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This study focused on evaluating the confinement requirements for glass fiber–reinforced polymer (GFRP) reinforcement in circular reinforced concrete (RC) columns subjected to seismic forces, including torsional effects. Seven large-scale GFRP-RC columns were tested under axial and quasi-static cyclic lateral loading. The test parameters included torsion-to-bending moment ratio (tm) and transverse reinforcement spacing and configuration (spiral and hoops). The experimental results revealed that introducing torsion to the loading scheme reduced the lateral load resistance and drift capacity of the columns. The study recommends adopting a spiral pitch equal to one-sixth of the effective core diameter, as per the Canadian provisions for FRP-RC structures. This spiral pitch significantly enhanced peak lateral load, torque, drift, and twist capacities while ensuring column stability at high drift ratios and preventing complex modes of failure under seismic loading, including torsion. The GFRP spirally reinforced columns consistently surpassed the drift threshold requirements specified by the Canadian provisions for FRP-RC structures. In contrast, hoop-reinforced columns failed at lower drifts, with a notable lap-splice failure observed in columns under tm of 0.4. It was concluded that using GFRP hoops with a lap splice length of 40 times the bar diameter is inadequate for columns subjected to seismic conditions with torsional effects. [ABSTRACT FROM AUTHOR]

Glass fiber–reinforced polymer (GFRP) reinforcements can be used as shear friction connectors at the interface of concrete composite elements to maintain structural integrity. However, the shear friction mechanism at the interface greatly depends on the interface condition and the stiffness of the reinforcement crossing the interface plane. A total of 18 GFRP-reinforced concrete (RC) push-off specimens were constructed and tested until failure under monotonic load. The test parameters included the shear plane condition (roughened or not roughened, cold joints and monolithic), type (steel and GFRP), and ratio (0.24%–0.47%) of reinforcement crossing the shear plane. Roughening the interface had a little effect on the overall behavior and shear capacity of the specimen. Conversely, the monolithic specimens carried approximately 60% higher load than their cold-joint counterparts; nevertheless, the failure was more brittle. The capacity prediction by the Canadian Highway Bridge Design Code showed conservative results. By contrast, the predictions of the American Concrete Institute's model for steel-RC elements overestimated the test results for cold-joint and monolithic specimens with reinforcement ratios of 0.43% or higher. [ABSTRACT FROM AUTHOR]

Under earthquake excitations, reinforced concrete (RC) columns could be subjected to lateral drift reversals and a combination of axial forces, bending moments, and torsional effects. This paper investigates the behavior of glass fiber-reinforced polymer (GFRP)-RC columns under seismic-simulated loading, including torsion, which has not been studied previously. Seven large-scale circular GFRP-RC column-footing connections were cast and tested under various combined reversed cyclic loading configurations to examine the effects of torsion-bending moment ratio (tm), transverse reinforcement ratio, and concrete compressive strength. The test results revealed that increasing the tm reduced the lateral load capacity and deformability of the GFRP-RC column, but resulted in a more symmetric torque-twist relationship. Increasing the transverse reinforcement ratio mitigated core damage and provided additional support (for example, spiral turns) for torsion-induced tensile stresses. Moreover, increased concrete compressive strength bolstered torque capacity and torsional stiffness, while, under a tm of 0.4, it resulted in decreased twist capacity. When torsion was present, increasing the concrete compressive strength had an insignificant impact on the bending-shear response, differing from findings for GFRP-RC columns subjected to seismic loading without torsion. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) bridge columns often encounter complex combinations of loads, including flexural, axial, shear, and torsional forces, during seismic events, especially in the presence of geometric irregularities such as skewed or curved bridges, unequal spans, or varying column heights. Corrosion-related deterioration in RC structures spurred the adoption of glass fiber-reinforced polymer (GFRP) as a promising alternative to steel reinforcement. This study experimentally investigates the performance of GFRP-RC circular columns under cyclic loading, including torsion with different torsion-to-bending moment ratios (tm and longitudinal reinforcement ratios. The results showed that, with the same reinforcement ratios, the addition of torsion to cyclic bending and shear significantly altered the behavior of the GFRP-RC column in terms of mode of failure, load resistance, drift capacity, and energy dissipation. The inelastic deformability hinge shifted upward with increased tm. Higher tm accelerated stiffness degradation, while increasing the longitudinal reinforcement ratio enhanced lateral load, drift, and twist capacities. [ABSTRACT FROM AUTHOR]

Interface shear transfer is vital to maintain the structural integrity of concrete composite elements. Therefore, shear connectors are provided at the concrete joint interface to maintain such integrity. Due to its high tensile strength and non-corrodible nature, glass fiber-reinforced polymer (GFRP) reinforcement can be used as shear connectors in composite elements, particularly those in harsh environments. Fifteen pushoff specimens were constructed and tested to failure. The specimen consisted of two L-shaped concrete blocks cast at two stages to provide the cold joint interface. The test parameters were the type, shape, and ratio of shear-friction reinforcement and concrete strength. It was demonstrated that GFRP-reinforced concrete RC) specimens with reinforcement ratios of 0.36% or more could resist the shear-friction stresses similarly to their steel-RC counterparts. Also, increasing the concrete strength increased the shear-friction capacity significantly. Moreover, the design model in the Canadian Highway Bridge Design Code resulted in very conservative predictions. [ABSTRACT FROM AUTHOR]

Corbels are characterized as low shear span-to-depth ratio (a/d) members that transfer vertical and horizontal loads to adjacent members such as columns or walls. Glass fiber–reinforced polymer (GFRP) reinforcement has linear-elastic behavior and a lower modulus of elasticity relative to steel leading to deeper and wider cracks, which is especially critical for low a/d members. Currently, Canadian bridge and building standards provide strut-and-tie modeling provisions to design steel– and GFRP–reinforced concrete (RC) corbels, but the United States (US) code for GFRP–RC structures prohibits the use of this method for GFRP–RC corbels because of lack of research. Eight full-scale GFRP–RC corbels were constructed and tested to failure. The test variables included main tie and secondary reinforcement ratios, a/d ratio, and concrete strength. The experimental results indicated that a/d and concrete strength have a considerable influence on concrete crack width development, deflection, and load-carrying capacity. The Canadian standard for FRP–RC buildings provided conservative shear capacity predictions for all eight corbels. The US code for steel–RC structures overestimated the shear capacity predictions for seven of the eight corbels, suggesting that revisions are required to better predict the capacity of GFRP–RC corbels. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced polymer (GFRP) reinforcement is a proven noncorrodible alternative to conventional steel reinforcement. Over the past two decades, a deliberate effort has been put toward developing a comprehensive set of design provisions, culminating in the release of ACI CODE-440.11-22. Absent from this Code is the strut-and-tie method commonly used in short shear-span applications due to uncertainty in GFRP-reinforced concrete (RC) behavior. Corbels are short shear-span, shear-controlled elements used to transfer vertical and horizontal loads to columns or walls. This study presents the results of 10 full-scale corbel specimens with varying reinforcement ratios and shear span-depth ratios to better understand the behavior of GFRP-RC corbels under monotonic loading. The results indicate that the cracking behavior, strain development, deflection, capacity, and mode of failure are all dependent on the presence of secondary reinforcement and the shear span-depth ratio. The thermoplastic headed-end bars used were found to be a viable anchorage method. [ABSTRACT FROM AUTHOR]

Different rehabilitation techniques have been utilized to extend the service life of wooden utility poles, which are mainly affected by degradation and decay. This paper presents an evaluation of the performance of wooden utility poles rehabilitated using sprayed glass fiber–reinforced polymer (GFRP) composites and near-surface-mounted (NSM)-GFRP bars. Seven full-size (305-mm diameter) new wooden poles and five full-size old wooden poles, taken out of service, were tested under monotonically increasing lateral load. The test parameters included the thickness (4, 6, and 8 mm) and length (1.0 and 2.0 m) of the sprayed-GFRP coating, and rehabilitation methods (sprayed-GFRP composites, NSM-GFRP bars). The results showed that the sprayed-GFRP coating can restore the load-carrying capacity and enhance the stiffness of both old and damaged poles. In addition, the load-carrying capacity of the wooden poles was not affected by the increase in GFRP thickness after the thickness reached 6 mm. It was also concluded that using the NSM-GFRP bars is not cost-effective compared to the sprayed-GFRP composites. A simple analytical procedure was introduced to estimate the load-carrying capacity of retrofitted poles and to calculate the required thickness of the sprayed-FRP layer, which yielded reasonably conservative results. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) corbels are commonly utilized in bridges and industrial buildings to support primary beams and girders. Using glass fiber–reinforced polymer (GFRP) reinforcement in corbels can be advantageous due to its corrosion-resistance properties. However, GFRP reinforcement, with a lower modulus of elasticity and shear strength than steel, could affect the capacity of direct shear. This paper presents the experimental results of nine full-scale, double-sided corbels reinforced with either GFRP or steel bent bars. Large-scale double-sided corbels were constructed and tested for failure under monotonic concentric loads. The test parameters included the reinforcement type (GFRP and steel), the main reinforcement ratio (0.5% and 0.7%), the shear span-to-depth ratio (a/d = 0.33 and 0.66), and the amount of crack-control horizontal reinforcement (0.7% and 1.3%). The predictions of corbel capacity using the Canadian standards for FRP-RC structures were conservative, especially for the corbels with crack-control reinforcement. In contrast, the predictions of the American and European codes overestimated the corbel strength, particularly for the higher a/d ratio of 0.66. [ABSTRACT FROM AUTHOR]

Wooden utility poles are vulnerable to degradation and decay, which requires maintenance or replacement. The strengthening and retrofitting techniques for wooden poles are either prone to corrosion or encountering installation difficulties. However, the use of sprayed fiber-reinforced polymer (FRP) composites seems to be a viable solution as it has proven its efficiency and applicability for reinforced concrete members and connections. This study includes a comprehensive experimental program where the mechanical properties of the sprayed-glass FRP (GFRP) composite was evaluated in terms of tensile, compressive and shear strength, in addition to its bond strength to wood and confinement efficiency. Afterwards, the results of the material testing phase were implemented on full-scale old utility poles to evaluate their structural performance with varying composite thicknesses and sprayed zone lengths. The behavior of the retrofitted poles reflected remarkable effectiveness for the sprayed-GFRP composite and highlighted the need for a design model for the optimum length for the sprayed zone. Two simplified analytical models were introduced which predicted the failure loads and locations for the tested poles and estimated the required length for the retrofitted zone, which all agreed well with the experimental results of the tested poles. [ABSTRACT FROM AUTHOR]

Hollow-core slab (HCS) floors supported on steel beams require the use of steel reinforcement as connections to avoid slab displacement caused by lateral loads. However, current North American design codes offer limited provisions on the design and behavior of such connections. In this study, the results of an experimental investigation conducted on such connections to assess their capacity and mode of failure are presented. Eleven full-scale assemblies of HCS reinforcing bar connections to steel beams were tested to failure under monotonic in-plane loading (compression, tension, or shear). Test results revealed that connections tested under compression failed by bar buckling without yielding. Under tension, the connection bar reached close-to-yielding or yielding strains at the unrestrained portion of the bar, followed by grout splitting in the shear key or the grouted core. Finally, the mechanism of failure of specimens subjected to shear was governed by bar yielding. [ABSTRACT FROM AUTHOR]

This paper describes an experimental investigation to evaluate the shear strength and behavior of concrete deep beams reinforced with fibre-reinforced polymer (FRP) bars. A total of ten full-scale reinforced concrete beams without web reinforcement were constructed and tested in four-point bending. The test variables were the reinforcement ratio and the modulus of elasticity of the longitudinal reinforcing bars as well as the shear span to depth ratio. The test beams included five beams reinforced with glass FRP bars and five beams reinforced with carbon FRP bars. The behavior of the deep beams is described in terms of load-deflection response, cracking patterns and modes of failure, strains in reinforcement and concrete, inclined cracking, and ultimate shear strengths. All ten beams showed significant reserve strength after the inclined cracking was fully developed. The test results also indicated that the ultimate shear strength of the tested beams considerably increased with the decrease of the shear span to depth ratio. In addition, the ultimate shear strengths of the tested beams were predicted using the shear design provisions recommended by the new version of the Canadian Standard CSAS806- 11 and compared with the experimental results, showing good agreement. Key words: deep beams, experimental results, fibre-reinforced polymer, shear strength. Cet article presente une etude experimentale servant a evaluer la resistance en cisaillement et le comportement de poutres-cloisons en beton armees de tiges en polymere renforce de fibres (PRF). Un total de 10 poutres en beton arme a pleine echelle sans armature d'ame a ete construit et mis a l'epreuve sous flexion a quatre points. Les variables d'essai etaient le rapport d'armature et le module d'elasticite des tiges d'armature longitudinales ainsi que le rapport portee en cisaillement--profondeur. Les poutres a l'essai comprennent cinq poutres armees de tiges en polymere renforce de fibres en verre (PRFV) et cinq poutres armees de tiges en polymere renforce de fibres en carbone (PRFC). Le comportement des poutres-cloisons est decrit en termes de la reponse en deformation en raison de la charge, les motifs de fissuration et les modes de defaillance, les contraintes dans l'armature et le beton, la fissuration inclinee ainsi que les resistances a la rupture en cisaillement. Les 10 poutres ont montre de bonnes reserves de resistance une fois la fissuration inclinee pleinement developpee. Les resultats des essais ont egalement indique que la resistance a la rupture en cisaillement des poutres mises a l'epreuve a considerablement augmente avec la diminution du rapport portee en cisaillement--profondeur. De plus, les resistances a la rupture en cisaillement des poutres a l'essai ont ete predites en utilisant les dispositions de calcul du cisaillement recommandees dans la nouvelle version de la norme canadienne CSA-S806-11 et elles montraient une bonne concordance lorsque qu'elles etaient comparees aux resultats experimentaux. Mots-cles : poutres-cloisons, resultats experimentaux, polymere renforce de fibres, resistance en cisaillement. [Traduit par la Redaction], Introduction The use of fibre-reinforced polymer (FRP) bars is gaining acceptance as an alternative to conventional steel reinforcement in structural members subjected to severe environmental exposure. FRPs are non-corrodible materials [...]

A three-dimensional non-linear finite-element model (FEM) was constructed using a commercial software (ATENA-Studio) to investigate the transverse load distribution behavior of adjacent precast prestressed concrete box-girder bridges. An innovative connection between box girders was used, where transverse post-tensioning was applied at the top flanges only eliminating the need for intermediate transverse diaphragms. The FEM was validated in terms of deflections, strains, cracking and ultimate loads against experimental results previously reported by the authors. The validated FEM was then used to perform a parametric study investigating the influence of adding concrete topping, load location, and bridge width on the transverse load distribution behavior of the newly developed connection. The results of the FEM demonstrated the efficiency of concrete topping in limiting mid-span deflections up to 25%. Additionally, the maximum live load moment distribution factors (LLMDFs) for different load locations and bridge widths were evaluated. [ABSTRACT FROM AUTHOR]

The available provisions for the seismic design of fiber-reinforced polymer (FRP)-reinforced concrete (RC) columns were fundamentally derived from design models created for steel-RC ones due to the limited research data on the former. This, in turn, may justify the conservativeness of such provisions, particularly those concerning the design of confinement reinforcement for columns with different aspect ratios. This study investigates the effect of the aspect ratio and axial load level on the seismic response of columns reinforced with glass FRP (GFRP) by testing six full-scale GFRP-RC circular columns under earthquake-simulated loading. The experimental results revealed that, unlike steel-RC columns, changing the aspect ratio insignificantly influenced the hysteretic response of GFRP-RC columns, indicating that the available code provisions for confinement reinforcement design are overly strict. Furthermore, recommendations are proposed for the seismic design of confinement reinforcement in GFRP-RC columns. [ABSTRACT FROM AUTHOR]

In this study, the bond behavior of sand-coated glass fiber-reinforced polymer (GFRP) bars embedded in cementitious composite matrix reinforced with the recently developed basalt fiber (BF) pellets and steel fibers (SF) was evaluated. Several studies have attempted to introduce empirical models to estimate the bond strength of FRP-reinforced concrete (RC) specimens. In this study, the applicability of these models to predict the bond stress of straight and headed-end FRP bars embedded in normal concrete and fiber-reinforced concrete (FRC) was assessed. Test results of 413 pullout specimens, which were divided into four groups based on the type of the FRP bar or the cementitious matrix, were used to evaluate the available models. In addition, a proposed model to predict the bond performance of headed-end FRP bars with FRC pullout specimens was introduced. The model was calibrated against experiments conducted previously by the authors on FRP–FRC specimens. The model was capable of predicting the maximum bond strength with a mean experimental-to-predicted value of 1.09 and a standard deviation of 0.19. [ABSTRACT FROM AUTHOR]

The seismic behavior of fiber-reinforced polymer-reinforced concrete (FRP-RC) columns is far from being fully explored. Therefore, numerical and analytical studies were performed to address the effects of different parameters and evaluate the current design provisions for confinement reinforcement under seismic loading. Using a commercially available software package, a three-dimensional nonlinear finite-element model (FEM) was constructed and validated against the experimental results of full-scale glass FRP (GFRP)-RC circular columns previously tested by the authors. The validated FEM was, then, used to conduct an extensive parametric study investigating the effect of concrete compressive strength, spiral pitch, axial load level, and column aspect ratio (i.e., shear span-to-depth ratio). It was found that increasing the concrete strength caused an increase in lateral load capacity and initial stiffness, whereas the drift capacity decreased. The latter property was also significantly affected by the variation of spiral pitch and axial load level. On the other hand, the aspect ratio had a marginal effect on moment or drift capacities. Using the results of the FEMs, two new design models were proposed. The proposed models showed remarkably better predictions than the equation adopted by the Canadian standard for the design of FRP-RC structures. [ABSTRACT FROM AUTHOR]

Ten large-scale high-strength concrete (HSC) circular columns were constructed and tested to failure. Nine columns were internally reinforced with glass fiber-reinforced polymer (GFRP) bars and spirals, whereas one was reinforced with steel bars and spirals to serve as a reference. All columns had a diameter of 350 mm. The variables tested were reinforcement type, spiral pitch, slenderness ratio, eccentricity-to-diameter ratio (e/D), and type of loading (axial or four-point bending). Experimental results showed that both reinforcement types (steel or GFRP) and the spiral pitch did not have a significant effect on the behavior of GFRP-reinforced HSC columns up to the peak load. In addition, a decrease in the axial capacity of the columns as the e/D ratio increased was observed. This was consistent for specimens of both slenderness ratios of 14 and 20. Columns with a higher slenderness ratio showed a lower axial capacity for all specimens tested under the same e/D ratio. Furthermore, slender columns with higher e/D ratio underwent much larger deformations; both axially and laterally. For columns of both slenderness ratios, axial load–bending moment interaction diagrams were produced using the experimental results and were compared to the predictions of available codes and guidelines. [ABSTRACT FROM AUTHOR]

Recently, developing a nonferrous reinforcement system (corrosion-free system) using durable and ductile cement-based materials that incorporate discrete fibers has been a promising option for exposed concrete structures in cold regions or marine environments. Therefore, in this study, properties of a novel type of cementitious composite comprising nano-silica and a high dosage of slag were investigated. The hybrid (layered) composites assessed in this study were composed of two layers of different types of cementitious composites. Normal concrete (NC) was used in the top layer combined with a layer of fiber-reinforced cementitious composite (FRCC) reinforced with either the recently developed basalt fiber (BF) pellets (basalt fiber strands encapsulated by a polymeric resin or steel fibers (SF)) that were used at different dosages. The post-cracking behavior in terms of residual strength, residual index, and toughness are presented and discussed. The analysis of results showed the effectiveness of the BF pellets in enhancing the post-cracking behavior of specimens, as they behaved comparably to counterpart specimens comprising SF, which makes them a good candidate for infrastructural applications including rehabilitation such as new bridge girders or overlays. [ABSTRACT FROM AUTHOR]

In this study, the performance of basalt pellet–reinforced cementitious composites (BPRCC) was evaluated after exposure to harsh conditions. The exposure consisted of consecutive 300 freeze–thaw cycles followed by 75 wet–dry cycles simulating successive winter and summer seasons. The mixtures, incorporated general-use cement, slag, and nanosilica, and reinforced with either the recently developed basalt fiber pellets (BP)—basalt fiber strands coated by a polymeric resin—or steel fibers. The resilience of composites was assessed by internal damage, residual compressive and flexural strengths, as well as their compatibility with base/parent concrete, when used in a layered system with normal concrete. The presence of BP at a dosage of 4.5% or 6.9% in the nanomodified cementitious composites effectively discounted the rate of deterioration, resulting in lower reductions in stiffness, compressive and flexural capacities, as well as toughness after the exposure to aggravated environmental conditions. Hence, such composite may present a promising option for construction of exposed infrastructural elements. [ABSTRACT FROM AUTHOR]

When reinforced concrete (RC) slabs are supported directly on columns, a combination of shear forces and unbalanced bending moments is transferred between the slab and the columns at slab–column connections. The unbalanced moment transferred between a slab and a column can be significantly increased by the application of horizontal loads, such as wind and seismic loads. According to current design codes and standards for steel–RC structures in North America, a portion of the unbalanced moment is assumed to be transferred by the eccentricity of shear, while the remaining portion is assumed to be transferred by flexure. Previous research shows that the slab width that contributes to transferring the flexure portion is bounded by lines located at a distance of 1.5 times the slab thickness on each side of the column. This study investigates whether the same slab width can be used to transfer the unbalanced moments in slab–column connections reinforced with glass fiber–reinforced polymer (GFRP) reinforcement. A similar approach to that used for steel–RC connections is followed to analyze data from 27 GFRP-RC connections without shear reinforcement reported in the literature. Furthermore, a previously validated finite-element model is used to investigate the strain distribution in the longitudinal slab reinforcement along the transverse direction of the slab. The results show that a smaller slab width bounded by lines located at a distance of 0.5 times the slab thickness on each side of the column is recommended for GFRP-RC slabs. [ABSTRACT FROM AUTHOR]

In this study, the bond behavior of sand-coated glass fiber-reinforced polymer (GFRP) bars embedded in a novel type of cementitious composite, containing nanosilica, slag, and reinforced with recently developed basalt fiber pellets (BPs), was evaluated. Steel fibers (SFs) were incorporated in control mixes for comparison purposes. Ninety-five cubic pullout specimens were prepared and tested according to Canadian standards. The test parameters were the type of cementitious composite, the bar diameter, the type of fibers, the dosage of BP, and the type of GFRP bar end. The bond performance was elucidated through the compressive strength of the composite and load–slip response of GFRP bars. In addition, the fiber bridging mechanism was determined by evaluating the residual bond strength and toughness indices. The provisions for bond strength in the Canadian and American codes were also assessed. The test results showed the effectiveness of the BP in enhancing the failure pullout load compared to counterpart specimens comprising SF, which makes them a good candidate for infrastructural applications including rehabilitation. [ABSTRACT FROM AUTHOR]

The linear elastic behavior of fiber-reinforced polymer (FRP) reinforcement makes it controversial to implement in seismic-resistant reinforced concrete (RC) structures. More concerns could be raised when such reinforcement is associated with high-strength concrete (HSC). Columns in multi-story buildings or bridges are common examples of structural members constructed using HSC. To date, all available research data on glass FRP (GFRP)-RC columns have shown that they have a maximum limit of concrete compressive strength equal to approximately 55 MPa (8000 psi). The results of five full-scale column-footing specimens are presented to study the seismic response of GFRP-RC columns, highlighting the effect of concrete compressive strength alongside other factors such as spiral pitch and axial load. It is concluded that when properly confined, GFRP-reinforced HSC circular columns can exhibit a stable seismic response with sufficient deformability. Moreover, several confinement and performance indexes were adjusted and evaluated to introduce an informative relationship for the design of GFRP-RC columns. [ABSTRACT FROM AUTHOR]

This study aims at assessing the long-term bond behavior of headed-end glass fiber-reinforced polymer (GFRP) bars to basalt fiber-reinforced cementitious composite (BFRCC) exposed to 300 consecutive freezing-and-thawing cycles, followed by 75 cycles of wetting and drying, mimicking successive winter and summer seasons. A total of 85 pullout specimens reinforced with recently developed basalt fiber pellets and steel fibers were tested. The durability of the specimens was quantified in terms of visual analysis, residual compressive strength, relative dynamic modulus of elasticity, as well as the residual pullout capacity. The addition of fibers was capable of retaining approximately 90% of the pullout capacity for specimens exposed to harsh conditions owing to the restriction of cracks in the fiber-reinforced cementitious composites. Therefore, the results confirmed the suitability of steel-free reinforcement systems for long-term application under severe freezingand- thawing and wetting-and-drying environments. [ABSTRACT FROM AUTHOR]

The purpose of this study is to assess the feasibility of using a non-metallic basalt fiber (BF) pellets to enhance the ductility of glass fiber-reinforced polymer (GFRP) reinforced concrete deep beams. In addition, the ability of BF pellets to supplant conventional web reinforcement was evaluated. To achieve the goals of this study, seven large-scale concrete deep beams reinforced with GFRP headed-end bars were constructed and tested to failure under three-point loading over a span of 1390 mm. The beams had a rectangular section of 250 x 590 mm with overall length of 2100 mm. Experimental variables included the volumetric percentage of BF pellets and transverse web reinforcement. The addition of fibers improved the post-peak behavior by increasing the ductility index by more than 50%, when compared to the counterpart control beam. The results provide support for replacing conventional web reinforcement in deep beams with a layer containing BF pellets in the tie zone. [ABSTRACT FROM AUTHOR]

Test results of nine continuous concrete deep beams reinforced with glass fiber-reinforced polymer (GFRP) bars are presented. The main objectives of this study are to evaluate the shear capacity of GFRP-reinforced concrete (RC) continuous deep beams and to examine the applicability of the strut-and-tie model to such beams. The test parameters are the shear span-to-depth ratio and the top longitudinal reinforcement ratio. Test results revealed that decreasing the area of the top reinforcement increased the shear capacity of test beams. On the other hand, as expected, the shear capacity decreased with an increase in the shear span-to-depth ratio. Moreover, provisions of strut-and-tie models available in current codes need to be revised to better predict the capacity of GFRP-RC continuous deep beams. [ABSTRACT FROM AUTHOR]

In this study, a new transverse post-tensioning (TPT) technique for box girder bridges is investigated, where TPT is applied at the top flange of the girder resulting in eliminating the intermediate transverse diaphragms. A one-third-scale bridge model consisting of four adjacent box girders with partial-depth shear keys was erected and tested. The bridge model was investigated for the optimal TPT force and spacing to ensure a uniform distribution of the clamping prestress. The efficiency of the proposed technique in transversely distributing live loads during simulated service and ultimate conditions was also investigated. Test results demonstrated that distributing the TPT force at a shorter spacing along the length of the bridge is more efficient than increasing the TPT force at discrete distant locations in producing the minimum required concrete prestress. It was observed that the effect of TPT force and spacing was insignificant during the simulated service condition, where shear keys remained intact or partially cracked. However, at failure, the presence of TPT added redundancy to the bridge model and mitigated any sudden failure when shear keys were fully cracked. DOI: 10.1061/(ASCE)BE.1943-5592.0001699. © 2021 American Society of Civil Engineers. [ABSTRACT FROM AUTHOR]

A series of finite-element analyses for slab-–column edge connections reinforced with fiber-reinforced polymer (FRP) reinforcement and subjected to reversed-cyclic lateral load is conducted and discussed. A three-dimensional nonlinear finite-element model (FEM) is constructed using a commercially available software. The FEM is validated against the results of experimental studies conducted previously by the authors. Subsequently, the validated FEM is used to carry out an extensive parametric study investigating the influence of key parameters including the gravity shear ratio (0.2–0.8), flexural reinforcement type [glass and carbon FRP (GFRP and CFRP, respectively)], column aspect ratio (0.25–4.00), flexural reinforcement ratio (0.7%–1.4%), and slab thickness (150–400 mm). The results showed that the drift capacity of edge connections reinforced with either GFRP or CFRP reinforcement is reduced when the applied gravity shear ratio increases. However, GFRP-reinforced concrete (RC) connections were able to undergo larger drift ratios than their CFRP-RC counterparts. In addition, increasing the slab thickness reduced the punching shear strength of GFRP-RC connections, even for slabs with an effective depth less than 300 mm. [ABSTRACT FROM AUTHOR]

Several empirical models have been introduced during the last two decades to estimate the punching capacity of two-way slabs reinforced with fiber-reinforced polymer (FRP) reinforcement. In this study, the applicability of these models on FRP-reinforced concrete (RC) slab-column interior and edge connections subjected to gravity loads is assessed. The models are also calibrated against experiments conducted previously by the authors on FRP-RC edge connections subjected to reversed-cyclic lateral loads. Test results of 68 interior and 25 edge specimens, 6 of which were tested under reversed-cyclic lateral loads, were used to evaluate the available models. Based on the analysis, a universal model capable of accurately predicting the capacity of both interior and edge specimens subjected to gravity or cyclic loads is proposed. The proposed model provided a mean test-to-predicted strength of 1.01 ± 0.14 and 1.01 ± 0.09 for interior and edge specimens, respectively. Furthermore, a design model is proposed to estimate gravity shear limits for FRP-RC connections without shear reinforcement and subjected to cyclic load. [ABSTRACT FROM AUTHOR]

When reinforced concrete (RC) flat-plate systems are used as gravity force-resisting systems in regions of high seismic activities, they are required to accommodate at least 1.50% drift ratio without jeopardizing their gravity load capacity. The current codes and standards in North America limit the allowable gravity shear ratio in steel-RC flat-plate systems without shear reinforcement to 0.4 for the system to be able to sustain the 1.50% drift capacity. This paper reports the results of an inaugural experimental study investigating the effect of gravity shear ratio on the drift capacity of slab-column edge connections reinforced with glass fiberreinforced polymers (GFRP) reinforcement. Three full-scale GFRP-RC edge connections were tested under a combination of gravity and uniaxial reversed-cyclic lateral loads. It was concluded that the 0.4 limit on the gravity shear ratio can be relaxed in the case of GFRP-RC connections. [ABSTRACT FROM AUTHOR]

Reinforced concrete deep beams are common structural elements in bridges and high-rise buildings because of their ability to support higher concentrated loads compared with slender beams. In this study, three simply supported deep beams and three continuous deep beams reinforced with glass fiber-reinforced polymer (GFRP) bars were constructed and tested to failure. The test variable was the shear span-to-depth ratio, which varied between 1.0 and 2.0. Test results are presented in terms of cracking, deflection, strains in concrete and reinforcement, load capacity, and mode of failure. The cracking pattern and measured strains indicated the development of the arch action mechanism in all specimens. Test results indicated that increasing the shear span-to-depth ratio led to a significant decrease in the load-carrying capacity of the beams. Moreover, continuous beams exhibited higher load capacity than did their simply supported counterparts. In addition, a comparison between the experimental and code-predicted load capacity of beams is presented. [ABSTRACT FROM AUTHOR]

The effect of various factors on the contribution of slabs to the seismic performance of beam-column joints in steel-reinforced concrete (RC) frames has been extensively investigated. However, no research data is available on the behavior of beam-column slabs reinforced with alternative materials such as glass fiber-reinforced polymers (GFRPs). To fill this gap, two full-scale GFRP-RC exterior beam-column slabs were tested under reversal loading to investigate their seismic performance with a focus on the effect of lateral beams on the effective slab width. The results were compared with two previously tested beam-column specimens. Moreover, a series of finite element models were generated to determine the influence of lateral beams' size and slab thickness on the contribution of slabs. The results indicated that the contribution of cast-in-place slabs in the bending moment capacity of the main beams when the top fiber of the slab is in compression is insignificant. [ABSTRACT FROM AUTHOR]

This paper deals with punching shear behavior of flat plates reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bars. Six full-scale reinforced concrete (RC) slab-column interior connections were constructed and tested to failure. Two variables were investigated; the flexural reinforcement ratio when high-strength concrete (HSC) is used and the type of GFRP shear reinforcement (headed studs and corrugated bars) when normal-strength concrete (NSC) is used. All specimens were tested under concentric shear force and unbalanced bending moment with a constant moment-to-shear ratio. Increasing the reinforcement ratio increased punching capacity and post-cracking stiffness for HSC connections. Both types of shear reinforcement increased the punching capacity and deflection of NSC connections. Test results were compared with the predictions of the available fiber-reinforced polymer (FRP) design provisions in North American codes. [ABSTRACT FROM AUTHOR]

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This paper evaluates the performance of carbon and glass fibre-reinforced polymer (FRP) stirrups and the accuracy of the shear design provisions incorporated in the currently available design codes and guidelines. A total of seven large-scale T-beams were constructed and tested: three reinforced with carbon fibre-reinforced polymer (CFRP) stirrups, three reinforced with glass fibre-reinforced polymer (GFRP) stirrups, and one reinforced with a steel stirrup for comparison, when applicable. The test results revealed that the design strength of the tested beams is not affected by the reduced strength of FRP stirrups at bend locations. Also, the recent CAN/CSA-S6 update is capable of adequately predicting the shear strength of the beam specimens reinforced with FRP stirrups. The software, Response-2000, which is based on the modified compression field theory (MCFT), predicted well the shear strength and the average strain in the stirrups of the tested beams; however, it overestimated the shear crack width. [ABSTRACT FROM AUTHOR]

Using fiber-reinforced polymer (FRP) reinforcing bars as the main reinforcement for concrete structures in severe environments is becoming a widely accepted solution to overcome the problem of steel corrosion and the related deteriorations. Due to the relatively lower cost of glass FRP (GFRP) bars compared to the other commercially available FRP bars, the use of GFRP bars in reinforced concrete (RC) structures has been widely investigated in the last few years. This paper reports experimental data on the shear strength of concrete beams reinforced with GFRP stirrups. A total of four large-scale RC beams with a total length of 7000 mm (276 in.) and a T-shaped cross section were constructed and tested up to failure. The test variables were type and ratio of shear reinforcement (stirrups). The test beams comprised three beams reinforced with sand-coated GFRP stirrups of 9.5 mm (3/8 in.) diameter spaced at d/2, d/3, and d/4 (where d is the beam depth), and a reference beam reinforced with conventional steel stirrups of 9.5 mm (3/8 in.) diameter spaced at d/2. As designed, the beams failed in shear due to GFRP stirrup rupture or steel stirrups yielding. ACI 440.1R-06 and the updated version of CAN/CSA S6-06 are able to predict the shear strength of beams reinforced with GFRP stirrups with a reasonable accuracy. The analytical approach using Response 2000 (R2K), which is based on the modified compression field theory (MCFT), predicted well the shear capacity of the beams reinforced with GFRP stirrups, but overestimated their shear crack width. [ABSTRACT FROM AUTHOR]

One of the main components in girder-type bridges is bridge girder. This paper presents experimental data on the behavior and shear strength of concrete bridge girders reinforced with carbon fiber-reinforced polymer (CFRP) stirrups. A total of four large-scale reinforced concrete beams with a total length of 7,000 mm and a T-shaped cross section were constructed and tested up to failure. The test variables were the type and ratio of shear reinforcement (stirrups). The test beams included three beams reinforced with sand-coated CFRP stirrups of 9.5-mm-diameter spaced at d/2, d/3, and d/4 (where d is the beam depth) and a control beam reinforced with conventional steel stirrups of 9.5-mm-diameter spaced at d/2. The geometry of the test prototypes were selected to simulate the New England Bulb Tee (NEBT) beams that are being used by the Ministry of Transportation of Québec, Canada. As designed, three beams failed in shear due to CFRP stirrup rupture or steel stirrup yielding. While, the forth one, reinforced with CFRP stirrups spaced at d/4, failed in flexure due to yielding of longitudinal reinforcement. The test results were compared to predictions provided by different codes and design guidelines. The current ACI 440.1R-06 design method provides conservative predictions; however, the CAN/CSA S6-06 and JSCE 1997 underestimate the contribution of the FRP stirrups due to low strain limits. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study conducted on the pullout capacity of glass fiber reinforced polymer (GFRP) postinstalled adhesive anchors embedded in concrete. A total of 90 adhesive anchors were installed using sand-coated GFRP reinforcing bars and tested under monotonic tension loading in accordance with ASTM E-488-96 in 1996. The test parameters were: (1) the GFRP bar diameter (25.4, 15.9, and 6.4 mm); (2) the embedment depth (5, 10, and 15 db where db=bar diameter); (3) the adhesive type (epoxy-based and cement-based adhesives); and (4) installation conditions (wet or partially submerged and dry holes). The tested GFRP adhesive anchors were installed in concrete slabs measuring 3,750 mm long, 1,750 mm wide, and 400 mm deep. The test specimens were kept outdoors for 7 months to be subjected to real environmental conditions including freeze-thaw cycles, wet and dry cycles, and temperature variations. The experimental results indicated the adequate performance of GFRP adhesive anchors installed in wet or partially submerged condition using epoxy-based adhesive. Similar behavior was observed for those installed with cement-based adhesive in dry conditions as well. The capacity of the GFRP bars installed with both adhesive types was achieved at an embedment depth ranging from 10 to 15 db. [ABSTRACT FROM AUTHOR]

This paper reports experimental data on the behavior and shear strength of high-strength concrete slender beams reinforced with fiber-reinforced polymer (FRP) bars. Shear tests were conducted on six large-scale reinforced concrete beams without stirrups using high-strength concrete (f'c = 65 MPa) along with three beams using normal-strength concrete (f'c = 35 MPa). The beams measured 3250 mm long, 250 mm wide, and 400 mm deep, and were tested in four-point bending. The test variables were strength of concrete, and the reinforcement ratio and modulus of elasticity of the longitudinal reinforcing bars. Carbon and glass FRP bars and conventional steel bars were used as longitudinal reinforcement in this investigation. The experimental shear strengths of the FRP-reinforced concrete beams were compared to theoretical predictions provided by ACI 440.1R-03 and the modified form of this method proposed by the authors. The test results indicated that the high-strength concrete beams exhibited slightly lower relative shear strength compared to normal-strength concrete beams. In addition, the ACI 440.1R-03 design method provided very conservative predictions whereas the proposed modified equation gave better results. [ABSTRACT FROM AUTHOR]

The behavior and shear strength of concrete slender beams reinforced with fiber-reinforced polymer (FRP) bars were investigated. A total of nine large-scale reinforced concrete beams without stirrups were constructed and tested up to failure. The beams measured 3250 mm long, 250 mm wide, and 400 mm deep and were tested in four-point bending. The test variables were the reinforcement ratio and the modulus of elasticity of the longitudinal reinforcing bars. The test beams included three beams reinforced with glass FRP bars, three beams reinforced with carbon FRP bars, and three control beams reinforced with conventional steel bars. The test results were compared with predictions provided by the different available codes, manuals, and design guidelines. The test results indicated that the relatively low modulus of elasticity of FRP bars resulted in reduced shear strength compared to the shear strength of the control beams reinforced with steel. In addition, the current ACI 440.1R design method provided very conservative predictions, particularly for beamy reinforced with glass FRP bars. Based on the obtained experimental results, a proposed modification to the current ACI 440.1R design equation is presented and verified against test results of other researchers. [ABSTRACT FROM AUTHOR]