Beam Bond Tests of GFRP and Steel Reinforcement to Concrete (original) (raw)
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It is becoming accepted that glass-fibre-reinforced polymer (GFRP) is a credible and effective replacement for steel in reinforced concrete (RC) to meet structural requirements whilst addressing durability concerns posed by steel over the long term. A better understanding of the bond behaviour between GFRP and concrete is essential for reliably and efficiently designing concrete structures with reinforced GFRP bars. This paper presents a parametric study of the bond behaviour of GFRP bars to concrete where the effects of the length, diameter, concrete strength, concrete cover thickness and rebar surface morphology of GFRP bars were investigated via a series of pull-out tests. The test results indicate that the bond strength of GFRP bars is predominantly influenced by their surface morphology, embedment length and diameter. On the other hand, the effects of concrete strength and cover thickness appear to have a limited impact on the bond strengths of GFRP rebars to concrete. It is sh...
Bond Behavior of GRFP Bars to Concrete in Beam Test
Procedia Engineering, 2017
Bond behavior between reinforcing bars and concrete is a key problem to understand behavior of reinforced concrete members. The introduction of the new reinforcing system made of fiber reinforced polymer (FRP) to construction industry forced the study of FRP-to-concrete bond behavior as one of the main mechanical properties. The application of FRP reinforcement in concrete structures increased rapidly in last years. Their excellent corrosion resistance, high tensile strength, good non-magnetic properties were the reason why they have become an alternative to traditional steel reinforcement, especially in harsh environments on bridges, outside garages and offshore structures. The GFRP bars are very different from steel, mainly due to much lower elasticity modulus and their anisotropic structure. Good performance of FRP reinforced concrete requires adequate interfacial bond between bars and concrete, mainly due to surface preparation. The authors' own experimental program includes twelve beam bond tests carried out on rectangular beams consisted of two concrete blocks connected by a continuous GFRP bar in tension and by a steel hinge in compression. Two main parameters were investigated in the tests: bar diameter and thickness of a bottom concrete cover. The GFRP bars indicated good bond behavior to concrete, mainly due to the ribs on the bar surface. The results of the test indicated the decrease in the ultimate shear bond stress with the increase in the bar diameter regardless of the thickness of the concrete cover. The decrease in the concrete cover caused the decrease in the shear bond stress for all bars diameters. The increase in bar diameter caused the decrease in the ultimate bond strength.
Materials, 2021
FRP bars and steel strands are widely used in civil engineering. In this study, three different types of high-strength reinforcement materials, carbon fiber reinforced polymer (CFRP) bar, glass fiber reinforced polymer (GFRP) bar, and steel strand, were investigated for their interfacial bond performance with concrete. A total of 90 sets of specimens were conducted to analyze the effects of various parameters such as the diameter of reinforcement, bond length, the grade of concrete and stirrup on the bond strength and residual bond strength. The results show that CFRP bars possess a higher bond strength retention rate than steel bars in the residual section. In addition, with the increase in bond length and diameter of the CFRP bar, the residual bond strength decreases, and the bond strength retention rate decreases. Furthermore, the bond strength retention rate of GFRP bars was found to be higher than that of CFRP bars. With the increase in grade of concrete, the bond strength and ...
Bond mechanism and bond strength of GFRP bars to concrete: A review
Glass fiber-reinforced polymer (GFRP) reinforcements are taken as an alternative solution for the deterioration of civil infrastructures. GFRP bars have received increasing attention due to low cost compared to carbon fiber-reinforced polymer (CFRP) bars. Bond characteristic of GFRP bars in concrete is the most critical parameter for implementation of the material to the corrosion-free concrete structures. Unlike steel reinforcement, GFRP materials behave anisotropic, non-homogeneous and linear elastic properties, which may result in different force transfer mechanism between reinforcement and concrete. With the purpose of covering the most valuable contributions regarding bond mechanism in the past work, a comprehensive review focusing on the failure mode and bond strength is carried out in this paper. A database consisted of 682 pullout-test specimens was created to observe the factors affecting bond behavior. Basic relationship between bond strength/slip and factors was analyzed accordingly. In addition , the development of bond degradation under environmental conditions, such as freezing-thawing cycling, wet-dry cycling, alkaline solutions and high temperature was presented thereafter. These environmental influences need to be further investigated.
Investigation of bond in concrete member with fibre reinforced polymer (FRP) bars
Construction and Building Materials, 1998
Bond strength of fibre reinforced polymer FRP rebars was experimentally investigated in this study and compared to that of steel rebars. A total of 64 concrete beams reinforced with two types of FRP rebars, respectively, were tested. Four nominal diameters of FRP and steel rebars, namely, 12.7, 15.9, 19.1 and 25.4 mm and three embedment lengths, six, 10 and 16 times the rebar diameter were used. Moreover, three concrete depths of 200, 600 and 1000 mm were investigated in the 18 pullout specimens. Results of the tests indicated that the applied tensile load approached the tensile strength of rebars as the embedment length increased and the GFRP rebars showed lower bond strength values compared to steel rebars. The average maximum bond strength of the FRP rebars varied from 5.1 to 12.3 MPa depending on the diameter and the embedment length. The GFRP rebars showed lower bond strength values compared to steel rebars. A modification factor of 1.30 is recommended for computing the development length, to account for the top bar effect. A new model is proposed for the ascending branch of the bond᎐slip law.
Bond behavior of Concrete Beam Reinforcement by GFPR Bars
2014
In recent years, some attempts have been performed to extend general design rules reported in the codes for steel reinforced concrete to Fiber Reinforced Polymer (FRP) materials; this is the case of relationships adopted in the evaluation of the development length clearly derived by extension of the formulations used for steel bars. However, such relationships seem to be inappropriate for FRP reinforcing bars: in fact, experimental test results have shown that bond behavior of FRP bars is different from that observed in case of deformed steel ones. As a consequence, a new procedure for the evaluation of development length based on an analytical approach is needed in order to directly account for the actual bond-slip constitutive law as obtained by experimental tests on different types of FRP reinforcing bars. During this research contribution, an experimental study of GFRP bar concrete bond test is carried out and presented to investigate the bond stress–slip behavior for normal and...
Effect of Bonding Area on Bond Stress Behavior of GFRP Bars in Concrete
Civil Engineering Journal, 2023
The application of Glass Fiber Reinforced Polymer (GFRP) bars is suitable for concrete structures that are susceptible to corrosion, owing to their corrosion-resistant characteristics. Therefore, it is feasible to reduce the concrete cover on reinforced concrete beams by utilizing GFRP bars. However, this can reduce the bonding strength between GFRP bars and concrete. Therefore, this study aims to investigate the bonding behavior between GFRP bars and concrete as a preliminary test for structural applications. The bond stress behavior between GFRP bars and concrete was analyzed by 18 pull-out tests. The test specimens comprised GFRP bars with three different variations, namely GFRP bars with concrete cover (GFRP-C), GFRP bars without concrete cover (GFRP-E), and GFRP bars with a complete wrapping of GFRP sheet (GFRP-C-Sheet). The bond stress-slip curve, bond strength, and failure pattern were utilized to analyze the effect of each variation. The research results indicate that the bonding stress between GFRP bars and concrete was strongly influenced by the concrete cover, where the bonding strength decreased by 65%. Nevertheless, the utilization of a complete wrapping GFR) sheet resulted in a 26.4% increase in bonding stress. The present study has identified three distinct modes of failure, including pull-out (GFRP-C), concrete crushing (GFRP-E), and GFRP sheet debonding (GFRP-C-Sheet).
Bond of GFRP Bars in Concrete: Experimental Study and Analytical Interpretation
Journal of Composites for Construction, 2006
The local bond mechanics of glass-fiber reinforced polymer ͑GFRP͒ bars in normal strength concrete was investigated through experimental testing and analytical modeling. The experimental program was comprised of 30 direct tension pullout specimens with short anchorages. A novel test setup, specially designed so as to minimize the spurious influence of testing conditions on measured bond properties was adopted in the study. Parameters considered were the bar roughness and diameter, the size effect expressed by the constant cover to bar diameter ratio, and the external confining pressure exerted over the anchorage length by transverse externally bonded FRP sheets. Results of the study were summarized in the form of local bond-slip curves, whereby performance limit states were quantified by the amount of loaded end slip and bond strength. An analytical model of the bond stress-slip response of a GFRP bar was derived from first principles and calibrated against the test data of the present investigation. Using the calibrated model, design values for bond and slip were estimated with reference to the code limit state model for bond.
Bond Behavior of GFRP-reinforced lightweight concrete beams
Zenodo (CERN European Organization for Nuclear Research), 2023
More study is required to better understand the flexural behaviour and cracking performance of fiberreinforced polymer (FRP) bars used in lightweight concrete (LWC) beams because there is a paucity of experimental research in this field. This article describes an experimental investigation that evaluated the flexural behaviour, cracking capability, and bond-dependent (Kb) properties of beams made of lightweight concrete. There are three thin concrete beams in all (one of them reinforced with steel bars as a reference beam and the other beams reinforced with GFR bars) measured 150 mm wide x 300 mm deep x 2000 mm long were constructed and tested up to failure in four-point bending over a clear span of 1800 mm. The test parameters were: (a) reinforcement type (Steel bars and GFRP bars), and (b) concrete cover (20 mm and 35 mm). The test results included information on the cracking behaviour, deflection, crack width, reinforcing strain, flexural capacity, and mechanism of failure. The experiment's findings showed that the GFRP-reinforced beams behaved linearly to cracking until concrete crushing caused them to fail. Additionally, the predicted moment capacities of the GFRP beams were computed using the straincompatibility approach in the design standards. The outcomes showed that the experimental results and predictions had a good degree of agreement. According to the analysis of the kb factor, recommended Kb values for smooth GFRP bars are thus given as = 1.65 based on the experimental findings of the tested beams.