• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.337-345
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• 2009

The purpose of this study is to investigate the shear strengthening effectiveness of the beams strengthened with near surface mounted (NSM) and external bonded (EB) CFRP strips. A total of nine concrete beams were made and tested. From this study, it was found that the shear stiffness and strength of the beams strengthened with NSM and EB strips were significantly improved compared to the control beam. Failure of the beam strengthened with NSM and EB strips was initiated by shear cracks, propagated diagonally to the adjacent epoxy grooves without crossing the epoxy and finally sudden diagonal crack connecting the point of application of load and flexural crack was occurred. For the beam strengthened combined with NSM and EB CFRP strips, the tensile strains in the NSM CFRP strips were observed in the range of 0.35% to 0.45% and strains with EB strips were measured about 0.3%.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.108-113
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• 2018

Researches on strengthening and rehabilitation methods are being widely conducted due to the deterioration of existing concrete structures. Use of externally bonded Carbon Fiber Reinforced Polymers (CFRP) strips for the rehabilitation is a cost-effective and time-saving method. Generally, the CFRP layout for the shear strengthening was a uni-directional layout. Many researches have focused on the variables of the uni-directional CFRP layout such as the amount of material, angle, and spacing. Pilot tests indicated that the effective confinement of the concrete member can be provided with the bi-directional CFRP layout than the uni-directional layout. Therefore, the test was carried out after the uni- and bi-directional strengthening work using the same amount of CFRP material. CFRP anchors were installed to prevent unexpected premature CFRP delamination failure before reaching CFRP fracture strain. The effectiveness of the CFRP anchor and bi-directional CFRP layout for shear strengthening was verified based on the principal tensile strain contours.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3A
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• pp.259-266
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• 2009

This study is to develop equations that consider the elastic modulus ratio of FRP bar and steel reinforcement, shear span to depth ratio, and flexural reinforcement ratio of FRP bar, to determine concrete shear strength of FRP reinforced concrete beams without shear reinforcement. As experimental parameters, 2 types of FRP bar, 3 types of shear span to depth ratio, and 3 types of flexural reinforcement were used. Experimental results for two of shear span to depth ratio were quoted from previous study to evaluate effect of shear span to depth ratio in more detail. Shear strength correction factors needed for evaluating concrete shear strength were proposed from regression analysis using above experimental results. Equations suggested from this study and other codes were examined and compared with 31 experimental results available in the literature. From this comparison, it could be known that the equation suggested from this study gives the most approaching result to experimental results.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.685-693
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• 2012

The yield strength of shear reinforcement is restricted in the present design codes. In this study, the possibility of the yield strength increase in shear reinforcement is evaluated according to ACI318-08, EC2-02 and CSA-04 by comparing the experimental and calculated results. Three cases were used to analyze the shear strength of the beam. One had no limitation in the yield strength of shear reinforcement, another had restriction on the yield strength of shear reinforcement, and the other had a restriction on the yield strength of shear reinforcement and the shear reinforcement ratio. The study results showed that the case with unlimited shear reinforcement yield strength predicted the test result better than other two cases. Even though the rebar yield strength higher than the strength required in present code was applied to existing shear design equation, the result was reasonable. Therefore, the design equation seemed to be appropriate even if the high-strength shear reinforcement is used in practice based on the existing shear design method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.187-194
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• 2005

The purpose of this study is to investigate experimentally the shear resisting behavior of the reinforced concrete beams strengthened with reinforcement materials. Seven specimens were manufactured and tested under static monotonic loading. The main variables in the test were the method and direction of reinforcement. This research is about the experiment of shear capacity of reinforced concrete beams strengthened with CFRP-rod, in the filling-up method. The test result indicated that the method of CFRP increase significantly the ultimate shear strength of a reinforced concrete beam.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.213-220
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• 2004

The purpose of this study is to evaluate the shear strength of SFRC beam that has no stirrups by steel fiber strengthening factor. To achieve the goal of this study, two stage investigation, which is material and member level, is studied with literature and experimental side. From the reviewing of previous researches and analyzing of material and member test results, strengthening parameter of SFRC is defined as steel fiber coefficient. Based on above results, steel fiber strengthening factor is proposed. And by reviewing the proposed equation of shear strength estimation, equation of Shin was well estimated the shear strength of SFRC beams. Therefore, shear strength equation of SFRC, which is composed by Shin's Eq. and steel fiber strengthening factor, is proposed by regression analysis of test results.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.173-176
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• 2008

The aim of this paper is to clarify the shear behavior of RC beams strengthened with channel-type Fiber Reinforced Polymer(FRP) plates. Fourteen RC beams were specifically designed. All the beams were tested under four point bending and extensively instrumented to monitor strains, cracking, load capacity and failure modes. The structural response of all beams is then critically analyzed in terms of deformability, strength and failure processes. It is shown that with channel-type Fiber Reinforced Polymer(FRP) plates, a brittle debonding failure of beams bonding FRP in the concrete surface can be transformed to an almost ductile failure with well-defined enhancement of structural performance in terms of both deformation and strength.

• 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.26 no.2
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• pp.51-58
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• 2022

Flat plate slab is cost-efficient structural system widely used in high rise building, apartment and parking garages. But flat plate-column connections are so weak against punching shear failure that it may cause collapse of overall structure. In this study, spiral type shear reinforcement which increases the shear strength and ductility of the plate-column connection and has good workability was proposed. And experimental test was performed to verify the punching shear capacity of spiral type shear reinforcement. The current code does not accurately estimate the punching shear strength of slab-column connection with shear reinforcement because slab is so slender that punching failure may occurred before shear reinforcement reached yield stress. Therefore modified equation of ACI code for punching shear strength was proposed base on finite element analysis using LUSAS program, and data analysis from CEB-FIP database.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.3
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• pp.269-275
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• 2016

In this paper, shear performance of concrete wide beams was evaluated through shear failure tests. The specimens were designed to have two continuous spans with a column at the center of the wide beam. Also the specimens were reinforced with plates with openings as shear reinforcements. For the test, total eight specimens, including five specimens were reinforced with steel plates and the other three specimens were reinforced with GFRP plates were manufactured. And the shear strengths obtained from the tests were compared with ones from the equation provided by ACI 318. Support width of wide beam, support section of wide beam and shear reinforcement material were considered as variables. The results showed that the support width was proportional to the increase of shear strength. Also, regardless of material type of shear reinforcement, the shear reinforcing effect was similar when the amount of shear reinforcement was the same.