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Jin-guang Teng - One of the best experts on this subject based on the ideXlab platform.
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Shear-BEnding Interaction in Debonding Failures of FRP-Plated RC Beams
Advances in Structural Engineering, 2020Co-Authors: Scott T Smith, Jin-guang TengAbstract:Fibre reinforced polymer (FRP) Plates can be bonded to the tension face of a reinforced concrete (RC) beam to increase its flexural capacity. Many studies have reported premature failure by debonding of the FRP Plate before the ultimate flexural capacity of the Plated section is reached, and the most commonly reported debonding failure mode occurs at or near the Plate End. This paper presents the results of an experimental investigation into the interaction between shear force and bEnding moment at the Plate End at debonding for FRP Plated beams by varying the length of Plate. The experimental results are compared with a Plate End debonding strength model recently proposed by the authors in which this interaction is ignored. A bi-linear approximation is then proposed to describe the interaction between the shear force and the bEnding moment at the Plate End at debonding based on the present results. The effect of U strip End anchorage, used to delay or prevent Plate End debonding, is also assessed in this...
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DEBONDING FAILURES IN FRP-PlateD RC BEAMS WITH OR WITHOUT U STRIP End ANCHORAGE
2020Co-Authors: Scott T Smith, Jin-guang TengAbstract:Fibre reinforced polymer (FRP) Plates can be bonded to the tension face of a reinforced concrete (RC) beam to increase its flexural capacity. Many studies have reported premature debonding failures at the Plate End before the ultimate flexural capacity of the Plated section is reached. This paper presents the results of an experimental investigation into such debonding failures, focussing on the interaction between shear force and bEnding moment at the Plate End and the effect of U strip End anchorage. The study shows that there is significant interaction between shear force and bEnding moment at the Plate End and that U strip End anchorage provides only limited strength enhancement. For the covering abstract see ITRD E123557.
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Coupled mixed-mode cohesive zone modeling of interfacial debonding in simply supported Plated beams
International Journal of Solids and Structures, 2020Co-Authors: Laura De Lorenzis, Dilum Fernando, Jin-guang 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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Concrete Cover Separation in FRP-Plated RC Beams: Mitigation Using FRP U-Jackets
Journal of Composites for Construction, 2016Co-Authors: B. Fu, Jin-guang Teng, Jian Fei Chen, Guangming ChenAbstract:AbstractConcrete cover separation is a common failure mode of RC beams strengthened with a fiber-reinforced polymer (FRP) Plate externally bonded to the tension face (FRP-Plated RC beams). This failure mode initiates at the critical Plate End and then propagates at the level of steel tension reinforcement in the direction of increasing moment. Plate-End anchorage by FRP U-jackets has been specified in some design guidelines as a mitigation measure to delay or suppress concrete cover separation, although its effectiveness is far from clear. This mitigation method is more attractive than other options because the same strengthening material is used and the installation procedure is simple. This paper presents the first systematic experimental study on the use of FRP U-jackets for mitigating Plate-End concrete cover separation failure, with particular attention to the effect of inclination angle between the U-jacket and the beam axis. A total of 10 full-scale FRP-Plated RC beams were tested. The test results...
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Finite element modelling of debonding failures in steel beams flexurally strengthened with CFRP laminates
Engineering Structures, 2015Co-Authors: Jin-guang 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.
Weiming Li - One of the best experts on this subject based on the ideXlab platform.
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Research on a New Kind of High Directivity End-Fire Antenna Array
Progress in Electromagnetics Research B, 2020Co-Authors: Weiming LiAbstract:In this paper, a new kind of End-flre array was built by employing high directivity Plate End-flre antenna as the basic element based on electromagnetic surface wave theory. Being difierent from normal End-flre array, in the new array, high directivity Plate End- flre antenna elements were arranged End to End along the End-flre direction, and the interelement spacing and uniform progressive phase were carefully adjusted to achieve high directivity. The simulations and measurements showed that the whole array achieved 19.2dB directivity with four elements at 14.7dB directivity each.
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Research on the relationship between the structure parameters and directivity of Plate End-fire antennas
2013 IEEE Antennas and Propagation Society International Symposium (APSURSI), 2013Co-Authors: Weiming LiAbstract:In this paper, the relationship between and the directivity the structural parameters of Plate End-fire antennas was investigated. According to the analysis and experiments, the phase velocity of the slow surface wave propagating along this antenna is demonstrated to be a link between the structure parameters and antenna directivity. The point is the extEnded Hansen-Woodyard End-fire condition must be satisfied also in this kind of antenna to achieve optimum directivity just like in normal End-fire arrays.
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Analysis on the pattern distortions of Plate End-fire antenna array caused by mutual coupling
CSQRWC 2012, 2012Co-Authors: Weiming Li, Xiaowen XuAbstract:In this paper, the far field pattern distortions of Plate End-fire antenna array caused by mutual coupling were analyzed. The pattern distortions of two typical array forms were shown. And the ones of array arranged along the broadside direction were further discussed through the inter-space experiment and the surface current experiment. The relationship between array inter-space and distortion extent was quantitatively analyzed, and some surface current variation rules in array had been got.
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Research on the array weighting of Plate End-fire antenna with the effect of mutual coupling
2012 International Conference on Microwave and Millimeter Wave Technology (ICMMT), 2012Co-Authors: Weiming Li, Xiaowen XuAbstract:This paper focus on the array weighting of the Plate End-fire antenna array with the effect of mutual coupling. The far field pattern distortions of array caused by mutual coupling were analyzed. Then, the efficacies of amplitude weighting and phase weighting in Plate End-fire antenna array were discussed. Under strong mutual coupling, the efficacy of amplitude weighting was affected evidently, and the designing target was hard to be achieved. Meanwhile, the efficacy of phase weighting was achieved exactly in a large range of scanning.
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Plate End-fire antenna design based on genetic algorithm
ISAPE2012, 2012Co-Authors: Weiming LiAbstract:A modified genetic algorithm (GA) is used to design Plate End-fire-antennas. Six kinds of new Plate End-fire antennas with ten monopoles each have been designed, in which the parasitic monopoles and broadband structure have been used. Compared with the antenna designed by the Hansen-Wood yard condition, the feeding characteristics of the antennas have been improved remarkably and then the gain has been increased accordingly, while the directivity of the antennas with new structure has been kept at the same level.
J G Teng - One of the best experts on this subject based on the ideXlab platform.
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FINITE ELEMENT PREDICTION OF Plate-End COVER SEPARATION IN FRP-STRENGTHENED RC BEAMS
2020Co-Authors: Shi Shun Zhang, J G TengAbstract:The flexural strength of reinforced concrete (RC) beams can be effectively increased using either externally bonded (EB) or near-surface mounted (NSM) fibre-reinforced polymer (FRP) reinforcement. A likely failure mode of such FRP-strengthened RC beams is the Plate-End cover separation failure mode which involves debonding of the bonded FRP reinforcement and the cover concrete along the level of the steel tension reinforcement. Despite many existing studies on this failure mode, the accurate prediction of this failure mode using the finite element (FE) method has remained a great challenge. This paper presents a novel FE smeared-crack approach for accurate prediction of Plate-End cover separation in which the radial stresses generated by the steel tension reinforcement are taken into account for the first time. The capability and validity of the proposed FE model are verified using existing experimental results.
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DEBONDING FAILURES IN FRP-PlateD RC BEAMS WITH OR WITHOUT STRENGTHENED ANCHORAGE
2020Co-Authors: Scott T Smith, J G TengAbstract:The flexural strength of reinforced concrete (RC) beams can be increased by bonding a fiber reinforced polymer (FRP) Plate to its tension face. Premature bonding failures have been reported at the Plate End before the ultimate flexural capacity of the Plated section is reached. Presented here are the results of an experimental investigation into such debonding failures, with a focus on the interaction between shear force and bEnding moment at the Plate and the effect of U-strip End anchorage. Significant interaction between shear force and bEnding moment at the Plate End and that U-strip anchorage provides only limited strength enhancement are shown by the study.
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Plate End debonding in frp Plated rc beams ii strength model
Engineering Structures, 2007Co-Authors: J G TengAbstract:RC beams strengthened in flexure by bonding an FRP or steel Plate to the tension face can fail by debonding at or near the Plate End in a number of different modes. This paper presents a simple, rationally-based predictive model for such Plate End debonding failures. 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 any national or international design codes and guidelines.
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Plate End debonding in frp Plated rc beams i experiments
Engineering Structures, 2007Co-Authors: J G TengAbstract:Abstract 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.
L Hollaway - One of the best experts on this subject based on the ideXlab platform.
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an experimental study of the influence of Plate End anchorage of carbon fibre composite Plates used to strengthen reinforced concrete beams
Composite Structures, 1998Co-Authors: H N Garden, L HollawayAbstract:Abstract Carbon fibre reinforced polymer (CFRP) materials are well suited to the rehabilitation of civil engineering structures due to their corrosion resistance, high strength-to-weight ratio and high stiffness-to-weight ratio. Their application in the field of strengthening is envisaged to expand due to the vast number of bridges and buildings in need of strengthening. In order to apply these materials effectively, it is necessary to understand the behaviour of members strengthened with externally bonded composite Plates, one aspect of which is the response to the installation of anchorage at the Ends of the Plates to resist Plate separation from the beam. A number of 1.0 m long Plated beams were tested in four point bEnding and as cantilevers to demonstrate that the structural benefit of Plate End anchorage diminishes as the shear span/depth ratio of the beam increases. Under a low shear span/depth ratio (3.00 in the present work), the anchorage improves the composite action between the Plate and the beam, giving rise to greater structural stiffness after yield of the internal rebars. This beneficial influence can be achieved using a bolted anchorage system which provides the same improvement in composite action as a large Plate End clamping force generated by trapping the Plate under the beam supports. Although the Plate End anchorage has most structural benefit under a low shear span/depth ratio, it is recommEnded that anchorage be applied in every case until long term practical experience suggests otherwise.
H N Garden - One of the best experts on this subject based on the ideXlab platform.
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an experimental study of the influence of Plate End anchorage of carbon fibre composite Plates used to strengthen reinforced concrete beams
Composite Structures, 1998Co-Authors: H N Garden, L HollawayAbstract:Abstract Carbon fibre reinforced polymer (CFRP) materials are well suited to the rehabilitation of civil engineering structures due to their corrosion resistance, high strength-to-weight ratio and high stiffness-to-weight ratio. Their application in the field of strengthening is envisaged to expand due to the vast number of bridges and buildings in need of strengthening. In order to apply these materials effectively, it is necessary to understand the behaviour of members strengthened with externally bonded composite Plates, one aspect of which is the response to the installation of anchorage at the Ends of the Plates to resist Plate separation from the beam. A number of 1.0 m long Plated beams were tested in four point bEnding and as cantilevers to demonstrate that the structural benefit of Plate End anchorage diminishes as the shear span/depth ratio of the beam increases. Under a low shear span/depth ratio (3.00 in the present work), the anchorage improves the composite action between the Plate and the beam, giving rise to greater structural stiffness after yield of the internal rebars. This beneficial influence can be achieved using a bolted anchorage system which provides the same improvement in composite action as a large Plate End clamping force generated by trapping the Plate under the beam supports. Although the Plate End anchorage has most structural benefit under a low shear span/depth ratio, it is recommEnded that anchorage be applied in every case until long term practical experience suggests otherwise.
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AN EXPERIMENTAL STUDY OF THE ANCHORAGE LENGTH OF CARBON FIBRE COMPOSITE PlateS USED TO STRENGTHEN REINFORCED CONCRETE BEAMS
Construction and Building Materials, 1998Co-Authors: H N Garden, R J Quantrill, L C Hollaway, A M Thorne, G. A. R. ParkeAbstract:Abstract Concrete structures deteriorate for various reasons and upgrading has been achieved for over 20 years by bonding steel Plates using epoxy resins. Disadvantages of this method include transporting, handling and installing heavy Plates and corrosion of the Plates. The use of composite materials overcomes these problems and provides equally satisfactory solutions. The rehabilitation of concrete structures represents a large demand for efficient strengthening methods and composite materials are well suited to this application. It is now necessary to understand more about the factors that are important in the design of composite Plate bonding, such as the influence of the Plate anchorage length and additional Plate End anchorage. Four point bEnding and cantilever loading are used to show that the ultimate capacities and failure modes of reinforced concrete beams, externally strengthened with bonded composite Plates, are depEndent on the shear span/depth ratio. Strengthened members are found to fail by separation of the concrete cover from the internal rebars throughout the whole of one shear span under low shear span/depth ratios, while a thinner concrete layer is separated at higher ratios. Peeling of the Plate End is thought to occur under low shear span/depth ratios. The End of the bonded Plate in the failed shear span experiences strain increases relatively soon after yield of the internal steel when the shear span/depth ratio is low, but the Plate Ends are less sensitive to yield under higher ratios, indicating the lower shear transferred into the concrete via the adhesive at the Plate Ends. Ultimate bEnding moments are found to reach an upper limit with increasing shear span/depth ratio in the range of ratios studied. Adhesive shear stresses are of greatest magnitude at the Ends of the Plate under low shear span/depth ratios.
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A PARAMETER STUDY OF THE STRENGTHENING OF REINFORCED CONCRETE BEAMS WITH BONDED COMPOSITES
1996Co-Authors: H N Garden, L C Hollaway, A M Thorne, G. A. R. ParkeAbstract:Concrete structures deteriorate for various reasons and upgrading has been achieved for over twenty years by bonding steel Plates using epoxy resins. The method has been applied mainly to bridges. Disadvantages of this method include transporting, handling and installing heavy Plates and corrosion of Plates. The use of composite materials overcomes these problems and provides equally satisfactory solutions. An experimental parameter study of the strengthening of reinforced concrete beams by bonded composite Plates is presented. Plate geometry and applied load configuration are studied, revealing that bonded Plates increase the ultimate capacity of beams, but reduce ductility. Ultimate capacities decreased with reducing ratios of Plate width to thickness. Failure was always accompanied by concrete cover separation from internal reinforcement. Separated cover widths at Plate Ends were equal to beam widths for wide Plates and Plate widths for narrower Plates. Increasing shear span/depth ratios resulted in improved ultimate capacities. Bonded Plates are effective in carrying increased proportions of internal moment couples beyond yield of conventional reinforcement. Various Plate End anchorages were also applied, revealing that anchorage delays failure by resisting Plate separation. (A) For the covering abstract see IRRD 882313.