• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.5
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• pp.69-77
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• 2004

FRP rebar has low bond performance than steel rebar. Usually, FRP rebar has about 60% of bond strength of steel rebar. Without adequate bond to concrete, the full composite action between reinforcement and concrete matrix can not be achieved. Therefore, FRP rebars must also have surface deformations that provide good bond to concrete. The purpose of this research was decided an optimum surface deformation patterns through bond test of FRP rebar. Eighteen surface deformation patterns of FRP rebar with widely different geometries were investigated. Based on the test results, we established optimum surfale deformation pattern. Bond tests were performed for three types of surface deformation patterns of FRP rebar including sand coated rebar, ribbed rebar, and wrapped and sand coated rebar that commercially available, and two types of FRP rebar including CFRP, GFRP rebars that optimum surface deformation pattern is applied. According to bond test results, FRP rebars that optimum surface deformation pattern is applied were found to have better bond strength with concrete than currently using FRP rebar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.117-124
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• 2007

An experimental research has been performed to evaluate the load transfer capacity for the planar joints between existing and new slab in an apartment remodelling constructions expecially for enlarging the interior space. Post-installed dowel bars were used as a joint connector. The existing slabs were obtained from the existing apartment housing which will be demolished, and were retrofitted with carbon fiber plate. Test results showed that the planar joints with post-installed dowel bars behaved in full composite modes until ultimate capacity of test specimens, so sufficient ultimate and serviceability performance are confirmed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.183-190
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• 2006

From the result of this research above, it may be summed up as follows. As a summary of results from each experiment, as the test body reinforced with the carbon rods was embedded inside the concrete section and made it possible uniform movement, this study has shown that it had excellent characteristics in improving the flexural strength and ductility. Also, it was considered as the carbon-steel sheet composite plate was to exert the strength more if it would complement the adherence with the concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.694-701
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• 2018

Larger crack widths can be observed more in FRP-reinforced concrete members than in steel-reinforced concrete members as a result of the lower elastic modulus and bond strength of FRP reinforcement. The ACI 440.1R-15 design guide provides equations derived as the maximum bar spacing to control the crack widths indirectly. On the other hand, it is not concerned with long-term effects on the crack control design provisions. This study provides suggestions for how to incorporate time-dependent effects into the crack width equation. The work presented herein includes the results from 8 beams composed of four rectangular and T-shaped FRP-reinforced concrete beams tested for one year under four-point bending. Over a one year period, the crack widths increased as much as 2.6~3.0 times in GFRP and AFRP-reinforced specimens and 1.1~1.4 times in the CFRP-reinforced specimens compared to steel-reinforced specimens. In addition, the average multiple for crack width at one year relative to the instantaneous crack width upon the application of the sustained load was 2.4 in the specimens with a rectangular section and 3.1 in the specimens with a T-shaped section. As a result, it is recommended conservatively that the time-dependent coefficient be taken as 2.5 for the rectangular beams and 3.5 for T-beams.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.491-497
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• 2014

The corrosion of steel reinforcement in reinforced concrete bridge decks significantly affects the degradation of the capacity. Due to the advantageous characteristics such as high tensile strength and non-corrosive property, fiber reinforced polymer (FRP) has been gathering much interest from designers and engineers for possible usage as a alternative reinforcement for a steel reinforcing bar. However, its application has not been widespread, because there data for short- and long-term performance data of FRP reinforced concrete members are insufficient. In this paper, seven full-scale decks with dimensions of $4000{\times}3000{\times}240mm$ were prepared and tested to failure in the laboratory. The test parameter was the bottom reinforcement ratio in transverse direction. The decks were subjected to various levels of concentrated cyclic load with a contact area of $577{\times}231mm$ to simulate the vehicle loading of DB-24 truck wheel loads acting on the center span of the deck. It was observed that the glass FRP (GFRP) reinforced deck on a restraint girder is strongly effected to the level of the applied load rather than the bottom reinforcement ratio. The study results showed that the maximum load less than 58% of the maximum static load can be applied to the deck to resist a fatigue load of 2 million cycles. The fatigue life of the GFRP decks from this study showed the lower and higher fatigue performance than that of ordinary steel and CFRP rebar reinforced concrete deck. respectively.

• Composites Research
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• v.36 no.1
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• pp.16-24
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• 2023

This paper presents a multi-scale progressive fatigue damage model incorporating the model for interfacial debonding between fibers and matrix. The micromechanics model for the progressive interface debonding was adopted, which defined the four different interface phases: (1) perfectly bonded fibers; (2) mild imperfect interface; (3) severe imperfect interface; and (4) completely debonded fibers. As the number of cycles increases, the progressive transition from the perfectly bonded state to the completely debonded fiber state occurs. Eshelby's tensor for each imperfect state is calculated by the linear spring model for a damaged interface, and effective elastic properties are obtained using the multi-phase homogenization method. The fatigue damage evolution formulas for fiber, matrix and interface were proposed to demonstrate the fatigue behavior of CFRP laminates under cyclic loading. The material parameters for the fiber/matrix fatigue damage were characterized using the chaotic firefly algorithm. The model was implemented into the UMAT subroutine of ABAQUS, and successfully validated with flat-bar UD laminate specimens ([0]₈,[90]₈, [30]₁₆) of AS4/3501-6 graphite/epoxy composite.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.947-953
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• 2005

Previous test results showed that the current ASTM(American Standard for Testing and Materials) grip adapter for GFRP(Glass Fiber Reinforced Polymer) rebar was not fully successful in developing the design tensile strength of GFRP rebars with reasonable accuracy. It is because the current ASTM grip adapter which is composed of a pair of rectangular metal blocks of which inner faces are grooved along the longitudinal direction does not take into account the various geometric characteristics of GFRP rebar such as surface treatment, shape of bar cross section as well as physical characteristics such as poisson effect, elastic modulus in the transverse direction and so on. The objective of this paper is to provide how to proportion the optimum diameter of inner groove in ASTM grip adapter to develop design tensile strength of GFRP rebar. The proportioning of inner groove in ASTM grip adapter is based on the force equilibrium of GFRP rebar between tensile capacity and minimum frictional resistance required along the grip adapter. The frictional resistance of grip adapter is calculated based on the compressive strain compatibility in radial direction induced by the difference between diameter of GFRP rebar and inner groove In ASTM grip. All testing procedures were made according to the CSA S806-02 recommendations. From the preliminary test results on round-type GFRP rebars, it was found that maximum tensile loads acquired under the same testing conditions is highly affected by the diameter of inner groove in ASTM grip adapter. The grip adapter with specific dimension proportioned by proposed method recorded the highest tensile strength among them.