Glass Fiber Reinforced Polymer Reinforcement Research Articles

Structural behavior of one-way slabs reinforced by a combination of GFRP and steel bars: An experimental and numerical investigation

Abstract Glass- fiber-reinforced polymer (GFRP) offers a significant alternative to steel in reinforced concrete, with superior corrosion and fire resistance. Though less ductile and more brittle in stress–strain behavior than steel, it is very helpful to combine GFRP with steel reinforcement that improves the structural behavior. This research investigates the flexural characteristics of a one-way slab reinforced by a combination of GFRP and steel reinforcement. Three identical concrete slabs ((1500 × 550 × 120) mm and 43 MPa) were tested under static load with GFRP replacement ratios of (0, 20, and 40)%. The experimental data were utilized to verify a numerical model. The experimental outcomes indicated a substantial impact of the GFRP replacement ratio on the failure mode. The failure mode was flexural, flexural-shear, and shear regarding the reference slab, 20%, and 40% replacement, respectively. GFRP replacement influenced ductility and ultimate load by (9.13 and 10.7)% and (−21 and 5.0)% for replacement ratio (20 and 40)%, respectively. Based on the numerical analysis, the parametric study (considerably affected the structural response. Failure mode changed to flexural, and shear-flexural concerning (20 and 40)%, respectively. The optimum load was characterized at 40%, while max toughness and ductility were achieved at 20%.

An integrated optimization and ANOVA approach for reinforcing concrete beams with glass fiber polymer

Concrete beams are commonly used in construction projects to provide structural support. Reinforcing these beams with steel and Glass Fiber Reinforced Polymer (GFRP) can increase their strength and durability. Steel reinforcement is a traditional method used for decades, while GFRP is a newer material that offers several advantages, including corrosion strength and lighter weight. Combining both materials to reinforce concrete beams can result in a stronger and more resilient structure, making it an ideal choice for many construction projects. In this study, the behavior of reinforced concrete beams with steel and GFRP reinforcement is numerically investigated, and the effect of steel percentage and GFRP percentage on the mechanical strength and energy response of the beam is determined using the Response Surface Methodology (RSM). Using the ABAQUS software, a widely used Finite-Element Analysis (FEA), the numerical modeling is first verified, and then targeted analyses are performed on the beam using the tests specified by the RSM. Then, based on the strength and energy of the beam, a two-variable Analysis of Variance (ANOVA) and two-objective optimization are performed to investigate the effect of changing each parameter of steel percentage and GFRP percentage on beam strength and energy. Several laboratory studies have been conducted on the behavior of concrete beams with steel and GFRP bars, but no research has statistically and numerically examined their behavior. We also simultaneously optimized both strength and energy parameters based on the ratio of steel and GFRP and compared them with numerical values. We show an interaction relationship between steel and GFRP ratio in the strength and energy of concrete beams. In the beam with hybrid reinforcement, with the increase of steel and GFRP ratios, the amount of strength and energy does not increase linearly, and there is a quadratic relationship between them.

Design and flexural behavior of steel fiber-reinforced concrete beams with regular oriented fibers and GFRP bars

In this study, steel fiber-reinforced concrete (SFRC) beam structures with regular oriented steel fibers are designed and prepared by using an assembled solenoid device. Fiber orientation is not arranged in a single direction but is similar to the direction of tensile stress of the beam in bending load conditions. With application of inductive test method and image processing technology, fiber orientation coefficient of SFRC was evaluated and increased from 0.5 to 0.7–0.8 after fiber alignment. To describe and analyze the flexural behavior of SFRC beams with regular oriented fibers and glass fiber-reinforced polymer (GFRP) rebars, 14 concrete beams with different parameters were fabricated and subjected to a four-point bending test. Specifically, the parameters included fiber content, fiber orientation, GFRP reinforcement ratio and different layer sections. The results showed that optimizing fiber orientations to the tension zone of the section led to a higher flexural strength and can well restrain the development of crack widths with comparison to randomly distributed fibers. The peak load and energy absorption increased by 7 % and 12.4 % after fiber alignment with a fiber volume fraction of 1.5 %. The combination of randomly and regularly distributed steel fibers in the form of two-layer composite members can be an efficient solution to improve the flexural performance for purpose of the optimum distribution and direction of steel fibers, and reduce the engineering cost.

Experimental Study of Dimensional Effects on Tensile Strength of GFRP Bars

This study explores the mechanical properties of Glass Fiber-Reinforced Polymer (GFRP), a high-performance composite material, focusing on how varying diameters affect its tensile strength, modulus, and elongation. Experimental data obtained from three sets of tensile tests on 10, 12, and 25 mm bars helped establish a stress–strain relationship for GFRP reinforcements, considering diameter changes, and a formula for calculating the ultimate tensile strength based on diameter. Utilizing the weakest chain theory and the Weibull distribution, the research found that GFRP’s tensile strength diminished with increased diameter, while the elastic modulus behaves oppositely. The analysis, grounded in the weakest chain theory, identifies the specimen’s effective volume as a critical factor in the size effect of GFRP bars. Moreover, the study proves a significant size effect on GFRP’s tensile properties, validating the theory’s application in predicting the strength of GFRP bars of varying sizes and recommending a specimen length range of 30–40 times its diameter for standardization purposes.

Performance of GFRP-RC precast cap beam to column connections with epoxy-anchored reinforcement: a numerical study

In this study, a detailed finite element investigation was conducted to evaluate the performance of glass fibre-reinforced polymer (GFRP) RC precast cap beam to column connections connected with epoxy-anchored reinforcement (epoxy duct connection). The developed model was initially validated against three experimental results with different anchored GFRP reinforcement considering the effect of reinforcement slippage. Different interaction models for slippage simulation were evaluated and discussed. The validated model was then utilized to investigate the effect of anchored length, bar diameters, anchored reinforcement amount, and the geometry of the connection. The results indicate that an optimum anchored length, equal to 25 times the bar's diameter, should be provided. It was also found that the precast beam-to-column element connection should be designed for a moment capacity at least 25% higher than that of the column section. Moreover, a minimum beam width, depth and beam overhanging length of 1.75, 1.6 and 0.25 times the column width respectively were recommended to be considered in design. The results from this study can provide direct guidelines for the design of precast GFRP-RC cap beam to the column connection with epoxy anchored reinforcement, especially in applications where precast elements need to be erected quickly, a novel method that can accelerate the construction of jetties and bridges.

Structural behavior of concrete slabs made of seawater sea sand and reinforced with GFRP reinforcement under flexural loading

Seawater sea sand concrete (SSC) structures reinforced with glass fibre-reinforced polymer (GFRP) reinforcing bars offer a promising alternative to conventional reinforced concrete, especially in the face of depleting clean water and river sand. However, comprehensive studies on the flexural performance and cracking behaviour of SSC structures reinforced with GFRP reinforcing bars are currently limited. This study delves into the influence of longitudinal reinforcement ratio on the flexural and cracking behaviour of SSC slabs reinforced with GFRP reinforcing bars under quasi-static loads, as well as the bond behaviour of GFRP reinforcing bar and SSC. The experimental program included 9 large-scale slabs and 30 pull-out specimens, revealing that the longitudinal reinforcement ratio significantly affects the flexural performance, particularly at higher load levels. Increased reinforcement ratio improved flexural stiffness, reduced deflection and crack width, enhancing load-carrying capacity and energy absorption. Although bond strength decreased at the serviceability load (up to 47%), a marginal reduction was observed at the ultimate state. The study proposes a semi-empirical equation for the effective moment of inertia of SSC slabs, accounting for the influence of reinforcement ratio on cracking moment and reduced bond strength of GFRP reinforcing bars. This equation aligns well with experimental results, demonstrating low error and coefficient of variation.

Size effect on compressive behavior of GFRP bars

In the last three decades, studies investigating the use of Glass Fiber Reinforced Polymer (GFRP) bars as an alternative to conventional steel rebars have increased due to their corrosive resistance. In addition to corrosion resistance, GFRP bars utilize high specific tensile strength, which makes them highly desirable in civil engineering applications. However, major design guidelines for GFRP-reinforced concrete structures currently do not consider their compressive contribution. Nevertheless, there is a growing trend in utilizing GFRP bars as compressive elements, driven by various studies demonstrating their ability to bear compressive loads effectively. This increasing demand underscores the need to comprehend the mechanical properties of GFRP bars, particularly in terms of their compressive behavior. Furthermore, a standardized test method to evaluate their compressive properties has not yet been developed. Addressing these gaps, this research paper focuses on investigating the influence of specimen size on the compressive strength of GFRP bars, specifically emphasizing on the compressive properties of GFRP bars. Compressive tests were conducted on GFRP specimens with varying diameters while maintaining a constant slenderness ratio. The findings from these compression tests shed light on the critical role of size in the compressive behavior of GFRP. This research emphasizes the importance of considering size as a significant parameter in designing mechanical properties for GFRP reinforcements.

Lap splice assessment of GFRP rebars in reinforced concrete beams under flexure

To increase the knowledge and experience gained from the existing literature regarding the bond behavior of glass fiber-reinforced polymer (GFRP) rebars, a total of sixteen full-scale GFRP-reinforced concrete beams were subjected to a four-point bending test. The GFRP reinforcement comprised a single M16 (No.5) GFRP sand-coated bar without confinement reinforcement in the constant moment region. The research parameters encompassed three different lap-spliced lengths (i.e., 40-, 60- and 80-db) and two distinct concrete clear covers (i.e., 19 mm and 38 mm) to assess their impact on bond strength and failure modes. Strain gauges along the GFRP rebar and small potentiometers positioned at the end of the splice within the constant moment zone allowed detailed measurements. Rebar slippage in lap-spliced specimens was observed to have a limited impact on bond stress transfer capacity and member flexural stiffness until reaching maximum slippage. Concrete cover significantly influenced the behavior of lap-spliced GFRP-RC beams, with 38 mm-cc specimens exhibiting an average 21% higher capacity compared to 19 mm-cc specimens. The ACI expression exhibited an average overestimation of 24% for 19 mm-cc specimens, whereas for 38 mm-cc specimens, it offered a more accurate estimation, with only a 10% over-prediction. However, the computed lap splice length to achieve the required tensile stress was reduced from the one required by ACI due to extra factors implemented in the development length equation. This aligns with prior research findings that identified unconservative values of bond stress when employing the ACI provisions for specific combinations of parameters, highlighting the necessity for refinements in predictive models.

Advanced Strengthening of Steel Structures: Investigating GFRP Reinforcement for Floor Beams with Trapezoidal Web Openings

Enhancing existing steel structures becomes imperative upon alterations in usage or geometric configurations, such as introducing web openings in floor beams to accommodate various services. The utilization of welded steel plate and conventional strengthening methods often presents challenges, which may be mitigated through the adoption of composite materials like Fiber Reinforced Polymers (FRP). However, research on the application of FRP to steel beams with web openings remains limited, predominantly focusing on beams with rectangular openings of modest dimensions. This study delves into the application of Glass Fiber Reinforced Polymers (GFRP) to strengthen reinforced steel floor beams featuring trapezoidal openings. Leveraging a rigorously validated numerical model derived from previously published findings by a contributing researcher, the investigation showcases that the proposed GFRP reinforcement scheme exhibits performance comparable to conventional steel plate welding techniques, while preserving the inherent strength of the original solid beams.

A NEW APPROACH TO TENSILE TESTING OF GFRP BARS

Tensile testing is a critical procedure for evaluating the mechanical properties of Glass Fiber Reinforced Polymer (GFRP) bars, which emerged as an alternative to traditional steel reinforcement in reinforced concrete structures. While significant research has led to the development of testing standards for GFRP bars, their implementation often necessitates additional specimens and specialized equipment compared to their steel counterparts. This study proposes a new method for conducting GFRP tensile tests using standard equipment designed for conventional structural steel rebar testing. By employing existing devices, our approach offers a practical and cost-effective solution for assessing the tensile properties of GFRP reinforcement. This simplified testing method aims to enhance efficiency, facilitate wider adoption of GFRP bars in reinforced concrete structures, and contribute to the advancement of sustainable construction practices.

Effect of Wood Densification and GFRP Reinforcement on the Embedment Strength of Poplar CLT

Embedment strength is an important factor in the design and performance of connections in timber structures. This study assesses the embedment strength of lag screws in three-ply cross-laminated timber (CLT) composed of densified poplar wood with densification ratios of 25% and 50%, under both longitudinal (L) and transverse (T) loading conditions. The embedment strength was thereafter compared with that of CLT reinforced with glass-fiber-reinforced polymer (GFRP). The experimental data was compared with results obtained using different models for calculating embedment strength. The findings indicated that the embedment strength of CLT specimens made of densified wood and GFRP was significantly greater than that of control specimens. CLT samples loaded in the L direction showed higher embedment strength compared to those in the T direction. In addition, 50% densification had the best performance, followed by 25% densification and GFRP reinforcement. Modelling using the NDS formula yielded the highest accuracy (mean absolute percentage error = 10.31%), followed by the Ubel and Blub (MAPE = 21%), Kennedy (MAPE = 28.86%), CSA (MAPE = 32.68%), and Dong (MAPE = 40.07%) equations. Overall, densification can be considered as an alternative to GFRP reinforcement in order to increase the embedment strength in CLT.

Analytical and experimental shear evaluation of GFRP-reinforced concrete beams

Reinforced Concrete (RC) technology is advancing towards new frontiers enhancing its sustainability and durability through innovative materials. In particular, the application of Glass Fiber Reinforced Polymer (GFRP) bars, in lieu of steel reinforcement, shows excellent performance, especially in aggressive environments. Nevertheless, current international design guidelines and standards tend to be rather conservative, especially concerning shear reinforcement. This element hinders the technology’s competitiveness, not only in terms of material consumption but also in construction efficiency. This research aims to conduct an analytical comparison and experimental validation of the formulations found in some international standards pertaining to shear capacity in a specific case. The focus is on scenarios involving reduced shear reinforcement and cases where the number of stirrups falls below the minimum recommended by these standards. In the sample beam tests, two distinct flexural GFRP reinforcement ratios were employed to evaluate their influence on shear capacity, leading to diverse failure mechanisms: rupture of longitudinal GFRP bars and concrete crushing. The experimental results were used to compare the North American ACI, French AFGC, and Italian CNR shear capacity design approaches in the case of reduced transversal reinforced ratio. Analytical capacity expressions of the standards above are discussed with some remarks aiming at structural optimization.

Axial bearing capacity and ductility of seawater sea sand coral aggregate concrete (SSCC) columns reinforced with hybrid GFRP and corrosion resistant rebars

The shortage of fresh water and river sand resources and steel corrosion are becoming increasingly prominent in engineering construction. Seawater sea sand coral aggregate concrete (SSCC) and corrosion resistant reinforcement are promising materials in replacement of conventional concrete and steel in building structures in island and reef construction. This study investigated the axial compression performance of GFRP (glass fiber reinforced polymer) and corrosion resistant rebars hybrid reinforced seawater sea sand coral aggregate concrete columns. A total of eighteen short columns were tested for axial compression performance, including three reinforcement ratios (1.01%, 1.56%, 2.26%) and 5 reinforcement types (pure GFRP reinforcement or G, pure stainless steel reinforcement or S, pure epoxy coated steel rebar (ECSB) reinforcement or E, GFRP-stainless steel reinforcement or GS and GFRP-ECSB or GE). The failure modes of the column are recorded and analyzed, and the axial bearing capacity and ductility are calculated and analyzed. Results show that the bearing capacity of columns is positively correlated with the reinforcement ratio. Generally, the bearing capacity of S-SSCC column and E-SSCC column are not significant different, but both are larger than that of G-SSCC column. The bearing capacity of hybrid reinforcement GS-SSCC and GE-SSCC column is between S-SSCC column and G-SSCC column. Meanwhile, it indicates that the theoretical calculation results of bearing capacity agree well with the experimental results. The ductility analytical results exhibit that the studied column specimens have the highest ductility when the reinforcement ratio is 1.56%. Among different reinforcement types, the ductility of G-SSCC is the smallest and the GE-SSCC and GS-SSCC column show improved ductility compared with G-SSCC columns.

Investigation of different parameters affecting the crack width and kb coefficient of GFRP-RC beams

Crack width control is one of the criteria affecting the design of glass fiber-reinforced polymer (GFRP)-reinforced concrete (RC) structural components. The provisions available in the CSA S806-12 standard and ACI 440.1R-15 guideline for controlling the crack width of GFRP RC elements account for the bond between the GFRP reinforcement and surrounding concrete through the bond-dependent coefficient (kb). In those design standards and guidelines, each GFRP bar surface profile is assigned a kb value obtained from four-point bending beam tests. This study aims to experimentally investigate the parameters that affect the crack width and kb coefficient of GFRP reinforcing bars, enrich the literature with more kb results for ribbed and sand-coated GFRP bars, determine whether kb is a fixed value that is solely dependent on the bar surface profile (as assumed by the above standard and guideline), recalibrate the kb coefficient considering the experimental results of this study and available experimental data in the literature, and provide the FRP engineering community with an equation that is capable of anticipating kb values based on different configurational and material parameters. To achieve the objectives of this study, 16 large-scale RC beams were tested under a four-point bending test setup. The studied parameters included the clear concrete cover, bar spacing, bar diameter, concrete compressive strength, bar surface profile, and confinement provided by transverse reinforcement. The experimental results of this study were combined with the available database to recalibrate the kb values and propose a kb equation. The results showed that the kb coefficient varies when changing the reinforcement configuration of the beam.

Experimental Analysis of an Innovative Double Strap Joint Splicing of GFRP Bars by NSM Methods for Strengthening RC Beams

The double strap joint splicing of glass fiber reinforced polymer (GFRP) bars for reinforced concrete (RC) beams strengthening, applying the near surface mounting (NSM) method, has been proposed in the paper. The proposed method consists of application of the supplementary GFRP bars symmetrically positioned in the cut-off zone of the main GFRP reinforcement. The performances of this splicing method have been experimentally tested for the most unfavorable case of the GFRP reinforcement cut-off in the maximal bending moment zones. During the experiment, the varied parameter has been overlapping length of the bars, taking values of 20∅ and 40∅. Evaluation of the splicing technique is done comparing the experimental results with the results of the behavior of beams strengthened by GFRP bars without cut-off and with cut-off, but without splicing. Experimental research encompassed analysis of strength, stiffness, ductility, crack pattern, strains in the steel, GFRP reinforcement and concrete, and the failure modes of the beams. It has been shown that in case of the cut-off of the GFRP bar, strengthening effectivity decreases for 39%, and that in the case of bypassing the cut-off using double strap 20∅ and 40∅ long, strengthening effectivity decreased 23%, and 14% respectively, compared to the beam without GFRP bar cut-off. Using extrapolation, it has been shown that double strap with length of 60∅ provided strength equivalent to the case without cut-off. The result of application of this splicing method of the additional GFRP bars is significant increase of strength and serviceability of the strengthened RC beams.

ANALYSIS OF FINGER-JOINTS IN GLASS FIBER-REINFORCED POLYMER (GFRP) COMPOSITE GLUED LAMINATED TIMBER BEAMS

The objective of this paper was to evaluate the effect of finger-joint reinforcement on thebending strength and stiffness of glulam beams made from high-density Eucalyptus spp. glued with resorcinol-formaldehyde adhesive.Six glulam beams were tested: three reinforced with glass fiber-reinforced polymer(GFRP) and three unreinforced for comparison. The GFRP was placed between the last two laminatesand at the bottom edge of theglulam only in the finger-joint position. The stiffness and strength of glulam beams were evaluated using static bending tests, which showed that the use of GFRP reinforcement resulted in a gain of more than 100% in average ultimate bending moment and about 10% in average bending stiffness. Tocalculate the theoretical bending stiffness and normal stresses, a theoretical analysis of beam bending was performed using the transformed section method, which showed agreement with the experimental results.

EXPERIMENTAL FLEXURAL STRENGTH OF GLASS FIBER REINFORCED POLYMER (GFRP) HYBRID REINFORCED CONCRETE BEAMS

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.

A new robust equation for shear strength of GFRP-RC deep beams using hybrid experimental and synthetic data based-FE quasi-static analysis procedure

The main objective of this article is to propose a new, more robust, and comprehensive design equation for Glass-Fiber-Reinforced-Polymer (GFRP) reinforced concrete (RC) Deep Beams (DBs). The investigation is based on a numerical model using Quasi-Static Two-Dimensional FE simulation of GFRP-RC DBs. The numerical model is validated by calibrating four parameters (concrete dilatation angle ψ, concrete tensile strength fct, fracture energy Gf, mesh size) against data from ten full-scale experiments on GFRP-RC DBs available in the literature. Additionally, a numerical parametric study based on a full factorial design with 5 factors (and between 2 and 5 modalities) is conducted using the validated quasi-static FE model, which includes 360 large-scale GFRP-RC DBs. The impacts of primary design variables on the concrete contribution Vc to the shear capacity of GFRP-RC DBs are assessed. The effects of various geometrical and mechanical variables, such as cross-sectional dimensions (width b × height H), concrete compressive strength grade (fc), GFRP properties (modulus Ef, and strength ffu), GFRP reinforcement ratio (ρf), and shear span to depth ratios (a/df), are examined to understand the shear behavior of GFRP-RC DBs.The numerical simulations demonstrate that the proposed FE model accurately captures the behavior of GFRP-RC DBs. Building upon these findings, a new shear design equation is proposed for DBs, and its accuracy and robustness are compared with five established international design codes (ACI-440.1R-15, ISIS-Canada, CAN/CSA-S806-12, JSCE-1997, and BS-8110). The existing design codes significantly underestimate the concrete contribution to shear capacity, leading to uneconomical designs. In contrast, the new design equation provides a fair prediction of Vc, with a standard error of 7.734 % and 20.84 % compared to the FE and experimental datasets, respectively. This represents a substantial improvement over the existing design guides.

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

Strengthening the steel-reinforced concrete (RC) beams by fiber-reinforced polymer (FRP) elements have become common several years ago. Recently, the RC beams internally reinforced with FRP reinforcement, especially Glass FRP (GFRP) bars, became popular worldwide. The carbon FRP (CFRP) elements (strips and bars) were recently used to strengthen the internally GFRP RC beams. In contrast, using the GFRP elements to upgrade the RC beams, especially those with GFRP bars as the main tensile reinforcement, was rarely studied. In this paper, the GFRP bars were implemented as near-surface mounted (NSM) elements to upgrade the beams reinforced in their tension side with GFRP or steel bars. All beams were experimentally loaded in flexure using a four-point loading scheme. The experimentally studied parameters were the main tensile reinforcement area, NSM area, and main reinforcement properties. Moreover, a numerical model was established and validated using the available experimental data to investigate the impact of main and NSM materials properties and areas on RC beam response. The experimental results highlighted that increasing the internal and NSM GFRP area by 96% and 100 % increased the beam capacity by 61.6% and 59.7%, respectively, which underlined a slightly higher efficiency of the main reinforcement than NSM bars on the beam load capacity. In addition, substituting the main steel with GFRP bars for the beams upgraded with NSM GFRP reinforcement enhanced their capacities by 11.33–15.1%. This emphasized the great effect of the linear response of the FRP materials and their higher tensile strengths than steel on the interaction between the main and NSM reinforcement, especially after the steel yielding. The FE results showed the highest load capacity using CFRP and GFRP bars as main and NSM reinforcement for the simulated beams. Conversely, using CFRP bars as NSM strengthening was more efficient than GFRP bars for the RC beams with steel or GFRP bars.

Experimental Study and Discrete Analysis of Compressive Properties of Glass Fiber-Reinforced Polymer (GFRP) Bars.

Glass fiber-reinforced polymer (GFRP) has superior characteristics over traditional steel, such as lightweight, high strength, corrosion resistance and high durability. GFRP bars can be a useful alternative to steel bars in structures, specifically those in highly corrosive environments, as well as structures subjected to high compressive pressure such as bridge foundations. Digital image correlation (DIC) technology is used to analyze the strain evolution of GFRP bars under compression. It can be seen from using DIC technology that the surface strain of GFRP reinforcement is uniformly distributed and increases approximately linearly, and brittle splitting failure of GFRP bars happens due to locally occurring high strain at the failure stage. Moreover, there are limited studies on the use of distribution functions to describe the compressive strength and elastic modulus of GFRP. In this paper, Weibull distribution and gamma distribution are used to fit the compressive strength and compressive elastic modulus of GFRP bars. The average compressive strength is 667.05 MPa and follows Weibull distribution. Moreover, the average compressive elastic modulus is 47.51 GPa and follows gamma distribution. In order to verify that GFRP bars still have certain strength under compressive conditions, this paper provides a parameter reference for their large-scale application.