99 research outputs found

    An overview on the application of FRP composites in piling system

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    Traditional pile materials such as steel, concrete and timber have limited service life when used in harsh marine environment. Problems coupled with these piles include deterioration of wood, corrosion of steel and degradation of reinforced concrete. To offset this problem, a relatively new trend in deep foundation industry is to use a fibre reinforced polymer (FRP) composite materials as a substitute in piling system. The fundamental advantages of FRP composites compared to other pile materials include lightweight, high strength and possess resistance against corrosion. However, composite materials face hurdle because they do not have a long track record of use in civil engineering application particularly in piling system. To partly address this obstacle, this paper presents an overview in testing, design, and practice of composite piles. Importance is given to history, material types and properties, structural behaviour, geotechnical performance, and durability of composite piles

    Concrete Encased with Engineering Plastics

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     Engineering plastic tubes are economic alternatives for the advanced composite tubing systems. The mechanical behavior of concrete-encased with engineering plastic tube (CFPT) is examined in the present study by testing short-stub CFPT columns under concentric loading. The test parameters include the plastic tube and coarse aggregate/cement ratio (a/c) ratio. Due to the low stiffness of plastic tubes, the cementitious systems have an important role to increase the stiffness of CFPT. For making concrete of consistent strength, a/c ratio is an important criterion since aggregate constitutes more than 70% of concrete. The proportion of this major component of concrete was altered in increments of 0.5 resulting in twelve mixes with a/c ratios from 3 to 8. Due to the limited test data, the mechanical performance of these structures continues to be pursued through experimental methods. The aim of the present study was to investigate experimentally the relationship between the strength of CFPT and a/c ratio which is also affected by variations in other constituent materials. The a/c ratio was the common variable in both control and CFPT specimens. The experimental results show that the ability of the engineering plastic tube in improving the load capacity of CFPT was considerably affected by the a/c ratio increment which yielded a beneficial effect on the tube confinement capacity

    Behaviour of GFRP Reinforced and GFRP Encased Square Concrete Members under Different Loading Conditions

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    The use of reinforcement with fibre reinforced polymer (FRP) composite materials have emerged as one of the alternatives to steel reinforcement for concrete structures prone to corrosion issues (ACI 440.1R–15 2015). However, the mechanical behaviour of FRP reinforcement is different from that of steel reinforcement. In general FRP bars have a higher strength-to-weight ratio, but lower modulus of elasticity as compared to steel. Furthermore, when subjected to tension, FRP bars do not experience any plastic behaviour before rupture. Also, the compressive strengths of FRP bars are relatively low compared to the tensile strengths and are subjected to significant variations. Therefore, due to the differences in properties, GFRP bars cannot simply replace steel bars (ISIS 2007). The level of understanding of the behaviour of FRP reinforced compression members has not reached a level where design standards are available for such members. Having said this, the current ACI 440.1R – 15 (2015) design guideline recommends neglecting the compressive contribution of FRP reinforcement when used as reinforcement in columns, in compression members, or as compression reinforcement in flexural members. Most of the findings of studies investigating FRP reinforced concrete columns have been reported based on testing under concentric loading with the behaviour of such members under eccentric axial loads not sufficiently addressed in the previous studies

    Évaluation de la durabilité des pieux en béton armé de barres et de spirales de PRFV en milieu marin

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    Abstract : Conventional concrete reinforced (RC) with black steel in marine environment suffers damage due to corrosion. Most field examination studies found heavy corrosion before achieving 75-100 years of the service life desired by the Federal Highway Administration (FHWA). Lately, glass fiber-reinforced polymers (GFRP) as internal reinforcement in concrete have proved outstanding structural and long-term durability performance in corrosive environments. The last three decades witnessed a significant revolution in the usage of GFRP in civil engineering projects to raise the service lives and reduce maintenance costs of RC structures. Over three-thousands bridges over Canada and U.S. included GFRP bars as reinforcement for constructing the most elements vulnerable to corrosion due to de-icing salts and annual thermal changes (i.e., deck slabs) as well as the usage in reinforcing the culvert bridges in the U.S. The field examination for the bridge’s barrier walls, deck slabs, and culvert built with GFRP bars after 10-20 years in service indicates good long-term durability. The usage of GFRP bars and spirals in the RC columns, piers, and piling system is widely accepted and recommended in most conclusions of previous studies. Most investigations in the past have focused mainly on the behavior of RC piles/columns under concentric, eccentric, and cyclic loading, disregarding the relationship between the structural and durability behavior. This thesis presents the results of the axial compression test for forty-eight RC square and circular piles exposed to the marine environment and two conditioning temperatures for 12-months. All specimens have laboratory-scale dimensions measuring 300 mm for square pile's width, 304 mm for circular pile's diameter, and 1000 mm general height. The durability conditioning regime is comprised of two environments; (i) simulation for the marine environment in sub-tropical regions (22°C), (ii) simulated marine environment at accelerated temperature (60°C). Phase (I) contains 18-concrete square piles and Phase (II) includes 18-concrete circular piles. The thirty-six concrete piles were: six specimens were without internal reinforcement, 6-specimens were reinforced with hybrid reinforcement (steel bars and GFRP spirals), and the remaining twentyfour specimens were fabricated with pristine GFRP bars and spirals. For each phase, twelve pile specimens were subjected to the conditioning regime for 12-months, six specimens for each conditioning temperature. Whereas phase (III) includes 6- square and 6-circular RC piles, which were made of GFRP reinforcement directly immersed in the simulated marine environment at 22 and 60°C for 12-months before integrating into concrete, three GFRP-cages for each aging temperature. Several structural variables were investigated through the three phases such as longitudinal reinforcement (ratio and diameter) and transverse reinforcement (pitch and configurations). In addition, a microstructural analysis program (SEM, DSC, and FTIR) was carried out on GFRP material extracted from the aged piles and those directly exposed to the conditioning regime. Concrete cores taken from the aged piles were examined by optical microscopy (OM) to assess the bond between concrete and bars/spirals. This thesis also introduces a characterization for GFRP bars exposed directly to the marine environment based on tensile, bond, and horizontal shear tests. The experimental axial compression capacities of GFRP-RC piles were compared with the values predicted using the available design equations in the current design codes. The results obtained from microstructural analyses showed that GFRP reinforcement used in this study possesses good long-term durability in concrete saturated with the marine environment or in solutions simulated seawater environments at 60°C after 12-months. OM images for the concrete/bar contact circumference revealed that bars/spirals firmly bond to concrete. A 0.85 is the lowest retention in the tensile and bond strengths of GFRP bars, while the retention in horizontal shear strength reaches 0.95 after direct exposure to the marine environment at 60°C for 12-months. Based on the compressive tests, the axial compression behavior of GFRP-RC square and circular pile did not adversely affect by immersion in the simulated marine environment at 22 or 60°C for 12-months or using pre/conditioned GFRP material. The axial compression capacity of ten GFRP-RC pile specimens submerged in the simulated marine environment at 60°C was enhanced by 116-125% compared to their unconditioned counterparts as a result of an increase in the concrete compressive strength. Specimens fabricated with GFRP material aged at 60°C exhibited similar ductile behavior and axial compression capacities of their counterparts constructed with pristine GFRP material. Despite the tensile strength reduction after exposure to aggressive environments, GFRP reinforcing materials effectively perform their structural function as internal reinforcement of RC piles. All investigated structural variables effectively affect the compressive behavior of GFRP-RC piles in the marine environment. The reduction factors for GFRP-RC structures specified in CSA (2019a) and AASHTO (2018a), and CSA (2017) yielded lower axial compression capacities than those obtained experimentally. A more accurate design equation to calculate the axial load capacity of the GFRP RC piles should consider the contribution of longitudinal GFRP bars even when exposed to severe marine environments.Le béton conventionnel armé (RC) avec de l'acier noir dans un environnement marin subit des dommages dus à la corrosion. La plupart des études d'examen sur le terrain ont révélé une forte corrosion avant d'atteindre les 75-100 ans de la durée de vie souhaitée par la Federal Highway Administration (FHWA). Récemment, les polymères renforcés de fibres de verre (PRFV) utilisés comme armature interne dans le béton ont prouvé qu'ils présentaient des performances structurelles et de durabilité à long terme exceptionnelles dans des environnements corrosifs. Les trois dernières décennies ont vu une révolution significative dans l'utilisation des PRFV dans les projets de génie civil pour augmenter la durée de vie et réduire les coûts de maintenance des structures en béton armé. Plus de trois mille ponts au Canada et aux États-Unis ont inclus des barres GFRP comme renforcement pour la construction des éléments les plus vulnérables à la corrosion due aux sels de déglaçage et aux changements thermiques annuels (c'est-à-dire les dalles de pont), ainsi que pour le renforcement des ponceaux aux États-Unis. L'examen sur le terrain des murs de protection, des dalles de pont et des ponceaux construits avec des barres GFRP après 10 à 20 ans de service indique une bonne durabilité à long terme. L'utilisation de barres et de spirales en GFRP dans les colonnes, les piliers et les systèmes de pilotis en béton armé est largement acceptée et recommandée dans la plupart des conclusions des études précédentes. La plupart des recherches dans le passé se sont concentrées principalement sur le comportement des pieux/colonnes en béton armé sous des charges concentriques, excentriques et cycliques, sans tenir compte de la relation entre le comportement structurel et la durabilité. Cette thèse présente les résultats de l'essai de compression axiale pour quarante-huit pieux RC carrés et circulaires exposés à l'environnement marin et à deux températures de conditionnement pendant 12 mois. Tous les spécimens ont des dimensions à l'échelle du laboratoire mesurant 300 mm pour la largeur du pieu carré, 304 mm pour le diamètre du pieu circulaire, et 1000 mm de hauteur générale. Le régime de conditionnement de durabilité est composé de deux environnements ; (i) simulation pour l'environnement marin dans les régions subtropicales (22°C), (ii) environnement marin simulé à température accélérée (60°C). La phase (I) comprend 18 pieux carrés en béton et la phase (II) comprend 18 pieux circulaires en béton. Les trente-six pieux en béton étaient les suivants : six spécimens n'avaient pas d'armature interne, six spécimens étaient renforcés par une armature hybride (barres d'acier et spirales GFRP), et les vingt-quatre spécimens restants étaient fabriqués avec des barres et des spirales GFRP vierges. Pour chaque phase, douze spécimens de pieux ont été soumis au régime de conditionnement pendant 12 mois, six spécimens pour chaque température de conditionnement. Tandis que la phase (III) comprend 6 pieux RC carrés et 6 circulaires, qui ont été réalisés avec des armatures GFRP directement immergées dans l'environnement marin simulé à 22 et 60°C pendant 12 mois avant d'être intégrées dans le béton, trois cages GFRP pour chaque température de vieillissement. Plusieurs variables structurelles ont été étudiées au cours des trois phases, telles que les armatures longitudinales (ratio et diamètre) et les armatures transversales (pas et configurations). De plus, un programme d'analyse microstructurelle (SEM, DSC, et FTIR) a été réalisé sur le matériau GFRP extrait des pieux vieillis et ceux directement exposés au régime de conditionnement. Des carottes de béton prélevées sur les pieux vieillis ont été examinées par microscopie optique (OM) pour évaluer la liaison entre le béton et les barres/spirales. Cette thèse présente également une caractérisation des barres GFRP exposées directement à l'environnement marin, basée sur des essais de traction, de liaison et de cisaillement horizontal. Les capacités expérimentales de compression axiale des pieux en GFRP-RC ont été comparées aux valeurs prédites en utilisant les équations de conception disponibles dans les codes de conception actuels. Les résultats obtenus à partir des analyses microstructurales ont montré que le renforcement GFRP utilisé dans cette étude possède une bonne durabilité à long terme dans du béton saturé de l'environnement marin ou dans des solutions simulant des environnements d'eau de mer à 60°C après 12 mois. Les images OM de la circonférence de contact béton/barre ont révélé que les barres/spirales adhèrent fermement au béton. Une rétention de 0,85 est la plus faible dans les résistances à la traction et à l'adhérence des barres GFRP, tandis que la rétention de la résistance au cisaillement horizontal atteint 0,95 après une exposition directe à l'environnement marin à 60°C pendant 12 mois. D'après les essais de compression, le comportement en compression axiale des pieux carrés et circulaires en GFRP-RC n'a pas été affecté par l'immersion dans l'environnement marin simulé à 22 ou 60°C pendant 12 mois ou par l'utilisation de matériau GFRP pré-conditionné. La capacité de compression axiale de dix spécimens de pieux RC en GFRP immergés dans un environnement marin simulé à 60°C a été augmentée de 116-125% par rapport à leurs homologues non conditionnés en raison d'une augmentation de la résistance à la compression du béton. Les spécimens fabriqués avec un matériau GFRP vieilli à 60°C ont présenté un comportement ductile et des capacités de compression axiale similaires à ceux de leurs homologues construits avec un matériau GFRP vierge. Malgré la réduction de la résistance à la traction après exposition à des environnements agressifs, les matériaux de renforcement GFRP remplissent efficacement leur fonction structurelle en tant que renforcement interne des pieux RC. Toutes les variables structurelles étudiées affectent efficacement le comportement en compression des pieux GFRP-RC dans l'environnement marin. Les facteurs de réduction pour les structures en GFRP-RC spécifiés dans CSA (2019a) et AASHTO (2018a), et CSA (2017) ont donné des capacités de compression axiale inférieures à celles obtenues expérimentalement. Une équation de conception plus précise pour calculer la capacité de charge axiale des pieux RC en GFRP devrait tenir compte de la contribution des barres longitudinales en GFRP, même lorsqu'elles sont exposées à des environnements marins sévères

    Strengthening of heat damaged reinforced concrete cylinders

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    The purpose of this study is to investigate the effectiveness of various strengthening techniques in restoring heat damaged reinforced concrete. A series of 40 reinforced concrete cylinders were tested under concentric compression after being jacketed externally with high strength fiber reinforced concrete (HSFRC), Ferrocement (FC) and Glass fiber reinforced polymer (GFRP) jackets. Concrete specimens were exposed to elevated temperatures ranging from room temperature to 900 ºC. The overall response of strengthened specimens was investigated vis-à-vis un-strengthened specimens in terms of axial compression, axial displacement and axial stress strain behaviour. The results indicate that important gains in strength and ductility can be achieved by strengthening heat – damaged R.C cylinders by HSFRC, FC and GFRP external Jacketing. GFRP jacketing was found to be the most effective method of strengthening fire or heat damaged concrete structures

    Experimental Behavior and Analysis of Hybrid Low-High Strength Reinforced Concrete Columns

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    In this paper, the behavior of hybrid short columns made from low strength reinforced concrete core and an outer skin made from high strength concrete was studied. For this purpose, laboratory tests were carried out on ten small-scale column specimens. For bonding, the outer skin portion to the main column epoxy resin was used. Results revealed that bonding low strength concrete core with high strength outer skin was successful and able to produce a hybrid section. For the same section area, load capacity increased by 28% to 80% depending on the compressive strength of the provided outer skin, for concentrically loaded columns. In general, the behavior of eccentrically loaded hybrid specimens was good, indicating that the process of making hybrid columns according to the technique presented in this paper is successful and can be used in practice

    FRP Sheets Contribution in Common Repair Techniques of Concrete Structures with Emphasis on Concrete Columns

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    The history of composites dates back to few thousand years ago. Actually, natural fibrous composites were used by ancient Egyptians to build small houses. Numerous studies have revealed that Fibre Reinforced Polymer (FRP) is a convenient material for repair and strengthening of concrete structures compared to the traditional materials. Since the presentation of fibre reinforced polymer (FRP) in the concrete structures, the need for practice codes containing FRP in field of strengthening and repair has emerged. Many parts of structures are usually replaced simply, instead of repair due to the lack of knowledge about the techniques of repair. Hence, in this review, advantages and disadvantages of FRP repair, different types of FRP repair systems, repair stages and principles of repair theory for concrete structures with FRP are reviewed. In addition, modern repair techniques are reviewed in detail for different damaged levels of concrete structures. Recent developments in the field of repair with FRP have highlighted the need for assessment of repaired concrete columns. Thus, in one part of this review, the authors emphasise different damaged concrete column repaired with CFRP. Finally, the recent needs for further researches in field of repair with FRP are discussed

    Experimental study on compressive behavior and failure analysis of composite concrete confined by glass/epoxy ±55° filament wound pipes

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    YesThis paper investigates the strength and ductility of concrete confined by Glass/Epoxy ±55° Filament Wound Pipes (GFRP) under axial compression. A total of 24 cylinderical specimens were prepared with expansive and Portland cements, properly compacted and un-compacted for different composite fresh concrete matrix. Test results showed that compressive strength and axial deformation at failure of concrete confined with GFRP tubes increased by an average of 2.85 and 5.57 times these of unconfined concrete, respectively. Macro and micro analyses of GFRP pipes after failure were also investigated. Debonding, whitening, matrix/transfer cracking, delamination and splitting mechanisms were detected at failure, respectively. The experimental results were also employed to assess the reliability of design models available in the literature for confined concrete compressive strength

    Doctor of Philosophy

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    dissertationDespite numerous experimental and analytical investigations on the compressive behavior of fiber-reinforced polymer (FRP) confined concrete sections, researchers have been unable to develop a unified theoretical stress-strain model that can accurately capture and describe the axial compressive and resultant transverse dilation behavior of various FRP-jacketed concrete column shapes. In this dissertation, a mechanics-based unified stress-strain model is introduced; this model is applicable to FRP-confined concrete sections of various shapes that can accurately capture both the compressive and dilation behavior of rectangular, square, oval, circular, and elliptical FRP-confined concrete members using the concept of diagonal dilation and diagonal equilibrium of the FRP-confined concrete section with a minimum number of curve-fitting parameters based on experiments. This is accomplished by including the general concepts of elasticity, damage mechanics, soils mechanics, and plasticity theory in the development of a theoretically sound mechanics-based stress-strain model for FRP-confined concrete that takes into consideration the macrostructural effects of the increase in internal damage (i.e., increase in dilation) and the beneficial effects contributed by the kinematic restraint provided by the confining elastic FRP jacket. The proposed stress-strain model's ability to accurately describe the compressive behavior of FRP-confined concrete of various geometrical shapes will depend on its ability to capture the restraint sensitivity of the confined concrete core and the effects that the shape of the confining FRP jacket has on the jacket's ability to restrain the transverse dilation of the confined concrete core

    Flexural Behaviour of Stay-In-Place PVC Encased Reinforced Concrete Walls with Various Panel Types

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    The use of stay-in-place (SIP) formwork has become an increasingly popular tool for concrete structures, providing advantages in construction scheduling and labour reduction. Stay-in-place formwork made of strong materials such as fibre reinforced polymer (FRP) and steel have proven to supplement and even replace reinforcement in concrete elements. The use of polyvinyl chloride (PVC) SIP formwork has also been explored. Current research suggests that PVC provides an enhancement to reinforced concrete strength and ductility. The research herein outlines tests on reinforced concrete walls with a compressive strength 25MPa, utilizing two types of PVC panels; flat or hollow, in order to further understand the polymer’s contribution to flexural resistance. The PVC forming system consisted of panels on the tension and compression faces with evenly spaced connectors securing the faces of the wall. Variables studied included concrete core thickness (152 mm, 178 mm, and 203 mm), reinforcing ratio (3-10M bars or 3-15M bars), and panel type (hollow or flat). The walls were tested in four point bending. The concrete control walls failed due to steel yielding followed by concrete crushing. The failure of the flat panel encased walls was dependent on the reinforcing ratio. Wall reinforced with 10M bars and encased with flat panels failed due to steel yielding followed by concrete crushing, PVC buckling, and PVC rupture while walls with 15M bars did not experience PVC rupture. Finally the failure for walls encased in hollow panels was due to steel yielding, followed by concrete crushing and PVC buckling. The hollow panel encased specimens also experienced slip of the panels on the tensile face. The PVC encasement enhanced the yield load, ultimate load, ductility, and toughness of the concrete walls. For flat panel encased walls, the average improvement at yield and ultimate loads were 21% and 27% respectively. Hollow panel encased walls recorded average yield and ultimate load improvements of 8% and 27% respectively. Flat panel encased walls improved ductility by an average of 71% and toughness by 122%. Hollow panel encased walls improved ductility by an average of 29% and toughness by 70%. Concrete cores were taken from the tested PVC encased specimens and compressive strength was found to be the same as the control walls. An analytical model was developed to estimate the yield and ultimate load of PVC encased concrete walls. Calculated yield loads were in good agreement with the experimental data, with an average error of 8% for the control walls and 6% for the PVC encased walls. In addition, calculated ultimate (peak) loads showed good correlation with the experimental data. The average error for the control, flat panel and hollow panel encased walls were 3%, 3% and 8% respectively. Calculated and experimental PVC tensile strain values were in good correlation at ultimate load conditions. The average error for the calculated PVC tensile strain was 21%. With the proposed model providing results in good agreement with the test data, other PVC encased wall cross-sections were explored. An “optimized” panel layout was proposed that utilized flat panels on the compression side of the wall and hollow panels on the tension side. This configuration of panels resulted in the greatest estimated improvement at both yield and ultimate load levels
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