Polymer Rebars Research Articles

Improving the reliability of FRP bars tests by increasing the adhesive strength in specimen anchor

Test methods for reinforcing steel is not suitable for fiber reinforced polymer (FRP) rebars because it can cause destruction of the edge zones of the samples. The polymer matrix and fibers are not able to resist compression across the fibers. Existing test methods for FRP rebars do not contain information about the equipment and composition of the adhesive composition. The purpose of the study is to clarify the adhesive composition and design of the FRP specimen anchor. Methods. There were experimental studies of fiberglass reinforcement polymer rebars samples carried out. The following factors varied: the proportion of the components of the adhesive composition; the area of the adhesive contact of the FRP specimen anchor. Results and Discussion. The proportion of epoxy glue and quartz sand providing the test of automatic transmission is determined. The influence of the thread on the inner surface of the FRP specimen anchor on the adhesive strength in the contact zone «adhesive composition-steel» is estimated. A universal three-dimensional model of the centering plug for manufacturing using additive technologies has been developed. Conclusions. The results of the investigation can be used to upgrade the FRP rebars test methods.

Analytical Study on Seismic Performance of Self-Compacting Concrete Column Reinforced with Steel and GFRP Rebar

The self-compacting concrete is described as one of the environment friendly concrete which has several benefits over ordinary concrete. The main advantages of self-compacting concrete are that problem associated with vibration is eliminated. It is a non-segregating concrete that have benefits such as high bond to reinforcing steel, superior strength and durability, improved structural integrity etc. The Glass Fiber reinforced Polymer (GFRP) rebars are preferable alternative to steel rebars for minimizing corrosion problems In this paper, analytical study is carried out to investigate the seismic performance of self-compacting concrete circular columns reinforced with GFRP rebars and are compared with columns reinforced with steel rebars. The main parameters considered for the study are slenderness ratio and confinement techniques. The circular column of slenderness ratio 4, 6, and 8 are considered for the study. The seismic performance is carried out by Push over analysis using ANSYS software.

Experimental investigation into the flexural behaviour of basalt FRP reinforced concrete members

The durability of reinforced concrete structures is an ongoing challenge for engineers, particularly in harsh environments. In these conditions, concrete is susceptible to excessive cracking which allows water or other aggressive agents to penetrate the structure, thereby accelerating the deterioration, mainly through corrosion, of the steel reinforcement. The deteriorated concrete structures require frequent maintenance to achieve and extend their service life and may need expensive rehabilitation measures. The use of fibre-reinforced polymer (FRP) rebars, such as carbon and glass FRPs, can be an effective, sustainable and durable solution to enhance the durability of reinforced concrete structures in aggressive environments. Another type of FRP that has gained popularity in construction in the last two decades is basalt fibre-reinforced polymer (BFRP), which is the subject of the current paper. In order to investigate their behaviour, an experimental programme comprising five reinforced concrete beams and seven one-way spanning slabs has been conducted, and is described herein in detail. Three different types of reinforcement were included in the tests, namely sand-coated BFRP bars, ribbed BFRP bars as well as regular carbon steel reinforcement, for comparison. All of the members were tested up until failure. The test results are presented and analysed, with particular focus given to the cracking moment, ultimate moment capacity, deflections and also crack opening widths. The results are compared with the guidance currently available in several international design codes. In addition, based on the results and analysis presented herein, design recommendations for reinforced concrete with BFRP rebars are proposed.

Experimental investigation for GFRP rebar couplers for reinforced concrete

The use of fiber reinforced polymer (FRP) rebars is nowadays becoming popular in reinforced concrete (RC) construction due to their excellent inherent properties such as corrosion resistance, lightweight, and high strength to weight ratio. The steel rebars, being susceptible to corrosion, are being replaced by FRP rebars. The higher strength of FRP rebars, as compared to steel, requires larger lap lengths when embedded in concrete. Although laps in steel rebars can be replaced by mechanical couplers, this is not feasible for FRP rebars. Thus, the present study investigates the use of couplers for Glass FRP (GFRP) rebars. Three types of couplers were tried: (i) steel pipe coupler, (ii) CFRP pipe coupler, and (iii) CFRP sheet coupler. These couplers were tested in direct tension for assessing their feasibility and establishing the design requirements. Although the steel pipe coupler demonstrated excellent performance, the use of CFRP pipe and CFRP sheet couplers were not successful. However, the performance of CFRP sheet couplers can be improved by increasing the length of sheet, and/or number of wraps.

Effects of Grouting Defects in a Duct on the Bonding of Prestressing Strands

Insufficient grouting has a great effect on the bonding performance of pressing stand for a post-tensioned prestressed concrete beam, which leads to a decrease of beam's bending capacity. This study focused on the influence of defects of local grouting length and grouting fullness on the prestressing strand's bond performance. The prestressing strand pull-out test was used to evaluate the bonding performance of pressing stand with different defects of local grouting length and grouting fullness. The results indicate that two forms of grouting defects reduce the bonding properties of a prestressing strand, when the slip of the free end of prestressing strand is 0.12 mm (s = 0.12 mm), the bond stress decreases briefly. To analyze the bonding mechanism of the prepressing strand in duct, the bond stresses τ0 and τu at s = 0.12 mm and s = 25 mm were adopted as the characteristic parameters of bond stress to deduce the calculation formula of the bond strength by fitting the test data. A bond-slip constitutive model of prestressing strand in duct under two classes defects was proposed by improving the modified Eligehausen, Popov and Bertero (BPE) model of fiber reinforced polymer (FRP) rebars.

Seismic Assessment of Concrete Column Reinforced with Fiber Reinforced Polymer and Stainless Steel Rebars

The fiber reinforced polymer (FRP) rebar is utilized as a corrosion resistive reinforcement in the structural elements like a beam, column, and slab. The FRP rebar offers excellent mechanical and durability properties, like high strength to weight ratio, high stiffness, and corrosion resistance to structures. However, a lower ductility subjected to linear-elastic behaviour, and the brittle nature of FRP particularly in the case of column applications is getting attention among researchers. Whereas stainless steel (SS) having adequate ductility, low maintenance, and resistance to corrosion make it an ideal material for reinforcing applications. To improve the performance of FRP-reinforced elements and diminish the brittle behaviour, the present research is focused on the utilization of SS rebar in the plastic hinge region of the column along with FRP rebar in rest portion of a column. This hybrid configuration is adopted here to improve the ductility and corrosion resistance capacity of the RC column. The damage concentration of the hybrid column is analysed under the effect of nonlinear static loads. The parametric analysis is performed over the hybrid column to study the behaviour of different factors under pushover loading. The results indicate that the ductility of the SS-FRP RC column is achieved under seismic loads. The study reveals that axial load, the yield strength of steel and aspect ratio significantly affect the behaviour of the SS-FRP RC column.

Flexural Behavior of a Precast Concrete Deck Connected with Headed GFRP Rebars and UHPC.

Steel bent reinforcing bars (rebars) are widely used to provide adequate anchorage. Bent fiber-reinforced polymer (FRP) rebars are rarely used because of the difficulty faced during the bending process of the FRP rebars at the construction site. Additionally, the bending process may cause a significant decrease in the structural performance of the FRP rebars. Therefore, to overcome these drawbacks, a headed glass fiber-reinforced polymer (GFRP) rebar was developed in this study. The pull-out tests of the headed GFRP rebars with diameters of 16 and 19 mm were conducted to evaluate their bond properties in various cementitious materials. Moreover, structural flexural tests were conducted on seven precast concrete decks connected with the headed GFRP rebars and various cementitious fillers to estimate the flexural behavior of the connected decks. The results demonstrate that the concrete decks connected with the headed GFRP rebar and ultra-high-performance concrete (UHPC) exhibited improved flexural performance.

Comparison of steel and fiber-reinforced polymer rebars for mining applications: A numerical approach

Underground mines offer various non-favourable environmental conditions, one among them is the presence of corrosive elements which are not suitable for conventional materials such as steel. This problem can be avoided to a certain extent by using glass reinforced polymer (GRP) rebars. GRP rebars show high tenacity and excellent corrosion resistance compared to conventional steel which extends these materials application to constructions roofing supporting and columns. Thus this paper aims to carry out a comparative study of between steel and GRP rebars strength under tensile, compressive and bending forces using LS-DYNA. Numerical analysis results showed that the stresses generated under tensile and compressive loading are 25% and 37.25% higher for GRP rebars when compared to steel but within the safe limits. Similarly, deformation under tensile and compressive loading for GRP rebar is 62.16% and 87.12% higher compared to steel, respectively. However, load carrying capacity of GRP rebar of GRP rebar is the almost same as steel. Since both the materials showed no sign of damage under 40 kN, thus GRP rebar could be used as a replacement material instead of steel in roof supporting and column in mines.

Performance of hybrid bars in corrosion and flexure in concrete beams

Corrosion of reinforcing steel is a serious problem worldwide; the problem of steel rebar corrosion leads to a reduction in the lifespan of the structure and adds to the maintenance costs. Many techniques have been developed in recent past to reduce corrosion but none of these solutions seem to be applicable as an adequate solution to the corrosion problem. Besides the use of Fiber Reinforced Polymer (FRP) rebar, hybrid rebar consisting of both FRP and steel are also being tried to control the problem of steel corrosion. This research evaluates the performance of hybrid rebar in corrosion resistance by inducing natural corrosion in a number of concrete cylinders with a hybrid rebar embedded symmetrically. The research also studies the performance of hybrid rebar as a tension reinforcement in concrete beams.

Bond Behavior between BFRP Rebar and Seawater Sea Sand Concrete

Seawater sea sand concrete (SWSSC) is a promising alternative to ordinary concrete in terms of saving valuable natural resources of freshwater and river sand. Basalt fiber reinforced polymer (BFRP) rebars can be a good solution to corrosion of steel rebars in SWSSC. This paper presents an experimental study on the bond behavior between SWSSC and BFRP rebars through pullout testing. Concrete mixed with freshwater and river sand was also prepared for comparison with SWSSC. BFRP rebars with two different surface configurations were selected, that is, ribbed surface and sand‐coated surface. Fly ash as a replacement of cement was also investigated in terms of its effect on bond behavior. Failure modes, bond‐slip relationships, and bond strengths were reported and discussed in terms of the previously mentioned parameters. It was found that ribbed surface of BFRP rebar could achieve better mechanical interlocking with surrounding concrete. SWSSC could have comparative bond strength with BFRP rebar compared with ordinary concrete. However, using fly ash to replace cement is not recommended because it would significantly reduce concrete strength leading to much lower bond at the interface between SWSSC and BFRP rebar.

Неразрушающий контроль композитной полимерной арматуры

Неразрушающий контроль композитной полимерной арматуры

Research of Formation of Macro-Damages on Surface of Basalt Fiber Reinforced Polymer Rebar in an Extremely Cold Climate

In the work, basalt fiber reinforced polymer rebars exposed in the climatic conditions of the North for 51 months have been investigated. To study the formation of macrodamages, fractographic and structural studies of longitudinal sections of the rebars were carried out. The open porosity of basalt fiber reinforced polymer rebars was investigated by the method of hydrostatic weighing. The influence of microdamages on the formation of open porosity of basalt fiber reinforced polymer rebars during their aging is shown. It has been found that degradation of basalt fiber reinforced polymer rebars leads to a significant increase in their open porosity. A linear expression is proposed to assess the average porosity of basalt fiber reinforced polymer rebars depending on their diameter, the concentration of reinforcing fiber rovings, etc. Estimated calculations of the average porosity of basalt fiber reinforced polymer rebars with their uniform degradation from the outer surface under the influence of the external environment have been carried out. A satisfactory correlation of estimated calculations and experimental data of average porosity at small diameters of basalt fiber reinforced polymer rebars (with diameters of 6 and 8 mm.)

Application of non-metallic composite reinforcement for contact line supports

The technology for pre-stressing and anchoring of the composite rebar was developed. It makes possible to reinforce concrete products and produce the contact line supports of high quality, which possesses advantages in comparison with the steel reinforced concrete. The prototypes of supporting structures with the use of the composite BFRP reinforcement were developed. They were tested for strength, rigidity and crack resistance. In the course of testing, the value of a pole deflection in the plane of the application of the control load was determined. Poles with composite reinforcement (with vibratory load and after vibratory load) and steel reinforced poles were tested and compared. Results obtained show that the vibratory load had no significant impact on the properties of supports reinforced with pre-stressed composite rebars and confirm the practical possibility to use them. In the future, it is necessary to develop the working drawings for the replacement of the steel reinforcement by a composite polymer rebar and the technical requirements for supports of the contact lines of Russian Railways as well as the technical regulations for their design and manufacturing.

Forecasting the strength properties of the large diameter polymer rebar based on the experimental analysis of its structure

Fiber reinforced plastic bar (FRP-rebar) is a two-component material consisting of polymer matrix (resin) and reinforcing filler (roving). Large-scale implementation of FRP-rebar and improvement of its manufacturing process have resulted in larger bar diameters. However, it is extremely complicated or even impossible to experimentally determine the mechanical properties of this kind of rebar when using standard testing machines. The reason for this is the low cross-direction strength of the rebar. The purpose of the research is to determine the elastic and strength properties of large diameter FRP-rebar by means of finite-element simulation as well as to analyze the influence of the components’ mass fractions and grooving on the mechanical properties being studied. In order to specify the parameters of the FE simulation model the authors performed some supplementary tests aimed at determining the structure of the fiber. A comparative study of the obtained numerical results against the experimental data is presented in the paper.

“The plastic cathedral”: Innovation to extend the service life of a heritage structure

AbstractDue to its severely damaged condition, former La Laguna cathedral was demolished and rebuilt between 1905 and 1913, saving only its neo‐classical façade. Reinforced concrete, at the time an innovative technology, was deployed to expedite construction and reduce costs. The trade‐off for these benefits was the risk associated with the use of a scantily understood material. Although a reliability‐based assessment of the corrosion‐damaged load‐bearing system showed that structural safety requirements were fulfilled for the future service life, less than 100 years after its reconstruction, the temple was so profoundly deteriorated that the roof had to be replaced entirely. Reconstruction began on the healthy part of the existing columns, underneath the capitals. The solution adopted retains the geometry of the 1913 structure, while improving its ventilation and lighting as well as its aesthetics by reconfiguring the proportions as nearly as possible to the golden ratio. The ribs in the vaults and main dome, characteristic of the neo‐gothic style of the building, were built with self‐compacting concrete, reinforced with glass‐fiber polymer rebars, and joined monolithically to the shells, as well as to the existing walls and columns. The 0.08 m thick shells are also made of a relatively unknown material, self‐compacting concrete reinforced with polypropylene fibers. In order to reduce to acceptable levels the uncertainties associated with innovative technologies, in addition to laboratory tests, a full‐scale prototype of a typical dome was constructed prior to the execution of the new roof. Nearly a century after the previous, negative experience, thanks to modern structural engineering and materials science, new challenges can be assumed.

Experimental Studies on Bond Performance of BFRP Bars Reinforced Coral Aggregate Concrete

Basalt fiber reinforced polymer (BFRP) rebars reinforced coral aggregate concrete is a new type of concrete used in ocean engineering. In order to investigate the bond performance between BFRP rebars and coral concrete, 30 pull-out tests were carried out in 10 groups with different diameters of BFRP rebars, bonding lengths and strength of the coral concrete. The results show that good bonding between BFRP rebars and coral concrete were achieved. The main failure modes can be categorized as BFRP rebars pull out destruction, splitting failure of coral concrete and BFRP rebars fracture. The bond slip (tau{text{-}}s) curves of the BFRP rebars and coral concrete were obtained during the tests. It was found to be similar to the common concrete using fiber reinforced polymer (FRP) bars. The bond-slip relation can be roughly divided into micro-slip phase, slip phase, decline phase, and the residual stress stage. The bond between BFRP rebars and coral concrete increases with the increase of the bond length and diameter of BFRP rebars, but the average bond stress will decrease. Moreover, increasing the strength of coral concrete is effective to improve the bond performance of BFRP rebars. In this paper, the continuous bond slip model (Gao et al. in J Zhengzhou Univ 23:1–5, 2002) was used to represent the tau{text{-}}s constitutive relationship of BFRP rebars and coral concrete. The analysis show that the proposed model has a high degree of accuracy in representing tau{text{-}}s curve of BFRP rebars and coral concrete.

Bond behavior between basalt fiber‐reinforced polymer rebars and coral‐reef‐sand concrete conditioned in saline solution

AbstractThis paper studies the bond behavior between basalt fiber‐reinforced polymer (BFRP) rebars and coral‐reef‐sand (CRS) concrete exposed to a saline environment. The gradation and mix proportion of CRS concrete was firstly selected, through compressive tests on CRS concrete cubes. A series of pullout tests were conducted on a total of 84 pullout specimens after conditioning in a saline solution. The experimental variables included type of rebar (steel and BFRP), diameter of BFRP rebar, conditioning duration and temperature, and type of conditioning (continuous immersion and wet–dry cycle). The stress–slip curves and bond strength of the pullout specimens were analyzed and discussed. The results show that 0.54 is selected as the water/cement ratio for CRS concrete, among the range of analyzed concrete mixes. The bond behaviors of BFRP rebars depend on their diameter. BFRP rebars with 12‐mm‐diameter have the best bond durability after conditioning in a saline solution, when compared with their counterparts with 8‐ and 16‐mm‐diameters. The effects of conditioning temperature and type of conditioning on the bond behavior of 12‐mm‐diameter BFRP rebar are negligible. A design‐oriented formula was proposed for the prediction of the development length of a BFRP rebar in CRS concrete based on the experimental data. Furthermore, modified BPE models were calibrated to describe the bond–slip relationship of BFRP rebars in CRS concrete in a saline environment.

Durability Prediction of GFRP Rebar Based on Elastic Modulus Degradation

A conventional method to study the durability of Glass Fiber Reinforced Polymer (GFRP) rebars is to carry out tensile tests on the corroded GFRP bars. The degree of corrosion of the GFRP bars could be quantified based on the measured ultimate tensile strength and the calculated strength reduction. However, it is difficult to directly monitor the reduction in tensile strength of the GFRP rebars that are embedded in concrete; therefore, this method cannot be implemented in real engineering practices. This study presents the reduction in elastic modulus of the GFPR rebars by real-time monitoring of the strain of the GFRP rebars, and then establishes the degradation model of the elastic modulus for the GFRP rebars in an alkaline corrosion environment. Therefore, the relationship between tensile strength and elastic modulus of GFRP rebars is proposed and verified by the experimental data obtained from the literature. The results show that it is feasible to use the Arrhenius equation to simulate the degradation model of the elastic modulus of the GFRP rebars. Thus, the tensile strength of the GFPR rebars can be related to its elastic modulus. Using the proposed relationship, the durability of GFRP rebars can be predicted by real-time monitoring of the elastic modulus of the GFRP rebars.

Cost and environmental analyses of reinforcement alternatives for a concrete bridge

Reinforced Concrete (RC) and Prestressed Concrete (PC) structures using conventional materials in aggressive exposure conditions are susceptible to corrosion. Non-corrosive reinforcement materials such as: Glass Fiber-Reinforced Polymer (GFRP) rebars; Carbon Fiber-Reinforced Polymer (CFRP) strands; Stainless-Steel (SS); and Epoxy-coated steel (ECS) reinforcing bars, are attracting attention as more appropriate options in concrete structures. This paper addresses a Life Cycle Cost (LCC) analysis that verifies the cost performance of four different alternative reinforcement bars for the design of a demonstration FRP-RC/PC bridge in Florida, namely Halls River Bridge (HRB). The four different alternatives to be compared are namely Carbon Steel (CS), SS, FRP, and ECS, and the analysis is performed over 100-years. Additionally, a Life-Cycle Assessment (LCA) is included in the analysis to investigate the environmental credentials of the four design alternatives. Cost sensitivity analyses over specific parameters are included. The parameters analyzed are: reinforcement cost, changes in chloride concentration levels over the bridge service life, and discount rate values. Conclusions and recommendations for standard practices and design of future alternative solutions are then presented.

Flexural Behaviour of HYFRC Beam Reinforced with GFRP Rebar

This paper offers the experimental have a take a look at at the flexural behaviour of HYFRC beams bolstered with glass fiber bolstered polymer (GFRP) rebar and in comparison with everyday metal reinforcement beams. Three beams reinforced with GFRP rebar and three beams of traditional concrete metal strengthened with absolutely six beams have been casted and tested under two points loading. The partner specimens were casted along with beam and tested for concrete homes. Steel and glass fibres are used toimprove the concrete assets. From checking out, load carrying capability, loaddeflection traits, crack sample, crack width, concrete traces throughout move phase and failure mode have been mentioned stiffness, ductility and power dissipation potential had been additionally calculated. The average ultimate load wearing potential of GFRP rebar and normal steel reinforcement beam is one hundred twenty five.8KN and ninety seven.5KN respectively. The most deflection cited at their closing load inside the GFRP rebar and regular metal reinforcement beam is 27. Three mm and sixteen. 3 mm respectively. It changed into also found that after load elimination, deflected GFRP beam regain its authentic function and crack width also reduced. In metal beam, metallic rebar were yielded, after load elimination, no deflection regain and crack width reduction have been observed