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Journal ArticleDOI

Failure Mode Analyses of Reinforced Concrete Beams Strengthened in Flexure with Externally Bonded Fiber-Reinforced Polymers

TL;DR: In this paper, a nonlinear RC beam element model with bond-slip between the concrete and the fiber-reinforced polymer plate is used to study how the failure mechanism of simply supported strength-ened RC beams is affected by the following parameters: plate length, plate width, plate stiffness, and loading type.
Abstract: As existing structures age or are required to meet the changing demands on our civil infrastructure, poststrengthening and retrofitting are inevitable. A relatively recent technique to strengthen reinforced concrete ~RC! beams in flexure uses fiber-reinforced polymer ~FRP! strips or sheets glued to the tension side of the beam. A number of researchers have reported that the failure mode of an FRP-strengthened RC beam can change from the desired ductile mode of an underreinforced beam to a brittle one. This paper analyzes the effects of this strengthening technique on the response and failure modes of a reference RC beam. A nonlinear RC beam element model with bond-slip between the concrete and the FRP plate is used to study how the failure mechanism of simply supported strength- ened RC beams is affected by the following parameters: plate length, plate width, plate stiffness, and loading type. The beam geometry is kept constant. The parametric studies confirm the experimentally observed results according to which the most commonly observed failure modes due to loss of composite actions are affected by the plate geometric and material properties. In addition, distributed loads ~difficult to apply in an experimental test! may not be as sensitive to plate debonding in the region of maximum bending moment as are beams subjected to point loads.
Citations
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Journal ArticleDOI
TL;DR: Different applications of fiber reinforced polymer composites (FRPCs) for external strengthening in civil construction are reviewed in this paper, where experimental as well as analytical and numerical research contributions have been focussed in the review.

275 citations


Cites background or methods from "Failure Mode Analyses of Reinforced..."

  • ...[87], for example, developed non-linear finite element models using bond-slip relationship between concrete and FRPC to evaluate delamination failure mode....

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  • ...[87] Thomsen H, Spacone E, Limkatanyu S, Camata G....

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Journal ArticleDOI
TL;DR: In this article, the efficiency of external strengthening systems for reinforced concrete beams using FRP fabric (Glass-Carbon) is examined. And an analytical model to predict the flexural failure of strengthened concrete elements is also developed.

269 citations

Journal ArticleDOI
TL;DR: In this paper, the brittle failure modes of RC members strengthened in flexure by FRP plates are studied and the finite element analyses are based on nonlinear fracture mechanics, and the actual crack pattern observed in the tests by using a smeared and an interface crack model.
Abstract: This paper presents a joint experimental–analytical investigation aimed at studying the brittle failure modes of RC members strengthened in flexure by FRP plates. Both midspan and plate end failure modes are studied. The finite element analyses are based on nonlinear fracture mechanics. The model considered the actual crack pattern observed in the tests by using a smeared and an interface crack model. This paper shows how concrete cracking, adhesive behavior, plate length, width and stiffness affect the failure mechanisms. The numerical and experimental results show that debonding and concrete cover splitting failure modes occur always by crack propagation inside the concrete.

127 citations


Cites background from "Failure Mode Analyses of Reinforced..."

  • ...[23] suggested an energybased definition of ductility, which is shown in Fig....

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Journal ArticleDOI
TL;DR: In this article, the authors presented an experimental program conducted to study the flexural behavior and redistribution in moment of reinforced high strength concrete (RHSC) continuous beams strengthened with carbon and glass fiber reinforced polymer (CFRP and GFRP) sheets.

112 citations

Journal ArticleDOI
TL;DR: In this paper, the results of experimental studies on damaged reinforced concrete beams repaired by external bonding of carbon fiber reinforced polymer (CFRP) composite laminates to the tensile face of the beam were summarized.

109 citations

References
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01 Jan 2002
TL;DR: The Emerging Technology Series as mentioned in this paper is a series of information and recommendations based on available test data, technical reports, limited experience with field applications, and the opinions of committee members, with a focus on the development and appropriate use of new and emerging technologies.
Abstract: *Co-chairs of the subcommittee that prepared this document. Note: The committee acknowledges the contribution of associate member Paul Kelley. ACI encourages the development and appropriate use of new and emerging technologies through the publication of the Emerging Technology Series. This series presents information and recommendations based on available test data, technical reports, limited experience with field applications, and the opinions of committee members. The presented information and recommendations, and their basis, may be less fully developed and tested than those for more mature technologies. This report identifies areas in which information is believed to be less fully developed, and describes research needs. The professional using this document should understand the limitations of this document and exercise judgment as to the appropriate application of this emerging technology.

2,963 citations

Journal ArticleDOI
TL;DR: In this paper, it is shown that mid-pan debond action is triggered by high shear stresses transmitted from the plates through the adhesive to the cover concrete and corrosion of the embedded steel.
Abstract: Reinforced concrete beams enhanced in flexure with adhesively-bonded fibre reinforced polymer plates are susceptible to a brittle form of failure, defined by delamination of the cover concrete attached to the adhesive that causes the plates to debond from the beam. This paper demonstrates that, while previous research has focused almost singularly on one debond mode in which concrete delamination progresses from the ends of the plates inwards, there exists another critical debond mode that initiates near flexural cracks in the midspan region of the plated beam and propagates out to the ends of the plates. Data from large-scale experimental work are presented to show that midspan debond action is triggered by high shear stresses transmitted from the plates through the adhesive to the cover concrete. These stresses arise initially from tension stiffening in the cracked concrete and corrosion of the embedded steel. It is shown that strain gauge data are required from both the bonded and exposed surfaces of t...

188 citations

Journal ArticleDOI
TL;DR: The performance of conventionally reinforced concrete (RC) beams strengthened in flexure with externally bonded fiber-reinforced polymers (EB-FRP) was studied by compiling and analyzing an experimental database.
Abstract: The performance of conventionally reinforced concrete (RC) beams strengthened in flexure with externally bonded fiber-reinforced polymers (EB-FRP) was studied by compiling and analyzing an experimental database. A total of 127 specimens from 23 separate studies were included in the database. A profile of specimens in the database is given, followed by an analysis of trends in failure mode, strength gain, and deformability. Failure by debonding of FRP was prevalent among specimens in the database. One-third of the specimens with external reinforcement added showed strength increases of 50% or more in combination with considerable deflection capacity. It was clear from the experimental studies that the procedures followed were most representative of member strengthening rather than repair. Most of the specimens in the database were not subjected to sustained loading or damage causing loss of original capacity before external reinforcement was added. To assess the real potential of using FRP for expedient and economical field repair and strengthening of RC members, it was concluded that future research on the application of FRP to RC members should focus on conditions that are similar to what is observed in the field, including the effects of sustained load during repair/strengthening as well as corrosion- and load-induced damage.

166 citations

Journal ArticleDOI
TL;DR: In this article, the authors present the results of flexural tests on ten reinforced concrete beams strengthened with different plate configurations, and a strain compatibility and force equilibrium method of analysis, coupled with an empirical rule derived from the test data, is demonstrated to be effective in predicting the ultimate response of simply supported beams in bending with and without end plate anchorages and irrespective of plate length.
Abstract: Poststrengthening and retrofitting is a growing reality, as existing structures are required to meet the demands of modern society. Apart from the need to increase load capacity, upgrading of a structure may be necessitated through deterioration of the structure by corrosion or accidental damage, a change in the structural system, or to rectify initial design and construction faults. A commonly observed mode of failure for beams strengthened using carbon-fiber-reinforced polymer composite material plates is one due to the plate peeling off prematurely and unpredictably at relatively low magnitudes of applied loading. End plate anchorages and long unanchored plate lengths, which can add significantly to the overall cost of a strengthening solution, overcome this problem. This paper presents the results of flexural tests on ten reinforced concrete beams strengthened with different plate configurations. A strain compatibility and force equilibrium method of analysis, coupled with an empirical rule derived from the test data, is demonstrated to be effective in predicting the ultimate response of simply supported beams in bending with and without end plate anchorages and irrespective of plate length.

141 citations

Journal ArticleDOI
TL;DR: In this paper, a parametric analysis is conducted to investigate the effects of FRP reinforcement on serviceability, strength, and failure mechanisms of repaired RC beams, and the results of the analysis are shown in terms of repaired-to-unrepaired strength and deflection ratios.
Abstract: FRP reinforcement may be externally bonded to the soffit of existing flexural members in order to increase their strength and rigidity. A parametric analysis is conducted to investigate the effects of FRP reinforcement on serviceability, strength, and failure mechanisms of repaired RC beams. FRP reinforcement parameters considered in the analysis are: stiffness, bonded length, thickness, and the adhesive stiffness. The choice of the repair material parameters is important in the design phase in order to obtain the desired results of strengthening or stiffening without other unforeseen effects. In this paper, three typical RC beam cross sections are considered with height-to-width ratios of 0.5, 1, and 4. Two characteristic compressive strength levels (20 and 30 MPa), and two shear span-to-reinforcement depth ratios (4.5 and 7) are considered. All other parameters related to material and geometry of the beams are maintained constant. The results of the analysis are shown in terms of repaired-to-un-repaired strength and deflection ratios. They indicate that brittle failure mechanisms can develop at loads much lower than expected when considering only flexural performance controlled by concrete crushing and FRP tensile rupture. The analytical model used for the parametrization accounts for brittle failure mechanisms induced by debonding of the FRP reinforcement or shear-tension failure in concrete in the plane of the main longitudinal steel reinforcing bars. Even when considering the limitation of the RC member due to its un-modifiable shear resistance, it is shown that the application of FRP reinforcement can considerably increase load resistance capacity and limit deflection at service.

135 citations

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