Effect of Bonding Area on Bond Stress Behavior of GFRP Bars in Concrete

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). Doi: 10.28991/CEJ-SP2023-09-010 Full Text: PD

Experimental Research on Material Behaviour of Glass Fiber Reinforced Polymer Bars in Tension

Glass Fiber Reinforced Polymer (GFRP) rebars have been widely used to solve the corrosion problem of steel bars in concrete structures. It has been produced as a lightweight and corrosion-resistant than steel reinforcement in many structural applications. They are regarded as a promising substitute for steel bars in concrete infrastructures. It is necessary to test GFRP bars to fully understand their material properties to ensure the safe and efficient use of the material. In this study, five specimens of each type of GFRP bars with a diameter of 6, 8, 10, 12, and 14 mm were tested under tension. Therefore, a total of 25 samples were examined from the same manufacturer. According to ASTM’s recommendations (D7205/D7205M-06) for tensile tests of GFRP bars, the diameter and thickness of the steel pipes for both ends were considered in the preparation of the test specimens to keep the GFRP bars consistent and aligned throughout the experiment. The experimental test results included the stress-strain curves, tensile strength, ultimate strain, and modulus of elasticity. The study showed an accurate result that indicated the tensile strength of the GFRP bars can be expressed by a linear distribution. For a bar diameter of 10mm, the length to diameter ratio Le/db=8 showed a maximum tensile to compressive strength ratio. In the failure results of the test, there were two-mode failures of GFRP bars: fracture failure and pull-out failure of GFRP bars. Most of the specimens had GFRP bar fracture failures, only two specimens (GBT1-10-2 and GBT1-10-3) were damaged due to the pull-off of the GFRP bars which was not a typical failure mode. Keywords: GFRP Bars, Tensile Test, Stress-Strain Curve, Fracture Failure DOI: 10.7176/CER/13-5-05 Publication date:August 31st 202

Flexural behaviour of concrete slabs reinforced with GFRP bars and hollow composite reinforcing systems

Glass Fibre Reinforced Polymer (GFRP) bars are now attracting attention as an alternative reinforcement in concrete slabs because of their high resistance to corrosion that is a major problem for steel bars. Recentlyhollow concrete slab systems are being used to reduce the amount of concrete in the slab and to minimise the self-weight, but the internal holes makes them prone to shear failure and collapse. A hollow composite reinforcing system (CRS) with four flanges to improve the bond with concrete has recently been developed to stabilise the holes in concrete members. This study investigated the flexural behaviour of concrete slabs reinforced with GFRP bars and CRS. Four full-scale concrete slabs (solid slab reinforced with GFRP bars; hollow slab reinforced with GFRP bars; slab reinforced with GFRP bars and CRS; and slab reinforced with steel bars and CRS) were prepared and tested under four-point static bending to understand how this new construction system would perform. CRS is found to enhance the structural performance of hollow concrete slabs because it is more compatible with GFRP bars than steel bars due to their similar modulus of elasticity. A simplified Fibre Model Analysis (FMA) reliably predicted the capacity of hollow concrete slabs

A Feasibility Study on Using Gfrp Composites Bar in Rc Flexural Member

Steel reinforcements are commonly used for Reinforced Concrete (RC) beams all around the world to take flexural tension. But, the durability of the structure is reduced due to reinforcement steel corrosion. Avoiding reinforcement corrosion and finding alternative material to take flexural tension is the contemporary research work in the field of structural engineering. In the present study, RC beams are reinforced with Glass Fibre Reinforced polymer (GFRP) composites bar at tension zone and flexural test was carried out to determine the bending moment resistance of the beam. GFRP bars were prepared in the industry with the help of pultruded U-section box formwork. GFRP bars were coated with sand using epoxy resin to increase the bond between bars and the RC beam. Three GFRP reinforced concrete beam specimens of size 700 mm × 200 mm × 200 mm were prepared. Also, same size of normal steel reinforced cement concrete beam member was prepared. After 28 days curing, three point bending test was carried out for all the four beams. Flexural capacity of beams with GFRP bars were compared with RC beam with steel bars. The results revealed that the flexural capacity of RC beams with GFRP bars is more than that of RC beam with steel bars. Also, theoretical analysis was carried out to determine the flexural strength of RC beam with steel and GFRP bars and compared with experimental results

Study a Structural Behavior of Eccentrically Loaded GFRP Reinforced Columns Made of Geopolymer Concrete

This study investigated a modern composite material, which is a short geopolymer concrete column (GPCC) reinforced by GFRP bars. The structural performances of GPCC subjected to eccentric load were studied and compared to the normal strength concrete column (NSCC) reinforced by steel bars. In this study, the primary experimental parameters were the reinforcement bars types, load eccentricity, and concrete types. Seven short columns were tested: three normal strength concrete columns reinforced by steel bars, three geopolymer concrete columns reinforced by GFRP bars and one normal strength concrete column without reinforcement. The model dimensions chosen in the present study was a square section of 130×130 mm and a total height of 850 mm. It was shown that the steel bars contribute about 16.47% of column capacity under concentric load. Comparing with the normal strength concrete column, a geopolymer concrete column reinforced by GFRP bars showed a little increase in ultimate load (5.17%) under concentric load. Under the load eccentricity of 130 mm, a geopolymer concrete column reinforced by GFRP bars showed a significant increase in the ultimate load (69.37%). Under large eccentricity, a geopolymer concrete column reinforced by GFRP bars has an outstanding effect on the columns' ultimate load capacity. Also, the sine form can be utilized for GPCC to find the lateral deflection along with the column high at different load values up to the failure

Experimental study on bond performance of GFRP bars in self-compacting steel fiber reinforced concrete

Reinforcing bars made of Glass-Fiber-Reinforced Polymers (GFRP) are more and more common as internal reinforcement of concrete structures and infrastructures. Since the design of GFRP reinforced concrete members is often controlled by serviceability limit state criteria (i.e., deflection or crack width control), an accurate knowledge of the GFRP-concrete bond behavior is needed to formulate sound design equations. Furthermore, bond laws currently available and widely accepted for conventional steel rebars cannot be straightforwardly applied for GFRP ones. Hence, an experimental program consisting of 36 pullout bending tests was carried out to evaluate the bond performance between GFRP bars and steel fiber reinforced self-compacting concrete (SFRSCC) by analyzing the influence of the following parameters: GFRP bar diameter, surface characteristics of the GFRP bars, bond length, and SFRSCC cover thickness. Based on the results obtained in this study, pullout failure was occurred for almost all the specimens. SFRSCC cover thickness and bond length plaid important role on the ultimate value of bond stress of GFRP bars. Moreover, the GFRP bars with ribbed and sand-coated surface treatment showed different interfacial bond behaviors.Fundação para a Ciência e a Tecnologia (FCT

Development of an AC-DC buck power factor correction

Generally all devise used in industrial, commercial and residential applications need to undergo rectification for their proper functioning and operation. It connected to the non-linear loads which results in production of non-sinusoidal line current. Due to the increasing demand of these devices, the line current non-sinusoidal pose a major problem by degrading the power factor of the system thus affecting the performance of the devices. Hence there is a need to reduce the line current non-sinusoidal so as to improve the power factor of the system and led to designing of Power Factor Correction circuits. Power Factor Correction (PFC) involves two techniques, Active PFC and Passive PFC. In our project work we have designed an active power factor circuit using Buck Converter for improving the power factor. The advantage of using Buck Converter in power factor correction circuits is that better line regulation is obtained with appreciable power factor. Simulation and experimental are conducted to validate the theoretical analysis. The results show that the power factor can be improved

Doctor of Philosophy

dissertationThe present research investigates lightweight and normal weight precast concrete panels for highway bridges. The panels are reinforced with Glass Fiber Reinforced Polymer (GFRP) bars. A benefit of precast concrete panels reinforced with GFRP bars for bridge decks is that they are essentially immune to environments where chloride-induced deterioration is an issue. Twenty panels constructed using lightweight and normal weight concrete reinforced with GFRP bars for flexure without any shear reinforcement were tested to failure. The variables investigated were concrete compressive strength, deck span, panel thickness and width, and reinforcement ratio. The experimental performance of lightweight precast GFRP reinforced panels versus normal weight precast GFRP reinforced panels was investigated in terms of shear capacity, deck deflections, and moment of inertia. The experimental results show that lightweight concrete panels performed similar to normal weight concrete panels; however, they experienced larger deflections under the same load and had a lower ultimate shear strength than normal weight concrete panels. An extended database of 97 test results including normal weight and lightweight concrete restricted to members reinforced with GFRP bars for flexure without any shear reinforcement was compiled. The extended database including 77 normal weight concrete members from literature, 8 normal weight concrete panels and 12 lightweight concrete panels tested in the current research; no lightweight concrete members reinforced with GFRP has been found. ACI 440.1R predicted smaller shear strength conservatism of lightweight concrete panels compared with normal weight concrete panels. A reduction factor has been recommended for the ACI 440.1R shear strength prediction equation when lightweight concrete is used. Modified Compression Filed Theory (MCFT) was also used for the prediction of ultimate shear strength of GFRP reinforced concrete panels. The comparison of prediction to the experimental results shows that MCFT can predict accurately the shear strength for both lightweight and normal weight concrete panels reinforced with GFRP bars. All the tested panels both normal weight and lightweight concrete panels designed according to ACI 440.1R satisfy the service load deflection requirements of the AASHTO LRFD Bridge Design Specifications. The experimental results indicate that the moment of inertia for precast panels reinforced with GFRP bars with initial cracks was less than the gross moment of inertia even before the cracking moment is reached. An expression for predicting deflection using a conservative estimate of the moment of inertia for precast concrete panels reinforced with GFRP bars is proposed. Using the proposed equation, a better deflection prediction is obtained for precast concrete panels reinforced with GFRP bars under service load

Thermal analysis of GFRP-reinforced continuous concrete decks subjected to top fire

Citation: Hawileh, R. A., & Rasheed, H. A. (2017). Thermal analysis of GFRP-reinforced continuous concrete decks subjected to top fire. International Journal of Advanced Structural Engineering. https://doi.org/10.1007/s40091-017-0168-7This paper presents a numerical study that investigates the behavior of continuous concrete decks doubly reinforced with top and bottom glass fiber reinforced polymer (GFRP) bars subjected to top surface fire. A finite element (FE) model is developed and a detailed transient thermal analysis is performed on a continuous concrete bridge deck under the effect of various fire curves. A parametric study is performed to examine the top cover thickness and the critical fire exposure curve needed to fully degrade the top GFRP bars while achieving certain fire ratings for the deck considered. Accordingly, design tables are prepared for each fire curve to guide the engineer to properly size the top concrete cover and maintain the temperature in the GFRP bars below critical design values in order to control the full top GFRP degradation. It is notable to indicate that degradation of top GFRP bars do not pose a collapse hazard but rather a serviceability concern since cracks in the negative moment region widen resulting in simply supported spans

Evaluation of physical and durability characteristics of new headed glass fiber–reinforced polymer bars for concrete structures

This paper presents the results of a collaborative research project with Quebec’s Ministry of Transportation and the Ontario’s Ministry of Transportation, which aimed at characterizing a new type of headed glass-fiber-reinforced-polymer (GFRP) reinforcing bar and evaluating its suitability as internal reinforcement for concrete structures. To achieve these objectives, the project was implemented in three stages: (1) evaluation of the physical and mechanical properties; (2) determination of the pullout behavior in concrete; and (3) characterization of the long-term durability of the headed GFRP bars. A total of 57 specimens embedded in a 200 mm concrete cube were tested with the direct pullout test to investigate the effect of confinement, bar size, concrete compressive strength, and exposure conditions on the pullout behavior of the headed GFRP bars. Simultaneously, microstructural analyses and measurements of the physicochemical and mechanical properties were carried out on conditioned and unconditioned headed GFRP bars. The results show that the materials, geometry, and interface configuration of the head provided very good mechanical interlocking to the GFRP bars. Up to 63% and 53% of the guaranteed tensile strength of the straight GFRP bars were achieved for 15.9 mm and 19 mm diameter bars with headed ends, respectively. Scanning electron microscopy and differential scanning calorimetry showed no material changes in the head and bars after exposure to alkaline solution and freeze–thaw cycling. Exposure to the alkaline solution under sustained loading had the most detrimental effect, with the bar retaining 79.4% of its pullout strength. The results indicate that the tested headed GFRP bar has suitable mechanical and durability properties for use as reinforcement in concrete bridge components