• Title/Summary/Keyword: 체적변형률

Search Result 112, Processing Time 0.022 seconds

Axial Behavior of Concrete Cylinders Confined with FRP Wires (FRP 와이어 보강 콘크리트 공시체의 압축거동)

  • Cho, Baiksoon;Lee, Jong-Han;Choi, Eunsoo
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.33 no.5
    • /
    • pp.1765-1775
    • /
    • 2013
  • The application of FRP wire as a mean of improving strength and ductility capacity of concrete cylinders under axial compressive load through confinement is investigated experimentally in this study. An experimental investigation involves axial compressive test of three confining amounts of FRP wire and three concrete compressive strengths. The effectiveness of FRP wire confinement on the concrete microstructure were examined by evaluating the internal concrete damage using axial, circumferential, and volumetric strains. The axial stress-strain relations of FRP wire confined concrete showed bilinear behavior with transition region. It showed strain-hardening behavior in the post-cracking region. The load carrying capacity was linearly increased with increasing of the amount of FRP wire. The ultimate strength of the 35 MPa specimen confined with 3 layer of FRP wire was increased by 286% compared to control one. When the concrete were effectively confined with FRP wire, horizontal cracks were formed by shearing. It was developed from sudden expansion of the concrete due to confinement ruptures at one side while the FRP wire was still working in hindering expansion of concrete at the other side of the crack. The FRP wire failure strains obtained from FRP wire confined concrete tests were 55~90%, average 69.5%, of the FRP wire ultimate uniaxial tensile strain. It was as high as any other FRP confined method. The magnitude of FRP wire failure strain was related to the FRP wire effectiveness.

Axial Behavior of Reinforced Concrete Columns Externally Strengthened with Unbonded Wire Rope and T-Shaped Steel Plate (와이어로프와 T 강판으로 비부착 보강된 철근콘크리트 기둥의 중심 축하중 거동)

  • Yang, Keun-Hyeok;Sim, Jae-Il;Byun, Hang-Yong
    • Journal of the Korea Concrete Institute
    • /
    • v.20 no.2
    • /
    • pp.221-229
    • /
    • 2008
  • An improved unbonded-type column strengthening procedure using wire rope and T-shaped steel plate units was proposed. Eight strengthened columns and an unstrengthened control column were tested under concentric axial load. The main variables considered were the volume ratio of wire rope and the flange width and configuration of T-shaped steel plates. Axial load capacity and ductility ratio of columns tested were compared with predictions obtained from the equation specified in ACI 318-05 and those of conventionally tied columns tested by Chung et al., respectively. In addition, a mathematical model was proposed to evaluate the complete stress-strain relationship of concrete confined by the wire rope and T-plate units. Test results showed that the axial load capacity and ductility of columns increased with the increase of the volume ratio of wire rope and the flange width of T-plates. In particular, at the same lateral reinforcement index, a much higher ductility ratio was observed in the strengthened columns having the volume ratio of wire rope above 0.0039 than in the tied columns. A mathematical model for the stress-strain relationship of confined concrete using the proposed strengthening procedure is developed. The predicted stress-strain curves were in good agreement with test results.

Axial Load Behavior of Concrete Cylinders Confined with Fiber-Sheet and Steel-Plate Composites Plate (FSP) (섬유-강판 복합플레이트로 보강된 콘크리트 압축부재의 압축성능)

  • Cho, Baik-Soon;Choi, Eunsoo;Chung, Young-Soo;Kim, Yeon-Wook
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.31 no.4A
    • /
    • pp.331-340
    • /
    • 2011
  • The application of newly developed fiber-sheet and steel-plate composite plate (FSP) as a means of improving strength and ductility capacity of concrete cylinders under axial compression load through confinement is investigated experimentally in this study. An experimental investigation involves axial load tests of two types of FSP strengthening material, two anchoring methods, and three concrete strengths. The FSP-confined cylinder tests showed that FSP provided a substantial gain in compressive strength and deformability. The performance of FRP-confined cylinders was influenced by type of the FSP strengthening material, the anchoring method, and concrete compressive strength. The FSP failure strains obtained from FSP-confined cylinder tests were higher than those from FRP-confined cylinder tests. The magnitude of FSP failure strain was related to the FSP composite effectiveness. The effects of FSP confinement on the concrete microstructure were examined by evaluating the internal concrete damage using axial, radial, and volumetric strains. From the observations obtained in this investigation, it is believed that FSP is one of the best solutions for the confinement of concrete compressive members.

Recompression Properties of Sand in Post-Liquefaction Process According to Relative Density and Cyclic Loading History (상대밀도와 반복전단이력의 차이에 의한 모래의 액상화 후 재압축 특성)

  • Kwon, Youngcheul
    • Journal of the Korean GEO-environmental Society
    • /
    • v.13 no.1
    • /
    • pp.21-29
    • /
    • 2012
  • Ground failure by liquefaction can occur not only during shaking but also as the result of the post-liquefaction process after an earthquake. During the process of ground deformation and failure, excess pore water pressure in soil is redistributed, which can then lead to changes in the effective stress of soils. Therefore, in order to provide a further understanding of the phenomenon, we have to estimate the properties of effective stress during the recompression process in post-liquefaction as well, not only the total amount of pore water drained. The primary objectives of this study are to determine and compare the recompression properties in the post-liquefaction process in terms of the relationship between volumetric strains and mean effective stresses under the various conditions of relative density and shear stress history. In all experimental cases, the volumetric strains increase greatly in the low effective stress level, almost to the zero zone, and granite soil, which has fine grains, undergoes gradual changes in the relationship between volumetric strains and mean effective stresses compared with fine sand. And, we can also find that recompression properties in the post-liquefaction process by cyclic loading depend highly on the dissipation energy and maximum shear strain, and this fact can be obtained in all cases regardless of the existence of fine content, relative density, and loading history. Especially, granite soil having fine grains can be defined uniformly in the relationship between dissipation energy and maximum volumetric strain, while fine sand cannot be so uniformly defined.

An Anisotropic Hardening Constitutive Model for Dilatancy of Cohesionless Soils : I. Formulation (사질토의 체적팽창을 고려한 비등방경화 구성모델 : I. 정식화)

  • 오세붕;박현일;권오균
    • Journal of the Korean Geotechnical Society
    • /
    • v.20 no.6
    • /
    • pp.75-83
    • /
    • 2004
  • This study is focused on the constitutive model in order to represent brittleness and dilatancy of cohesionless soils. The constitutive model was proposed on the basis of an anisotropic hardening rule with generalized isotropic hardening rule. The shape of yield surface is a simple cylinder type in stress space and it makes the model practically useful. Flow rule was approximated by a concrete function on dilatancy. A peak stress ratio was defined to model brittle stress-strain relationships. The proposed model was formulated and implemented to calculate the stress-strain relationship from triaxial tests. In the companion paper the proposed model will be verified by comparison with the triaxial test results.

A Study on the Sample Characteristics Obtained from Large Diameter Sampler and Piston Sampler (피스톤 샘플러와 대구경 샘플러로 채취한 시료의 특성에 관한 연구)

  • Kim, Young-Chin;Kang, Jae-Mo
    • Journal of the Korean GEO-environmental Society
    • /
    • v.6 no.3
    • /
    • pp.5-15
    • /
    • 2005
  • A large diameter sampler that can take undisturbed samples from soft ground was developed by KICT. In order to compare the quality of samples taken by the sampler with those of the traditional piston sampler, a series of laboratory tests were performed. Samples were taken at different sites such as Incheon, Gimhae, Yangsan and Busan. The results showed that the values of unconfined compression strength, secant modulus, pre-consolidation pressure, undrained shear strength, and shear modulus exhibited higher in samples taken by the large scale sampler. Strains at shear failure and volumetric strains were low for the new sampler. It was proved from the comparison that better quality samples could be obtained by the KICT sampler.

  • PDF

A Study on the Effect of Transportation and Storage on Sample Disturbance (시료의 이동과 보관이 시료 교란에 미치는 영향에 관한 연구)

  • Kim, Byoung-Il;Lee, Seung-Hyun;Yoo, Wan-Kyu
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.8 no.5
    • /
    • pp.1159-1165
    • /
    • 2007
  • This study aims to determine the effects of sample movement and storage on sample disturbance. To this end, non-disturbed samples collected from the OOregion, Gwangyang City, Jeonranam-do. Then, unconfined compression and consolidation tests were performed on the samples in the field, Seoul Lab and Seoul Lab after 4 weeks. Based on failure strain rate$(\epsilon_f)$, volume strain rate$(\epsilon_{\nu})$, and void ratio change$({\Delta}e/e_0)$ obtained from the test results, sample disturbance was evaluated. The sample disturbance level was used to compare and analyze the influences of transportation and storage on sample disturbance.

  • PDF

Stress-Strain Behavior and Electrical Resistive of Conductive Silver Particle/Silicone Composite Pastes with Surface Modification (표면처리에 따른 도전성 은입자/실리콘 복합 페이스트의 응력-변형율 거동 및 전기비저항 특성)

  • 이건웅;방대석;박민;조동환
    • Composites Research
    • /
    • v.17 no.5
    • /
    • pp.61-67
    • /
    • 2004
  • This paper reports the electrical conductivity and the stress-strain behavior of silver particle-filled silicone composite pastes for electromagnetic interference (EMI) shielding gasket materials. The percolation threshold (critical concentration) of the composite paste obtained by incorporating irregular sphere-shaped silver particles and room temperature vulcanizing (RTV) silicone resin was determined from the electrical conductivity result. At about 28 vol% Beading of untreated silver particles, the percolation phenomenon occurred and at this critical concentration, the volumetric resistivity, the tensile strength, and the elongation of the pastes were investigated. This work also suggests that the stress-strain characteristics of a composite paste filled with metal particles above the percolation threshold may be effectively improved by properly selecting a coupling agent.

Characteristics of Shear Behavior of Remolded Nak-dong River Sandy Silt (재성형된 낙동강 모래질 실트의 전단거동 특성)

  • Kim Young-Su;Tint Khin Swe;Kim Dae-Man
    • Journal of the Korean Geotechnical Society
    • /
    • v.23 no.3
    • /
    • pp.41-50
    • /
    • 2007
  • The results from normally consolidated isotropic drained and undrained triaxial compression tests (NCIU and NCID) on sand with high silt content were presented in this paper. The experiments were performed on specimens of Nak-dong River sand with 63% silt content under effective confined pressures, 100 kPa to 400 kPa. From test results, Sandy silt became initially compressive but eventually appeared to provide dilatancy response throughout the entire stress-strain curve The behavior of sandy silt was more difficult to characterize than that of clay and sand due to lower plastic characteristic. Especially, the samples exhibited dilatancy development during shear after failure. The shear behavior and shear strength parameters of sandy silt can be determined as stress-strain behaviors are described by the Mohr-Coulomb failure criterion. The shear behaviors were observed increasing dilatancy volume change tendency with strain-softening tendency after failure. In this paper, the behavior of dilatancy depends on not only sand content but also fine content with low-cohesion during shear in the samples of sandy silt.

A Study on Strain-Void Growth Mechanism of Dual Phase Steel by Statistical Method (통계적 방법을 이용한 복합조직강의 변형률과 보이드 성장거동에 관한 연구)

  • 오경훈;유용석;오택열
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2000.11a
    • /
    • pp.533-538
    • /
    • 2000
  • Ductile fracture of dual phase steel begins with void nucleation, at martensite-ferrite interface of deformed martensite particle. In this study, void nucleation, growth, and coalescence under various strain were studied in dual phase steel. Therefore, by means of the heat treatment of low carbon steel, the study deals with void nucleation and growth for ferrite grain size and martensite volume fraction of dual phase steel using statistical method. Void nucleation and growth with increasing strain are shown depend upon the ferrite grain size. Voids volume fraction generally increase as ferrite grain size decease.

  • PDF