Flexural Performance of Glass Fiber-Reinforced Polymer and Highly Ductile Stainless-Steel Bar Hybrid-Reinforced Concrete Beams

To investigate the flexural performance of hybrid-reinforced concrete (HRC) beams before and after exposure to chloride environment comparatively, 12 HRC beams with two types of reinforcements of glass fiber reinforced polymer (GFRP) bars and steel bars, and four steel-reinforced concrete (SRC) beams were fabricated. Based on definitions of the balanced reinforcement ratio and the appropriate HRC beam, the calculation model of the flexural capacity of HRC beams after exposure to chloride environment was proposed in this study. The experimental results verified the validity of the plane section assumption on all test HRC beams. It is found that the deflection of unconditioned HRC beams increases faster than that of unconditioned SRC beams but slower than that of conditioned HRC beams exposed to chloride environment. Besides, the flexural capacity of conditioned HRC beams decreases due to the exposure and the retention ratio of flexural capacity correlates positively with the ratio of nominal reinforcement ratio converted by the elastic modulus to balanced reinforcement ratio converted by the elastic modulus ( ρ nom,E / ρ b,E ). The good agreement between the predicted values of flexural capacity and measured ones shows the applicability of the calculation model proposed for HRC beams.

Behaviour and design of welded stainless steel beams with compact sections under flexure and shear

Research progress on short-term mechanical properties of FRP bars and FRP-reinforced concrete beams

Fiber reinforced polymer (FRP) has been applied not only for the simple structures but also for the advanced structures such as bridges or highway bridges for sustainable construction. In case of bridges or highway bridges, the structures experience not only static loadings but also fatigue loadings that may limited the serviceability of the bridge structures. In order to extend of the application of FRP on the such bridge structures to have a sustainable structures, the flexural capacity due to fatigue loading should be clarified. Glass composed FRP sheet namely Glass Fiber Reinforced Plastics (GFRP) is most commonly used due to its relatively lower cost compared to the other FRP materials. GFRP sheet is applied externally by bonding it on the concrete surface. Many studies have been done to investigate the flexural capacity of concrete beams strengthened using GFRP sheets. However, studies on the flexural capacity after fatigue loadings are still very rarely. This study presented the results of experimental investigation on the flexural capacity of the strengthened concrete beams after fatigue loadings. A series of concrete beams strengthened with GFRP sheet on extreme tension surface were prepared. Results indicated that after 800000 time of load cycle, the flexural capacity of beams specimens may decrease to only approximately 60%. The beam failed due to delaminating of GFRP sheet.

Experimental and analytical investigation on structural behavior of two-layer fiber-reinforced concrete beams reinforced with steel and GFRP rebars

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.

This study aims at experimentally and theoretically investigating the cracking moment (Mcrc) of hybrid Fiber Reinforced Polymer (FRP)/steel Reinforced Concrete (RC) beams. Six hybrid Glass FRP (GFRP)/steel and three GFRP RC beams with various GFRP and steel reinforcement ratios are tested in four-point bending scheme. Experimental results indicate that both GFRP and steel rebars affect Mcrc, but the effect of steel reinforcement is more significant. When the steel reinforcement ratio increases to 1.17%, Mcrc goes up to 15.9%, while the same value for GFRP is only 9.7%. An analytical method is proposed based on the plain section assumption and nonlinear behavior of materials for estimating Mcrc. The proposed model shows a good agreement with the experimental data conducted in this study and collected from the literature. The results of the parametric study give evidence of the positive effects of hybrid reinforcement ratios and elastic modulus of FRP on Mcrc of hybrid RC beams.

To address the issue of steel corrosion, fiber-reinforced polymer (FRP) bars, particularly glass fiber-reinforced polymer (GFRP) bars, have been increasingly employed as alternatives to steel rebars in various applications. However, GFRP exhibits a reduced elastic modulus compared to steel rebars. GFRP demonstrates a linearly elastic behavior till failure, indicating that it is a brittle material. To overcome such disadvantages, engineered cementitious composite (ECC) concrete that has a high ductility can be used instead of traditional concrete in tension region. In this paper, nine partial ECC beams, reinforced either solely with GFRP bars or with a GFRP-steel bars hybrid configuration, were designed and experimentally evaluated to examine their flexural performance. In order to provide a composed beam with excellent serviceability, ECC concrete was used in key parts inside the tension zone. The primary variables examined in this research included the type of reinforcement used, ECC configurations either in a U-shaped form work or as a bottom layer only, ECC bottom layer thickness in tension, and the influence of incorporating GFRP bars on the flexural performance. Beams were tested under four-point bending to evaluate failure modes, cracks distribution, load capacity, deflection, and crack width. The experimental findings indicated that the observed failure mode aligned with the intended design failure mode. The data obtained for cracking, yielding, and ultimate capacity showed a good agreement with proposed models and codes equations. The deflection and crack width of hybrid-reinforced concrete (RC) beams were less than GFRP-RC beams. The proposed U-shaped ECC form work had a significant effect in increasing the distribution of vertical cracks, minimizing the mean distance between adjacent cracks, and reducing the measured crack width by 40%. In addition, increasing the thickness of ECC layer in tension area or adding side ECC concrete led to an increase in the distribution of vertical cracks, decreasing in the measured crack width, and had a slightly effect on deflection and load capacity. Finally, increasing the ratio of GFRP bars to steel bars (Af/As) increased the deflection, while the measured crack width almost has the same value due to the existing of ECC concrete layer.

Strengthening of shear critical RC beams with various FRP systems

The use of fiber reinforced polymer (FRP) bars to reinforce concrete beams has received significant attention in the past decade due to their corrosion resistance, high tensile strength, and excellent non-magnetic properties. Glass FRP (GFRP) reinforcing bars have gained popularity due to the relatively lower cost compared to carbon FRP (CFRP) bars. In this study, sixteen concrete beam finite element models were created using the finite element computer program ANSYS to perform linear and non-linear analyses. Twelve beams were longitudinally reinforced with GFRP bars, while the remaining four beams were reinforced with conventional steel bars as control specimens. In terms of mechanical properties, FRP reinforcing bars have lower modulus of elasticity compared to conventional reinforcing steel and remain linear elastic up to failure. This leads to lack of plasticity and a brittle failure of beams reinforced with FRP bars. The objective of this study is to investigate flexural behavior of concrete beams reinforced with GFRP reinforcing bars. Some of the parameters incorporated in the numerical analysis include longitudinal reinforcement ratio and compressive strength of concrete, both of which affect the flexural capacity of beams. It is shown in this study that replacement of traditional reinforcing steel reinforced bars by GFRP bars significantly decreases mid-span deflection and increases ultimate load. The strain distribution along GFRP longitudinal reinforcing bars is totally different from that of traditional steel bars.

Materials technology is an excellent opportunity to be developed industrially and on a needs scale according to the demands of society, namely supporting the environment, low maintenance, and long-term use. Using composite materials with reinforced polymers is a hot topic of discussion in civil engineering as new materials, strength/stiffness enhancers, or applications in building rehabilitation or renovation. Fiber Reinforced Polymer (FRP) is excellent as a new material because, in addition to being lightweight, corrosion resistant, and easy to work with, it also has high flexural strength, so it is a consideration to replace and or strengthen steel materials that are high in cost value. However, until now there has not been found the correct pattern or variant and volume of fibre so that it can be an alternative to the use of steel. The purpose of the study was to experimentally determine the flexural strength of Glass Fiber Reinforced Polymer (GFRP) hybrid beams either with steel reinforcement, with GFRP reinforcement, or with steel and GFRP combination reinforcement and different GFRP ratios (variants) through two-point load bending tests.The designed model is a development of a previous study that used one layer of 4 mm and produced a flexural strength smaller than the targeted flexural strength, so in this study, two layers of 8 mm were used. In addition, other experimental data that has been carried out from the literature is also used where the results of parametric studies provide evidence of the positive effect of hybrid steel and GFRP reinforcement ratios when obtaining GFRP models and volumes.The materials used to manufacture concrete beam test specimens 53x15x15 cm3 with quality of fc'35MPa have been tested according to SNI standards and meet both the minimum and maximum requirements specified. Based on the results of the material test, it is planned that the characteristic concrete quality fcr'=40.31 MPa, and based on the compressive strength test, the quality fcr'=41.68MPa is produced.The hybrid designed material with concrete or concrete and steel has been tensile tested with a maximum arcing load for the two layers = 8 mm variant; the tensile strength of the GFRP woven roving type with two layers 2 x 4 mm is 92.66 MPa. While plain steel reinforcement Diameter 8mm quality 280 MPa has a minimum tensile strength of 350 MPa (3.8 times the tensile strength of GFRP 8 mm).The results of testing and calculating the effect of GFRP as a substitute for steel reinforcement contributed to the flexural strength of concrete beams on average by 47.52%. In comparison, the contribution of flexural strength produced by concrete with steel reinforcement was 107.09%. The concrete variant of hybrid steel reinforcement and GFRP contributes to an increase in the average flexural strength of 117.02% > 4.8% compared to steel-reinforced concrete beams alone.

Effect of the NSM material and area on the flexural response of normal strength concrete beams internally reinforced with GFRP and steel bars

Based on existing experimental data and analysis, seven different fiber-reinforced polymer (FRP) bar models including carbon fiber-reinforced polymer (CFRP), basalt fiber-reinforced polymer (BFRP), aramid fiber-reinforced polymer (AFRP), glass fiber-reinforced polymer (GFRP), GFRP and CFRP combined (G–C), GFRP and AFRP combined (G–A), BFRP and CFRP combined (B–C), and BFRP and AFRP combined (B–A) were established. Finite element simulation analysis was conducted on seven different FRP bar combinations under static load bending tests. The flexural behavior of the specimens reinforced with different FRP bar combinations and their influencing factors were analyzed. The results showed that using AFRP as the reinforcement material for FRP composite bars in FRP reinforced concrete beams cannot effectively enhance the overall load-carrying capacity of the composite bars. The combination of CFRP with GFRP and BFRP bars significantly increases the stiffness of the FRP bar structure and improves the structural load-carrying capacity of the concrete beams.

The behavior of structural elements under different loading conditions decides the performance of the built structures. Fiber-reinforced concrete and fiber-reinforced polymers (FRPs) have received increasing attention in recent years for many structural applications. Steel fibers, when added into concrete as micro-reinforcement, impart a bridging effect, resulting in enhanced mechanical properties. FRPs are most commonly composed of glass, aramid, or carbon fibers in a polymeric matrix and can be tailor-made to provide a large variety of material properties to suit the prerequisites of the engineer. This article presents an experimental investigation of steel fiber reinforced concrete beams externally strengthened with glass fiber reinforced polymer (GFRP) laminates to study their static flexural behavior and failure modes. The experimental program consisted of six concrete beams strengthened with GFRP laminates, and one concrete beam was left unstrengthened to serve as the control beam. The beams were designed for under-reinforced conditions and cast with different fiber volume fractions (Vf) and GFRP laminate thickness (tf). The beams were tested under monotonic loading until failure. The experimental results showed that the strengthened beams exhibit significantly improved performance compared with the control beams in terms of strength, deformation, ductility, and crack resistance under monotonic loads.

Corrosion of steel reinforcement is one of the main problems facing the construction industries throughout the world. Many methods have been used to minimize the problem but without success. Thus, more durable reinforcements are highly needed to replace conventional steel. Glass Fibre Reinforced Polymer (GFRP) bars provide a good alternative reinforcement due to its non-corrodible characteristic. This paper presents the flexural behaviour of concrete beams, each measuring 150 x 255 x 2400 mm and reinforced with GFRP and stainless steel bars. The performance of the beams was analysed in terms of their load carrying capacity, load-deflection, load-concrete strain, load-reinforcement strain, cracking and mode of failure. The experimental results show that beams reinforced with GFRP bars experienced lower ultimate load, lower stiffness, and larger deflection at the same load level compared with control beam. However, the performance of the GFRP reinforced concrete beams improved slightly when stainless steel mesh was used as shear reinforcement.