Sprayed fibre-reinforced polymers for repairs

The use of fibre-reinforced polymers for repair and retrofit is growing at an unprecedented rate. This technique has been used for strengthening and rehabilitation of columns, beams, masonry, joints, etc. and has also found significant suitability for seismic applications. All research to date has focused, however, on wraps and jackets with continuous, unidirectional fibres. Within the auspices of Network of Centers of Excellence on Intelligent Sensing for Innovative Structures (ISIS) program, an entirely new method of fibre reinforced polymer coating is being developed. In this method, the composite with short, randomly distributed fibres is sprayed on the surface of concrete to be repaired. Composite gets pneumatically compacted on the application surface and develops a strong bond with concrete during the hardening process. In this paper, the effectiveness of the spray technique is compared with wraps carrying continuous fibres when applied to concrete cylinders under compression. To assess size effects, a companion test series involving larger cylinders was carried out. It was found that sprayed composites with randomly distributed short fibres performed equally well as or even better than wraps with continuous fibres. Within the continuous fibre wraps, those with a 0-90° fibre orientation are far more effective than those with a ±45° orientation.Key words: concrete, repair, glass fibre, polymer matrix, spray, wraps, deformability, size effects.

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Compressive Strength of FRP-Confined Concrete at Elevated Temperatures

Polymers and Polymer Composites ◽

10.1177/096739110801600905 ◽

2008 ◽

Vol 16 (9) ◽

pp. 611-620 ◽

Cited By ~ 1

Author(s):

Y.A. Al-Salloum

Keyword(s):

High Temperature ◽

Elevated Temperatures ◽

Small Scale ◽

Engineering Structures ◽

Widespread Application ◽

Reinforced Polymers ◽

Reinforced Polymer ◽

Concrete Cylinders ◽

Fibre Reinforced Polymer ◽

Loss Of Strength

Many research studies have shown that fibre-reinforced polymers (FRPs) can be efficiently, economically, and safely used for strengthening and rehabilitation of reinforced concrete structures. However, relatively little is known about the behaviour of FRP materials at high temperature, and this is a primary factor that is limiting the widespread application of FRP materials in civil engineering structures. This paper presents the results of an experimental programme to investigate the effect of high temperature on the performance of concrete cylinders externally confined with fibre-reinforced polymer (FRP) sheets. For this purpose, 42 small-scale concrete cylinders measuring 100 × 200 mm were cast. Of these 42 specimens, 14 specimens were left unwrapped to be used as baseline or control specimens, 14 specimens were wrapped with one layer of CFRP sheets, and the remaining 14 specimens were wrapped with GFRP sheets. These specimens were exposed to room temperature and heating regimes of 100 and 200 °C for a period of 1, 2, and 3 h. The specimens were tested in compression, and their performance was evaluated after they had been exposed to specific heating regimes. The test results demonstrate that, at a temperature around the glass transition temperature (Tg) of the resin, CFRP- and GFRP-wrapped specimens experienced a small loss of strength, resulting from melting of epoxy. This damage was more pronounced when the temperature reached 200 °C.

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Effect of freeze-thaw cycles on the bond durability between fibre reinforced polymer plate reinforcement and concrete

Canadian Journal of Civil Engineering ◽

10.1139/l00-031 ◽

2000 ◽

Vol 27 (5) ◽

pp. 949-959 ◽

Cited By ~ 65

Author(s):

Mark F Green ◽

Luke A Bisby ◽

Yves Beaudoin ◽

Pierre Labossière

Keyword(s):

Experimental Investigation ◽

Reinforced Concrete ◽

Bond Length ◽

Failure Mode ◽

Concrete Repair ◽

Reinforced Polymers ◽

Freeze Thaw ◽

Reinforced Polymer ◽

Fibre Reinforced Polymer ◽

Frp Strips

Deterioration of infrastructure is one of the most pressing concerns facing today's civil engineering community. As a result, new rehabilitation techniques, such as the external bonding of fibre reinforced polymer (FRP) plates and sheets, are being developed. To apply these rehabilitation methods in Canada, the durability of the rehabilitated structures in cold regions must be assessed. This paper examines the effects of freeze-thaw cycling on the bond between FRP and concrete. An experimental investigation was conducted using both single lap pull-off and bond beam specimens. Only uniaxial carbon FRP strips were considered. The specimens were exposed to up to 300 freeze-thaw cycles consisting of 16 h of freezing and 8 h of thawing in a water bath. After exposure, the specimens were tested to failure. The development of strain along the bond length and the failure mode are presented for both types of specimens. Load deflection curves are presented for the beam specimens. The results indicate that the bond between carbon FRP strips and concrete is not significantly damaged by up to 300 freeze-thaw cycles.Key words: reinforced concrete, repair, rehabilitation, strengthening, fibre reinforced polymers, freeze-thaw, bond damage.

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Performance in Fire of Fibre Reinforced Polymer Strengthened Concrete Beams and Columns: Recent Research and Implications for Design

Journal of Structural Fire Engineering ◽

10.1260/2040-2317.5.4.353 ◽

2014 ◽

Vol 5 (4) ◽

pp. 353-366 ◽

Cited By ~ 2

Author(s):

Mark Green ◽

Kevin Hollingshead ◽

Noureddine Bénichou

Keyword(s):

Conceptual Model ◽

Concrete Beams ◽

Design Tool ◽

Fire Performance ◽

Reinforced Polymers ◽

Reinforced Polymer ◽

Practical Design ◽

Fibre Reinforced Polymer ◽

Full Scale Tests ◽

In Fire

This paper considers the fire performance of concrete beams and columns that have been strengthened with fibre reinforced polymers (FRPs). Results from four recent full-scale tests are presented. A newly developed type of insulation was employed and the thickness of the insulation (15 to 20 mm) was approximately half that provided in earlier tests. All of the members survived four hours of the fire exposure. A conceptual model for design to determine when insulation is required is also presented. Further research needed to fully develop the conceptual model to a more practical design tool is outlined.

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Minimum thickness of concrete members reinforced with fibre reinforced polymer bars

Canadian Journal of Civil Engineering ◽

10.1139/l01-021 ◽

2001 ◽

Vol 28 (4) ◽

pp. 583-592 ◽

Cited By ~ 3

Author(s):

Amin Ghali ◽

Tara Hall ◽

William Bobey

Keyword(s):

Reinforced Concrete ◽

Minimum Thickness ◽

Reinforced Polymers ◽

Flexural Members ◽

Steel Reinforced Concrete ◽

Concrete Members ◽

Reinforced Polymer ◽

Steel Bars ◽

Fibre Reinforced Polymer ◽

Frp Bars

To avoid excessive deflection most design codes specify the ratio (l/h)s, the span to minimum thickness of concrete members without prestressing. Use of the values of (l/h)s specified by the codes, in selecting the thickness of members, usually yields satisfactory results when the members are reinforced with steel bars. Fibre reinforced polymer (FRP) bars have an elastic modulus lower than that of steel. As a result, the values of (l/h)s specified in codes for steel-reinforced concrete would lead to excessive deflection if adopted for FRP-reinforced concrete. In this paper, an equation is developed giving the ratio (l/h)f for use with FRP bars in terms of (l/h)s and (εs/εf), where εs and εf are the maximum strain allowed at service in steel and FRP bars, respectively. To control the width of cracks, ACI 318-99 specifies εs = 1200 × 106 for steel bars having a modulus of elasticity, Es, of 200 GPa and a yield strength, fy, of 400 MPa. At present, there is no value specified for εf; a value is recommended in this paper.Key words: concrete, cracking, deflection, fibre reinforced polymers, flexural members, minimum thickness.

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Comparison of Analytical Approaches Predicting the Compressive Strength of Fibre Reinforced Polymers

Materials ◽

10.3390/ma11122517 ◽

2018 ◽

Vol 11 (12) ◽

pp. 2517 ◽

Cited By ~ 4

Author(s):

Christian Leopold ◽

Sergej Harder ◽

Timo Philipkowski ◽

Wilfried Liebig ◽

Bodo Fiedler

Keyword(s):

Compressive Strength ◽

Prediction Accuracy ◽

Volume Fraction ◽

Fibre Volume Fraction ◽

Experimental Results ◽

Analytical Models ◽

Reinforced Polymers ◽

Reinforced Polymer ◽

Fibre Reinforced Polymer ◽

Analytical Approaches

Common analytical models to predict the unidirectional compressive strength of fibre reinforced polymers are analysed in terms of their accuracy. Several tests were performed to determine parameters for the models and the compressive strength of carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP). The analytical models are validated for composites with glass and carbon fibres by using the same epoxy matrix system in order to examine whether different fibre types are taken into account. The variation in fibre diameter is smaller for CFRP. The experimental results show that CFRP has about 50% higher compressive strength than GFRP. The models exhibit significantly different results. In general, the analytical models are more precise for CFRP. Only one fibre kinking model’s prediction is in good agreement with the experimental results. This is in contrast to previous findings, where a combined modes model achieves the best prediction accuracy. However, in the original form, the combined modes model is not able to predict the compressive strength for GFRP and was adapted to address this issue. The fibre volume fraction is found to determine the dominating failure mechanisms under compression and thus has a high influence on the prediction accuracy of the various models.

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SEISMIC RETROFITTING OF REINFORCED CONCRETE SHEAR WALL USING CARBON FIBER REINFORCED POLYMERS (CFRP)

JOURNAL OF MECHANICS OF CONTINUA AND MATHEMATICAL SCIENCES ◽

10.26782/jmcms.2020.12.00007 ◽

2020 ◽

Vol 15 (12) ◽

Author(s):

Shahzad Khan

Keyword(s):

Shear Wall ◽

Seismic Retrofitting ◽

Fiber Reinforced Polymers ◽

Carbon Fiber Reinforced Polymers ◽

Reinforced Polymers ◽

Reinforced Polymer ◽

Before And After ◽

Carbon Fibre Reinforced Polymer ◽

Fibre Reinforced Polymer ◽

Constant Axial Load

In this paper, the experimental results of a partially retrofitted non-compliant with code concrete shear wall using uni-directional carbon fibre reinforced polymer (CFRP) are introduced. The common deficiencies in the wall were insufficient reinforcement, un-confinement at boundary zone, the lake of in-plane stiffness, and ductility. The adopted retrofitting technique consists of the CFRP strips bonded to both wall face with mesh anchors installed in the wall panel and foundation to avoid debonding. The wall was tested before and after retrofitting under a constant axial load, and the displacement control lateral cyclic load was applied to the head beam level. The retrofitted wall showed satisfactory results in terms of drift and shear strength. The test results include the failure pattern, load-displacement behaviours, and deflected shape.

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Influence of temperature on the adhesion of fibre reinforced polymers to timber surface

Ambiente Construído ◽

10.1590/s1678-86212019000300322 ◽

2019 ◽

Vol 19 (3) ◽

pp. 25-38 ◽

Cited By ~ 1

Author(s):

Ângela do Valle ◽

Poliana Dias de Moraes ◽

Giancarlo Zibetti Mantovani ◽

Hudson Fagundes

Keyword(s):

Room Temperature ◽

Timber Structures ◽

Reinforced Polymers ◽

Reinforced Polymer ◽

Glass Fibre Reinforced Polymer ◽

Influence Of Temperature On ◽

Fibre Reinforced Polymer ◽

Glass Fibre Reinforced ◽

The Mean ◽

Pinus Spp

Abstract Carbon and glass fibre reinforced polymer composites are being increasingly used in timber structures, where they can be exposed to harsh temperature conditions. In order to be properly used, information is needed on their adhesion to the substrate. The objective of this research is to evaluate the influence of temperatures between 20 and 80 ºC on the adhesion of these reinforcements to the wood. The shear test of adhesive line and pull-off test of the reinforcement from wood surface were carried out using specimens made of Pinus spp. The results demonstrated that temperature causes the nonlinear reduction of the reinforcement adhesion. The specimens exposed to a temperature of 80 °C presented residual bond strength means of 34% and 20% of the mean strength at room temperature for CFRP and for GFRP, respectively. Caution in using the applied resins is required due to the presented behaviour even in the service temperature range specified by the manufacturers.

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A stress-relaxation approach to determine onset of delamination in angle ply laminates

Journal of Composite Materials ◽

10.1177/0021998319899131 ◽

2020 ◽

Vol 54 (19) ◽

pp. 2521-2527

Author(s):

Yi Xiao ◽

Jiaxin Lv ◽

P-Y Ben Jar

Keyword(s):

Stress Relaxation ◽

Viscoelastic Model ◽

Test Method ◽

Relaxation Test ◽

Relaxation Behaviour ◽

Reinforced Polymers ◽

Loading Mode ◽

Reinforced Polymer ◽

Fibre Reinforced Polymer ◽

High Possibility

A new test method, named multi-relaxation test, is proposed for detecting on-set of delamination in fibre-reinforced polymers. Multi-relaxation test is based on the principle that uses change of stress relaxation behaviour of fibre-reinforced polymer to detect the occurrence of delamination. In this study, angle-ply laminated fibre-reinforced polymer (APL-FRP) is used to demonstrate and evaluate multi-relaxation test for detection of the delamination occurrence. The stress relaxation behaviour is characterized using a standard, three-element viscoelastic model in which the Eyring’s law is used to govern the time-dependent stress response to deformation. Results suggest a high possibility of using the trend line change of viscous stress at the beginning of stress relaxation to determine the critical stroke for the onset of delamination. The results also suggest that value for the corresponding static stress is very close to the value reported in the literature for APL-FRP of the same fibre lay-up. The major advantage of multi-relaxation test over other tests for the same purpose is that multi-relaxation test is able to detect delamination without relying on ancillary information such as acoustic signals. Therefore, multi-relaxation test can be used to characterize critical loading and deformation in fibre-reinforced polymer structures of any size and geometry, even when subjected to a loading mode that mimics the in-service loading.

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