• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.866-873
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• 2000

Reinforced concrete structure can be strengthened by glass fiber reinforced plastic thin panels. The GFRP-Thin Panels are manufactured by pressing form and their application technique are similar to steel plates. The use of FGRP-Thin Panels presents several advantages. The advantages of this structural system are the case of application, the elimination of joint and corrosion at the epoxy-panel interface. This paper introduces the method of manufacturing about GFRP-Thin Panels, mechanical properties and the application of reinforced concrete structures.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.471-474
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• 1999

An interface always appears when a repair is applied to an aged infrastructure system for repair. These repaired structures have the high chance to fail along the interface because of the stress concentration/discontinuity along the interface. So, mechanical properties of the interface have much influence on the behavior of repaired structure systems. In this paper, numerical tool that can predict effectively the interfacial fracture behavior is developed using axial deformation link elements, and this numerical technique is applied to the interfacial failure behavior. The results coincide with the ultimate strength and failure profile on the interfacial behavior of carbon fiber sheets for strengthening with epoxy adhesion. Thus, the mechanical behavior of the interface up to failure can be predicted using numerical technique with the proposed axial deformation link elements.

• Computers and Concrete
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• v.22 no.4
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• pp.395-405
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• 2018

In this paper, the performance of post-installed adhesive bonded anchor embedded in concrete is assessed using numerical simulations. This study aims at studying the influence of parameters on the performance of a chemically bonded anchorage system. Non-linear finite element modelling and simulations are carried out by properly using the material properties and phenomenon. Materials parameters such as characteristic length, fracture energy, damage criteria, tension retention and crack width of concrete and interface characteristics are carefully assigned so as to obtain a most realistic behaviour of the chemical anchor system. The peak strength of two different anchor systems obtained from present numerical studies is validated against experimental results. Furthermore, validated numerical models are used to study the load transferring mechanism and damage progression characteristics of various anchors systems where strength of concrete, strength of epoxy, and geometry and disposition of anchors are the parameters. The process of development of strain in concrete adjacent to the anchor and energy dissipated during the course of damage progression are analysed. Results show that the performance of the considered anchorage system is, though a combined effect of material and geometric parameters, but a clear distinction could be made on the parameters to achieve a desired performance based on strength, slip, strain development or dissipated energy. Inspite the increase in anchor capacity with increase in concrete strength, it brings some undesirable performance as well. Furthermore, the pullout capacity of the chemical anchor system increases with a decrease in disparity among the strength of concrete and epoxy.

• Advanced Composite Materials
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• v.17 no.3
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• pp.277-299
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• 2008

High quality and expedient processing repair methods are necessary to enhance the service life of bridge structures. Deterioration of concrete can occur as a result of structural cracks, corrosion of reinforcement, and freeze.thaw cycles. Cost effective methods with potential for field implementation are necessary to address the issue of the vulnerability of bridge structures and how to repair them. Most infrastructure related applications of fiber-reinforced plastics (FRPs) use traditional hand lay-up technology. The hand lay-up is tedious, labor-intensive and relies upon personnel skill level. An alternative to traditional hand lay-up of FRP for infrastructure applications is Vacuum Assisted Resin Transfer Molding (VARTM). VARTM uses single sided molding technology to infuse resin over fabrics wrapping large structures, such as bridge girders and columns. There is no work currently available in understanding the interface developed, when VARTM processing is adopted to wrap fibers such as carbon and/or glass over concrete structures. This paper investigates the interface formed by carbon fiber processed on to a concrete surface using the VARTM technique. Various surface treatments, including sandblasting, were performed to study the pull-off tensile test to find a potential prepared surface. A single-lap shear test was used to study the bond strength of CFRP fabric/epoxy composite adhered to concrete. Carbon fiber wraps incorporating Sikadur HEX 103C and low viscosity epoxy resin Sikadur 300 were considered in VARTM processing of concrete specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.396-401
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• 1995

Epoxy coated reinforcing steels (ECRs) were acquired from ten sources and coatings from each source were initially characterized in terms of defects, thickness, solvent extraction weight loss and hardness. Testing involved exposure in three aqueous solutions at elevated temperature (8$0^{\circ}C$) and in chloride-contaminated concrete slabs under outdoor exposure, It was found that the density and size of coating defects was the promary factor affecting ECR performance. The equivalent circuit analysis using electrochemical impedance spectroscopy (EIS) data indicated that the impedance response for well-performing ECR specimens showed no signs of active degradation at the interface although diffusional processes similar to those noted for poorly performing bars occurred here. Experimental results also indicated a relationship between corrosion behavior and bar source. Weight loss upon solvent extraction correlated with impedance reduction from hot water exposure. Coating defects during most of the tests, especially in high pH solutions containing chloride ions. ECRs with excessive coating defects, either initially present or ones which developed in service, performed poorly in every test category regardless of source. Forms of coating failure were extensive rusting at defects, blistering, wet adhesion loss, cathodic delamination, underfilm corrosion and coating cracks. These occurred sequentially or concurrently, depending on the condition of the ECR and nature of the environment

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.85-94
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• 2016

In this study, the hydrophilic chemical grout using silanol (HCGS) was introduced to overcome the limitations of conventional epoxy resin which have been used for strengthening reinforced concrete (RC) structures. Then, flexural tests on the RC slabs strengthened by FRP sheets were conducted. Three slab specimens were tested in this study; a control specimen with no strengthening, and two specimens strengthened by a typical epoxy resin or HCGS, respectively, as a binder between the slabs and the FRP sheets. In addition, an analytical model was developed to evaluate the flexural behavior of strengthened slab members, considering the horizontal shear force at the interface between concrete slabs and FRP sheets. The analysis results obtained from the proposed model indicated that the strengthened specimens showed fully composite behavior before their flexural failure. Especially, the specimen strengthened by HCGS, which can overcome the limitations of conventional epoxy resin, showed a similar flexural performance with that strengthened by a conventional epoxy resin.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.713-719
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• 2008

Various types of coatings have been developed for use as reinforcement in concrete and to resist chloride environment. The most commonly used coatings are inhibited and sealed cement slurry coating, cement polymer compositing coating and epoxy coating. Cement slurry offers passive protection, epoxy coating offers barrier protection whereas polymer coating offers both passive protection and barrier protection. Moreover, damage during handling of the steel may result in disbondment of the epoxy coating, which would increase the risk of localized corrosion. In the present study, inhibiting technique was used to increase the calcium hydroxide content at the interface up to 20%. Calcium hydroxide provides a high buffering capacity that resists a local fall in pH and thus maintains the alkaline environment necessary to prevent chloride corrosion. This study examines the use of a calcium hydroxide coating on the steel surface to enhance the pH buffering capacity of steel-concrete interface. Finally, the chloride threshold level (CTL) of polymer inhibitive coating calcium hydroxide is evaluated.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.79-85
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• 2003

In this study, the behavior characteristics of specimen strengthened with CFRP plate were analyzed according to the change of temperature. CFRP plate itself has a good resistance at the high temperature, but epoxy used as a adhesive is lost its bonding strength at the relatively low temperature. Therefore, this study carries out experiment on the beams slot-bonded with CFRP plates in order to maintain the successful bonding strength of epoxy at high temperature. It is presented that the range of glass transition temperature is 60-8$0^{\circ}C$ and RC beams slot-bonded with CFRP plate shows more increasing resistance and failure load than that of interface bonded at the high temperature.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.177-183
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• 2023

Various failure modes occur in the concrete beams reinforced with GFRP(Glass Fiber Reinforced Plastic) under initial condition and repairing patterns. In this study, the failure behaviors of concrete beams restrengthened with GFRP sheet with slightly higher elastic modulus than concrete were investigated. For the tests, concrete beams with 24 MPa were manufactured, and the effects of initial notch, overlapping, end-strip reinforcement, and fiber anchors were analyzed on failure load. The cases of GFRP overlap around notch and the initial notch showed increasing failure loads similar to those of normal restrengthened case since the epoxy of the saturated GFRP sufficiently repaired the notch area. Compared to the control case without restrengthening of GFRP, the concrete with initial notch showed 0.78 of loading ratio and normal restrengthening showed 4.43~5.61 times of increasing ratio of failure loading, where interface-debonding from flexural crack were mainly observed. The most ideal failure behavior, break of GFRP, was observed when end-strip over 1/3 height from bottom and fiber anchor were installed, which showed increasing failure load over 150 % to normal restrengthening.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.10a
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• pp.160-166
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• 1994

In general, the problems of strengthening and repairing of deteriorated or damaged reinforced concrete members are usually worked out in situ by externally bounding steel plates using epoxy resins, which has been recognized to be one of effective and convenient methods. But the disadvantages of strengthening/repairing concrete members with externally bonded steel plates include ; (a) deterioration of the bond at the steel-concrete interface caused by the corrosion of steel ; (b) difficulty in manipulating the plate at the construction site ; (c) improper formation of joints, due to the limited delivery lengths of the steel plates ; and etc. Therefore these difficulties eventually have led to the concept of replacing the steel plates by fiber-reinforced composite sheets which are characterized by their light weight, extremely high stiffness, excellent fatigue properties, and outstanding corrosion resistance. In the paper, for the reliability assessment of reinforced concrete beams externally strengthened by carbon fiber plastic(CFRP) laminates, an attempt is made to suggest a limit state model based on the strain compatibility method and the concept of fracture mechanics. And the reliability of the proposed models is evaluated by using the AFOSM method. The load carrying capacity of the deteriorated and/or damaged RC beams is considerably increased. Thus, it may be stated that the post-strengthening of concrete beams with externally bonded CFRP materials may be one of very effective way of increasing the load carrying capacity and stiffeness characteristics of existing structures.