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Since the 1980s and after the aerospace industries faced several periods of economic difficulty, the companies that produced fibre-reinforced polymers (FRPs) started to introduce them as new materials for construction purposes. In one such application, FRPs were proposed for use instead of steel reinforcement in concrete due their mechanical properties including corrosion-resistance, high tensile strength, and light weight. On the other hand, FRPs have a lower modulus of elasticity compared to the steel reinforcement, which can lead to excessive deflection of the reinforced concrete member. Prestressing of the FRP reinforcement was a solution to overcome this serviceability concern. Previous research has been conducted to study the mechanical properties of carbon and aramid fibre reinforced polymers as prestressed reinforcement. Less attention has been given to glass fibre reinforced polymers as prestressing reinforcement because of its high relaxation and creep rupture. Only limited data on the behaviour of the prestressed GFRP under fatigue loading is available. Also, no design guidelines are provided in CAN/CSA-S806-12 or ACI 440.4R-04 for using prestressed GFRP bars in concrete members. In order to address this knowledge gap, the current study included testing of forty-six GFRP reinforced concrete beams to investigate the bond mechanisms between the GFRP bar and concrete under monotonic and fatigue loading. Each beam was reinforced on the tension side with a single GFRP bar. This study was divided into two phases: a first phase (preliminary study) and a second phase (main study). The main objectives of the preliminary study were to investigate the effect of different variables on the bond mechanism between the GFRP bar and the concrete and choose the most important variables that affect the bond strength between the GFRP bar and the concrete for the main study. Sixteen reinforced concrete beams were cast and tested under monotonic loading. The test variables included in the preliminary study were bar diameter, bar surface type, concrete cover, and prestressing level. The beam geometry was 150 mm wide by 225 or 250 mm high by 2400 mm long with concrete cover equal to 25 mm. For the main study, thirty reinforced concrete beams were cast and tested under monotonic and fatigue loading. The beams dimension was 200 mm in width and 2000 in length. The beams depth and height were varied depends on the clear concrete cover. For the beams with concrete cover of 25 mm the beams height and depth to the flexural reinforcing were 265 mm and 235 mm, respectively. For the beams with concrete cover of 45 mm the beams height and depth were 295 mm and 240 mm, respectively. The test variables included in the main study were bar surface type, concrete cover, and prestressing level. For the beams tested under fatigue loading, the minimum applied load was 10 % of the static failure load. The peak load was varied to study the effect of load range on fatigue life. The test frequency for all cyclic test was 1.0 Hz. All of the beams that were tested under monotonic loading failed in bond between the GFRP bar and the concrete. Increasing the concrete cover increased the ultimate beam capacity by almost 20%. For all of the beams tested under monotonic loading, there was no noticeable difference in ultimate load between the beams reinforced with a sand coated GFRP bar and beams reinforced with a ribbed GFRP bar. For the beams tested under fatigue loading, two failure modes were observed, bond failure between the GFRP bar and the concrete and rupture of the GFRP bar. For the beams that failed in bond, the slope of the load and stress versus fatigue life curves is shallow and consequently a small change in load range will result in a large change in the fatigue life. Increasing the concrete cover thickness increased the fatigue strength. Comparing the load range (kN) versus life curve for the non-prestressed and prestressed beams that failed in bond, shows that the prestressed beams had longer lives than the non-prestressed beams. A crack growth model based on the one developed by Wahab et al., 2015 was used to calculate fatigue lives and to predict the crack length versus the number of cycles. The calculated number of cycles was in good agreement with the data for the beams with different concrete thicknesses. The model captured the general trends in the test data (e.g. shape of the crack length versus number of cycle curves) and gave good representations of the initial crack length.
Since the 1980s and after the aerospace industries faced several periods of economic difficulty, the companies that produced fibre-reinforced polymers (FRPs) started to introduce them as new materials for construction purposes. In one such application, FRPs were proposed for use instead of steel reinforcement in concrete due their mechanical properties including corrosion-resistance, high tensile strength, and light weight. On the other hand, FRPs have a lower modulus of elasticity compared to the steel reinforcement, which can lead to excessive deflection of the reinforced concrete member. Prestressing of the FRP reinforcement was a solution to overcome this serviceability concern. Previous research has been conducted to study the mechanical properties of carbon and aramid fibre reinforced polymers as prestressed reinforcement. Less attention has been given to glass fibre reinforced polymers as prestressing reinforcement because of its high relaxation and creep rupture. Only limited data on the behaviour of the prestressed GFRP under fatigue loading is available. Also, no design guidelines are provided in CAN/CSA-S806-12 or ACI 440.4R-04 for using prestressed GFRP bars in concrete members. In order to address this knowledge gap, the current study included testing of forty-six GFRP reinforced concrete beams to investigate the bond mechanisms between the GFRP bar and concrete under monotonic and fatigue loading. Each beam was reinforced on the tension side with a single GFRP bar. This study was divided into two phases: a first phase (preliminary study) and a second phase (main study). The main objectives of the preliminary study were to investigate the effect of different variables on the bond mechanism between the GFRP bar and the concrete and choose the most important variables that affect the bond strength between the GFRP bar and the concrete for the main study. Sixteen reinforced concrete beams were cast and tested under monotonic loading. The test variables included in the preliminary study were bar diameter, bar surface type, concrete cover, and prestressing level. The beam geometry was 150 mm wide by 225 or 250 mm high by 2400 mm long with concrete cover equal to 25 mm. For the main study, thirty reinforced concrete beams were cast and tested under monotonic and fatigue loading. The beams dimension was 200 mm in width and 2000 in length. The beams depth and height were varied depends on the clear concrete cover. For the beams with concrete cover of 25 mm the beams height and depth to the flexural reinforcing were 265 mm and 235 mm, respectively. For the beams with concrete cover of 45 mm the beams height and depth were 295 mm and 240 mm, respectively. The test variables included in the main study were bar surface type, concrete cover, and prestressing level. For the beams tested under fatigue loading, the minimum applied load was 10 % of the static failure load. The peak load was varied to study the effect of load range on fatigue life. The test frequency for all cyclic test was 1.0 Hz. All of the beams that were tested under monotonic loading failed in bond between the GFRP bar and the concrete. Increasing the concrete cover increased the ultimate beam capacity by almost 20%. For all of the beams tested under monotonic loading, there was no noticeable difference in ultimate load between the beams reinforced with a sand coated GFRP bar and beams reinforced with a ribbed GFRP bar. For the beams tested under fatigue loading, two failure modes were observed, bond failure between the GFRP bar and the concrete and rupture of the GFRP bar. For the beams that failed in bond, the slope of the load and stress versus fatigue life curves is shallow and consequently a small change in load range will result in a large change in the fatigue life. Increasing the concrete cover thickness increased the fatigue strength. Comparing the load range (kN) versus life curve for the non-prestressed and prestressed beams that failed in bond, shows that the prestressed beams had longer lives than the non-prestressed beams. A crack growth model based on the one developed by Wahab et al., 2015 was used to calculate fatigue lives and to predict the crack length versus the number of cycles. The calculated number of cycles was in good agreement with the data for the beams with different concrete thicknesses. The model captured the general trends in the test data (e.g. shape of the crack length versus number of cycle curves) and gave good representations of the initial crack length.
Over the past decade, extensive research has been conducted on the strengthening of reinforced concrete (RC) structures using externally bonded fibre reinforced polymer (FRP). More recently, near-surface mounted (NSM) FRP reinforcement has attracted an increasing amount of research as well as practical applications. In the NSM method, grooves are first cut into the concrete cover of an RC element and the FRP reinforcement is bonded inside the groove with an appropriate filler (typically epoxy paste or cement grout). The FRP reinforcement is either prestressed or non-prestressed depending on the required level of strengthening. In all cases, the bond between an NSM bar and the substrate material plays a key role in ensuring the effectiveness of NSM strengthening. The present work investigated experimentally the bond behaviour of non-prestressed and prestressed beams reinforced with near surface mounted carbon fibre reinforced polymer (CFRP) bars under monotonic and fatigue loading. Forty concrete beams were cast and tested in seven groups. The test variables considered in this study were: presence of internal steel reinforcement or not, the type of CFRP rod (spirally wound or sand coated) and the prestressing force (non-prestressed or prestressed).
Basalt fibers have recently been introduced as a promising alternative to the existing fiber reinforced polymer (FRP) family. The mechanical properties of basalt FRP (BFRP) bars are, generally, better than those of glass FRP (GFRP) bars. However, they are still lower than those of carbon FRP (CFRP) bars. Also BFRP bars have now been developed that have a higher modulus of elasticity than typical GRFP bars. Only a limited amount of research is available on BFRP bars in structural concrete applications and there is no information on the performance of prestressed basalt bars in reinforced concrete elements subjected to fatigue loading. Most studies that are available deal only with the flexural behaviour of concrete beams reinforced with non- prestressed and prestressed GFRP and CFRP bars under monotonic and fatigue loading. This thesis presents an experimental study of the flexural behaviour of concrete beams reinforced with non-prestressed and prestressed basalt bars under monotonic and fatigue loading and compares these beam fatigue results with the fatigue behaviour of similar machined basalt rebars tested under fatigue loading in air. Sixteen beams with dimensions of (2400x 300x150mm) and thirteen BFRP bare rebars were tested. The parameters that varied were the level of prestress of the bars (0%, 20% and 40% of their static tension capacity) and the fatigue load ranges. The experimental findings showed a difference in the long life fatigue strength between the beams prestressed to 40% 20% and 0% of the bar strength with the beams with the bars prestressed to 40% of the bar strength showing a higher fatigue strength than of those prestressed to 0% and 20%. For 40% and 20 % prestressed beams, there is no benefit in fatigue performance above 20% and 13% of the ultimate capacity of the beams a level at which calculations showed that the remaining prestress did not close cracks at the minimum load in the fatigue load cycle. When compared on the basis of load range versus cycles to failure, the data for the three beam types fell onto a single curve at load levels where the remaining prestress after fatigue creep relaxation no longer closed the crack at the minimum load.
Dealing with a wide range of non-metallic materials, this book opens up possibilities of lighter, more durable structures. With contributions from leading international researchers and design engineers, it provides a complete overview of current knowledge on the subject.
Fibre-reinforced polymer (FRP) reinforcement has been used in construction as either internal or external reinforcement for concrete structures in the past decade. This book provides the latest research findings related to the development, design and application of FRP reinforcement in new construction and rehabilitation works. The topics include FRP properties and bond behaviour, externally bonded reinforcement for flexure, shear and confinement, FRP structural shapes, durability, member behaviour under sustained loads, fatigue loads and blast loads, prestressed FRP tendons, structural strengthening applications, case studies, and codes and standards.
Corrosion-resistant, electromagnetic transparent and lightweight fiber-reinforced polymers (FRPs) are accepted as valid alternatives to steel in concrete reinforcement. Reinforced Concrete with FRP Bars: Mechanics and Design, a technical guide based on the authors more than 30 years of collective experience, provides principles, algorithms, and pr
Nowadays, it is quite easy to see various applications of fibrous composites, functionally graded materials, laminated composite, nano-structured reinforcement, morphing composites, in many engineering fields, such as aerospace, mechanical, naval and civil engineering. The increase in the use of composite structures in different engineering practices justify the present international meeting where researches from every part of the globe can share and discuss the recent advancements regarding the use of standard structural components within advanced applications such as buckling, vibrations, repair, reinforcements, concrete, composite laminated materials and more recent metamaterials. For this reason, the establishment of this 19th edition of International Conference on Composite Structures has appeared appropriate to continue what has been begun during the previous editions. ICCS wants to be an occasion for many researchers from each part of the globe to meet and discuss about the recent advancements regarding the use of composite structures, sandwich panels, nanotechnology, bio-composites, delamination and fracture, experimental methods, manufacturing and other countless topics that have filled many sessions during this conference. As a proof of this event, which has taken place in Porto (Portugal), selected plenary and keynote lectures have been collected in the present book.
The use of fiber reinforced plastic (FRP) composites for prestressed and non-prestressed concrete reinforcement has developed into a technology with serious and substantial claims for the advancement of construction materials and methods. Research and development is now occurring worldwide. The 20 papers in this volume make a further contribution in advancing knowledge and acceptance of FRP composites for concrete reinforcement. The articles are divided into three parts. Part I introduces FRP reinforcement for concrete structures and describes general material properties and manufacturing meth.