• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1765-1775
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• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.331-340
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• 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.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.675-681
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• 2008

This study introduced a new steel-jacketing method to retrofit RC columns. It also estimated the performance of steel-jacketed concrete cylinders. Twelve concrete cylinders were fabricated with varying steel jacket thicknesses of 1.0, 1.5, and 2.0 mm. Lateral confining pressure was applied with three clamps and the performance of plain concrete cylinders was compared with that of steel-jacketed cylinders. Steel jacket proved to be effective in increasing the strength of the cylinder. Finally, Li's constitutive model was compared with that of the experimentalresults. However, Li's model showed incongruity in Region II, which indicates the region after the yield of steel jackets. Therefore, the modified value of n was used for the region and the model showed a good agreement.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.39.1-39.1
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• 2010

본 연구에서는 정하중 및 충격하중 하에서 FRP(fiber reinforced polymer) sheet의 보강 성능을 평가하기 위해 섬유와 레진의 종류, sheet 종류, 보강 방법에 따른 휨 실험을 실시하였다. 이를 위해 GFRP와 CFRP, AFRP sheets로 보강된 $100{\times}100{\times}400mm$ 각주형 콘크리트 공시체의 하면 보강, 중앙 U형 스트립, 그라고 이 둘을 동시에 보강한 시험체를 제작하였고, 정하중 휨 실험과 낙하식 충격하중 실험을 실시하였다. 정하중 실험에서 중앙부 U형 스트립으로 보강한 시험체는 섬유의 방향과 균열의 진전 방향이 일치하여 보강효과가 거의 없었지만 CFRP와 AFRP로 하면 및 이중 보강한 시험체는 높은 휨성능을 보였다. 반면 충격하중 실험에서는 중앙부 U형 스트립 보강이 다소 성능을 향상 시켰고, 하면 및 이중 보강한 시험체는 큰 변형과 높은 에너지 소산 능력을 보였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.5
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• pp.287-297
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• 2022

This paper presents experimental and analytical studies on the lateral cyclic behavior of RC columns actively confined with iron-based shape memory alloy (Fe-SMA) strips. Based on the Anexperimental study, we investigated the effectiveness of active confinement through compression testings of concrete cylinders confined by Fe SMA strips and carbon fiber-reinforced polymer (CFRP) sheets. The test results showed that the specimens confined with Fe SMA strips significantly increased the deformation capacity of the concrete, even under lower confining pressures, compared to those specimensconfined with CFRP sheets. The experimental results were used to develop finite-element models of RC columns confined with Fe SMA or CFRP in their plastic-hinge region. After validating the proposed analytical model through comparison with the results from a previous RC column test, a series of lateral cyclic load analyses were carried out for the RC columns confined with Fe SMA and CFRP. The analytical results revealed that the lateral cyclic behavior of the Fe SMA-confined column was greatly enhanced in terms of deformation and energy dissipation capacities compared with tothat of the as-built and CFRP-confined columns.

• Magazine of the Korea Concrete Institute
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• v.5 no.3
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• pp.125-132
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• 1993

콘크리트의 인성개선을 위하여 횡보강근을 사용할 수 있으나 보통강도으 철근ㅇ르 사용하였을 경우에는 조속한 철근의 강상으로 인한 콘크리트으 인성개선효과가 급격히 떨어지기 때문에 고강도 횡보강도에 의한 압축인성 개선효과를 이론 및 실험으로 고찰하였다. 실험결과 각 공시체의 변형능력을 비교해 보면 보통강도근의 경우 콘크리트 응력블록계수가 최대일 때 콘크리트의 압축단 변형도가 1%내외인데 비하여 고강도근으로 횡보강하였을 경우가 콘크리트의 압축변형도는 2%로서 충분한 휨압축 인성개선용으로 콘크리트의 충분한 인성개선이 가능하다고 볼 수 있다.

• Journal of the Society of Disaster Information
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• v.19 no.1
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• pp.138-145
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• 2023

Purpose: In accordance with the increase in the number of buildings repaired and reinforced following deterioration from when a fire occurs in a previously reinforced building, the impact on the structure after the fire is analyzed to establish standards for repair and reinforcement measures. Method: After curing for 28 days, the process was to measure the compressive strength and induce destruction through a compressor, repair and reinforce it with epoxy, and conduct a re-compressive strength test on some specimens after curing for 3 days to understand the degree of strength restoration. The rest of the repaired and reinforced specimens as well as the unrepaired and unreinforced specimens were then put into an oven and heated according to the temporal and temperate conditions listed below, and then the compressive strength was tested to estimate the impact of fire. Result: After reinforcing the yielded specimen with epoxy, the process was to then put it in an oven and heat it at different temperatures over time. It was found that there was a decrease in the strength of the reinforcement more than that of the actual specimen. Conclusion: Based on this, it was found that a building repaired and reinforced with epoxy resin is actually more dangerous than a general unrepaired building when it is damaged by fire, and thus, that it must be prepared for fire vulnerabilities.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.36-41
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• 2011

This study proposes a experimental method to evaluate bonding strength of FRPs used for retrofitting concrete structures. Specimens are designed so that debonding failure of FRPs can be induced from reinforced concrete beams retrofitted with two layers of carbon and glass FRPs. And three-point loading tests are performed to see if debonding failure with proper debonding strength is observed from the specimens. The test results show that the tested beams are failed due to debonding of FRPs, therefore, the proposed test method is capable of evaluating debonding strength of FRPs using relatively small normal strength concrete beams.

• International Journal of Highway Engineering
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• v.2 no.4 s.6
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• pp.101-109
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• 2000

This study was performed to estimate fatigue life of polymer-modified and reinforced overlay asphalt mixtures with respect to reflection cracking in asphalt overlay pavement. In order to achieve the goal, the expedited reflection cracking test method was developed and applied to various mixtures and the results were compared one another with respect to the resistant characteristics of reflection cracking. The theoretical prediction equation of fatigue life for each mixture was suggested based on statistical analysis of experimental test results in the flexural failure mode. Since coefficients of correlation between estimated values and measured values were very high ($r^2=0.95$ or higher), the prediction model can be used for relative comparison of various pavement overlay choices to be used in the field.

• Magazine of the Korea Concrete Institute
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• v.2 no.3
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• pp.65-72
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• 1990

Theoretical expressions were dcrived for the numher of fibers per unit cross-sectional area in fiber reinforced concrete, with due consideration given to the effects of the surrounding boundaries. The number of fibers per unit cross-sectional area in steel fiber reinforced concrete was also measured experimentally for the specimens incorporating various volume fractions of fibers of different types. Statistical evaluation of the measured value was then performed in order to assess the differences in fiber concentration at different location on tbe cross section. Degree of reorientation of steel fibers in concrete occuring during vibration was examined by com¬paring the differences in the computed and measur'ed values of the number of fibers per unit cross-sectional area.