• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.225-232
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• 2008

The object of this paper is to study the flexural strengthening effectiveness on the construction method of bonding of the FRP. The existing FRP flexural strengthening methods were divided into FRP sheet strengthening and FRP plate strengthening according to the FRP condition. For improving the existing construction method, this paper proposed the velcro type anchorage system for temporary bonding material, and flexural strengthening effects were tested. Test variables were bonding methods of the FRP strengthening materials, and total 4 specimens were tested. Following to the test results, it is shown that FRP-plate strengthening method using the velcro can get better workability than existing construction methods, and have excellent strengthening performance including flexural strength, stiffness, ductility and failure aspect.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.193-202
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• 2008

This paper investigates experimentally the confining effect, strengthening capacity and rebound rate of sprayed Fiber-Reinforced-Polymer (SFRP). From the method, resin and chopped fibers are sprayed separately from the nozzle with high pressure, and then they are attached to the concrete surface, so structure could be repaired. To evaluate the strengthening effect of sprayed FRP, cylindrical specimens and beam specimens were strengthening with SFRP. As main material of FRP, glass fiber and polyester resin are used. To investigate the optimum condition of sprayed FRP, the effects of fiber length, coating thickness, fiber volume ratio and concrete strength were examined. Capacities of sprayed FRP method were also compared to the FRP sheet method. In case of the sprayed FRP, rebound rate is important parameter considering economical efficiency and constructibility, so rebound rate of was discussed. From the test results, optimum conditions of sprayed FRP were determined. SFRP method showed superior strengthening capacities than FRP sheet method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.171-178
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• 2019

Fiber-reinforced polymer (FRP) composites have proved to be reliable as strengthening materials. Most of existing studies used single types of FRP composites. Therefore, in this experimental study, carbon FRP sheet, aramid FRP sheet, and hybrid FRP plate including glass fibers were fabricated, and the effect of pre-stressed FRP composites on flexural strengthening of reinforced concrete (RC) beams was investigated. In total, eight RC beam specimens were fabricated, including one control beam (specimen N) without FRP composites and seven FRP-strengthened beams. The main parameters were type of FRP composite, the number of anchors used for pre-stressing, and thickness of FRP plates. As a result, the beam strengthened with pre-stressed FRP plate showed superior performance to the non-strengthened one in terms of initial strength, strength and stiffness at yielding, and ultimate strength. As the number of anchors and thickness of FRP plate (i.e., amount of FRP plates) increased, the strengthening effect increased as well. When hybrid FRP plates were pre-stressed, the strengthening effect was higher in comparison with pre-stressed single type FRP plate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.18-26
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• 2012

Recently, research about Near-Surface-Mounted Rertofit (NSMR) method has been being widely performed as a method for retrofit of RC structure using FRP. This method requires additional work to make grooves during retrofit but makes it possible to improve retrofit effect and reduce the attack by environment. In this paper, the retrofit effect of NSMR method, especially the method using FRP plate instead of bar is investigated through experiment. Six RC beams were made and retrofitted using by FRP plate following the planned methods; Surface-Bonding Retrofit (SBR), NSMR without debonding region and NSMR with debonding region. Flexural capacity of all specimens was evaluated by beam test with simple support condition. As a result, NSMR method with FRP plate had more improved structural capacity than SBR method. The calculation process of ACI 440-2R can be used to predict the member retrofitted by NSMR with FRP plate with consideration on the three anchorage failure mechanism.

• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.165-168
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• 2008

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.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.811-819
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• 2003

The corrosion of steel reinforcing bar(re-bar) has been the major cause of the reinforced concrete deterioration. FRP(Fiber-reinforced polymer) reinforcing bar has emerged as one of the most promising and affordable solutions to the corrosion problems of steel reinforcement in structural concrete. However, FRP re-bar is pone to deteriorate due to other degradation mechanisms than those for steel. The high alkalinity of concrete, for instance, is a possible degradation source. Other potentially FRP re-bar aggressive environments are sea water, acid solution and fresh water/moisture. In this study long-term durability performance of FRP re-bar were evaluated. The mechanical and durability properties of two type of CFRP-, GFRP re-bar and one type of AFRP re-bar were investigated; the FRP re-bars were subjected to alkaline solution acid solution, salt solution and deionized water. The mechanical and durability properties were investigated by performing tensile, compressive and short beam tests. Experimental results confirmed the desirable resistance of FRP re-bar to aggressive chemical environment.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.445-452
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• 2012

In this study, experimental research was carried out to evaluate the structural performance of the reinforced concrete beam using strengthening materials (embedded FRP rod, metal fittings) in existing reinforced concrete buildings. Seven reinforced concrete beams comprised of retrofitted embedded FRP rod (BCR series), embedded FRP rod with metal fittings (BCR-AC series), and standard specimen (BSS) were constructed and tested under monotonic loading. Design parameters of test specimens were amount of embedded FRP rod and metal fittings. The test results showed that the maximum load carrying capacity of specimens with embedded FRP rod (BCR series) and embedded FRP rod with metal fittings (BCR-AC series) increased by 21~55% and 21~63%, respectively, in comparison with the standard specimen BSS. BCR series test specimens failed by the adhesion slip and concrete cover separation. BCR-AC series test specimens failed by the adhesion slip due to the confining effect of metal fittings.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.256-262
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• 2022

The purpose of this study is to define the shear reinforcing effect of Near-Surface-Mounted (NSM) FRP strips in reinforced concrete (RC) member through a test. Three T shaped RC beams were made and two of them were strengthened with NSM FRP strips for increase shear strength. And those were tested to find the shear strengthening effect. In the test, two case of shear strengthening methods were considered such as 1) with NSM FRP strips having full embedded length and 2) with NSM FRP strips having some what short embedded length and additional externally bonded FRP sheet. As a result, the shear strengthening effect could be obtained when the NSM FRP strips are embedded to have full length up to the bottom of slab. However the shear strength was not increased in the case of having somewhat short embedded length of NSM FRP strips even additional EB sheet was enhanced.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.73-81
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• 2002

Nowadays , the grouted-reinforcing method, which is called FRP(Fiberglass-reinforced-plastic) pipe .reinforcing method, has been introduced in the community of pound reinforcements. The resistance to corrosion and chemical attack high strength to weight ratio, and ease of handling make these pipes a better alternative to steels in tunnel. However, to fully utilize FRP pipes as grouted reinforcing members at the face and the crown in tunnel, their mechanical properties and behaviors and the grout-reinforced underground have to be verified. Laboratory shear tests were conducted to evaluate the mechanical properties for FRP pipes, the grout-reinforced members and the grout-reinforced body of FRP pipes. According to the test results, it was observed that FRP pipes play a dominant role in shearing behavior of the grout-reinforced members and that their shearing resistance exerts after the shearing displacement increases to some extent.