CFRP Bars Research Articles

STRAIN AND DILATION OF GFRP CONFINED CONCRETE MEMBERS

The fiber reinforced polymer (FRP) composite materials have recently been used as internal, and external reinforcement in the field of civil engineering constructions. This paper presents the results, of strain and dilation of glass-FRP (GFRP), concrete members. The objective is to characterize and to investigate the compressive behaviors of the GFRP columns. The parameters were used in the investigation the effect of laminate thickness of the GFRP tubes, and concrete strength. The composite GFRP tubes are fabricated using the filament, winding technique. The diameter of the GFRP tubes which used in this investigation was 152 mm, the fibre orientation mainly in the hoop direction. The final failure modes, stress-strain, steel, GFRP and CFRP bars strain and, finally load-deformation behaviours were presented for all specimens.

Experimental Investigations on Bond Behavior between FRP Bars and Advanced Sustainable Concrete.

In response to resource shortage and carbon dioxide emissions, an innovative type of sustainable concrete containing LC3, seawater, sea sand, and surface-treated recycled aggregates is proposed in this study to replace traditional concrete. To understand the bond properties between the sustainable concrete and CFRP bars, an investigation was conducted on the bond behavior between sand-coated CFRP bars and advanced sustainable concrete. Pull-out tests were carried out to reveal the failure mechanisms and performance of this bond behavior. The results showed that the slip increased monotonically along with the increase in confinement. The bond strength increased up to approximately 15 MPa, and the critical ratio of C/D was reached. The critical ratio approached 3.5 for the Portland cement groups, while the ratio was determined as approximately 4.5 when LC3 was introduced. When the proportion of LC3 reached 50%, there was a reduction in bond strength. A multisegmented modified bond–slip model was developed to describe the four-stage bond behavior. In terms of bond strength and slip, the proposed advanced concrete exhibited almost identical bond behavior to other types of concrete.

Flexural Behavior of One-way Concrete Slabs Reinforced with Combined Steel - CFRP bars

Flexural Behavior of One-way Concrete Slabs Reinforced with Combined Steel - CFRP bars

Identification of the bond between ribbed CFRP bars and novel ARs anchorage

The novel additional aluminum alloy ribs (ARs) anchorage, fabricated through radially extruding the aluminum alloy (AA) tube to attach to the CFRP bar, was recently developed by the authors. Though effectiveness of using the ARs anchorage to improve the bond quality of CFRP bar in concrete has been already validated, the bond at bar-anchorage interface itself has yet been unclear. In order to afford an overall insight into the bond performance between ribbed CFRP bar and ARs anchorage, the present study initiated a pull-out test for a total of 81 bar-anchorage bonded joints. The investigated design parameters of the ARs anchorage consisted of the initial wall-thickness, radial deformation, and the extruded length. Scanning-Electron-Microscope (SEM) observations were also performed to accurately observe the interfacial zone before and after pull-out test. Based on the analysis of the tested results, four typical bond stress-slip laws of the bar-anchorage interface were identified, and recommendations for the anchorage design were further given. Meanwhile, this paper proposed a mathematical model for predicting the nominal bond strength for bar-anchorage interface.

Numerical Simulations of Composite Materials

Throughout the last decade, the usage of fiber reinforced polymer (FRP) reinforcements in civil infrastructure has risen exponentially, owing to its superior corrosion protection, high durability, and non-magnetization characteristics. Furthermore, as a result of the poor modulus of elasticity of the FRP composites and its non-yielding properties, significant deflection and broad fractures are seen in the FRP reinforced concrete components under consideration. The emphasis of present study is on the behavior of FRP-reinforced concrete beams. The total of nine finite element-based simulations were carried out (ABAQUS). The concrete damage plasticity modelling was considered while performing the analysis. Three different kinds of FRP bars such as CFRP, BFRP, and GFRP, were utilized as reinforcement in longitudinal and transverse direction for concrete beams. Literature was used to validate the numerical findings, and the parametric research has been carried out for varying factors, such as the diameter size, number of bars, the kind of FRP bars used, and the longitudinal arrangement of FRP bars. When CFRP bars were utilized, the load capacity increased by anywhere from 8.88% to 62.92%. Beams that have been reinforced with CFRP carry more weight than beams reinforced with GFRP and BFRP. The increase in CFRP bars tends to give some ductility to the beam via the bi-linear load-to-ductility curve. In similarly, the GFRP reinforced beams improve the ductility of the structure as a whole.

Exploratory study on the short- and long-term bond between ribbed CFRP bars and additional aluminum alloy ribs anchorage

Innovative additional aluminum alloy ribs (ARs) anchorage has been recently developed to enhance the bond for FRP bars in pretensioned prestressed concrete. Studies have demonstrated the feasibility of using the ARs anchorage to improve the bond of FRP bars to concrete. However, the bond performance between FRP bar and ARs anchorage remains unclear. The present study reported an experimental programme to explore both the short- and long-term bond performance at ribbed CFRP bar-AR interface. The failure modes and bond-slip curves of short-term pull-out specimens were presented. Microstructure at the bar-AR interface was identified to explain the bond failure characteristic. Besides, the short beam test for the CFRP bars was conducted to support the findings obtained from the short-term pull-out test. The long-term bond at bar-AR interface was evaluated by subjecting the pull-out specimens to sustained loading for 500 days. Through the testing results, the bond mechanism of the bar-AR interface was identified, and the reasons behind bond enhancement caused by the prsence of ARs anchorage for CFRP bars in concrete were revealed. This exploratory study could be regarded as the most basic support for the application of ARs anchorage for enhancing the performance of prestressed CFRP reinforced concrete.

Utilizing alkali-activated materials as ordinary Portland cement replacement to study the bond performance of fiber-reinforced polymer bars in seawater sea-sand concrete

Alkali-activated materials (AAMs) are considered an eco-friendly alternative to ordinary Portland cement (OPC) for mitigating greenhouse-gas emissions and enabling efficient waste recycling. In this paper, an innovative seawater sea-sand concrete (SWSSC), that is, seawater sea-sand alkali-activated concrete (SWSSAAC), was developed using AAMs instead of OPC to explore the application of marine resources and to improve the durability of conventional SWSSC structures. Then, three types of fiber-reinforced polymer (FRP) bars, that is, basalt-FRP, glass-FRP, and carbon-FRP bars, were selected to investigate their bond behavior with SWSSAAC at different alkaline dosages (3%, 4%, and 6% Na2O contents). The experimental results manifested that the utilization of the alkali-activated binders can increase the splitting tensile strength ( ft) of the concrete due to the denser microstructures of AAMs than OPC pastes. This improved characteristic was helpful in enhancing the bond performance of FRP bars, especially the slope of bond-slip curves in the ascending section (i.e., bond stiffness). Approximately three times enhancement in terms of the initial bond rigidity was achieved with SWSSAAC compared to SWSSC at the same concrete strength. Furthermore, compared with the BFRP and GFRP bars, the specimens reinforced with the CFRP bars experienced higher bond strength and bond rigidity due to their relatively high tensile strength and elastic modulus. Additionally, significant improvements in initial bond stiffness and bond strength were also observed as the alkaline contents (i.e., concrete strength) of the SWSSAAC were aggrandized, demonstrating the integration of the FRP bars and SWSSAAC is achievable, which contributes to an innovative channel for the development of SWSSC pavements or structures.

Replacement of Flexural and Shear Reinforcement of Double-Column Bridge Bent with CFRP under Combined loadings

The bridge bent is the most critical structural component of short span bridge that highly affected by different types of loadings. The bent failure has been observed due to in plane and out of plane loadings. Strengthening techniques are utilized for existing bridges. However, a replacement technique can be used for the new bridges to avoid bent failure. Moreover, the effect of combined loading on bent performance need to be evaluated. Therefore, this study assessed the performance of bridge bent under in plane, out of plane and combined loadings. Furthermore, replace the traditional flexural and shear steel reinforcement of the columns with CFRP bars. The performance of bent is assessed numerically by finite element analysis. For this purpose, six numerical bent models are developed. The first three models with traditional steel bars and the remaining models with CFRP rebars. The results demonstrated that out of plane loadings has more impact on the bent structural performance than other loading cases. Flexural and shear failures are observed in the columns for models with steel rebars. The failure started from lower side of the column for both in plane and out of plane loadings showing low resistance. The steel rebars yielded in early stage of loading indicating limited stiffness. However, the bent performance has been enhanced by replacing rebars with CFRP. The bent stiffness has slightly improved by replacing with less diameter of CFRP rods and stirrups. In addition, the CFRP bars showed considerable resistance and hardly showed plasticity during apply loading indicating that the CFRP is suitable material to replace steel reinforcement.

Mechanical Properties of Cfrp Bar with Different Elevated-Temperature Experiences

Mechanical Properties of Cfrp Bar with Different Elevated-Temperature Experiences

Shear Behavior of Composite Stone Beams Reinforced with Nsm Longitudinal Cfrp Bars

Shear Behavior of Composite Stone Beams Reinforced with Nsm Longitudinal Cfrp Bars

Strengthening effect of prestressed near-surface mounted CFRP bar system according to material properties of aged reinforced concrete beams

The flexural performance improvement of age-deteriorated reinforced concrete (RC) beams by a near-surface mounted carbon fiber-reinforced polymer (NSM CFRP) bar system was experimentally investigated. Ten 6.4 m long RC beams were fabricated and tested in four-point bending using different concrete compressive strengths to distinguish between old and new concrete, different steel reinforcement ratios to reflect deterioration with age, and different quantities of prestressed and non-prestressed CFRP bars. The results indicated that the ultimate strengths of the NSM CFRP-strengthened RC beams were up to twice that of the un-strengthened control beam, and the strengthening effect increased with the material properties of the RC beam. A finite element model of the strengthened RC beam was constructed and verified against the experimental results, then used to conduct a parametric study of the influence of the concrete compressive strength and steel reinforcement ratio on the strengthening effect of the prestressed NSM CFRP bar system.

Effect of Heating Level on the Contribution of CFRP Bars in the Axial Load-carrying Capacity of RC Columns

Effect of Heating Level on the Contribution of CFRP Bars in the Axial Load-carrying Capacity of RC Columns

Innovative additional aluminum alloy ribs anchorage for improving the bond reliability of pretensioned CFRP bar: A feasibility study

An innovative anchorage method for CFRP bars through providing additional aluminium alloy ribs (ARs for brevity) is proposed in this paper. The results of the pull-out tests are firstly summarized to comprehensively evaluate the bond performance of ARs anchored CFRP bars in concrete and the arrangement of the ARs along the bond length of the CFRP bars was meanwhile optimized. The transfer length test for the pretensioned CFRP bar was then performed to investigate the effect of the ARs on the bond transfer at prestress releasing. It was found that ARs anchored bar had resulted in a shorter transfer length in comparison to that of the unanchored bar due to an improved bond mechanism. Finally, the feasibility of using such ARs anchored CFRP bars in pretensioned prestressed concrete (PPC) members was explored by performing short- and long-term tests, respectively. The results showed that the ARs presence could lead to benefits of enhancing the shear anti-cracking capacity, reducing the end slips, and delaying the long-term deflection increase of the CFRP reinforced PPC beams, proving that the ARs can act as a reliable end anchorage system for pretensioned CFRP bars in PPC members.

Shear Strengthening of Deep T-Section RC Beams with CFRP Bars.

Deep T-section beams have been widely used in engineering structures due to their high bearing capacity, high construction efficiency and economic benefits, while the current beam design theory can hardly interpret reasonably the mechanical behaviors of deep beams. The performance features of the deep T-beam were investigated, involving in strain distribution and principal stress trace using experimental tests. Different near surface mounted (NSM) reinforcement schemes were proposed for deep T-beams aiming at improving the shear capacity. The results show that the behaviors of deep T-beams dissatisfy the assumption of plane cross-section, and the ‘strut-and-tie’ model is applicable in such structures. The reinforcement systems can significantly relieve the strain concentration, mid-span deflection and crack width in deep T-beams, consequently improving the shear capacity range from 45 to 65%. The scheme is preferential for the reinforcement of deep T-beams when the applied angles, positions and lengths of CFRP bars are optimized based on the ‘strut-and-tie’ model.

NUMERICAL EVALUATION OF SLAB THICKNESS EFFECT ON THE IMPACT BEHAVIOR OF CONCRETE SLABS REINFORCED WITH CFRP BARS

Theoretical investigation of the nonlinear behavior of concrete slabs reinforced with CFRP bars subjected to a single impact load is presented in this paper. For predicting the impact load on a concrete slab, there are several methods, some of which are impractical or prohibitively pricey; however, due to significant technological advancements, simulation methods instead of experimental approaches have become common methods and a cost-effective matter for developing detailed responses. The purpose of this paper is to numerically investigate the effect of slab thickness on the impact response of concrete slabs reinforced with (CFRP) bars when subjected to a single impacting load, so as to well understand their behavior which are considered modern topics and rarely highlighted. Three specimens (1800×1800) mm, with three thicknesses 80, 130 and 180 mm, simply supported by their corners, have been modelled, one reference specimen of 130 mm thickness. The reference slab numerically validated with an experimental work from literature under dropping-weight of 150 kg, it was a flat-nosed rigid steel (300*300*700) mm projectile, used to apply impacting load, which is falling freely from a height of 3.26 m. To assess slab behavior, impact force-time, displacement-time and reaction force-time histories had been plotted and discussed. The analytical results showed that slab thickness is a control factor and better performance in slabs reinforced with CFRP bars, can be achieved by increasing slab stiffness via its thickness increase.

EFFICIENCY OF FLEXURAL STRENGTHENING OF REINFORCED CONCRETE BEAMS BY NEAR SURFACE MOUNTED CARBON FIBER REINFORCEMENT POLYMER RODS AND EXTERNALLY BONDED SHEETS

This study investigated the flexural behavior of reinforcement concrete beam strengthened with different techniques. The purpose of this research to study the various techniques of strengthening and knowing the effect of each technique on the beam behavior .Ten simply supported beams tested in this study. The total length of the beams and clear span were 1800mm and 1650mm, respectively. The cross section was (180×250) mm. Tested beams were divided into two categories’ the first category consist of one beams and considered as reference, while the second category consist of nine beams divided into Two groups according to the Strengthening techniques such as near surface mounted (NSM) and external bonded reinforcement (EBR).The experimental results showed improvement in ultimate load capacity for strengthened beams ranging from (6 to 89%) for NSM and (31 to 96%) for EBR and reduction in deflection for strengthened beams ranging from (6 to 43%) as compared with reference beam. When the number and length of CFRP bars are increased, the number of cracks increase while the width of the cracks and the spacing decrease, and the same observation is made when the width of the CFRP sheet is increased. The experimental load capacities of strengthened beams were compared with the design provisions given by ACI440.2R-17 guideline for NSM and EBR technique and EC2 guideline for EBR technique, the average ratio (1.2 and 0.97) respectively ,which showed that reasonable and a good agreement for all strengthened beams.

Numerical Modeling for Flexural Behavior of UHPC Beams Reinforced with Steel and Sand-Coated CFRP Bars

Many properties of advanced materials need to be studied, including ultra high performance concrete (UHPC) as well as the Carbon Polymer Reinforcing Fiber (CFRP) rods of sand coated surfaces. The combined action of (UHPC) with (CFRP) is of constructive importance for researchers to know the behavior of the structural members in different loading stages. Eight samples were prepared with dimensions of 2.4 meters in length, 0.25 meters in depth, and 150 mm in width. The compressive strength of 110 MPa was selected after preparing many trail mixes. A computer model by ANSYS 11 program was made for the representation of all inputs, including steel fibers. All Parts of beams, testing accessories, and loads were simulated with adequate elements. The study examined the effect of the orientation of steel fibers on the flexural capacity in terms of load-deflection response. It was concluded that the distribution of the steel fibers plays a fundamental role in the behavior of the models, and thus the optimal distribution was found to be orthogonal distribution to the longitudinal direction of UHPC beam in equal ratios.

Tensile behavior of FRP bar butt joints built with new FRP sleeves

This paper reports a comprehensive investigation on the tensile behavior of FRP bar butt joints built with new FRP sleeves. The simplified bond-slip constitutive relationship between FRP bars and bonding medium was firstly established by using the existing research results. Based on five proposed assumptions, the stress–strain analysis of the FRP bar butt joint was performed on the FRP bar, bonding medium and sleeve under tensile load. The bond-slip behavior and the shear force between FRP bars and bonding medium were discussed in detail. According to the stress–strain analysis, the key design parameters of the FRP sleeve and the anchor length of FRP bars were determined, which is also verified by comparing test data. According to the design parameter and anchor length, two types of FRP sleeves with two different internal structures and lengths were designed, and then these FRP sleeves were made of GFRP by professional manufacturers. In addition, the axial tensile tests were conducted on a total of 10 BFRP bar butt joints, GFRP bar butt joints and CFRP bar butt joints which are connected by the proposed GFRP sleeves. Based on the test results, the failure modes of various FRP bar butt joints built with GFRP sleeves were observed, and the corresponding tensile load–displacement curves, maximum tensile load and strain were analyzed. Finally, it is found that all fractures occur on the connected FRP bars instead of the GFRP sleeves, which indicates that various FRP bars can be effectively connected by the two types of GFRP sleeves. The load–displacement curves of the GFRP sleeves exhibit a small linear elastic deformation before the FRP bars rupture. The maximum elongated length of the GFRP sleeves is only 13% of the maximum tensile displacement of FRP bar butt joints uner tensile load, while the maximum circumferential strain of GFRP sleeves is about 41.72% of their corresponding longitudinal strain.

Pull-Out Behavior of CFRP Bars in Glued-In Glubam Joints

Abstract Glubam (glued-laminated bamboo) is a newly developed structural material with properties comparable to other wood and wood-based materials. Fiber-reinforced polymer (FRP) bar is an attract...

Bond Coefficient kb of Concrete Beams Reinforced with GFRP, CFRP, and Steel Bars

There are several reasons why civil and structural engineers should use Fiber Reinforced Polymer bars in concrete. The primary reason is durability, and other relevant parameters, high strength and, lightweight. Non-corrosive attributes make their use particularly suitable in different situations. Due to low elastic modulus and poor bonding, the use of Fiber Reinforced Polymer results in larger crack widths under serviceability limit state especially beams reinforced with glass fiber bars. The study purpose of this paper is to investigate the kb values. The methodology of this paper is comparing the analytical and experimental results. The investigation included 12 beams, using the four-point load test. The geometrical parameters of tested beams with dimensions: 130×220×2200 mm, reinforced with different diameters, helically-grooved glass fiber bars, and sand-coated carbon fiber bars. The measured cracks were used to assess the current kb values recommended in the design codes and guides. The findings did not support the use of the same kb value for different bars because, in addition to the type of bar, the value of kb is also affected by the type of surface and the diameter of the bar. What is observed based on results shows that CFRP bars have a more constant value depending on the diameter, while GFRP bars have large value changes depending on the diameter. Doi: 10.28991/cej-2021-03091722 Full Text: PDF