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This paper reports an experimental study on the behavior and shear strength of concrete beams reinforced with longitudinal GFRP bars mixed with sea water. In order to evaluate how much concrete contributes to shear resistance, seven beams were tested in bending. Similar in size and concrete strength, the beams were longitudinally reinforced with glass fiber-reinforced polymer bars; however, they did not even have shear reinforcement. The beams, which measured 3,100 mm in length, 400 mm in depth, and 200 mm in width, were conducted and tested up to failure. The test variables were longitudinal reinforcement ratios (1.0, 1.4, and 2.0%), chopped fiber content (0, 0.5, 2, and 3 kg/m3), and mixing water type (freshwater and seawater). The test findings showed that increasing the reinforcement ratio increased the neutral-axis depth and allowed the formation of more closely spaced fractures while decreasing the loss of flexural stiffness after cracking. By increasing the area of concrete in compression, this in turn enhances the contribution of aggregate interlock as well as the contribution of uncracked concrete. Furthermore, increasing the reinforcement ratio improves the dowel action, which reduces the tensile stresses that are created in the concrete around it. Doi: 10.28991/CEJ-2023-09-04-05 Full Text: PDF

There is a limited design guidance for practitioners regarding the shear design equations of circular-concrete members with fiber reinforced polymer (FRP) reinforcements, especially the case of incorporating FRP bars and spirals. The objective of this study is to enhance the methods used for estimating the shear capacity of reinforced concrete (RC) beams with FRP bars and spirals. A database of 44 circular concrete beams reinforced with FRP bars tested under shear were compiled from different experimental studies. Two proposed models based on approaches developed for rectangular sections, to predict the shear capacity of beams without and with stirrups, were compared with the selected available shear design equations. The shear strength estimated using the proposed models are slightly more accurate. The comparison indicates that the shear capacity of FRP-reinforced concrete members with circular cross sections may be determined with the V cf and Vsf approaches developed for rectangular sections provided that certain modifications are made to take into account the effective shear depth, equivalent breadth, the mechanical properties and geometry of GFRP spirals.

Legal challenges to child education create barriers to assisting abused children and their families. The purpose of this study was to describe legal challenges to child education. A qualitative study was conducted to explore the legal challenges. Individual interviews with about 20 people. Grounded theory methodology was used to develop categorical themes that reflected experiences and challenges. Three themes emerged from the data: legal challenges create complex dilemmas for education rights. Also, it has a common denominator with the legislative decree. The Islamic Shariah has taken great care of human life, particularly children. The Shariah system has introduced many legislations that preserve children’s rights, including their right to education, reform and education. Thus, this study is faced with a considerable amount of primary legislation in the child’s life to preserve it and its development, and from this I chose to address it (the rights of the child in education and education in the legal and legal perspective. It focused on the essential legislative dimensions that preserve children’s rights to education and read the following international law

A numerical analysis investigation, using finite element model (FEM) and modified compression field theory (MCFT), was conducted to evaluate the shear capacity and behavior of circular concrete piles reinforced with steel and FRP bars by considering shear behavior, shear strength, and deflection shape. The FEM and MCFT models were verified against the experimental results of full-scale circular concrete speciemns previously tested by the authors. Load-deformation response curve, load-strain for the concrete and reinforced rebars were predicted using finite element analysis were compared to experimental results. The FEM outcomes showed that the model was able to capture the behavior of the specimens with good accuracy. While, the modified compression field theory using Response 2000 (R2K) software provided good predictions of the shear strength with an average value of Vexp/VResponse2000 for specimens is 1.17. Subsequently, a parameric study was performed to study the effect of member’s depth (300, 400, and 600 mm), longitudinal reinforcement ratio (1.5, 2.5, and 3.5%), and reinforcing bars material (Steel, Glass-FRP, Carbon-FRP) on the behaviour of circular concrete piles.

Marine, coastal structures, and bridges deteriorate prematurely due to corrosion. Numerous failures have occurred in substructure members of these structures, such as piles, leading to ver...

Prestressed concrete girders and piles with steel strands are used in construction of bridges in North America, due to their economy of design, fabrication, and installation. However, they are often exposed to harsh environments, which results in rapid degradation. Therefore, carbon fiber reinforced polymer (CFRP) tendons have successfully been introduced as prestressing reinforcement for pile applications. This paper presents a study on the physical characterization, microstructural analysis, and durability performance of unstressed and stressed carbon-fiber composite cables (CFCCs) for prestressing applications. This is achieved through testing 120 CFCC specimens, subjected to stress levels of about 40% and 65% of their guaranteed strength, and 51 specimens without sustained load under tension. Moreover, prediction models were introduced to assess the long-term performance and retentions of CFCC strands. The models included Arrhenius model, Fick's law, Fib Bulletin (40) model, and a developed approach that incorporates the effects of temperature, design life, and relative humidity of exposure into the environmental reduction factor. Based on the predication model, the tensile strength retention (CE) for CFCC strands, is predicted to retain over 0.95 and 0.84 of ultimate tensile strength for a relative humidity (RH)

This paper presents a study to investigate serviceability, strength, and deformability of normal- and high-strength concrete beams reinforced with deformed glass-fiber-reinforced-polymer (GFRP) bars under flexural loading. Understanding the flexural behavior of concrete beams reinforced with deformed GFRP bars with normal- and high-strength concrete would contribute to the existing literature and would provide information critical to the further use of deformed GFRP bars as internal reinforcement for concrete structures. Eight beams with a cross-sectional width and height of 200 mm and 300 mm, respectively, and a clear span of 2700 mm were tested under two-point flexural loading until failure. Four beams were made with 35 MPa normal-strength concrete (NSC); the other four with 65 MPa high-strength concrete (HSC). The bottom/tensile reinforcement of each beam consisted of two GFRP bars. Four different GFRP bar sizes (12 mm, 16 mm, 20 mm, and 25 mm in diameter) were used with reinforcement ratios ranging from 0.38% to 1.63%. Seven beams failed in concrete compression and the eighth beam failed in tension when the FRP ruptured. The test results showed that increasing the FRP reinforcement ratio had a greater effect on the service moment than the resistance moment. The effects of bar spacing on the behavior of wide beams were also investigated, revealing that the service moment increased when the bar spacing decreased, while the resistance moment increased when the concrete strength increased. In addition, the deformability concept produced significantly higher ductility indices than the energy-based concept. Neither method evidenced a clear trend in the ductility indices of the tested beams. A new approach was proposed to determine the ductility index of concrete beams with FRP bars based on beam curvature. This approach demonstrated a clear trend with the tested beams: the high-strength concrete beams had higher ductility indices than the normal-strength concrete beams.

In recent decades, high-strength concrete (HSC) has been widely used in bridge elements, tunnels, and precast-concrete members. Only a limited number of studies, however, have investigated the structural behavior of HSC columns reinforced with glass-fiber-reinforced-polymer (GFRP) bars. Moreover, most concrete codes do not explicitly cover concrete with strengths above 55 MPa. This paper investigates the structural behavior of HSC columns reinforced with GFRP bars and ties when subjected to eccentrically axial loads. Eight full-scale concrete columns with a 400 × 400 mm cross section and 2000 mm in height were tested under axial monotonic loading. The test variables were the eccentricity-to-width ratio, concrete strength, and reinforcement type using steel and GFRP bars and ties. The test results indicate that the failure of the test specimens under different levels of eccentricity was not triggered by rupture of the GFRP bars on the tension side, up to attaining the maximum section capacity governed by concrete-strain limitation. The load–axial displacement, load–lateral displacement, failure mode, and reinforcement strain responses of all the GFRP-reinforced HSC columns are presented and compared to that of the steel-reinforced HSC columns. The structural behavior of HSC columns reinforced with GFRP bars and ties subjected to eccentric axial loads were evaluated by drawing axial force–flexural moment interaction diagrams and comparing them to that for the steel-reinforced columns. An analytical method (layer-by-layer approach) was applied to predict the axial- and flexural-load capacity of the GFRP-reinforced HSC columns. A parametric study was used to examine the effect of increasing the reinforcement ratio and concrete strength and to investigate the strength contribution of GFRP compression bars.

This paper presents experimental data and theoretical studies on the effect of distributed glass fiber-reinforced-polymer (GFRP) bars in circular concrete members. Th experimental program reports the test results of eight full-scale circular reinforced-concrete (RC) specimens with a total length of 3020 mm and a diameter of 508 mm were constructed and tested under shear load up to failure. The test specimens comprised three specimens reinforced with GFRP bars and spirals, three specimens with only longitudinal GFRP bars, and two reference specimens reinforced with conventional steel bars, with and without steel spirals. The various experimental parameters included the longitudinal reinforcement ratio, the type of reinforcement (GFRP versus steel), and presence of shear reinforcement. The shear strengths of GFRP circular concrete specimens, obtained from the experimental results, were compared to current codes and design guidelines as well as to the recently available shear design equations on circular concrete members in the literature. The test results indicate that the use of more GFRP bars distributed uniformly in the cross section, of the specimens with and without spirals, reduces the loss of flexural stiffness after cracking and increase the shear strength. The comparison indicates that some of the available design methods provide reasonable predictions.

Basalt-fiber-reinforced polymer (BFRP) bars are expected to provide benefits that are comparable or superior to other types of FRP while being significantly cost-effective. However, extensive investigations are needed to evaluate the long-term characteristics and durability performance of these bars. This article presents an experimental study that investigated the physical, mechanical, microstructural, and durability characteristics of newly developed basalt-fiber-reinforced polymer (BFRP) bars. The physical, mechanical properties and microstructural characteristics were evaluated first on the unconditioned BFRP bars. The durability performance of the BFRP bars was then assessed by conducting the mechanical tests, such as transverse-shear test, flexural test, and interlaminar-shear test, on the specimens after different exposure periods (1000; 3000; and 5000 h) at 60 °C. Thereafter, the BFRP bar properties were assessed and compared with the values obtained on the unconditioned specimens. The test parameter was conditioning time (1000; 3000; and 5000 h). The test results revealed that the unconditioned BFRP bars had the best physical properties. On the other hand, the long-term durability performance revealed that the transverse shear-strength, flexural-strength, and interlaminar shear-strength retention were decreased by 12%, 19%, and 21%, respectively.

This paper reports the axial–flexural test results for 12 high-strength concrete (HSC) columns reinforced with glass fiber-reinforced polymer (GFRP) rebars to evaluate the implication of u...

The application of deicing salt on roads during the winter is one of the main reasons for steel corrosion in reinforced-concrete pavements in cold-weather regions such as Canada and the No...

Design for slender high-strength concrete (HSC) bridge compression members (columns, piers, and piles) reinforced with glass fiber-reinforced polymer (GFRP) has yet to be addressed in the ...

Designing reinforced concrete (RC) columns reinforced entirely with fiber-reinforced polymer (FRP) bars requires an explicit definition of the slenderness upper and lower limits for use in...

This paper reports on the experimental results of flexural tests on full-scale circular reinforced concrete members with a total length of 6000 mm and diameter of 500 mm reinforced with Basalt Fiber-Reinforced-Polymer (BFRP) reinforcement, followed by an intensive analytical study and finite-element analysis . The main investigated parameters were the ratio and type of longitudinal reinforcement. A steel-reinforced concrete specimen was fabricated as a reference. Test results show that the deformability of the tested circular BFRP-RC members significantly exceeded the limitations in North American codes. Moreover, the nominal flexural strength of one BFRP-RC specimen was almost two times that of its steel-reinforced counterpart with the same reinforcement ratio. The analytical model presented herein using a layer-by-layer analysis was capable of predicting the flexural strength of the circular BFRP-RC members. In addition, a non-iterative analysis method including simple design equations are presented. This method accurately and simply predicted the flexural capacity and can be considered a simple and more straightforward method for practicing engineers. In addition, the finite-element model developed predicted the response of the tested specimens with a reasonable degree of accuracy and was used to extend the range of the investigated parameters.

This research work presents new design equations to adequately determine the effective flexural stiffness (EIe) of concrete-filled fiber-reinforced polymer (FRP)-tubes (CFFTs) columns. Based on an experimental parametric study and theoretical simulation, factors influencing the effective stiffness of reinforced CFFT columns are discussed. The main variables considered are: the axial load ratio (Pu/Po), the eccentricity to diameter ratio (e/D) and the slenderness ratio (L/D). Approximately 3,400 reinforced CFFT columns with different combination of specified variables, in symmetric single curvature bending were simulated to generate the stiffness data. Extensive comparison for the proposed stiffness expressions is made with the results of 74 experimental tests conducted by the authors and others. It is shown that the proposed stiffness equations have a good correlation with the test results. The proposed equations are applicable for any load levels including both service and ultimate loads. Since the proposed expressions give a realistic representation of the actual column behavior, they are recommended for general use in the design of FRP-confined concrete columns under different load levels.

Nowadays, design guidelines and codes contain valuable shear provisions for the design of concrete bridge members reinforced with fiber-reinforced-polymer (FRP) bars. Limited researches seem to have assessed the shear strength of circular concrete members reinforced with FRP reinforcement. Therefore, these standards do not provide specific formulae for circular RC members designed with FRP bars, hoops and spirals under shear loads. This paper reports experimental data about the shear strength of circular concrete specimens reinforced with FRP bars, discrete hoops and continuous spirals. Full-scale circular concrete specimens with a total length of 3,000 mm and 508 mm in diameter were constructed and tested up to failure. The test parameters included the type of reinforcement (glass FRP and carbon FRP versus steel) and configuration of the shear reinforcement (discrete hoops versus continuous spirals). The investigation revealed that the specimen reinforced with FRP hoops exhibited high load-carrying capacity comparable to the counterpart reinforced with FRP spirals. The experimental shear strengths of the FRP-reinforced concrete specimens were compared to theoretical predictions provided by current codes, design guidelines. The results of this study can be used as a fundamental step toward code provisions for using GFRP or CFRP spirals and hoops as internal shear reinforcement.

Recent years have seen valuable research work on using glass-fiber-reinforced-polymer (GFRP) bars in reinforced-concrete (RC) members under compression. Nonetheless, lap splicing of GFRP bars under compression has not yet been explored with due consideration of its components. To address this knowledge gap, this paper comparatively demonstrates the results of an experimental investigation pertaining to the effect of splice length on the compression lap splicing of GFRP bars in concrete columns. The experiment comprised 11 large-scale circular columns measuring 300 mm in diameter and 1600 mm in height: seven specimens reinforced with GFRP bars, three specimens with steel bars for comparison purposes, and one specimen without reinforcement (plain concrete). All columns were tested under a monotonically increasing concentric load. The test variables included the reinforcement type (GFRP versus steel) and splice length. The results were compared in terms of the stress–strain curves, ultimate loading, displacement capacity, and splice strength. The test results indicate that the required compression splice length for GFRP bars is less than that required for steel. As the strength of a compression splice consists of end-bearing and bond components, the contribution of each part was scrutinized in detail using measured strain values. The required splice length for GFRP bars was considerably based on the end-bearing component. Based on the experimental results, a length of 8 d b can reliably be considered as the required splice length for No. 5 GFRP bars in compression.

Although the use of glass fiber–reinforced polymer (GFRP) bars as compression reinforcement in RC columns has been extensively investigated, no research has been conducted on spliced GFRP b...

This paper presents the test results of an experimental program to investigate the structural performance of short and slender concrete-filled fiber-reinforced polymer (FRP)-tubes (CFFTs) columns under pure axial compression load. The test parameters include: transverse reinforcement type (steel spirals versus glass-FRP (GFRP-tube), type of longitudinal reinforcement (steel and carbon-FRP (CFRP) bars), GFRP tube thickness, and slenderness ratio. Comparisons between the experimental test results and the theoretical design equations are performed in terms of ultimate load carrying capacity. The design equation is modified to accurately predict the ultimate load capacities of CFFT columns reinforced with FRP bars. Furthermore, the experimental results showed that the axial compressive strength of CFRP-reinforced CFFT columns was reduced by 22% with increasing the slenderness ratio from 8 to 20. In general, the use of the FRP tube induces a confinement effect for concrete columns which enhances the strength and ductility of such column’s section. This enhancement resulted in a slender section which increased the possibility of buckling instability of the CFFT columns. Thus, a theoretical model was conducted to develop a simplified formula for critical slenderness limit of FRP-reinforced CFFT columns to control the buckling instability mode of failure. Results indicated that the slenderness limit of 14 was suggested as a safe value for the design purposes. A parametric study was conducted which showed the significant effect of the concrete compressive strength and hoop stiffness of FRP tube on the critical slenderness ratio of FRP-reinforced CFFT columns.

The research work reported in this paper involves investigation of the mechanical and durability performance of unstressed and stressed Tokyo Rope carbon-fiber composite cables for prestressing applications. This research is critical in order to establish the critical (allowable) stress and safety factors for the use of carbon-fiber composite cable tendons for prestressed precast-concrete members. The carbon-fiber composite cable specimens were exposed to simultaneous high alkali environment and sustained loading at different elevated exposure temperatures (22℃ and 60℃) for 3000, 5000, and 7000 h. The high alkali environment (12.8 pH) simulated the concrete pore solution and the elevated temperature was used to accelerate the aging process. The applied sustained stress on the carbon-fiber composite cable strands was equivalent to 40% and 65% of their guaranteed tensile strength. This was achieved through testing 171 carbon-fiber composite cable specimens subjected to stress levels of 0%, 40%, and 65% of their guaranteed strength, under tensile load. Also, 136 carbon-fiber composite cable specimens were tested to investigate the transverse shear strength. In addition, the durability characteristics of the constituent materials of the carbon-fiber composite cable strands were assessed to understand the long-term behavior of these materials. The results showed the effect of sustained stress on the degradation of carbon-fiber composite cable strands. Under sustained stress of 40% and 65%, the reductions in tensile strength were 10.6% and 12.3%, respectively. Scanning electron microscope results on epoxy resin indicated that no degradation is detected since the surface remains smooth without any pitting or loose material.

This paper reports on the results of an experimental investigations and theoretical models of concrete filled fiber-reinforced polymer (FRP) tube (CFFT) columns reinforced with steel and carbon-FRP (CFRP) bars under concentric and eccentric compressive loads. The experimental test parameters were the type of the internal reinforcement (CFRP versus steel) and eccentricity to diameter ratios . It was found that the CFRP reinforced CFFT columns successfully maintained the axial load capacities under different eccentricities as compared with the steel reinforced CFFT columns. However, the strength and behavior of the steel and CFRP CFFT test specimens were mainly affected by the eccentric loading. The average compressive strength of CFFT columns was reduced by 42–75% with increasing the e/D ratio from 10 to 40%. Theoretical models using two approaches to predict the axial-moment interaction diagrams and moment curvature relationships were developed and validated through comparison with the experimental results. A nonlinear moment-curvature (M-φ) response was observed regardless the type of reinforcement and the applied eccentricity ratio. Furthermore, a comprehensive parametric study was performed to investigate the influence of different design variables on the moment capacity by creating numerous moment curvature relationships.

This paper presents the physical, mechanical, and durability characterization of glass fiber-reinforced polymer solid and tubular bars. These bars were subsequently used as rock bolts for ground control of the Jurong Rock Caverns in Singapore. The long-term performance of these bars was assessed under harsh environmental exposure (saline solution) simulating the subsea cavern water. The test parameters were (1) type of bars (solid and tubular), (2) temperature (20, 40, and 50℃), and (3) conditioning time (1000, 3000, and 5000 h). The measured tensile strengths of the bars before and after exposure were considered as a measure of the durability performance of the specimens and were used for long-term properties prediction based on a theoretical model. Moreover, microstructural analyzes using scanning electronic microscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry are also conducted to investigate the deterioration of fiber, matrix, and the fiber/matrix interface due to environmental conditioning. The results show the very high long-term durability of solid and tubular glass fiber-reinforced polymer rock bolts exposed to field conditions. The predicted tensile strength retention at a MAT of 32℃, with an RH of 100%, is 0.90 and 0.82 for a service life of 100 years for solid and tubular glass fiber-reinforced polymer bars, respectively. Based on the findings of this research, the tested glass fiber-reinforced polymer rock bolts were recommended as alternatives to stainless-steel rock bolts and successfully used as ground control in the Jurong Rock Caverns in Singapore.

This paper presents experimental investigation, statistical analysis, and theoretical predictions of tensile-strength retention of glass fiber-reinforced polymer bars, made with vinyl-ester, polyester, or epoxy resins. The durability of glass fiber-reinforced polymer bars was evaluated as a function of time of immersion in alkaline solution. The aging of the three glass fiber-reinforced polymer bar types consisted of immersion glass fiber-reinforced polymer bar samples in an alkaline solution (up to 5000 h) at different elevated exposure temperatures. Subsequently, the physical and tensile properties of the unconditioned bars were compared with that of the conditioned bars to assess the durability performance of the glass fiber-reinforced polymer bars. Microstructure of all of the glass fiber-reinforced polymer bar types was investigated with scanning electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy for both the conditioned and unconditioned cases, to qualitatively explain the experimental results and to assess changes and/or degradation in the glass fiber-reinforced polymer bars. In addition, the long-term performance of glass fiber-reinforced polymer bars was assessed considering the effect of service years, environmental humidity, and seasonal temperature fluctuations. The test results showed that the tensile strength of the glass fiber-reinforced polymer bars was affected by increased immersion time at higher temperatures and the reduction in tensile strength was statistically significantly dependent on the type of resin system. The prediction approach of the glass fiber-reinforced polymer bars based on the environmental reduction factor ( CE) after 200 years indicated that the CE values for vinyl-ester, epoxy, and polyester glass fiber-reinforced polymer bars can be conservatively recommended to 0.81, 0.75, and 0.71, respectively, for a moisture-saturated environment (relative humidity = 100%) and at 30℃. The polyester glass fiber-reinforced polymer bars experienced greater debonding at the fiber–resin interface than the vinyl-ester and epoxy glass fiber-reinforced polymer bars.