Flexural Performance of Structural Synthetic Fibers by Geometry and Sectional Area Change (구조용 합성섬유의 형상 및 단면적 변호에 따른 부착 및 휨 성능)

  • Won, Jong-Pil;Back, Chul-Woo;Park, Chan-Gi;Han, Il-Yeong;Kim, Bang-Lae
    • Journal of the Korea Concrete Institute
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    • v.15 no.5
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    • pp.643-649
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    • 2003
  • The purpose of this study were evaluated to flexural and bond performance by sectional area and geometry change through bond and flexural test of a structural synthetic fiber. Six deformed structural synthetic fibers were investigated and pullout and flexural test was conducted. Included parameters is three different geometries of fiber and two of fiber sectional area. The test result shows that the cycles and amplitude of structural synthetic fiber increased, pullout load and pullout fracture energy decreased and flexural strength increased, if sectional area is same. The sectional area increased, pullout load and pullout fracture energy increased and flexural strength decreased, if cycles and amplitude of structural synthetic fiber is same. Based on test results, structural performance of the concrete could know that is influence by pullout performance of fiber as well as various factor (fiber number, material properties etc).

Preliminary Evaluation of Leachate Recirculation Anaerobic Digestion System to treat Source Separated Food Waste (침출수 순환형 음식물류 폐기물 혐기성 소화공법에 대한 초기 특성 파악)

  • Lee, Byonghi;Lee, Jeseung
    • Journal of the Korea Organic Resources Recycling Association
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    • v.21 no.4
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    • pp.50-61
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    • 2013
  • In order to generate a renewable energy-Methane, anaerobic systems fed with source separated food waste from university cafeteria were studied. At first, four reactors were evaluated with same feed components; content non-mixing anaerobic reactor without leachate withdrawal/recirculation, content mixing anaerobic reactor without leachate withdrawal/recirculation, content non-mixing anaerobic reactor with leachate withdrawal/recirculation and content mixing anaerobic reactor with leachate withdrawal/recirculation. From the first study, content non-mixing anaerobic reactor with leachate withdrawal/recirculation showed the highest gas production. From further study with this system, it was observed that leachate permeation rate within anaerobic reactor was very important factor for gas generation. The higher permeation rate, the more gas production was observed. It is assumed that 1kg of gas collector weight and C/N ration above 10 in food waste may cause gas consumption in the anaerobic reactor. The gas consumption was estimated by negative pressure build-up at gas collector. The negative pressure build-up must be explained to produce Methane from Food Waste.

Evaluation of Geogrid-Reinforced Track substructure Effectiveness Using A Large-Scale Pullout Device (대형인발시험기를 이용한 지오그리드로 보강된 궤도하부구조층의 효율성 평가)

  • Oh, Jeongho
    • Journal of the Society of Disaster Information
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    • v.10 no.1
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    • pp.40-48
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    • 2014
  • A number of attempts has been made to reinforce ballasted track substructure to meet the requirement of high-speed operation and effective rehabilitation of existing railroads. For the purpose of this, the use of geogrid has been applied, and the benefit of its use has been recognized via previous studies. In this study, an experimental pullout test was carried out to investigate the influence of normal stress on pullout strength of geogrid using different types of soil and geogrid. The results revealed that the pullout resistance generally tends to increase proportional to normal stress while the pullout coefficient interaction decreases, which is a function of material interface properties, such as the friction angle of soil, and interlocking condition between soil and geogrid. In addition, a methodology based on work-energy concept was proposed to evaluate effectiveness of geogrid and limitedly verified using test results.

Optimum Geometry Factor of Structural Synthetic Fibers (구조용 합성섬유의 최적형상함수 결정)

  • 원종필;임동휘;박찬기;한일영;김방래
    • Journal of the Korea Concrete Institute
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    • v.14 no.4
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    • pp.474-482
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    • 2002
  • The purpose of the study is to establish an optimum geometry and optimum geometry factor through bond test of a structural synthetic fiber, which fully utilizes matrix anchoring without fiber fracturing with the maximum pullout resistance. Seven deformed structural synthetic fibers with widely different geometries were investigated and pullout test was conducted. Included parameters are seven different types of fiber and two of mortar matrixes. The test result shows that the crimped type structural synthetic fiber is significant improvement in the interface toughness(pullout energy) and pullout load. The pullout test was performed with various size of crimped type structural synthetic fiber in order to invest optimum geometry factor, In the basis of the test results, optimum geometry factor is established such as D=b$^{{\alpha}0{\alpha}}$h$^{λ{\beta}}$.

Expansion Ratio and Ultimate Load of Pulse-Discharge Bulbed Anchors (펄스방전 그라운드 앵커의 확공특성 및 극한인발력에 관한 연구)

  • Kim, Nak-Kyung;Kim, Sung-Kyu;Joo, Yong-Sun;Seo, Hyo-Kyun;Kim, Sun-Ju
    • Journal of the Korean Geotechnical Society
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    • v.25 no.7
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    • pp.5-10
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    • 2009
  • The ground anchor is not usually used in soft clay and loose sand, because the pullout resistance of anchors can not be guaranteed. However, there is a method to increase the capacity of anchors using electric discharge geotechnical technologies, which are also known as pulse discharge and electric-spark technologies. The pulse-discharge anchor has a bulbed (or underreamed) bond length that is expanded by high voltage electrokinetic pulse energy. 24 anchors were installed in the weathered soil and sandy clay at the Geotechnical Experimentation Site at Sungkyunkwan University in Suwon, Korea. In this study, in order to define a relation between expansion rate of the anchor diameter and ultimate load, anchor load tests were carried out in accordance with testing procedures by AASHTO (AASHTO 1990) and FHWA (Weatheb 1998). And then several anchors were exhumed to measure the diameter of the pulse discharge anchors.

Chip-Tool Friction and Shear Characteristics of Cold Drawn Free Machining Steels in Turning (냉각인발된 쾌삭강의 외경선삭시 칩-공구 마찰 및 전단 특성)

  • Lee, Young-Moon;Cho, Sam-Kyu;Choi, Soo-Joon;Song, Tae-Seong;Park, Tae-Joon
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.12
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    • pp.198-203
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    • 1999
  • In this study, chip-tool friction and shear characteristics of cold drawn free machining steels in turning were assessed. To do this, a newly developed equivalent oblique cutting model was adopted. And for comparison with those of free machining steels, chip-tool friction and shear characteristics of conventional carbon steels were also investigated. The Pb-S free machining steel shows superior machinability to others. In case of the Bi-S free machining steel, the shear stress and the specific friction energy are relatively lower than those of conventional carbon steels, but its shear strain is relatively high, so it does not show any remarkable improvement of machinability.

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