Investigation of bond between fibre-reinforced polymer bars and concrete under sustained loads

2006 ◽  
Vol 33 (11) ◽  
pp. 1426-1437 ◽  
Author(s):  
F Shahidi ◽  
L D Wegner ◽  
B F Sparling
Keyword(s):  
Reinforced Concrete ◽  
Sustained Load ◽  
Reinforcing Bars ◽  
Bond Slip ◽  
Reinforced Polymer ◽  
Sustained Loads ◽  
Fibre Reinforced Polymer ◽  
Term Performance ◽  
Frp Bars

Although the use of fibre-reinforced polymer (FRP) bars to replace steel in reinforced concrete is becoming more common, uncertainty remains concerning the long-term performance of FRP, including the effect of a sustained load on the bond between the FRP bars and the concrete. An experimental study was therefore undertaken to investigate the long-term durability of the bond for various types of bars embedded in concrete: one type of glass FRP, two types of carbon FRP, and conventional steel reinforcing bars. Pullout specimens were tested both statically to failure and under sustained loads for periods of up to 1 year while free-end slip was monitored. Results revealed lower short-term bond strengths for FRP bars relative to steel and significant variability in long-term bond-slip performance among FRP bars of different types. Post-testing investigations revealed damage to bar surfaces at the macroscopic level, as well as broken longitudinal fibres and damage to the surface coatings at the microscopic level.Key words: reinforced concrete, fibre-reinforced polymer (FRP), bond, creep, pullout, sustained loads.

Minimum thickness of concrete members reinforced with fibre reinforced polymer bars

2001 ◽  
Vol 28 (4) ◽  
pp. 583-592 ◽  
Author(s):  
Amin Ghali ◽  
Tara Hall ◽  
William Bobey
Keyword(s):  
Reinforced Concrete ◽  
Minimum Thickness ◽  
Reinforced Polymers ◽  
Flexural Members ◽  
Steel Reinforced Concrete ◽  
Concrete Members ◽  
Reinforced Polymer ◽  
Steel Bars ◽  
Fibre Reinforced Polymer ◽  
Frp Bars

To avoid excessive deflection most design codes specify the ratio (l/h)s, the span to minimum thickness of concrete members without prestressing. Use of the values of (l/h)s specified by the codes, in selecting the thickness of members, usually yields satisfactory results when the members are reinforced with steel bars. Fibre reinforced polymer (FRP) bars have an elastic modulus lower than that of steel. As a result, the values of (l/h)s specified in codes for steel-reinforced concrete would lead to excessive deflection if adopted for FRP-reinforced concrete. In this paper, an equation is developed giving the ratio (l/h)f for use with FRP bars in terms of (l/h)s and (εs/εf), where εs and εf are the maximum strain allowed at service in steel and FRP bars, respectively. To control the width of cracks, ACI 318-99 specifies εs = 1200 × 10–6 for steel bars having a modulus of elasticity, Es, of 200 GPa and a yield strength, fy, of 400 MPa. At present, there is no value specified for εf; a value is recommended in this paper.Key words: concrete, cracking, deflection, fibre reinforced polymers, flexural members, minimum thickness.

scholarly journals FLEXURAL CAPACITY OF CONCRETE BEAMS REINFORCED WITH STEEL AND FIBRE‐REINFORCED POLYMER (FRP) BARS

2004 ◽  
Vol 10 (3) ◽  
pp. 209-215
Author(s):  
Hau Yan Leung
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Concrete Members ◽  
Reinforced Polymer ◽  
Beam Design ◽  
Reinforced Concrete Member ◽  
Current Design ◽  
Fibre Reinforced Polymer ◽  
Steel Rebars ◽  
Frp Bars

Although much research on concrete beams reinforced with fibre‐reinforced polymer (FRP) rods has been conducted in recent years, their use still does not receive the attention it deserves from practicising engineers. This is attributed to the fact that FRP is brittle in nature and the collapse of FRP‐reinforced concrete member may be catastrophic. A rational beam design can incorporate a hybrid use of FRP rods and steel rods. Current design codes only deal with steel‐reinforced or FRP‐reinforced concrete members. Therefore in this study some design charts and equations for concrete beam sections reinforced with FRP rods and steel rebars were generated. Results from the theoretical derivations agreed well with experimental data.

scholarly journals Prediction of the Long-Term Performance and Durability of GFRP Bars under the Combined Effect of a Sustained Load and Severe Environments

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2341 ◽  
Author(s):  
Jianwei Tu ◽  
Hua Xie ◽  
Kui Gao
Keyword(s):  
Stress Level ◽  
Degradation Mechanism ◽  
Sustained Load ◽  
Research Results ◽  
Gfrp Bars ◽  
Sustained Loads ◽  
Long Term Performance ◽  
Term Performance ◽  
Durability Performance

With the continuous development of production technology, the performance of glass-fiber-reinforced polymer (GFRP) bars is also changing, and some design codes are no longer applicable to new materials based on previous research results. In this study, a series of durability tests were carried out on a new generation of GFRP bars in laboratory-simulated seawater and a concrete environment under different temperatures and sustained loads. The durability performance of GFRP bars was investigated by analysing the residual tensile properties. The degradation mechanism of GFRP bars was also analysed by scanning electronic microscopy (SEM). Furthermore, the long-term performance of GFRP bars exposed to concrete pore solution under different stress levels was predicted using Arrhenius theory. The research results show that the degradation rate of GFRP bars was increased significantly at a 40% stress level. By comparing the test results, design limits, and other scholars’ research results, it is demonstrated that the GFRP bars used in this test have a good durability performance. It is found that the main degradation mechanism of the GFRP bars is the debonding at the fiber-matrix interface. In the range test, the effects of a 20% stress level on the degradation of GFRP bars were not obvious. However, the long-term performance prediction results show that when the exposure time was long enough, the degradation processes were accelerated by a 20% stress level.

Stress along tensile lap-spliced fibre reinforced polymer reinforcing bars in concrete

2007 ◽  
Vol 34 (9) ◽  
pp. 1149-1158 ◽  
Author(s):  
Ragi Aly
Keyword(s):  
Mathematical Model ◽  
Large Scale ◽  
Bond Stress ◽  
Experimental Results ◽  
Reinforcing Bars ◽  
Reinforced Polymer ◽  
Pullout Tests ◽  
Fibre Reinforced Polymer ◽  
Displacement Theory ◽  
Frp Bars

A theoretical study was carried out to investigate stress along tensile lap-spliced spaced or bundled fibre reinforced polymer (FRP) bars in concrete. R. Tepfers developed a mathematical model, which could be applied for any type of reinforcing bar, based on the modulus of displacement theory. The mathematical model can predict the bond stress and stresses in the reinforcing bars and the surrounding concrete. In this paper, the model developed by Tepfers was represented by applying the modulus of displacement theory, and theoretical predictions are compared with the experimental results from testing 16 large-scale concrete beams. Good agreement between the theoretical values and experimental results was observed at three stages of loading. Recommendations for investigating the modulus of displacement from pullout tests have been included. Lastly, the maximum average bond stress of spliced FRP bars can be estimated using the ultimate failure pattern analysis, in which the contributions of the splitting resistance were included.Key words: beams, fibre reinforced polymer (FRP) bars, bundled bars, concrete, tensile lap-splice, pullout tests, modulus of displacement, flexural tests.

Flexural behaviour of concrete beams strengthened with near surface mounted fibre reinforced polymer bars

2010 ◽  
Vol 37 (10) ◽  
pp. 1371-1382 ◽  
Author(s):  
Shehab M. Soliman ◽  
Ehab El-Salakawy ◽  
Brahim Benmokrane
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Near Surface ◽  
Modes Of Failure ◽  
Reinforced Polymer ◽  
External Reinforcement ◽  
Fibre Reinforced Polymer ◽  
Near Surface Mounted ◽  
Frp Bars

Fibre reinforced polymer (FRP) composite materials have been used as internal and external reinforcement for concrete structures. Flexural strengthening of concrete elements using near surface mounted (NSM)–FRP materials are a promising technology. This research is designed to investigate the behaviour of reinforced concrete beams strengthened in flexure with NSM–FRP bars. A total of 20 reinforced concrete beams were tested. Different parameters including internal steel reinforcement ratio, type of NSM–FRP bars, FRP bar diameter, bonded length, and groove size were investigated in this research. Test results showed that the use of NSM–FRP bars is effective in increasing the flexural capacity of concrete beams. In addition, a nonlinear 3D finite element (FE) analysis was used to numerically simulate the behaviour of the test beams. Comparisons between the FE predictions and experimental results showed very good agreement in terms of the load−deflection and load−strain relationships, ultimate capacities, and modes of failure for the tested beams.

scholarly journals The numerical analysis of the long-term behaviour of the reinforced concrete beams strengthened with carbon fibre reinforced polymer: Cracking

2019 ◽  
Author(s):  
Mykolas Daugevičius ◽  
Juozas Valivonis ◽  
Tomas Skuturna
Keyword(s):  
Reinforced Concrete ◽  
External Load ◽  
Concrete Beams ◽  
Tensile Force ◽  
Reinforced Concrete Beams ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Cracking Process

The paper presents the analysis of the long-term deformability of the reinforced concrete beams strengthened with CFRP. The analysis is based on the obtained numerical and experimental data. The development of deformations is divided into stages. The comparison of the cracking process in the compressed and tensioned areas is performed. The comparative analysis of the results has shown that more attention should be paid to the creep of concrete and the influence of the tensioned reinforcement when the external load is decreased. The study has shown that the compression of the section subjected to long-term loading turns into tension when the external load is removed. Due to the effect of the tensile force, cracks appear on the top of the compressed section. Therefore, re-loading of the beam requires further evaluation of the strength degradation in the concrete of the compressed area.

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