• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.268-271
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• 2004

A strengthening technique for reinforced concrete beams using external unhanded reinforcement offers advantages in speed and simplicity of installation over other, established, strengthening techniques. The purpose of this paper is to investigate the capabilities of a new retrofitting technique, namely external prestressing out cable, for flexural strengthening of beams. The paper provides a general description of structural behavior of beams strengthened using the technique. Results of four physical tests on strengthened reinforced concrete beams are reported and compared. It is shown that the technique can provide greater strength enhancement to lightly reinforced sections and that provision of deflectors enhances efficiency.

• Journal of the Korean Institute of Rural Architecture
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• v.7 no.1
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• pp.121-128
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• 2005

This experimental study was conducted to investigate beam strengthening of RC buildings with expended steel plate(ESP) in rural area. Nine test specimens were manufactured, whose variables were tensile steel ratio and the amount and the shape of expanded steel plate. The test results indicated that strengthened beams with ESP showed the improvement of flexural strength of 50%~90%, and the beam strengthening of U type was excellent for shear reinforcement as well as flexural reinforcement, more over, the honeycomb shape of ESP and anchor bolts for development of ESP were very effective.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.99-102
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• 2005

This paper presents test results on strengthening details of reinforced concrete beams strengthened with near-surface mounted(NSM) CFRP rod and strip. A total of 8 specimens have been tested. The specimens can be classified into the same strengthening area group and the different spacing group. For the same strengthening area group, experimental results revealed that specimens strengthened with NSM CFRP strips improved the flexural capacity of RC beams. For the different spacing group, the flexural capacity of RC beams was almost the same, but it was different in case of NSM CFRP rods.

• Journal of Ocean Engineering and Technology
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• v.14 no.1
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• pp.52-59
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• 2000

Flexural fracture characteristics of newly-developed Grid-type carbon fiber plastics in the deteriorated reinforced concrete structures were investigated by the four-points fracture test to verify the strengthening effects in the beam specimens. Results showed that initial cracks appeared in the boundary layers of fibers embedded in the newly-placed mortar concrete slowly progressed to the direction of supports and showed fracture of fiber plastics and brittle failure of concrete in compression in sequence after the yielding of steel reinforcement. Accordingly the reasonable area of Grid-type carbon-fiber plastics in the strengthening design of deteriorated RC structures should be limited and given based on the ultimate strength design method to avoid the brittle failure of concrete structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.223-230
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• 2003

The purpose of this research are to investigate experimentally flexural strengthening effects and flexural behaviour of RC beams strengthened by carbon fiber sheet(CFS) with/without superimposed pre-load. Test parameters of experiment are tension reinforcement ratio(0.85, 1.32, 1.91%) and pre-load(80% of yield capacity of unstrengthened beams). The structural behaviour of strengthened beams are compared with in terms of yield load and ultimate load, load-deflection relation, ductility, strengthened efficiency. From the test results, it were shown that ultimate capacity and flexural failure behaviour of RC beams strengthened by CFS changed by initial stresses between original beams and bonded CFS.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.787-790
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• 2000

This paper presents an experimental study on flexural behavior of structural member enlarged with epoxy mortar system. The main test variable is flexural tensile strength. A series of 4 test beams was tested to shoe the corresponding effect of each variables on maximum load capacity, load-deflection and moment-curvature relationship, interface behavior and failure mode. The results show that the flexural tensile strength of retrofitted materials have no relation load-deflection, but to load-strain, and failure mode.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.417-422
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• 2002

Strength and Durability of reinforced concrete exposed at deteriorated environment are decreased by cover spatting and corrosion of reinforcement. The purpose of this paper is to evaluate capacity of strengthening axial member using admixture-modified mortar. To investigate the capacity of strengthened axial member, behavior and strength of strengthening specimens were compared with a monolithic basic specimen. Admixture-modified mortar was prepared with silica fume, zeolite, polymer as cement modifier. From the result of this experiment, strengthening specimens using polymer-modified mortar have apparrent strengthening capacity because of good flexural strength and tensile strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.355-360
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• 1995

A series of 15 reinforced concrete beams was tested to evaluate the flexural performance of the repaired RC beams. the key parameters for this study were the repair materials, polymer/cementitious materials, in addition to the strengthening material, steel plates and carbon fiber sheets. The repaired specimens failed by a typical flexural mode. showing minor interface failure. The results show that epoxy, polyester resins and latex modified cementitous mortars are effective for repairing the concrete beams. However, the flexural preformance of the strengthened beams are varied depending on the repaired materal.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.183-190
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• 2006

From the result of this research above, it may be summed up as follows. As a summary of results from each experiment, as the test body reinforced with the carbon rods was embedded inside the concrete section and made it possible uniform movement, this study has shown that it had excellent characteristics in improving the flexural strength and ductility. Also, it was considered as the carbon-steel sheet composite plate was to exert the strength more if it would complement the adherence with the concrete.

• Structural Engineering and Mechanics
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• v.56 no.6
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• pp.899-916
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• 2015

Upgrading or strengthening of existing reinforced concrete (RC) infrastructure is an emerging demand nowadays. Near Surface Mounted (NSM) technique is very promising approach for flexural strengthening of RC members. However, premature failure such as concrete cover separation failure have been a main concern in utilizing this technique. In this study, U-wrap end anchorage with carbon fiber reinforced polymer (CFRP) fabrics is proposed to eliminate the concrete cover separation failure. Experimental programs were conducted to the consequence of U-wrap end anchorage on the flexurally strengthened RC beams with NSM-steel. A total of eight RC rectangular beam specimens were tested. One specimen was kept unstrengthened as a reference; three specimens were strengthened with NSM-steel bars and the remaining four specimens were strengthened with NSM-steel bars and U-wrap end anchorage using CFRP fabrics. A 3D non-linear finite element model (FEM) was developed to simulate the flexural response of the tested specimens. It is revealed that NSM-steel (with and without end-anchors) significantly improved the flexural strength; moreover decreased deflection and strains compared with reference specimen. Furthermore, NSM-steel with end anchorage strengthened specimens revealed the greater flexural strength and improve failure modes (premature to flexure) compared with the NSM-steel without end anchorage specimens. The results also ensured that the U-wrap end anchorage completely eliminate the concrete cover separation failure.