Glass Fiber Reinforced Polymer Reinforcement Research Articles

Experiment on RC Beams Reinforced with Glass Fibre Reinforced Polymer Reinforcements

This study presents the flexural behaviour of rectangular concrete beams reinforced with surface treated Glass Fibre Reinforced Polymer (GFRP), Grooved bars and Sand sprinkled reinforcing bars. Beams cast with standard mix of M30 grade concrete, with a reinforcement ratios of 0.73%, and compared with that of conventional steel reinforced beams. Totally five rectangular beams of size 125 mm x 250 mm x 3200 mm were cast. The flexural study was carried under static two point loading. The experimental prediction was focused on observation of ultimate load capacity, cracks propagation and crack widths and failure modes of beams. The results indicate that both type of GFRP reinforcements are at par with the conventional steel reinforcements.

Splice Strength of Staggered and Non-Staggered Bundled Glass Fiber-Reinforced Polymer Reinforcing Bars in Concrete

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Nonlinear Finite Element Modeling of Shear Behavior of Concrete Deep Beams Reinforced with Internal Glass Fiber-Reinforced Polymer Bars by ANSYS

The purpose of this paper is to numerically trace the behavior of concrete deep beams reinforced with internal Glass Fiber-Reinforced Polymer (GFRP) bars and containing no web reinforcement by using ANSYS program. For this purpose, a finite element model is used for concrete deep beams that previously examined in an experimental study and its predicted failure loads were compared with the actual failure loads. The results of the finite element model were in a good agreement with observations from the experimental study. The comparisons showed that the used model has the ability to capture the shear behavior, as well as load-deflection response and crack patterns of deep beams reinforced with internal GFRP bars in the entire range of loading. The paper is also covered a parametric study on shear span-to-depth (a/d) ratio, GFRP reinforcement ratio and concrete compressive strength which they usually have high impacts on the behavior of fiber-reinforced concrete beams. The results of the parametric study showed that the ultimate failure load of beams reinforced with GFRP bars was higher than that of steel-reinforced concrete beams. The maximum failure load was observed to decrease by decreasing the a/d ratio. The stiffness and ductility of the beams were increasing by increasing the reinforcement ratio.

Experimental Study on Splice Strength of Glass Fiber-Reinforced Polymer Reinforcing Bars in Normal and Self-Consolidating Concrete

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Flexural capacity of bi-directional GFRP strengthened RC beams with end anchorages

Purpose The purpose of this paper is to present the results of experimental and theoretical studies on the flexural capacity of reinforced concrete (RC) beams strengthened using externally bonded bi-directional glass fibre reinforced polymer (GFRP) composites and different end anchorage systems. Design/methodology/approach A series of nine RC beams with a length of 1,600 mm and a cross-section of 200 mm depth and 100 mm width were prepared and externally strengthened in flexure with bi-directional GFRP composites. These strengthened beams were anchored with three different end anchorage systems namely closed GFRP wraps, GFRP U-wraps and mechanical anchors. All these beams were tested with four-point bending system up to failure. The experimental results are compared with the theoretical results obtained using the relevant design guidelines. Findings The experimental results demonstrate a significant increase in the flexural performance of the GFRP strengthened beams with regard to the ultimate load carrying capacity and stiffness. The results also show that GFRP strengthened beams without end anchorages experienced intermediate concrete debonding failure at the GFRP plate end, whereas all the GFRP strengthened beams with different end anchorage systems failed in rupture of GFRP with concrete crushing. The theoretical results revealed no significant difference among the relevant design guidelines with regard to the predicted ultimate moment capacities of the bi-directional GFRP strengthened RC beams. However, the results show that ACI Committee 440 Report (2008) design recommendation provides reasonably acceptable predictions for the ultimate moment capacities of the tested beams strengthened externally with bi-directional GFRP reinforcement followed by FIB Bulletin 14 (2001) and eventually by JSCE (1997). Originality/value The research work presented in this manuscript is authentic and could contribute to the understanding of the overall behaviour of RC beams strengthened with FRP and different end anchorage systems under flexural loading.

Structural behaviour of self-compacting concrete columns reinforced by steel and glass fibre-reinforced polymer rebars under eccentric loads

Glass fibre-reinforced polymer (GFRP) rebars are preferable alternatives to steel bars for minimizing corrosion problems. In this study, experimental and analytical work are carried out to investigate the behaviour of GFRP reinforcement versus traditional steel reinforcement in self-compacting concrete columns under eccentric loads. The GFRP-reinforced columns have lower carrying capacities than the steel-reinforced columns, with a difference of ∼24%. Furthermore, the two confining materials (of the tube and spirals) improve this reduction. The analytical results show good agreement with the experimental results for steel-reinforced columns, whereas the GFRP-reinforced columns report a noteworthy contrast.

Shear properties and durability of GFRP reinforcement bar aged in seawater

Pultruded glass fibre reinforced polymer (GFRP) composite rebars were aged in seawater and in dry at 23, 55 and 75 °C for 0, 8 and 20 months to analyse the changes in shear properties such as short beam shear strength (SBSS) and transverse shear strength (TSS). SBSS was found to remain up to 95 and 106% in wet and dry conditions, respectively, at 75 °C after 20 months. TSS was found to remain up to 91 and 107% in wet and dry conditions, respectively, at 75 °C after 20 months. Glass transition temperature (Tg) showed little change both in wet and dry conditions at different temperatures and time. Microscopic analysis indicated that the shear strength decreased due to fibre/matrix interfacial failure as a result of de-bonding and fibre pull-out. The transverse shear test appeared to be a useful technique to analyse the durability of pultruded GFRP rebar.

Experimental Study on Uniaxial Compression of Bamboo Poles with Different Reinforcements

The natural round bamboo is a kind of ecological building material with many excellent physical and mechanical characteristics, such as fast growth, high strength and good environmental performance. However, the natural round bamboos were barely used for its worse durability and easiness to crack compared other bamboo productions after secondary operation. In order to improve the safety and durability of the round bamboo structure, the axial compression test of the GFRP (glass fiber-reinforced polymer) and/or mortar reinforcing cracked bamboo was conducted. The 20 cm tall round bamboo column specimens were divided into five categories: the first without cracks and reinforcement, the second with cracks but without reinforcement, the third with cracks and full GFRP reinforcement, the forth with cracks and fulfil of cement motrar, and the last with cracks and reinforced using both GFRP and cement mortar. The bearing capacity and the failure modes were observed and studied. It was found that the composite reinforcement of GFRP and mortar could significantly increase the bearing capacity of the cracked round bamboos, and avoid brittle failure through improving the ductility of the specimens.

Flexural behavior of geopolymer-concrete beams longitudinally reinforced with GFRP and steel hybrid reinforcements

This paper presents the flexural behavior of geopolymer-concrete beams longitudinally reinforced with a hybrid of glass-fiber-reinforced-polymer (GFRP) and steel bars. Seven geopolymer-concrete beams with different ratios and configurations of GFRP-to-steel reinforcement were designed, cast, and tested up to failure using the four-point static bending test. Based on the experimental results, the hybrid beams showed better serviceability and ductility and up to 15% higher strength than their counterpart geopolymer-concrete beams reinforced solely with GFRP bars. Increasing the reinforcement ratio increased overall beam performance. The hybrid beams reinforced with steel bars at the top and with GFRP bars at the bottom produced higher stiffness and strength at concrete crushing than their counterpart beams with hybrid tensile reinforcement. The tested geopolymer-concrete hybrid beams yielded better bending-moment capacities than the normal-concrete hybrid beams. Both ACI 440.1R-15 and CSA S806-12 conservatively predicted the flexural strength and mid-span deflection at service load of the hybrid beams.

Influence of Bond Behaviour of Flexural GFRP Reinforcement on Failure Mechanisms in Beams Without Stirrups

AbstractThe aim of the paper is to investigate the shear failure mechanisms in T-shape, single span and simply supported beams exclusively reinforced with longitudinal glass fiber reinforced polymer (GFRP) bars. Usually the critical shear crack in RC beams without stirrups develops through the theoretical compression strut reducing the shear strength following the shear failure. The main parameter affecting the crack pattern and the shear strength of the beams is the shear slenderness. However, the test results presented in the paper indicated the new arching effect due to the bond losing between the GFRP flexural reinforcement and concrete. This failure mode revealed unexpected critical crack pattern and failure mode. The research of concrete beams flexurally reinforced with GFRP bars without stirrups indicated two failure modes: typical shear-compression and a new one leading by the bond losing between the ordinary reinforcement and concrete.

Relation between Tensile Strength and Modulus of Rupture for GFRP Reinforcing Bars

AbstractThis paper presents an investigation correlating tensile properties of glass fiber–reinforced polymer (GFRP) bars with the results obtained from flexural testing. Composite bars, in contras...

Flexural performance of hybrid GFRP-Steel reinforced concrete continuous beams

This paper presents the experimental results of five large-scale hybrid glass fiber reinforced polymer (GFRP)-steel reinforced concrete continuous beams compared with two concrete continuous beams reinforced with either steel or GFRP bars as reference beams. In addition, two simply supported concrete beams reinforced with hybrid GFRP/steel were tested. The amount of longitudinal GFRP, steel reinforcements and area of steel bars to GFRP bars were the main investigated parameter in this study. The experimental results showed that increasing the GFRP reinforcement ratio simultaneously at the sagging and hogging zones resulted in an increase in the load capacity, however, less ductile behaviour. On the other hand, increasing the steel reinforcement ratio at critical sections resulted in more ductile behaviour, however, less load capacity increase after yielding of steel.The test results were compared with code equations and available theoretical models for predicting the beam load capacity and load-deflection response. It was concluded that Yoon's model reasonably predicted the deflection of the hybrid beams tested, whereas, the ACI.440.1R-15 equation underestimated the hybrid beam deflections. It was also shown that the load capacity prediction for hybrid reinforced concrete continuous beams based on a collapse mechanism with plastic hinges at mid-span and central support sections was reasonably close to the experimental failure load.

Residual behaviour of glass FRP bars subjected to high temperatures

The adoption of glass fiber reinforced polymer (GFRP) bars is becoming an interesting solution for different structural application, as a replacement of ordinary steel reinforcement, mainly for durability performance. The behavior of GFRP reinforcement, after high temperature exposure, is of critical importance for applications in concrete structures potentially subjected to fire. Accordingly, the aim of this study is the experimental evaluation of the residual behavior of GFRP bars subjected to different temperatures treatments, ranging between 100 and 700 °C. In particular, tensile tests on E-CR Glass FRP bars with nominal diameter of 14 mm were carried out after thermal treatment in an electric muffle, in order to characterize the degradation of the material residual properties after high temperature exposure. Young’s modulus and tensile strength decay were recorded. The experimental results are discussed with reference to practical structural applications as tunnel segmental lining.

Effect of Glass Fiber-Reinforced Polymer Reinforcement Ratio on the Axial–Flexural Strength of Reinforced Concrete Columns

Effect of Glass Fiber-Reinforced Polymer Reinforcement Ratio on the Axial–Flexural Strength of Reinforced Concrete Columns

Life cycle cost analysis of structural concrete using seawater, recycled concrete aggregate, and GFRP reinforcement

Using seawater and recycled concrete aggregate (RCA) in a concrete mix is potentially advantageous from a sustainability perspective. However, the high chloride levels expected in such a case demands the use of non-corrosive reinforcement in lieu of normal black steel to avoid corrosion problems. Glass fiber reinforced polymer (GFRP) is considered promising as an alternative reinforcement owing to its corrosion resistance and acceptable mechanical properties that minimize maintenance and repairs and extend service life. However, the relatively high initial cost of GFRP bars may mitigate its potential use. To account for these factors, a life cycle cost analysis (LCCA) has been conducted to establish the relative cost savings of structural concrete combining seawater, RCA, and GFRP reinforcement in high-rise buildings compared with a traditional concrete mix and other reinforcement materials, such as black steel and stainless steel.The proposed combination of seawater, RCA, and GFRP in structural concrete was found to achieve cost savings over a 20-year period following initial construction. The life cycle cost (LCC) obtained for the proposed combination was approximately 50% less than that of the conventional counterpart (i.e. concrete with freshwater, natural aggregates, and black steel) based on a 100-year study period. The use of stainless-steel reinforcement to enhance durability was also found to be potentially advantageous but less cost-effective than using GFRP. The LCC of stainless-steel reinforced concrete was estimated to be 15% lower than that of the traditional steel-reinforced counterpart, with a payback period of 50 years.Results were found to be highly sensitive to the assumed discount rate and construction costs. The proposed combination achieved cost savings only with a real discount rate (r) of 5.9% or higher. Likewise, using stainless-steel reinforcement was found cost-effective at r⩽1.35% and nominal construction costs exceeding 85% of the material cost. The differences in concrete mixture cost, however, appeared to have insignificant influence on the ultimate LCCA results compared to those obtained from altering the reinforcement material.

The Bond Strength of Glass Fiber Reinforced Polymer (GFRP) Reinforcement with Monolith Concrete

One of the considerations in selecting Glass Fiber Reinforced Polymer (GFRP) as a substitute for conventional reinforcement is its ability against corrosion makes it suitable for structures directly related to land, water, and corrosive areas. In terms of strength, GFRP which has high yield strength is very suitable as a reinforcement to hold the shear force. Similarly as with steel bar, GFRP reinforcement is used as a composite material of reinforced concrete; therefore, it is worth to know the grade of the bond strength. The bond strength is one of the important factors in order to have a good interaction between GFRP and concrete in holding work loads on structures, so that the study is conducted to get the grade of the bond strength of GFRP reinforcement with monolith concrete casted. The experiment is using the pull out test with a cube specimens, sized 250 mm × 250 mm × 250 mm and GFRP bar sized 25 mm diameters. Bond strength of GFRP reinforcement will then be closely compared to the bond strength of BJTS40 deform rebar sized 25 mm diameters. The concrete used in this study has about f'c 100 MPa. The test results indicate the grade of bond strength of GFRP reinforcement with concrete reaches 6.54 MPa and the bond strength of steel bar with concrete reaches 8.22 MPa. The grade of bond strength of GFRP reinforcement is smaller 79.56% than the bond strength of the steel reinforcement. The failure happened on all test objects is the mode of splitting failure.

Durability and degradation mechanisms of GFRP reinforcement subjected to severe environments and sustained stress

Despite the large amount of research that has been carried out to date on the use of glass fibre reinforced polymer (GFRP) bars in concrete, one factor still hindering their widespread use in civil engineering applications is the lack of comprehensive data on their long-term in-service performance. This paper presents the test results of an experimental study investigating the physical and mechanical properties of GFRP bars exposed to severe environments and subjected to different levels of sustained load. The test environments included moist concrete, alkaline solution and tap water, with temperatures varying from 20 °C to 60 °C. The mechanical properties of the bars were characterized through direct tension, flexural and inter-laminar shear tests, while the physical and chemical properties were determined through the implementation of a series of complementary techniques, including moisture absorption measurements, scanning electron microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Energy dispersive X-ray analyses (EDX). The test results showed that the elevated temperatures play a key role in triggering and accelerating the development of critical degradation mechanisms. The reduction in the tensile strength of all conditioned samples subjected to a sustained stress equivalent to 3000 με was always within the limits recommended in existing codes for high durability bars, while a lower average strength retention was observed for higher levels of sustained stress (equivalent to 5000 με). Finally, it can be concluded that the long-term mechanical properties of the tested GFRP bars appeared to be mainly affected by moisture diffusion through the resin rich layer and debonding at the fibre/matrix interfaces due to the dissolution of the silane coupling agents.

GLASS FIBRE REINFORCE POLYMER STRUCTURAL SELECTION AS CONCRETE BEAM REINFORCEMENT

Fibre Reinforced Polymer (FRP) made of a combination of continuous fibre embedded in resin matrix is an advanced composite material that has been identified as a potential new construction material. Some of the advantages of FRP are high tensile strength, lightweight, non-magnetic and durable. Since it is a non-corrodible material it may be used as reinforcement in concrete member. This paper presents the performance of concrete beams reinforced with different types of glass Fibre Reinforced Polymer (GFRP) sections. Two concrete beams, 125x200x2400 mm, reinforced with GFRP I-section and GFRP plate were cast and tested to study their flexural behaviour. Comparison was made with a control beam on the aspect of ultimate load, load-deflection behaviour, load-reinforcement strain behaviour, and mode of failure. The experimental results show that beams reinforced with GFRP sections experienced lower load carrying capacity, lower stiffness, larger deflection and less number of cracks. The failure of the GFRP reinforced concrete beams was either by crushing of concrete at the compression zone or rupture of the GFRP reinforcement.

Experimental Research of Continuous Concrete Beams with GFRP Reinforcement

Continuous beams are often used within RC structures, which are exposed to aggressive environmental impact. The use of the fiber‐reinforced polymer (FRP) reinforcement in these objects and environments has a big significance, taking into account tendency of steel reinforcement to corrode. The main aim of these research studies is to estimate ability of continuous beams with glass FRP (GFRP) reinforcement to redistribute internal forces, as a certain way of ductility and desirable behaviour of RC structures. This paper gives the results of experimental research of seven continuous beams, over two spans of 1850 mm length, cross‐section of 150 × 250 mm, that are imposed to concentrated forces in the middle of spans until failure. Six beams were reinforced with different longitudinal GFRP and same transverse GFRP reinforcements, and one steel‐reinforced beam was adopted as a control beam. The main varied parameters represent the type of GFRP reinforcement and ratio of longitudinal reinforcement at the midspan and at the middle support, i.e., design moment redistribution. The results of the research have shown that moment redistribution in continuous beams of GFRP reinforcement is possible, without decreasing the load‐carrying capacity, compared to elastic analysis. The test results have also been compared to current code provisions, and they have shown that the American Concrete Institute (ACI) 440.1R‐15 well predicted the failure load for continuous beams with GFRP reinforcement. On the contrary, current design codes underestimate deflection of continuous beams with GFRP reinforcement, especially for higher load levels. Consequently, a modified model for calculation of deflection is proposed.

Evaluation of interface shear behavior of GFRP soil nails with a strain-transfer model and distributed fiber-optic sensors

A glass fiber reinforced polymer (GFRP) material is a newly developed material for slope reinforcement. In this study, distributed optical fiber sensors are developed to characterize the interface shear stress–strain behavior in GFRP soil nails with a strain-transfer model. The GFRP bar with a diameter of 40 mm was used as a reinforcing element in a soil slope subjected to excavations. A newly distributed fiber optic sensors are developed to measure the axial strains of the GFRP reinforcement which was then inserted into a drilled hole together with pressure grouting. The calibration of distributed fiber optic sensors indicated that the strains along the GFRP bar can be accurately measured by the distributed sensors. An analytical strain-transfer model is developed and then verified with a finite element model. The comparisons indicate that the strain-transfer model could be able to obtain the shear strain and stress at the cement grout–soil interface from arbitrary strain of the GFRP bar. Finally, a field project study is conducted for the condition assessment of a GFRP soil nail with the interface shear stress at different excavation depths. The potential failure surface is identified at the position where the maximum shear stress occurs, that is, at the point around 4.5 m away from the soil nail head. Results in terms of the shear stress are able to detect the active and passive zones of the soil nail. A further analysis indicates that the health condition of the GFRP soil nail can be determined with the distributed fiber sensors and strain-transfer model.