• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.230-231
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• 2013

A fire outbreak in a reinforcement concrete structure looses the organism by different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So, concrete reinforcement structure is damaged partial or whole structure system. Therefore accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. In this study, consider case of investigation methods and repair work in fire damaged structure concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.16-18
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• 2013

A fire outbreak in a reinforcement concrete structure looses the organism by different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So, concrete reinforcement structure is damaged partial or whole structure system. Therefore accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. In this study, consider case of investigation methods and repair work in fire damaged structure concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.153-161
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• 2010

Numerous past studies have shown that safety and serviceability of many concrete infrastructures and buildings built in 1970's have far less strength capacities than their original intended design capacities, thereby requiring repair and strengthening. Currently, aged concrete structures are being repaired using various methods developed in the past. Unfortunately, these methods do not consider the specific conditions that these members are under, but they merely attach repairing materials on the external surface for random strength improvements. Therefore, in order to improve repair and strengthening methods by considering composite behavior between repairing material and structural member, enhanced construction methodologies are needed. Also, the enhanced repairing and strengthening methods must be able to be implemented on structural members constructed using high performance concrete to meet the present construction demand of building mammoth structures. Therefore, in this study, a repairing and strengthening method for retrofitting high strength concrete (HSC) columns that can effectively improve column performance is developed. A square HSC column's cross-sectional shape is converted to an octagonal shape by attaching precast members on the surface of the column. Then, the octagonal column surface is surface wrapped using Carbon Fiber Sheets (CFS). The method allows maximum usage of confinement effect from externally jacketing CFS to improve strength and ductility of repaired HSC columns. The research results are discussed in detail.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.1
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• pp.40-46
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• 2013

This paper presents the design, fabrication and performance of a reinforced concrete beam strengthened by GFRP box plate and its possibility for structural rehabilitations. The load capacity, ductility and failure mode of reinforced concrete structures strengthened by FRP box plate were investigated and compared with traditional FRP plate strengthening method. This is intended to assess the feasibility of using FRP box plate for repair and strengthening of damaged RC beams. A series of four-point bending tests were conducted on RC beams with or without strengthening FRP systems the influence of concrete cover thickness on the performance of overall stiffness of the structure. The parameters obtained by the experimental studies were the stiffness, strength, crack width and pattern, failure mode, respectively. The test yielded complete load-deflection curves from which the increase in load capacity and the failure mode was evaluated.

• Smart Structures and Systems
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• v.5 no.4
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• pp.443-455
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• 2009

The use of fiber reinforced polymer (FRP) reinforcement in concrete structures has been on the rise due to its advantages over conventional steel reinforcement such as corrosion. Reinforcing steel corrosion has been the primary cause of deterioration of reinforced concrete (RC) structures, resulting in tremendous annual repair costs. One application of FRP reinforcement to be further explored is its use in RC frames. Nonetheless, due to FRP's inherently elastic behavior, FRP-reinforced (FRP-RC) members exhibit low ductility and energy dissipation as well as different damage mechanisms. Furthermore, current design standards for FRP-RC structures do not address seismic design in which the beam-column joint is a key issue. During an earthquake, the safety of beam-column joints is essential to the whole structure integrity. Thus, research is needed to gain better understanding of the behavior of FRP-RC structures and their damage mechanisms under seismic loading. In this study, two full-scale beam-column joint specimens reinforced with steel and GFRP configurations were tested under quasi-static loading. The control steel-reinforced specimen was detailed according to current design code provisions. The GFRP-RC specimen was detailed in a similar scheme. The damage in the two specimens is characterized to compare their performance under simulated seismic loading.

• Structural Engineering and Mechanics
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• v.26 no.4
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• pp.427-439
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• 2007

The exploitation of fibre reinforced polymer composites, as external reinforcement is an evergreen and well-known technique for improving the structural performance of reinforced concrete structures. The demand to use FRP composites in the civil engineering industry is mainly due to its high strength, light weight, and stiffness. This paper exemplifies the shear strength of partially precracked reinforced concrete rectangular beams repaired with externally bonded Bi-Directional Carbon Fibre Reinforced Polymer (CFRP) Fabrics strips. All specimens were cast in the laboratory environment without any internal shear reinforcement. The test parameters were longitudinal tensile reinforcement, shear span to effective depth ratio, spacing of CFRP strips, and orientation of CFRP reinforcement. It mainly focuses on the shear capacity and modes of failure of the CFRP strengthened shear beams. Results have shown that the CFRP repaired beams attained a shear enhancement of 32% and 107.64% greater than the control beams. This study underscores that the CFRP strip technique significantly enhanced the shear capacity of precracked reinforced concrete rectangular beams without any internal shear reinforcement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.127-128
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• 2017

Tests are conducted according to the ISO TS 16774, Part 3 standard for quality management of leakage repair materials used in cracks in underground concrete structures. These test methods are performed indirectly using a nonwoven fabric on a chalet containing leak repair materials. However, it is considered that it is appropriate to verify the resistance of the repair material, which is required to be applied directly to the cracks in the actual field and to exhibit the resistance of the flow velocity. In this study, mass change was measured by using nonwoven fabric and nonwoven fabric. As a result, both methods showed an increase in mass, which indicated that the maintenance material itself contained a large amount of water, and that the mass change occurred depending on the drying state. Also, depending on the use of nonwoven fabric, the error due to the indirect test could not be ruled out. Therefore, further verification is needed, and it is considered that the test for change of mass reduction measurement is necessary according to the drying time of other types of the same series.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.219-223
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• 1995

Since the mid of 1970's, the construction of infrastructure has been booming and accelerating to keep up with rapid economic growth. Fast achievement of most construction activities has caused unfavorable effects of civil petitions associated with damages and nuisances due to last hasty works. it is well known that the falling down of Sungsoo bridge and the collapse of Sampoong department and other structures have occurred because of the construction not conforming with the specification, and thereby incurred enormous loss of life and property. Now a days. a periodic inspection and maintenance have been strongly interested on aged RC structures, of repair and reinforcement technique in the country, most repairing and reinforcing works have been performed on the basis of the guidance of few experienced local company in this field.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.145-146
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• 2020

This study investigated the performance evaluation of polymer cement mortar for repairing concrete structures using calcium nitrite(Ca(NO₂)₂) and CO₂ nano-bubble mixing water to develop section-restoration methods for the repair and reinforcement of cracks. The evaluation items were strength and microstructure analysis at 28 days of age according to the change in the amount of calcium nitrite and the use of CO₂ nano-bubble water. As a result of the experiment, it was confirmed that the performance of polymer cement mortar for repairing concrete structures was improved by the generation of nitrite-based hydration products when calcium nitrite and CO₂ nano-bubble water were used.

• Structural Engineering and Mechanics
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• v.17 no.3_4
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• pp.347-356
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• 2004

In order to extend the lifetime of buildings and civil infrastructure, patch type fibrous composite retrofitting materials are widely used. Retrofitted concrete columns and beams gain stiffness and strength, but lose toughness and show brittle failure. Usually, the cracks in concrete structures are visible to the naked eye and the status of the structure in the life cycle is estimated through visual inspections. After retrofitting of the structure, crack visibility is blocked by retrofitted composite materials. Therefore, structural monitoring after retrofitting is indispensable and self diagnosis method with optical fiber sensors is very useful. In this paper, we try to detect the peel out effect and find the strain difference between the main structure and retrofitting patch material when they separate from each other. In the experiment, two fiber optic Bragg grating sensors are applied to the main concrete structure and the patching material separately at the same position. The sensors show coincident behaviors at the initial loading, but different behaviors after a certain load. The test results show the possibility of optical fiber sensor monitoring of beam structures retrofitted by the composite patches.