• 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 Korean Society for Railway
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• v.12 no.5
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• pp.641-648
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• 2009

Concrete structures become more common in railway systems with an advancement of high speed train technologies. As the service life of concrete structures increases, structural strengthening for concrete structures may be necessary. There are several typical strengthening techniques using steel plate and fiber reinforced polymer (FRP) materials, which have their own inherent shortcomings. In order to enhance greater durability and resistance to fire and other environmental attacks, basalt fiber material attracts engineer's attention due to its characteristics. This study investigates bonding performance of basalt fiber sheet as a structural strengthening material. Experimental variables include bond width, length and number of layer. From the bonding tests, there were three different types of bonding failure modes: debonding, rupture and rip-off. Among the variables, bond width indicated more significant effect on bonding characteristics. In addition the bond length did not contribute to bond strength in proportion to the bond length. Hence this study evaluated effective bond length and effective bond strength. The effective bond strength was compared to those suggested by other researches which used different types of FRP strengthening materials such as carbon FRP.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.473-480
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• 2012

In order to develop an effecive seismic strengthening metghod for existing concrete structure, structural tests of aramid FRP reinforced RC columns are performed. The test variables were strengthening methods of aramid sheet and strip. The test results were evaluated by comparing strength and energy dissipation capacities of non-reinforced and reinforced specimens. The test result comparison showed that aramid sheet reinforcement on RC column was evaluated as the most efficient way to increase strength and energy dissipation capacity.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.101-111
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• 1998

This study presents test results of RC beams strengthened by carbon fiber sheet(CFS), carbon fiber reinforced plastics(CFRP) or glass fiber reinforced plastics(GFRP) for increasing shear resistance. Nineteen specimens were tested, and the test was performed with different parameters including the type of strengthening materials(CFS, GFRP, CFRP), shear-strengthening methods(wing type, jacket type, strip type), strip-spacing, strengthening direction of FRP. The test results show that shear-damaged RC beams strengthened by FRP(CFS, GFRP, CFRP) have more improved the shear capacity. The mathematical model based on plastic theory was also developed to predict shear strength of shear-damaged RC beams strengthened by FRP. The predictions using the mathematical model. are agreed with the observations from the observed shear strengths for 19 test beams.

• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.509-510
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• 2009

In strengthening reinforced concrete beams using fiber reinforced polymer sheets, brittle structural failures occur due to the linear stress-strain relationship of the fibers. Hybrid fiber reinforced polymer sheets using two different types of fibers were investigated in this study

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.579-584
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• 2003

For strengthening deteriorated concrete structures, externally bonded FRP sheets or plates using epoxy resins are widely used. For the external FRP composites to be effective in improving the performance of the structure, bond between FRP composites and concrete is required. In general, the most frequently observed failure mode in FRP strengthened concrete structures is debonding failure at the interfacial section between FRP and concrete. Therefore, it is very important to find out the interfacial behavior properties. This paper presents experimental results of the relationship of concrete and FRP sheet for some conditions including concrete compressive strength, concrete surface preparation to observe the bond behavior between concrete and FRP sheet and various anchorage types to increase the bond capacity of FRP sheet.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.1
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• pp.49-56
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• 2011

The strengthening effect of CFRP sheet and AFRP sheet with buckling-restrained brace for Beam-Column joints under constant axial and cyclic lateral loading is evaluated experimentally in this paper. Six test specimens were constructed. The main test parameters included the FRP Sheet and Buckling-restrained braces. The results of the tests were analyzed by focusing on their mode of failure, maximum load, ductility indexes, and energy dissipation capacity. Test results indicated that CFRP Sheet with the buckling-restrained brace system significantly increased the strength and stiffness of the specimen and that it was the most adequate retrofitting method.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.645-652
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• 2002

This paper presents the flexural behavior and strengthening effect of reinforced concrete beams bonded with carbon FRP plate. Parameters involved in this experimental study were plate bond length and sheet web anchorage length. Test beams were strengthened with FRP plate on the soffit and anchored with FRP sheet on the web. In general, strengthened beams with no web anchorage were failed by concrete cover failure along the longitudinal reinforcement. On the other hand, strengthened beams with web anchorage were finally failed by delamination shear failure within concrete after breaking of CFRP sheet wrapping around web. The ultimate load and deflection of strengthened beams increased with an increased bond length of FRP plate. Also, the ultimate load and deflection increased with an increased anchorage length of FRP sheet. Particularly, the strengthened beams with web anchorage maintained high ultimate load resisting capacity until very large deflection. The shape of strain distribution of CFRP plate along beam was very similar to that of bending moment diagram. Therefore, an assumption of constant shear stress in shear span could be possible in the analysis of delamination shear stress of concrete. In the case of full bond length, the ultimate resisting shear stress provided by concrete and FRP sheet Increased with an increase of web anchorage length. In the resisting shear force, a portion of the shear force was provided by FRP anchorage sheet.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.75-80
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• 2001

This paper investigates the flexural behavior of reinforced concrete beams strengthened with externally bonded fiber reinforced plastic (FRP) sheets is investigated in this work. FRP is attractive for strengthening the RC beams due to its good tensile strength, low weight, resistance to corrosion, and easy applicability. A simple and direct analytical procedure for evaluating the ultimate flexural capacity of FRP strengthened reinforced concrete (SRC) beams is presented using the equilibrium equations and compatibility of strains. Upper and lower limits of FRP sheet area to ensure the ductile behavior are established. A parametric study is conducted to investigate the effects of design variables such as sheet area, sheet stiffness and strength, concrete compression strength, and steel reinforcement ratio. The analytical procedure is compared with results of experimental data available in the literature.