• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.3
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• pp.73-81
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• 2004

FRP reinforcing bars(rebars) are produced through a variety of manufacturing process includes pultrusion, and filament winding and braiding etc. Each manufacturing method produces a different surface condition of FRP rebar. The surface properties of FRP rebar is an important property for mechanical bond with concrete. Current methods of providing surface deformation to FRP rebars include helical wrapping, surfaces and coating and rib molding. The problem with the helical wrapping method is that it can not provide enough surface deformation for good bond and it can be easily sheard off from the FRP rebars. Sand coating and rib molding provide surface deformation only to the outer FRP skins. Therefore, FRP rebar has about 60% of bond strength of steel rebar. The main objective was to evaluate the bond properties of FRP rebar after environmental exposure. Five types of FRP rebar includes CFRP ISO, GFRP Aslan, AFRP Technora CFRP(Korea), and GFRP(Korea) rebars performed direct bond tests. Also, FRP rebar bond specimens were subjected to exposure conditions including alkaline solution, acid solution, salt solution and deionized water etc. According to bond test results, CFRP(Korea) and CFRP(Korea) rebars were found to have better bond strength with concrete than previous FRP rebars. Also, FRP(Korea) rebar had more than about 70% in bond strength of steel rebar.

• 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 Architectural Institute of Korea Structure & Construction
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• v.35 no.1
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• pp.3-10
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• 2019

The purpose of this paper is to find the fire-protection method for keeping on the bond capacity of Near-Surface-Mounted (NSM) FRP under high temperature. Experiments have been carried out to evaluate the bond capacity of NSM FRP by using CFRP-plates and to confirm the heat transfer to the concrete block when the refractory insulation is attached to the surface of NSM FRP. Bond test of NSM FRP under room temperature was conducted to obtain the maximum bond strength. And then a heating tests were carried out with keeping the bond stress of 30% of the maximum bond strength. As a result, the bond capacity of NSM FRP was disappeared when the temperature at epoxy reached to its glass transition temperature (GTT). In order to secure the bond capacity of the NSM FRP, it is necessary to protect the front as well as side by using insulation materials.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.415-422
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• 2012

This paper analyzed seventy eight previous test results to evaluate bond strength of Near Surface-Mounted (NSM) FRP and prediction formulas previously proposed by researchers. The results showed that the most reliable bond strength prediction was the one proposed by Seracino, who considered the shape coefficient (ratio of width-thickness) and stiffness of FRP. However, the equation tended to underestimate the bond strength, especially serious when FRP bond length was relatively short, because the equation did not consider the effect of bond length. Based on the analysis of previous test results, the relation between bond length and bond strength and the group effect due to close proximity of FRPs were determined. Based on the findings, the Seracino's formula was modified and it's applicability was evaluated. The result showed that the suggested formula can be used effectively to predict the bond strength of NSM FRP.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.279-286
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• 2011

FRP (Fiber Reinforced Polymer) tendons can be used as an alternative to solve the corrosion problem of steel tendons. Material properties of FRP tendons-bond strength, transfer length, development length-must be determined in order to apply to concrete structures. First of all, in case of application for pretension concrete members with CFRP tendons, transfer length is an important characteristic. The bond of the material characteristics should be demanded clearly to apply to PSC structures prestressed with FRP tendons. This paper investigated on the bond characteristics of FRP reinforcements with various surface-type. To determine the bond characteristics of FRP materials used in place of steel reinforcement or prestressing tendon in concrete, pull-out testing suggested by CAN/CSA S806-02 was performed. A total of 40 specimens were made of concrete cube with steel strands, deformed steel bar and 6 different surface shape FRP materials like carbon or E-glass. Results of the bonding tests presented that each specimen showed various behaviors as the bond stress-slip curve and compared with the bond characteristic of CFRP tendon developed in Korea.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.65-72
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• 2008

The use of hybrid FRP-concrete structures with a dual purpose of both permanent formwork and reinforcement, has been considered in some studies recently. For the FRP plank and the concrete to act as a composite structural member a satisfactory bond at the interface between the smooth surface of the pultruded plank and the cast-in-place concrete must be developed. Sand was bonded to the pultruded FRP plank using a commercially available epoxy system. In applying general analysis techniques to evaluate the performance of composite structures with FRP stay-in-place forming, it is essential that characteristics of the bond stress-slip relation be identified. In this study I would like to propose a simplified bilinear bond stress-slip model for FRP composite structures.

• Computers and Concrete
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• v.24 no.1
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• pp.73-83
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• 2019

Concrete reinforced with fiber reinforced polymer (FRP) bars (FRP-RC) has attracted a significant amount of research attention in the last three decades. A limited number of studies, however, have investigated the effect of bond slip on the performance of FRP-RC columns under eccentric loading. Based on previous experimental study, a finite-element model of eccentrically loaded FRP-RC columns was established in this study. The bondslip behavior was modeled by inserting spring elements between FRP bars and concrete. The improved Bertero-Popov-Eligehausen (BPE) bond slip model with the results of existing FRP-RC pullout tests was introduced. The effect of bond slip on the entire compression-bending process of FRP-RC columns was investigated parametrically. The results show that the initial stiffness of bond slip is the most sensitive parameter affecting the compression-bending performance of columns. The peak bond stress and the corresponding peak slip produce a small effect on the maximum loading capacity of columns. The bondslip softening has little effect on the compression-bending performance of columns. The sectional analysis revealed that, as the load eccentricity and the FRP bar diameter increase, the reducing effect of bond slip on the flexural capacity becomes more obvious. With regard to bond slip, the axial-force-bending-moment (P-M) interaction diagrams of columns with different FRP bar diameters show consistent trends. It can be concluded from this study that for columns reinforced with large diameter FRP bars, the flexural capacity of columns at low axial load levels will be seriously overestimated if the bond slip is not considered.

• Journal of the Korea Concrete Institute
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• v.26 no.1
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• pp.79-86
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• 2014

In this paper, a stress transfer mechanism between near surface-mounted (NSM) fiber reinforced polymer (FRP) plate and concrete was investigated and a reliable analytical procedure for it was presented by using bilinear bond-slip model simulating the bond behavior of NSM FRP plate. As a result, critical values in the bi-linear model such as maximum shear strength, slip at that time and failure slip at the initiation of softening de-bonding were suggested for being used in the differential equation considering he interfacial characteristic between NSM FRP and concrete. Also, it was found that the bond-slip behavior could be suitably redicted by using the proposed procedure even in the case of various bond lengths from the comparison with bond test result.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.333-336
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• 2004

In this study focuses on bond properties of hybrid FRP rebar after chemical environmental exposure. Hybrid FRP rebar bond specimens were subjected to four type of exposure conditions. Bond properties were investigated by direct bond test. Bond test results, hybrid FRP rebars were found to have better bond strength with concrete than currently using GFRP rebar. Also, hybrid FRP rebar had more than about $80\%$ in bond strength of steel rebar.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.37-43
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• 2013

Recently, experimental and analytical researches have been performed in order to find interface failure between FRP plate and concrete in near surface-mounted (NSM) retrofit using FRP plate. As a result, it was found that the bond strength between concrete and NSM FRP plate had a close relationship with shape of FRP, concrete compressive strength and bond length. However, research need is increasing about another factors such as suitable space of FRP plate and group effect. In this study, therefore, a bond test was performed with aforementioned factors and compared with a previous equation to verify its suitability for predicting bond strength of NSM FRP plate. From the test, it was found that the bond strength increased according to the increase of space of NSM FRP plates even if its bond length was same. The splitting failure of concrete governed when space of FRPs was too narrow and it changed to FRP's tensile failure with increase of the space. From the evaluation of test specimens using previous equation, it was found that the bond strength could be predicted properly with consideration of group effect.