• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.225-231
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• 2007

In the recent construction industry, FRP is highly interesting in strengthening members of structures because it has superior material properties. This paper is an experimental study on the structural behavior of reinforced concrete beam when in using various amount of CFRP and the ductility of beams using various type of CFRP. In the experiment, when it makes an experiment using various amount of CFRP, strengthening width is more efficient than strengthening layer. The failure of CFRP strengthened beams presented brittle modes with having flexural failures. Also, It represented that most of beams classify brittle failure in the side of energy ratio. Energy ratio of CFRP sheet comparing with CFRP plate exceeds overall 50% and it represents about 70% in case of beams without strengthening layer.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1003-1008
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• 2001

It is recently reported that bond failure can be initiated in the region where maximum bending moment and shear force is acted by accompanying shear deformation after flexural crack in full-scale RC beams strengthened by CFRP. Such a shear deformation effect causing bond failure is relatively little in the case of small-scale specimens. So, additional reinforcing details to the critical beam section where maximum moment and shear were acted is required to prevent the bond failure caused by the shear deformations. The U-type wrapping methods by CFRP to the critical beam section is proposed and tested in this paper. Also, the applicability of design bond strength derived from the tests of small-scale beam was investigated by the full-scale RC beam strengthened by CFRP.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.100-103
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• 2004

Bridges are deteriorating over service life due to over weight vehicles, environmental conditions and so on. In addition to that, those could be classified into low level bridges which are not fit for highway because of upgrade of the design load. Consequently, such reasons impel the bridges to be repaired or strengthened. Among the rehabilitating methods, FRP sheets and externally prestressing methods are preferred recently. This paper presents experimental results about the behavior of PSC beams strengthened by external tendons and CFRP sheets.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.535-544
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• 2016

This paper aims at examining the effects of sustained load and elevated temperature on the time-dependent deformation of a carbon fiber reinforced polymer (CFRP) sheets bonded to concrete as well as the pull-off strength of single-lap shear specimens after the sustained loading period using digital images. Elevated temperature during the sustained loading period resulted in increased slip of the CFRP composites, whereas increased curing time of the polymer resin prior to the sustained loading period resulted in reduced slip. Pull-off tests conducted after sustained loading period showed that the presence of sustained load resulted in increased pull-off strength and interfacial fracture energy. This beneficial effect decreased with increased creep duration. Based on analysis of digital images, results on strain distributions and fracture surfaces indicated that stress relaxation of the epoxy occurred in the 30 mm closest to the loaded end of the CFRP composites during sustained loading, which increased the pull-off strength provided the failure locus remained mostly in the concrete. For longer sustained loading duration, the failure mode of concrete-CFRP bond region can change from a cohesive failure in the concrete to an interfacial failure along the concrete/epoxy interface, which diminished part of the strength increase due to the stress relaxation of the adhesive.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.450-455
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• 1997

In recent years the research and development about the new material proceeds rapidly and actively in building industry. We are concerned with high-strength concrete as a new material. As the building structure becomes bigger, higher and more specialized, so does the demand of material and member with high strength for building expands greatly. In the future, we will quite need to research repair and rehabilitation to make high strength concrete structural building for our safe. So, I did an study on carbon fiber sheet rehabilitation(CFSR) of reinforced high strength concrete beams. The carbon fiber reinforced plastic(CFRP) bonding method is widely used for reinforcing the existing concrete structure among the various methods. The test results indicate that CFS is very effective for strengthening the damaged beams and controlling deflections of the repaired beams. When carbon fiber sheet rehabilitation of reinforced high strength concrete beams happened diagonal crack, the increase in the number of CFS layer didn't effect the increase in strength of beams. Also, by changing the CFS stick position gave diversified ultimate load in CFSR beams.