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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]

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]

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 [...]

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]

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]

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]

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]