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Journal ArticleDOI

Fracture mechanics of plate debonding: Validation against experiment

01 Jun 2011-Construction and Building Materials (Elsevier)-Vol. 25, Iss: 6, pp 2961-2971
TL;DR: In this article, an analytical model with energy calculations based on a revised version of Branson's model (to take account of the reaction to the force in the FRP) has been developed.
About: This article is published in Construction and Building Materials.The article was published on 2011-06-01. It has received 33 citations till now. The article focuses on the topics: Strain energy release rate & Fracture mechanics.
Citations
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Journal ArticleDOI
TL;DR: The results of single-lap shear tests, conducted on specimens with fiber reinforced cementitious matrix (FRCM) composite strips bonded to concrete blocks, are presented in this paper.

214 citations


Cites background from "Fracture mechanics of plate debondi..."

  • ...However, the weakness of FRCM–concrete joints appears to be at the matrix–fiber interface [18–23] rather than in the substrate or at the matrix–concrete interface, as is typically observed with FRP composites [24–38]....

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Journal ArticleDOI
TL;DR: In this paper, the authors investigated the cohesive stress transfer during the sub-critical crack growth associated with the debonding of FRP from concrete under fatigue loading using the direct shear test set-up.
Abstract: The cohesive stress transfer during the sub-critical crack growth associated with the debonding of FRP from concrete under fatigue loading is experimentally investigated using the direct shear test set-up. The study focused on high-amplitude/low-cycle fatigue. The fatigue sub-critical crack growth occurs at a load that is smaller than the static bond capacity of the interface, obtained from monotonic quasi-static loading, and is also associated with a smaller value of the interfacial fracture energy. The strain distribution during debonding is obtained using digital image correlation. The results indicate that the strain distribution along the FRP during fatigue is similar to the strain distribution during debonding under monotonic quasi-static loading. The cohesive crack model and the shape of the strain distribution adopted for quasi-static monotonic loading is indirectly proven to be adequate to describe the stress transfer during fatigue loading. The length of the stress transfer zone during fatigue is observed to be smaller than the cohesive zone of the interfacial crack under quasi-static monotonic loading. The strain distribution across the width of the FRP sheet is not altered during and by fatigue loading. A new formulation to predict the debonding crack growth during fatigue is proposed.

88 citations

Journal ArticleDOI
Abstract: In recent decades, the construction industry has witnessed a rapid growth of interest in strengthening and retrofitting of existing reinforced concrete (RC) and masonry structures. Fiber reinforced polymer (FRP) composites have gained great popularity, and several studies are now available in the literature on their use in strengthening and retrofit applications. Promising newly-developed composite materials are represented by the so-called fiber reinforced cementitious matrix (FRCM) composites. FRCM composites are comprised of high strength fibers embedded within a cementitious matrix that is responsible for the stress transfer between the existing structure and the strengthening material. FRCM composites are still in their infancy, and very limited results are available in the literature on RC and masonry strengthening applications. This study presents an experimental campaign conducted on different FRCM composites comprised of glass, carbon, or steel fibers embedded within two different cementitious matrices and applied to concrete prisms. The single-lap direct-shear test was used to study the stress-transfer mechanism between the FRCM composite and the concrete substrate. Two different composite bonded lengths were investigated. Debonding occurred at the matrix-fiber interface for some of the composites tested and at the concrete-matrix interface for others. This work contributes to the study of the bond behavior of FRCM composites, which represents a key issue for the effectiveness of FRCM composite strengthening.

43 citations


Cites background from "Fracture mechanics of plate debondi..."

  • ...The limited scientific literature available regarding FRCM composites reports that the weakness is located at the matrix-fiber interface [3-8] rather than within the substrate or at the matrix-concrete interface, as is typically observed with FRP composites [9-21]....

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Journal ArticleDOI
TL;DR: In this article, a detailed discussion of the mechanism of the FRP debonding is presented, and it is shown that the initiation of debonding can be regarded as a Mode I (tensile) fracture in concrete, despite being loaded primarily in shear.

41 citations


Cites background or methods or result from "Fracture mechanics of plate debondi..."

  • ...This is consistent with earlier analyses of FRP debonding [3] that have shown that cracks of about 20–30 mm and 2–5 mm long cause PE and IC debonding respectively (note: length of the FPZ 300 mm)....

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  • ...The authors have previously developed a fracture mechanics model to analyse FRP debonding; the model has been validated against many experiments carried out by others [3]....

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  • ...It has been shown that the incorporation of GCI determined this way in the debonding analysis gives predictions that match the test results reported in the literature [3]....

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  • ...The model predictions, based on this concept adopted in the analyses, matched well with test data reported in the literature [3]....

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  • ...The paper shows how the fracture energies of the beams quoted in the earlier papers by the authors [3] were determined....

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Journal ArticleDOI
TL;DR: In this article, a four-point bending test was performed on bi-layer structures to investigate interlayer debonding near skrinkage cracks or joints of composite pavements, and the strain energy release rate was calculated.

36 citations


Cites background or methods from "Fracture mechanics of plate debondi..."

  • ...Following the laboratory testing campaign [1] and r esults stemming from other applications [5-7, 21-25 , 34], a four-point bending test (4PB), used on concrete b ams strengthened by externally-bonded plates, has been adapted for the pair of bituminous and cement concr ete materials [35] (see Fig....

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  • ...effect and the loading rate on mechanical propertie s of bituminous material as well as to the position of the load close to the vertical crack, plays an importan t role in the long-term performance of the bond [34]....

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  • ...In addition, for few t ype I specimens and results stemming from the liter ature [7, 24, 34], some additional cracks at the bottom of th e cement concrete under point B or C in Figure 4a m ay have occurred prior to delamination at location poi nt A or D....

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References
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Book ChapterDOI
TL;DR: In this article, the authors describe the mixed mode cracking in layered materials and elaborates some of the basic results on the characterization of crack tip fields and on the specification of interface toughness, showing that cracks in brittle, isotropic, homogeneous materials propagate such that pure mode I conditions are maintained at the crack tip.
Abstract: Publisher Summary This chapter describes the mixed mode cracking in layered materials. There is ample experimental evidence that cracks in brittle, isotropic, homogeneous materials propagate such that pure mode I conditions are maintained at the crack tip. An unloaded crack subsequently subject to a combination of modes I and II will initiate growth by kinking in such a direction that the advancing tip is in mode I. The chapter also elaborates some of the basic results on the characterization of crack tip fields and on the specification of interface toughness. The competition between crack advance within the interface and kinking out of the interface depends on the relative toughness of the interface to that of the adjoining material. The interface stress intensity factors play precisely the same role as their counterparts in elastic fracture mechanics for homogeneous, isotropic solids. When an interface between a bimaterial system is actually a very thin layer of a third phase, the details of the cracking morphology in the thin interface layer can also play a role in determining the mixed mode toughness. The elasticity solutions for cracks in multilayers are also elaborated.

3,828 citations

Journal ArticleDOI
TL;DR: In this paper, the authors identify and analyse collapse mechanisms for reinforced concrete beams with externally bonded fiber-reinforced plastic (FRP) materials, and obtain equations describing each failure mechanism using the strain compatibility method and concepts of fracture mechanics.
Abstract: Strengthening of concrete beams with externally bonded fibre-reinforced plastic (FRP) materials appears to be a feasible way of increasing the load-carrying capacity and stiffness characteristics of existing structures. FRP-strengthened concrete beams can fail in several ways when loaded in bending. The following collapse mechanisms are identified and analysed in this study: steel yield-FRP rupture, steel yield-concrete crushing, compressive failure, and debonding. Here we obtain equations describing each failure mechanism using the strain compatibility method, concepts of fracture mechanics and a simple model for the FRP peeling-off debonding mechanism due to the development of shear cracks. We then produce diagrams showing the beam designs for which each failure mechanism is dominant, examine the effect of FRP sheets on the ductility and stiffness of strengthened components, and give results of four-point bending tests confirming our analysis. The analytical results obtained can be used in establishing an FRP selection procedure for external strengthening of reinforced concrete members with lightweight and durable materials.

374 citations


"Fracture mechanics of plate debondi..." refers background in this paper

  • ...L0_eff plot for Beam 8 (Triantafillou and Plevris [15])....

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  • ...Triantafillou and Plevris [15] investigated the effect of the CFRP plate area on the failure load and the failure mode of strengthened beams....

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  • ...Triantafillou and Plevris [15] Triantafillou and Plevris [15] investigated the effect of the CFRP plate area on the failure load and the failure mode of strengthened beams....

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Journal ArticleDOI
TL;DR: In this article, an analytical and numerical model is presented to simulate the failure of RC beams strengthened with FRP plates and flexible sheets, and different failure mechanisms, from ductile to brittle, can be simulated and verified.
Abstract: Analytical and numerical models are presented to simulate the failure of RC beams strengthened with FRP plates and flexible sheets Different failure mechanisms, from ductile to brittle, can be simulated and verified The proposed analytical model takes into account the influence of concrete confinement in the compression zone due to the presence of the stirrups and the tensile softening properties of concrete This allows following more accurately the crack propagation and the failure mechanism of the flexural member The numerical model is based on finite element analysis (FEA), follows the smeared crack approach, and uses standard elements available in a commercial package Comparisons with experimental data obtained from strengthened RC beams tested in the laboratory are presented Analytical and numerical models show good agreement with the experiments It is shown that FRP type, thickness, and bonded length produce different types of failure ranging from FRP rupture to concrete shear failure Particularly important is the characterization of the interface (FRP-concrete) mechanical properties, for which a simple test is proposed

255 citations


Additional excerpts

  • ...[8,9]); thus, the additional ineffective length of the FRP just before critical debonding is expected to be within one cover distance (c) from the actual plate end....

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  • ...[8] Beam A4 was strengthened with a single layer of CFRP plate (curtailed at L0 = 150 mm), and failed by PE debonding at the internal tension steel level which originated as a shear crack at the plate end....

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Journal ArticleDOI
TL;DR: In this article, the results of experimental and analytical studies concerning the flexural strengthening of reinforced concrete beams by the external bonding of high-strength, lightweight fiber reinforced plastic (FRP) plates to the tension face of the beam were summarized.
Abstract: A particularly challenging problem confronting engineers in the revival of U.S. infrastructure is the rehabilitation of concrete structures. This paper summarizes the results of experimental and analytical studies concerning the flexural strengthening of reinforced concrete beams by the external bonding of high-strength, lightweight fiber reinforced plastic (FRP) plates to the tension face of the beam. Twenty-four large-scale beams were tested experimentally to evaluate the strength enhancement provided by the FRP plates. An inelastic section analysis procedure was developed that accurately predicts the load displacement response of the retrofitted beams. A nonlinear finite element method analysis was also conducted that corroborates the results from the experimental study and inelastic section analysis.

201 citations


"Fracture mechanics of plate debondi..." refers background in this paper

  • ...[17]) for fractures starting at (a) different locations (b) 90% of the failure load....

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  • ...The observed IC debonding failures of three sets of beams (Groups 1–3) reported in [17] are analysed, assuming that debonding initiates by widening of a flexural crack in one of the shear spans at a half beam depth (h) away from the loading point....

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Journal ArticleDOI
TL;DR: In this article, the performance of a series of 1.5 m-long reinforced concrete beams with CFRP plates bonded to the soffit is analyzed and an analytical formulation to predict the failure load corresponding to the concrete ripping failure mode is proposed based on composite theory in combination with a strain limiting criterion.
Abstract: The performance of a series of 1.5 m-long reinforced concrete beams with CFRP plates bonded to the soffit is presented. Effects of the plate length, the reinforcing steel ratio, and the thickness of the concrete cover on behavior of the beams are discussed with particular emphasis on the brittle failure mode of the concrete ripping. It was found that before the brittle failure, the composite action of the beam could be divided into three distinct zones based on the distribution of the strains along the CFRP plate: (1) The “destressed” zone, (2) the “bond development” zone; and (3) the “fully composite” zone. Concrete ripping may be prevented by limiting the strain at the transition point of the composite zone of the plate. An analytical formulation to predict the failure load corresponding to the concrete ripping failure mode is proposed based on composite theory in combination with a strain limiting criterion. The strain limit can be determined based on simple bond tests with various bond lengths for a g...

183 citations


Additional excerpts

  • ...[10], Beams A950 and B2, with different internal tension steel arrangements, were strengthened with CFRP plates of different lengths (quoted in Table 1); both beams failed due to PE debonding....

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  • ...For example, Beam A950 in [10], discussed above, failed due to an infinitesimal interface crack developed at the actual plate end, but it would have also failed at 90% of the reported failure load if there had been a 20 mm long interface crack (Fig....

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