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J G Teng - One of the best experts on this subject based on the ideXlab platform.
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Finite element modelling of Debonding failures in steel beams flexurally strengthened with CFRP laminates
Engineering Structures, 2015Co-Authors: J G Teng, Dilum Fernando, Tao YuAbstract:A steel beam may be strengthened in flexure by bonding a carbon fibre-reinforced polymer (CFRP) Plate to the tension face. Such a beam may fail by Debonding of the CFRP Plate that initiates at one of the Plate Ends (i.e. Plate End Debonding) or by Debonding that initiates at a local damage (e.g. a crack or concentrated yielding) away from the Plate Ends (intermediate Debonding). This paper presents the first finite element (FE) approach that is capable of accurate predictions of such Debonding failures, with particular attention to Plate-End Debonding. In the proposed FE approach, a mixed-mode cohesive law is employed to depict interfacial behaviour under a combination of normal stresses (i.e. mode-I loading) and shear stresses (i.e. mode-II loading); the interfacial behaviour under pure mode-I loading or pure mode-II loading is represented by bi-linear traction–separation models. Damage initiation is defined using a quadratic strength criterion, and damage evolution is defined using a linear fracture energy-based criterion. Detailed FE models of steel beams tested by previous researchers are presented, and their predictions are shown to be in close agreement with the test results. Using the proposed FE approach, the behaviour of CFRP-strengthened steel beams is examined, indicating that: (1) if the failure is governed by Plate End Debonding, the use of a CFRP Plate with a higher elastic modulus and/or a larger thickness may lead to a lower ultimate load because Plate End Debonding may then occur earlier; (2) Plate End Debonding is more likely to occur when a short CFRP Plate is used, as is commonly expected; and (3) the failure mode may change to intermediate Debonding or other failure modes such as compression flange buckling if a longer Plate is used.
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Coupled mixed-mode cohesive zone modeling of interfacial Debonding in simply supported Plated beams
International Journal of Solids and Structures, 2013Co-Authors: Laura De Lorenzis, Dilum Fernando, J G TengAbstract:The development of predictive models for Plate End Debonding failures in beams strengthened with thin soffit Plates is a topic of great practical relevance. After the early stress-based formulations, fracture mechanics approaches have become increasingly established. More recently, the cohesive zone (CZ) model has been successfully adopted as a bridge between the stress- and fracture mechanics-based treatments. However, the few studies of this nature propose complex formulations which can only be implemented numerically. To date, the only available analytical solution based on CZ modeling for the prediction of interfacial stresses/Debonding in Plated beams is limited to the determination of interfacial shear stresses and thus neglects the mixed-mode effects generated by the presence of interfacial normal stresses at the Plate End. This paper presents a new analytical formulation based on the CZ modeling approach for the prediction of Plate End Debonding in Plated beams. A key enhancement with respect to the previous solution is the use of a coupled mixed-mode CZ model, which enables a full account of mixed-mode effects at the Plate End. The model describes the evolution of the interface after the End of the elastic regime, and predicts the value of the load at incipient Debonding. The achievement of a closed-form solution for this quite complex case entails the introduction of a crucial simplifying assumption, as well as the ad hoc modeling of an effective cohesive interfacial response. The paper presents the analytical theory and compares its predictions with numerical and experimental results.
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Coupled mixed-mode cohesive zone modeling of interfacial Debonding in simply supported Plated beams
International Journal of Solids and Structures, 2013Co-Authors: Laura De Lorenzis, Dilum Fernando, J G TengAbstract:The development of predictive models for Plate End Debonding failures in beams strengthened with thin soffit Plates is a topic of great practical relevance. After the early stress-based formulations, fracture mechanics approaches have become increasingly established. More recently, the cohesive zone (CZ) model has been successfully adopted as a bridge between the stress- and fracture mechanics-based treatments. However, the few studies of this nature propose complex formulations which can only be implemented numerically. To date, the only available analytical solution based on CZ modeling for the prediction of interfacial stresses/Debonding in Plated beams is limited to the determination of interfacial shear stresses and thus neglects the mixed-mode effects generated by the presence of interfacial normal stresses at the Plate End. This paper presents a new analytical formulation based on the CZ modeling approach for the prediction of Plate End Debonding in Plated beams. A key enhancement with respect to the previous solution is the use of a coupled mixed-mode CZ model, which enables a full account of mixed-mode effects at the Plate End. The model describes the evolution of the interface after the End of the elastic regime, and predicts the value of the load at incipient Debonding. The achievement of a closed-form solution for this quite complex case entails the introduction of a crucial simplifying assumption, as well as the ad hoc modeling of an effective cohesive interfacial response. The paper presents the analytical theory and compares its predictions with numerical and experimental results.Department of Civil and Environmental Engineerin
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Simple general solution for interfacial stresses in Plated beams
Journal of Composites for Construction, 2010Co-Authors: Linli Zhang, J G TengAbstract:The flexural strength of a reinforced concrete, metallic, or timber beam can be increased by bonding a thin Plate, made of steel or fiber-reinforced polymer, to its tension face. A main failure mode of such Plated beams involves Debonding of the Plate End from the beam and such Plate-End Debonding depEnds strongly on the interfacial stresses between the beam and the Plate. Consequently, many analytical solutions have been developed for the interfacial stresses of specific Plated beam problems, with almost all of them being for simply supported Plated straight beams of constant section subjected to simple loadings. The existing analytical solutions are therefore neither general enough nor simple enough for direct exploitation in assessing the risk of Plate-End Debonding failure. This paper corrects this deficiency by presenting a simple, accurate yet general solution for interfacial stresses. The solution is applicable to Plated beams of all geometric (e.g., curved beams), sectional (e.g., tapered beams), loading (e.g., a linearly varying distributed load), and boundary conditions (e.g., continuous beams). The accuracy of the solution is demonstrated through comparisons with finite element results. The paper also presents simple and accurate approximations for the peak values of interfacial shear and normal stresses at the Plate End. In these approximate expressions, only the sectional forces and properties of the Plate End section are involved, which greatly facilitates their direct exploitation in predicting Debonding failure.
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Plate End Debonding failure loads of FRP-or steel-Plated RC beams
2008Co-Authors: Jian Yao, J G TengAbstract:Plate End Debonding failure loads of RC beams strengthened in flexure by bonding an FRP or steel Plate to the tension face were investigated in detail.Based on studies of the controlling parameters,the available test data and comparisons of these test data with existing Debonding strength models,a simple,rationally-based predictive model for Plate End Debonding failure loads was presented.In this model,pure flexural Debonding for a Plate End located in a pure bEnding region and pure shear Debonding for a Plate End located in a high-shear zero(or low)-moment region are first dealt with.The general case of a Plate End under the combined action of shear and bEnding is treated as the interaction of these two extreme conditions.The proposed model is shown to be accurate through comparisons with available test results.The model relates the Debonding failure load to the shear capacity of the beam and a number of well-defined parameters,and can be easily incorporated in future design codes and guidelines,and may be used in practical applications.
Jg Teng - One of the best experts on this subject based on the ideXlab platform.
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Finite element modelling of Debonding failures in steel beams flexurally strengthened with CFRP laminates
Pergamon Press, 2015Co-Authors: Jg Teng, Fernando D, Yu TAbstract:A steel beam may be strengthened in flexure by bonding a carbon fibre-reinforced polymer (CFRP) Plate to the tension face. Such a beam may fail by Debonding of the CFRP Plate that initiates at one of the Plate Ends (i.e. Plate End Debonding) or by Debonding that initiates at a local damage (e.g. a crack or concentrated yielding) away from the Plate Ends (intermediate Debonding). This paper presents the first finite element (FE) approach that is capable of accurate predictions of such Debonding failures, with particular attention to Plate-End Debonding. In the proposed FE approach, a mixed-mode cohesive law is employed to depict interfacial behaviour under a combination of normal stresses (i.e. mode-I loading) and shear stresses (i.e. mode-II loading); the interfacial behaviour under pure mode-I loading or pure mode-II loading is represented by bi-linear traction-separation models. Damage initiation is defined using a quadratic strength criterion, and damage evolution is defined using a linear fracture energy-based criterion. Detailed FE models of steel beams tested by previous researchers are presented, and their predictions are shown to be in close agreement with the test results. Using the proposed FE approach, the behaviour of CFRP-strengthened steel beams is examined, indicating that: (1) if the failure is governed by Plate End Debonding, the use of a CFRP Plate with a higher elastic modulus and/or a larger thickness may lead to a lower ultimate load because Plate End Debonding may then occur earlier; (2) Plate End Debonding is more likely to occur when a short CFRP Plate is used, as is commonly expected; and (3) the failure mode may change to intermediate Debonding or other failure modes such as compression flange buckling if a longer Plate is used.Department of Civil and Environmental Engineerin
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Finite element modelling of Debonding failures in steel beams flexurally strengthened with CFRP laminates
'Elsevier BV', 2015Co-Authors: Jg Teng, Fernando D, Yu TAbstract:A steel beam may be strengthened in flexure by bonding a carbon fibre-reinforced polymer (CFRP) Plate to the tension face. Such a beam may fail by Debonding of the CFRP Plate that initiates at one of the Plate Ends (i.e. Plate End Debonding) or by Debonding that initiates at a local damage (e.g. a crack or concentrated yielding) away from the Plate Ends (intermediate Debonding). This paper presents the first finite element (FE) approach that is capable of accurate predictions of such Debonding failures, with particular attention to Plate-End Debonding. In the proposed FE approach, a mixed-mode cohesive law is employed to depict interfacial behaviour under a combination of normal stresses (i.e. mode-I loading) and shear stresses (i.e. mode-II loading); the interfacial behaviour under pure mode-I loading or pure mode-II loading is represented by bi-linear traction-separation models. Damage initiation is defined using a quadratic strength criterion, and damage evolution is defined using a linear fracture energy-based criterion. Detailed FE models of steel beams tested by previous researchers are presented, and their predictions are shown to be in close agreement with the test results. Using the proposed FE approach, the behaviour of CFRP-strengthened steel beams is examined, indicating that: (1) if the failure is governed by Plate End Debonding, the use of a CFRP Plate with a higher elastic modulus and/or a larger thickness may lead to a lower ultimate load because Plate End Debonding may then occur earlier; (2) Plate End Debonding is more likely to occur when a short CFRP Plate is used, as is commonly expected; and (3) the failure mode may change to intermediate Debonding or other failure modes such as compression flange buckling if a longer Plate is used.Department of Civil and Environmental Engineering2014-2015 > Academic research: refereed > Publication in refereed journa
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Simple general solution for interfacial stresses in Plated beams
American Society of Civil Engineers, 2010Co-Authors: Zhang L, Jg TengAbstract:The flexural strength of a reinforced concrete, metallic or timber beam can be increased by bonding a thin Plate, made of steel or fiber-reinforced polymer, to its tension face. A main failure mode of such Plated beams involves Debonding of the Plate End from the beam and such Plate-End Debonding depEnds strongly on the interfacial stresses between the beam and the Plate. Consequently, many analytical solutions have been developed for the interfacial stresses of specific Plated beam problems, with almost all of them being for simply supported Plated straight beams of constant section subjected to simple loadings. The existing analytical solutions are therefore neither general enough nor simple enough for direct exploitation in assessing the risk of Plate-End Debonding failure. This paper corrects this deficiency by presenting a simple, accurate yet general solution for interfacial stresses. The solution is applicable to Plated beams of all geometric (e.g., curved beams), sectional (e.g., tapered beams), loading (e.g., a linearly varying distributed load), and boundary conditions (e.g., continuous beams). The accuracy of the solution is demonstrated through comparisons with finite element results. The paper also presents simple and accurate approximations for the peak values of interfacial shear and normal stresses at the Plate End. In these approximate expressions, only the sectional forces and properties of the Plate End section are involved, which greatly facilitates their direct exploitation in predicting Debonding failure.Department of Civil and Environmental Engineerin
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Plate End Debonding in FRP-Plated RC beams-I : experiments
Pergamon Press, 2007Co-Authors: Yao J, Jg TengAbstract:RC beams strengthened with a tension-face FRP Plate (i.e. FRP-Plated RC beams) often fails by Debonding in one of several possible modes. This paper presents an experimental study on Plate End Debonding failures in FRP-Plated RC beams, which was conducted to develop a better understanding of the behaviour and failure mechanisms for the subsequent development of a predictive model. The results of ten four-point bEnding tests and eleven three-point bEnding tests conducted on simply-supported FRP- or steel-Plated RC beams are presented and discussed in detail. The test beams cover a variety of significant geometric and material parameters over a wide range. In these beams, the critical Plate End was subjected to either bEnding or shear only. Most of the beams failed by Debonding in the form of the separation of the concrete cover from the steel tension reinforcement (i.e. cover separation failure), and for both types of Plate Ends, the Debonding failure load depEnds strongly on the stiffness of the "composite Plate" composed of the bonded Plate and the concrete cover or the bonded Plate alone. For Plate Ends subjected to a high shear force but a low moment, cover separation failure often occurs following local shear-crack induced interfacial Debonding between the Plate and the concrete near the Plate End. The shear resistance of the beam contributed by the concrete alone provides a lower bound to the Debonding failure load of such Plate Ends, which can be significantly increased by the presence of internal steel shear reinforcement.Department of Civil and Environmental Engineerin
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frp to concrete interfaces between two adjacent cracks theoretical model for Debonding failure
International Journal of Solids and Structures, 2006Co-Authors: Jg Teng, H Yuan, J F ChenAbstract:Abstract External bonding of fibre reinforced polymer (FRP) composites has become a popular technique for strengthening concrete structures all over the world. The performance of the interface between FRP and concrete is one of the key factors affecting the behaviour of the strengthened structure. Existing laboratory research has shown that the majority of reinforced concrete (RC) beams strengthened with a bonded FRP soffit Plate fail due to Debonding of the Plate from the concrete. Two types of Debonding failures have been commonly observed: Plate End Debonding and intermediate crack induced Debonding. In order to understand and develop methods to predict such Debonding failures, the bond behaviour between concrete and FRP has been widely studied using simple shear tests on FRP Plate/sheet-to-concrete bonded joints and a great deal of research is now available on the behaviour of these bonded joints. However, for intermediate crack induced Debonding failures, the Debonding behaviour can be significantly different from that observed in a simple shear test. Among other factors, the most significant difference may be that the FRP Plate between two adjacent cracks is subject to tension at both cracks. This paper presents an analytical solution for the Debonding process in an FRP-to-concrete bonded joint model where the FRP Plate is subject to tension at both Ends. A realistic bi-linear local bond-slip law is employed. Expressions for the interfacial shear stress distribution and the load–displacement response are derived for different loading stages. The Debonding process is discussed in detail. Finally, results from the analytical solution are presented to illustrate how the bond length affects the behaviour of such bonded joints. While the emphasis of the paper is on FRP-to-concrete joints, the analytical solution is equally applicable to similar joints between thin Plates of other materials (e.g. steel and aluminium) and concrete.
Laura De Lorenzis - One of the best experts on this subject based on the ideXlab platform.
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an analytical cohesive crack modeling approach to the edge Debonding failure of frp Plated beams
International Journal of Solids and Structures, 2015Co-Authors: Pietro Cornetti, Laura De Lorenzis, Mauro Corrado, Alberto CarpinteriAbstract:This paper focuses on the prediction of edge Debonding for a beam retrofitted with a Fiber-Reinforced Polymer Plate. This failure mechanism, also known as Plate-End Debonding, stems from the concentration of interfacial stresses arising at the termination of the strengthening Plate. Early models of edge Debonding adopted failure criteria based on interfacial stresses. However, due to the typically catastrophic nature of this failure mechanism, approaches based on Linear Elastic Fracture Mechanics (LEFM) became increasingly established. In this paper, the problem is addressed by means of the Cohesive Crack Model (CCM) and of the Finite Fracture Mechanics (FFM). These models are able to bridge the gap between the stress- and the energy-based approaches and nevertheless have been used in a limited number of analytical studies to date. Based on a cohesive interface law with linear softening, closed-form solutions are derived for the interfacial stresses and the load–displacement curves, as well as for the ultimate load. It is found that LEFM usually overestimates the Debonding load, thus justifying the need for the proposed approach; on the other hand, Debonding load estimates based on FFM are in excellent agreement with the CCM predictions. Finally, a parametric analysis highlights the effect of the geometry/material properties on the structural response, as well as the ductile-to-brittle transition and the possible occurrence of structural instabilities depEnding on the test controlling parameters.
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Coupled mixed-mode cohesive zone modeling of interfacial Debonding in simply supported Plated beams
International Journal of Solids and Structures, 2013Co-Authors: Laura De Lorenzis, Dilum Fernando, J G TengAbstract:The development of predictive models for Plate End Debonding failures in beams strengthened with thin soffit Plates is a topic of great practical relevance. After the early stress-based formulations, fracture mechanics approaches have become increasingly established. More recently, the cohesive zone (CZ) model has been successfully adopted as a bridge between the stress- and fracture mechanics-based treatments. However, the few studies of this nature propose complex formulations which can only be implemented numerically. To date, the only available analytical solution based on CZ modeling for the prediction of interfacial stresses/Debonding in Plated beams is limited to the determination of interfacial shear stresses and thus neglects the mixed-mode effects generated by the presence of interfacial normal stresses at the Plate End. This paper presents a new analytical formulation based on the CZ modeling approach for the prediction of Plate End Debonding in Plated beams. A key enhancement with respect to the previous solution is the use of a coupled mixed-mode CZ model, which enables a full account of mixed-mode effects at the Plate End. The model describes the evolution of the interface after the End of the elastic regime, and predicts the value of the load at incipient Debonding. The achievement of a closed-form solution for this quite complex case entails the introduction of a crucial simplifying assumption, as well as the ad hoc modeling of an effective cohesive interfacial response. The paper presents the analytical theory and compares its predictions with numerical and experimental results.
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Coupled mixed-mode cohesive zone modeling of interfacial Debonding in simply supported Plated beams
International Journal of Solids and Structures, 2013Co-Authors: Laura De Lorenzis, Dilum Fernando, J G TengAbstract:The development of predictive models for Plate End Debonding failures in beams strengthened with thin soffit Plates is a topic of great practical relevance. After the early stress-based formulations, fracture mechanics approaches have become increasingly established. More recently, the cohesive zone (CZ) model has been successfully adopted as a bridge between the stress- and fracture mechanics-based treatments. However, the few studies of this nature propose complex formulations which can only be implemented numerically. To date, the only available analytical solution based on CZ modeling for the prediction of interfacial stresses/Debonding in Plated beams is limited to the determination of interfacial shear stresses and thus neglects the mixed-mode effects generated by the presence of interfacial normal stresses at the Plate End. This paper presents a new analytical formulation based on the CZ modeling approach for the prediction of Plate End Debonding in Plated beams. A key enhancement with respect to the previous solution is the use of a coupled mixed-mode CZ model, which enables a full account of mixed-mode effects at the Plate End. The model describes the evolution of the interface after the End of the elastic regime, and predicts the value of the load at incipient Debonding. The achievement of a closed-form solution for this quite complex case entails the introduction of a crucial simplifying assumption, as well as the ad hoc modeling of an effective cohesive interfacial response. The paper presents the analytical theory and compares its predictions with numerical and experimental results.Department of Civil and Environmental Engineerin
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Linear Elastic Fracture Mechanics Approach to Plate End Debonding in Rectilinear and Curved Plated Beams
Advances in Structural Engineering, 2010Co-Authors: Laura De Lorenzis, Marco Paggi, Alberto Carpinteri, Giorgio ZavariseAbstract:This paper proposes a linear elastic fracture mechanics approach for the prediction of Plate End Debonding in rectilinear and curved Plated beams. The analytical model results in simple equations, suitable for immediate design use. The load-deflection curve of a Plated beam, from the onset of Debonding up to the complete separation of the Plate, is obtained by controlling the length of the interfacial Debonding crack. Its shape clearly shows that snap-back or snap-through instabilities may arise when the beam is loaded under displacement or force control. Analytical predictions are also compared with finite element results based on an interfacial cohesive crack model. It is shown that the predictions of the proposed analytical model match closely the numerical solution, provided that an effective crack length accounting for the size of the fracture process zone is used in the calculations.
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Cohesive zone modeling of interfacial stresses in Plated beams
International Journal of Solids and Structures, 2009Co-Authors: Laura De Lorenzis, Giorgio ZavariseAbstract:The elastic analysis of interfacial stresses in Plated beams has been the subject of several investigations. These studies provided both first-order and higher-order solutions for the distributions of interfacial shear and normal stresses close to the Plate End in the elastic range. The notable attention devoted to this topic was driven by the need to develop predictive models for Plate End Debonding mechanisms, as the early models of this type adopted Debonding criteria based on interfacial stresses. Currently, approaches based on fracture mechanics are becoming increasingly established. Cohesive zone modeling bridges the gap between the stress- and energy-based approaches. While several cohesive zone analyses of bonded joints subjected to mode-II loading are available, limited studies have been conducted on cohesive zone modeling of interfacial stresses in Plated beams. Moreover, the few available studies present complex formulations for which no closed-form solutions can be found. This paper presents an analytical cohesive zone model for the determination of interfacial stresses in Plated beams. A first-order analysis is conducted, leading to closed-form solutions for the interfacial shear stresses. The mode-II cohesive law is taken as bilinear, as this simple shape is able to capture the essential properties of the interface. A closed-form expression for the Debonding load is proposed, and the comparison between cohesive zone modeling and linear-elastic fracture mechanics predictions is discussed. Analytical predictions are also compared with results of a numerical finite element model where the interface is described with zero-thickness contact elements, using the node-to-segment strategy and incorporating decohesion and contact within a unified framework.
Kequan Yu - One of the best experts on this subject based on the ideXlab platform.
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flexural strengthening of rc beams with cfrp grid reinforced ecc matrix
Composite Structures, 2018Co-Authors: Zhoudao Lu, Kequan Yu, Xu YangAbstract:Abstract This paper investigates the flexural performance of a series of RC beams externally bonded with carbon fiber-reinforced polymer (CFRP) grid-reinforced engineered cementitious composite (ECC) matrix. A total of 15 RC beams, including three control and twelve strengthened, were prepared and tested. The test variables included the longitudinal reinforcement ratio, the strengthening configurations that consisted of different cementitious matrices (ECC versus epoxy mortar), different installation methods (prefabricated versus cast-in-place), and different stiffness of CFRP grids. The test results showed that ECC is an ideal cementitious matrix for the strengthening applications where FRP grids are used as the external reinforcement. The flexural strengthening configuration using the epoxy adhesive to bond prefabricated CFRP grid-reinforced ECC Plate proved to be the most efficient solution. For such configuration, the Plate-End Debonding can be avoided and the mid-span Debonding can be almost suppressed. Flexural capacity analysis was conducted and demonstrated that the plane section assumption is valid and the full strength composite action can be nearly achieved for the strengthening system. The average ratio of the predicted peak loads to the experimental ones of the strengthened RC beams was 1.05.
Xu Yang - One of the best experts on this subject based on the ideXlab platform.
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flexural strengthening of rc beams with cfrp grid reinforced ecc matrix
Composite Structures, 2018Co-Authors: Zhoudao Lu, Kequan Yu, Xu YangAbstract:Abstract This paper investigates the flexural performance of a series of RC beams externally bonded with carbon fiber-reinforced polymer (CFRP) grid-reinforced engineered cementitious composite (ECC) matrix. A total of 15 RC beams, including three control and twelve strengthened, were prepared and tested. The test variables included the longitudinal reinforcement ratio, the strengthening configurations that consisted of different cementitious matrices (ECC versus epoxy mortar), different installation methods (prefabricated versus cast-in-place), and different stiffness of CFRP grids. The test results showed that ECC is an ideal cementitious matrix for the strengthening applications where FRP grids are used as the external reinforcement. The flexural strengthening configuration using the epoxy adhesive to bond prefabricated CFRP grid-reinforced ECC Plate proved to be the most efficient solution. For such configuration, the Plate-End Debonding can be avoided and the mid-span Debonding can be almost suppressed. Flexural capacity analysis was conducted and demonstrated that the plane section assumption is valid and the full strength composite action can be nearly achieved for the strengthening system. The average ratio of the predicted peak loads to the experimental ones of the strengthened RC beams was 1.05.