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Cj Burgoyne - One of the best experts on this subject based on the ideXlab platform.
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Parametric Study of FRP Plate Debonding Using Global Energy Balance
Journal of Composites for Construction, 2014Co-Authors: Gx Guan, Cj Burgoyne, Mithila AchinthaAbstract:Fiber-reinforced polymer (FRP) Plate Debonding is commonly caused by the fracturing of concrete, but few studies of fracture Debonding models exist, from which the failure load of the concrete cover layer can be evaluated. This paper presents a parametric study for Plate end Debonding using the global energy balance approach (GEBA), which has been proposed recently for determining the structure-Debonding load. GEBA determines the Debonding load using moment-curvature (M-?) models, and can thus be used to determine how Debonding is affected by the beam’s flexural design. This paper presents parametric results using Debonding contours on plots of moment capacity against the Plate curtailment locations, and shows that beams with the same depth-to-fracture energy ratio give virtually the same Debonding contour. This helps to generalize Debonding determination for beams with different depths, and can be conveniently used for design. The parametric study lays a foundation for the application of fracture mechanics in FRP-Plate retrofitting design using conventional M-? models to cover a wide range of flexural retrofitting situations.
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Parametric study of FRP Plate Debonding using global energy balance
2014Co-Authors: Gx Guan, Cj Burgoyne, Achintha MAbstract:© 2014 American Society of Civil Engineers. Fiber-reinforced polymer (FRP) Plate Debonding is commonly caused by the fracturing of concrete, but few studies of fracture Debonding models exist, from which the failure load of the concrete cover layer can be evaluated. This paper presents a parametric study for Plate end Debonding using the global energy balance approach (GEBA), which has been proposed recently for determining the structure-Debonding load. GEBA determines the Debonding load using moment-curvature (M-κ) models, and can thus be used to determine how Debonding is affected by the beam's flexural design. This paper presents parametric results using Debonding contours on plots of moment capacity against the Plate curtailment locations, and shows that beams with the same depth-to-fracture energy ratio give virtually the same Debonding contour. This helps to generalize Debonding determination for beams with different depths, and can be conveniently used for design. The parametric study lays a foundation for the application of fracture mechanics in FRP-Plate retrofitting design using conventional M-κ models to cover a wide range of flexural retrofitting situations
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Unified Design Method for Flexure and Debonding in FRP Retrofitted RC Beams
Journal of Composites for Construction, 2014Co-Authors: Gx Guan, Cj BurgoyneAbstract:Flexural retrofitting of reinforced concrete (RC) beams using fiber-reinforced polymer (FRP) Plate is a common way to increase the flexural capacity. There is a lack of rational design method to determine where the strengthening Plate can safely be curtailed. As a result, retrofitted beams commonly fail by Debonding of the FRP Plate, which occurs well before the target flexural capacity. Debonding is brittle failure; thus, ductility of the retrofitted beam needs to be ensured by Debonding prevention. With sufficient ductility the ultimate strength can continuously increase beyond steel yields with the elastic behavior of the FRP strengthening Plate. Debonding prevention has been accounted for empirically in most design approaches so far. The global energy balance approach (GEBA) using fracture mechanics has been proposed to determine the Debonding load of an FRP-RC beam that is affected by the Plate curtailment location. The GEBA results for various FRP-RC beams can be summarized using Debonding contours on plots of moment capacity against the safe Plate curtailment locations. The Debonding contours constructed in this way for the beams with the same ratio of depth to fracture energy are virtually the same. This paper shows how GEBA can be incorporated into the design process to prevent premature Debonding of the FRP Plate. The method makes use of the Debonding contours and derives from these simplified design charts that could be made available to designers. The retrofitting design consideration and the theoretical background of this unified design method are first explained, followed by the derivation of the conceptual design charts. Numerically correct design charts are then constructed for a wide range of design cases. Finally, a worked example is used to explain the way to apply the unified design method using design charts.
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Fracture mechanics of Plate Debonding: Validation against experiment
Construction and Building Materials, 2011Co-Authors: Mithila Achintha, Cj BurgoyneAbstract:Abstract The Debonding of FRP Plates from concrete beams is not amenable to finite-element analysis; fracture mechanics, based on a global energy balance, offers a better alternative. 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 already been developed. This paper presents comparisons with a variety of experiments reported in the literature and shows that the model can correctly determine both the failure load and the failure mechanism. The paper shows that Debonding often propagates in the concrete, just above the interface, and hence the failure load is dependent on the Mode I fracture energy of concrete. The method can also be used to determine when premature adhesive failure occurred prior to Debonding within the concrete substrate.
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Fracture mechanics of Plate Debonding: experimental validation
2009Co-Authors: Mithila Achintha, Cj BurgoyneAbstract:Premature Plate Debonding hampers the efficient use of externally bonded FRP Plates for flexural strengthening of concrete beams. Existing research mostly concentrates on finite element (FE) modelling of the concrete–FRP interface but such analyses are of dubious validity because they require far more details than will ever be available for the interface. A fracture-mechanics-based Plate Debonding model has been developed by the authors; since detailed stress analysis of concrete is unattainable the model is based on the global energy balance of the system. Flaws will inevitability be present in the vicinity of the interface; the model investigates the energy balance when such a flaw propagates. The energy released when the crack extends (GR) is compared with the interface fracture energy required to create the new surfaces GF: If GR > GF the crack will extend causing Debonding. Determination of both GR and GF associated with crack extension is not trivial because of the unknowable microstructure of concrete. The early work of the present study developed methods to find both parameters to accuracies sufficient for practical purposes. A modified version of Branson’s model, which takes account of the effects caused by the axial force in the FRP, has been developed for the moment–curvature and subsequent GR analyses, while GF has been determined according to the actual fracture mechanism that takes place in the interface. This paper presents comparisons with a variety of Plate Debonding test data (including steel Plate bonded beams) reported in the literature and shows that the present model can correctly determine both the failure load and the Debonding mode. Only simply-supported beams, without additional Plate end anchors, under short-term monotonic loads are considered here, but the model could be extended to analyse more complex practical problems.
Deric J. Oehlers - One of the best experts on this subject based on the ideXlab platform.
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Design for Moment Redistribution in RC Beams Retrofitted with Steel Plates
Advances in Structural Engineering, 2010Co-Authors: Martin Haskett, Deric J. Oehlers, M.s. Mohamed AliAbstract:It is now common practice to retrofit reinforced concrete members by adhesively bonding steel or fibre reinforced polymer Plates to their surfaces. However, tests have shown that these Plated RC structures tend to have less member ductility, or rotational capacity, than the unPlated structure because of premature Plate Debonding. In this paper, structural mechanics approaches are described for both: quantifying the moment rotation capacity, or member ductility, of steel Plated RC flexural members; and quantifying the moment redistribution capacity from the moment rotation capacity. It is shown how the moment redistribution structural mechanics model can be used to design for member ductility directly and, furthermore, it is applied to both externally bonded and near surface mounted steel Plates. As would be expected, it is shown that steel plating produces more ductile members than fibre reinforced polymer plating.
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Fundamental issues that govern the rotation of FRP retrofitted RC columns and beams: The intractable plastic hinge ductility problem
2007Co-Authors: Deric J. Oehlers, M. Mohamed Sadakkathulla, Michael C. Griffith, Togay OzbakkalogluAbstract:There is often a perception that FRP retrofitted concrete structures are unable to redistribute stress resultants nor absorb energy due to a lack of rotational capacity because FRP is a brittle material and the interface bond between the FRP Plate and concrete is also brittle. However in contrast to this perception, there is clear experimental evidence to show that FRP plating techniques can produce ductile members. Hence, it should be possible to develop ductility design rules for FRP strengthened reinforced concrete structures to considerably widen the application of FRP plating which is the subject of this paper. It is shown that the major problem is not in quantifying the rotational limit due to FRP Plate Debonding or fracture but in quantifying the rotational limit due to concrete softening which has been an intractable problem for over fifty years.
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Debonding Mechanisms in FRP Plated Unreinforced Masonry Under Out-of-Plane Loading
Advances in Structural Engineering, 2006Co-Authors: Shaohua Xia, Deric J. OehlersAbstract:Of major concern is the out of plane strength of unreinforced masonry (URM) structures subjected to seismic loads. Through tests and numerical simulations, this article shows that the application of externally bonded (EB) fibre reinforced polymer (FRP) Plates to URM members can substantially increase the out of plane strength. Of fundamental importance to the behaviour of EB FRP Plated masonry is the Plate Debonding mechanism as this affects not only the ultimate strength but also the ability to absorb energy. A numerical procedure, which can simulate Plate Debonding in EB FRP Plated masonry, is first described. The developed numerical program is then: used to explain the mechanism of Debonding and the parameters that affect this Debonding mechanism; compared with Plated beam tests first reported in this paper; and used to illustrate the Plate Debonding mechanism and the substantial increases in out of plane strength that can be achieved.
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FRP Plates Adhesively Bonded to Reinforced Concrete Beams: Generic Debonding Mechanisms:
Advances in Structural Engineering, 2006Co-Authors: Deric J. OehlersAbstract:Retrofitting reinforced concrete members by adhesively bonding fibre reinforced polymer Plates to their surfaces is now a well established technique as there has been substantial and much good research on the numerous individual Plate Debonding mechanisms which has allowed safe designs. In this paper, it is shown how the apparently numerous and individual Debonding mechanisms can be categorised into a few distinct generic Debonding mechanisms, which should help to simplify the problem and consequently, in the long term, allow the development of generic design rules.
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Shear deformation Debonding of adhesively bonded Plates
2005Co-Authors: Deric J. Oehlers, I. S. T. Liu, Rudolf SeracinoAbstract:Adhesive bonding of fibre reinforced polymer (FRP) and steel Plates to the surfaces of reinforced concrete structures is an efficient form of retrofitting, as the Plated structure is mechanically efficient, the Plate is unobtrusive, and—for FRP Plates—the Plate is durable and the application is inexpensive owing to the lightness and flexibility of the pultruded or wet lay-up Plate. In this paper it is shown: from a comparison of the main FRP plating guidelines, that there is now a general agreement on the major Plate Debonding mechanisms; that current rules in national standards for the shear capacity of prestressed beams can be used to quantify a major Plate Debonding mechanism due to beam shear deformations, that is critical diagonal crack (CDC) Debonding; and that these developments allow a simple design approach to be used for FRP and steel Plated beams and slabs with longitudinal Plates.
M.s. Mohamed Ali - One of the best experts on this subject based on the ideXlab platform.
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Design for Moment Redistribution in RC Beams Retrofitted with Steel Plates
Advances in Structural Engineering, 2010Co-Authors: Martin Haskett, Deric J. Oehlers, M.s. Mohamed AliAbstract:It is now common practice to retrofit reinforced concrete members by adhesively bonding steel or fibre reinforced polymer Plates to their surfaces. However, tests have shown that these Plated RC structures tend to have less member ductility, or rotational capacity, than the unPlated structure because of premature Plate Debonding. In this paper, structural mechanics approaches are described for both: quantifying the moment rotation capacity, or member ductility, of steel Plated RC flexural members; and quantifying the moment redistribution capacity from the moment rotation capacity. It is shown how the moment redistribution structural mechanics model can be used to design for member ductility directly and, furthermore, it is applied to both externally bonded and near surface mounted steel Plates. As would be expected, it is shown that steel plating produces more ductile members than fibre reinforced polymer plating.
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Debonding of steel Plates adhesively bonded to the compression faces of RC beams
Construction and Building Materials, 2005Co-Authors: M.s. Mohamed Ali, Deric J. Oehlers, Mark A. BradfordAbstract:Abstract Reinforced concrete beams in buildings and bridges are increasingly being retrofitted by adhesively bonding steel or FRP Plates to their tension faces. However, tests have shown that tension face Plates are prone to premature Debonding. One way of preventing or inhibiting Debonding of tension face Plates in continuous beams is to extend the Plate-ends past the points of contraflexure into the compression faces. In this paper: it is shown that compression face Plates are less likely to debond than tension face Plates; results of thirteen tests on Debonding due to vertical shear forces (critical diagonal crack Debonding) and curvature (flexural end Plate Debonding) are described; and critical diagonal crack and flexural end Plate Debonding models are developed for compression face Plates that can be used to ensure that beams with tension face Plates that are extended into the compression faces do not debond prematurely.
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Prestress model for shear deformation Debonding of FRP- and steel-Plated RC beams
Magazine of Concrete Research, 2004Co-Authors: Deric J. Oehlers, I. S. T. Liu, Rudolf Seracino, M.s. Mohamed AliAbstract:Adhesive bonding Plates to the surfaces of RC structures is a widely accepted form of strengthening or stiffening because of the ease of application and unobtrusive nature of this retrofitting procedure. Design guidelines have identified three major forms of Plate Debonding, one of which is Debonding due to the shear deformation across a critical diagonal crack (CDC). CDC Debonding is particularly important in RC beams with stirrups, as they are prone to debond before the shear capacity of the beam is attained. In this paper it is shown that the CDC Debonding resistance of a Plated RC beam is analogous to the shear resistance of a prestressed beam; a design procedure based on the shear resistance of prestressed beams is developed, and correlates well with 77 Plated beam tests. In a companion paper the prestress analogy developed here is taken further: it is shown that code approaches for determining the shear resistance of prestressed beams can be used to predict CDC Debonding. This has allowed the develo...
Gx Guan - One of the best experts on this subject based on the ideXlab platform.
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Parametric Study of FRP Plate Debonding Using Global Energy Balance
Journal of Composites for Construction, 2014Co-Authors: Gx Guan, Cj Burgoyne, Mithila AchinthaAbstract:Fiber-reinforced polymer (FRP) Plate Debonding is commonly caused by the fracturing of concrete, but few studies of fracture Debonding models exist, from which the failure load of the concrete cover layer can be evaluated. This paper presents a parametric study for Plate end Debonding using the global energy balance approach (GEBA), which has been proposed recently for determining the structure-Debonding load. GEBA determines the Debonding load using moment-curvature (M-?) models, and can thus be used to determine how Debonding is affected by the beam’s flexural design. This paper presents parametric results using Debonding contours on plots of moment capacity against the Plate curtailment locations, and shows that beams with the same depth-to-fracture energy ratio give virtually the same Debonding contour. This helps to generalize Debonding determination for beams with different depths, and can be conveniently used for design. The parametric study lays a foundation for the application of fracture mechanics in FRP-Plate retrofitting design using conventional M-? models to cover a wide range of flexural retrofitting situations.
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Parametric study of FRP Plate Debonding using global energy balance
2014Co-Authors: Gx Guan, Cj Burgoyne, Achintha MAbstract:© 2014 American Society of Civil Engineers. Fiber-reinforced polymer (FRP) Plate Debonding is commonly caused by the fracturing of concrete, but few studies of fracture Debonding models exist, from which the failure load of the concrete cover layer can be evaluated. This paper presents a parametric study for Plate end Debonding using the global energy balance approach (GEBA), which has been proposed recently for determining the structure-Debonding load. GEBA determines the Debonding load using moment-curvature (M-κ) models, and can thus be used to determine how Debonding is affected by the beam's flexural design. This paper presents parametric results using Debonding contours on plots of moment capacity against the Plate curtailment locations, and shows that beams with the same depth-to-fracture energy ratio give virtually the same Debonding contour. This helps to generalize Debonding determination for beams with different depths, and can be conveniently used for design. The parametric study lays a foundation for the application of fracture mechanics in FRP-Plate retrofitting design using conventional M-κ models to cover a wide range of flexural retrofitting situations
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Unified Design Method for Flexure and Debonding in FRP Retrofitted RC Beams
Journal of Composites for Construction, 2014Co-Authors: Gx Guan, Cj BurgoyneAbstract:Flexural retrofitting of reinforced concrete (RC) beams using fiber-reinforced polymer (FRP) Plate is a common way to increase the flexural capacity. There is a lack of rational design method to determine where the strengthening Plate can safely be curtailed. As a result, retrofitted beams commonly fail by Debonding of the FRP Plate, which occurs well before the target flexural capacity. Debonding is brittle failure; thus, ductility of the retrofitted beam needs to be ensured by Debonding prevention. With sufficient ductility the ultimate strength can continuously increase beyond steel yields with the elastic behavior of the FRP strengthening Plate. Debonding prevention has been accounted for empirically in most design approaches so far. The global energy balance approach (GEBA) using fracture mechanics has been proposed to determine the Debonding load of an FRP-RC beam that is affected by the Plate curtailment location. The GEBA results for various FRP-RC beams can be summarized using Debonding contours on plots of moment capacity against the safe Plate curtailment locations. The Debonding contours constructed in this way for the beams with the same ratio of depth to fracture energy are virtually the same. This paper shows how GEBA can be incorporated into the design process to prevent premature Debonding of the FRP Plate. The method makes use of the Debonding contours and derives from these simplified design charts that could be made available to designers. The retrofitting design consideration and the theoretical background of this unified design method are first explained, followed by the derivation of the conceptual design charts. Numerically correct design charts are then constructed for a wide range of design cases. Finally, a worked example is used to explain the way to apply the unified design method using design charts.
Narayan Swamy - One of the best experts on this subject based on the ideXlab platform.
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interface shear stress a new design criterion for Plate Debonding
Journal of Composites for Construction, 2001Co-Authors: Phalguni Mukhopadhyaya, Narayan SwamyAbstract:This paper critically assesses the applicability and reliability of existing analytical techniques to predict and/or prevent brittle Plate Debonding failure that occurs in reinforced concrete (RC) beams strengthened with externally bonded steel or fiber-reinforced-polymer composite Plates. The experimental results, available to date in literature, have been very carefully reviewed and analyzed for this purpose. A new approach, very different from existing methods, and based on the interface shear stress obtained from elastic analysis of RC beam cross section and the fundamentals of force transfer mechanism in a bonded joint, is presented to predict the premature Plate Debonding phenomenon. The paper identifies important structural, material, and force parameters that influence this critical interface shear stress value between the bonded Plate and concrete. The relations between these parameters and interface shear stress value are also examined and found to be consistent and logical to predict Plate Debonding at the Plate cutoff end. The validity of this new design-oriented approach and scope for further research are also discussed.