A new discrete method to model unidirectional FRP-to-parent material bonded joints subjected to mechanical loads (original) (raw)

Near free-edge stresses in FRP-to-concrete bonded joint due to mechanical and thermal loads

Scientia Iranica

Over the last few decades, a considerable amount of theoretical and experimental investigations have been conducted on the mechanical strength of composite bonded joints. Nevertheless, many issues regarding the debonding behavior of such joints still remain uncertain. The high near free-edge stress fields in most of these joints are the cause of their debonding failure. In this study, the performance of an externally bonded fiberreinforced polymer (FRP) fibrous composite to a concrete substrate prism joint subjected to mechanical and thermomechanical loadings is evaluated through employing the principles of lamination theory. An inclusive Matlab code is generated to perform the computations. The bond strength is estimated to take place in a region-2 also termed the boundary layer-where the peak interfacial shearing and transverse peeling stresses occur; whereas the preceding stress field is observed to be the main failure mode of the joint. The proposed features are validated through the existing experimental data points as well as the commercial finite element (FE) modeling software, Abaqus. Comparison between the calculated and experimental results demonstrates favorable accord, producing quite a high average ratio. The current approach is advantageous to failure modeling analysis, optimal design of bonded joints, and scaling analyses among others.

The Role of the Bond on the Structural Behaviour of Flexural FRP Reinforced Concrete Members

2005

The paper focuses on the bond between fibre-reinforced polymer (FRP) reinforcements and concrete including its modelling (local bond-slip law) and influence on the structural behaviour of FRP reinforced concrete members. The analysis, both theoretical and experimental, refers to flexural concrete beams upgraded by externally bonded FRP sheets, considering different bonding systems such as the commonly used resin-FRP system and novel bonding technologies (near surface mounted system, cementitious-FRP system). The structural behaviour of strengthened beams is analyzed by means of a non linear model derived from a cracking analysis based on slip and bond stress. By using some bond-slip models, the performances of beams under service conditions (cracking, deformability) are evaluated varying parameters governing the FRP-to-concrete bond behaviour. Results of the analysis furnish useful information to find interface bonding systems which can offer suitable bond characteristics to optimize the performances of FRP reinforced concrete members.

Modelling the behaviour of the bonding of fibre reinforced concrete at the plate end

2006

In this paper, the finite element method is used to analyse the behaviour of concrete externally strengthened by fibre reinforced polymers (FRP). This model aims to analyse the stress distribution in the FRP-concrete interface at the plate end of a bending beam. The behaviour of the concrete-epoxy-FRP arrangement is modelled with interface elements with initial zero thickness, using a discrete crack approach. A localized damage model is adopted for the interface and a parametric study is performed to approximate the material parameters adopted. The importance of each parameter is assessed. This model is subsequently verified using experimental data collected from the literature. Finally, a proposal is made concerning the adoption of a relation G F II /G F for the interface behaviour. Mention is also made to some of the main mathematical models found in the literature, which are compared to the present approach.

Three‐dimensional modelling of bond behaviour between concrete and FRP reinforcement

Engineering Computations, 2011

PurposeThe purpose of this paper is to investigate the bond behaviour between fiber reinforced polymer (FRP) sheets and concrete elements, starting from available experimental evidences, through a calibrated and upgraded 3D mathematical‐numerical model.Design/methodology/approachThe complex mechanism of debonding/peeling failure of FRP reinforcement is studied within the context of damage mechanics to appropriately catch transversal effects and developing a more realistic and comprehensive study of the delamination process. The FE ABAQUS© code has been supplemented with a numerical procedure accounting for Mazars's damage law inside the contact algorithm.FindingsIt has been shown that such an approach is able to catch the delamination evolution during loading processes as well.Originality/valueA Drucker‐Prager constitutive law is adopted for concrete whereas FRP elements are assumed to behave in a linear‐elastic manner, possibly undertaking large strains/displacements. Surface‐t...

Bond-slip model for FRP-to-concrete bonded joints under external compression

Composites Part B: Engineering, 2015

The influence of compressive stresses exerted on FRP-concrete joints created by external strengthening of structural members on the performance of the system requires better understanding especially when mechanical devices are used to anchor the externally bonded reinforcement (EBR). The numerical modelling of those systems is a tool that permits insight into the performance of the corresponding interfaces and was used in the present study, essentially directed to analyse the effectiveness of EBR systems under compressive stresses normal to the composite surface applied to GFRPto-concrete interfaces. The compressive stresses imposed on the GFRP-to-concrete interface model the effect produced by a mechanical anchorage system applied to the EBR system. An experimental program is described on which double-lap shear tests were performed that created normal stresses externally applied on the GFRP plates. A corresponding bond-slip model is proposed and the results of its introduction in the numerical analysis based in an available 3D finite element code are displayed, showing satisfactory agreement with the experimental data. The results also showed that lateral compressive stresses tend to increase the maximum bond stress of the interface and also 1 Assistant Professor originate a residual bond stress which has significant influence on the interface strength.

Experimental Study on Bond Behavior between Concrete and FRP Reinforcement

Journal of Composites for Construction, 2008

Bonding between fiber-reinforced polymer ͑FRP͒ sheets and concrete supports is essential in shear and flexural applications for transfer of stress between concrete structure and reinforcement. This paper aims at better understanding FRP-concrete bond behavior and at assessing some of the common formulations for effective bond length and bond-slip models ͑-s͒ by means of an extensive experimental program on 39 concrete specimens strengthened with various types and amounts of FRP strips and covering a wide range of FRP axial rigidities, subjected to both double-shear and bending tests. Effective bond length, maximum bond/shear stress, slip when bond stress peaks, and slip when bond stress falls to zero, were all experimentally measured. The influence of FRP stiffness on effective bond length and bond-slip behavior was observed. New expressions for ͑1͒ effective bond length; ͑2͒ maximum shear/bond stress; ͑3͒ slip at peak value of bond stress; and ͑4͒ slip at ultimate, taking into account the influence of FRP stiffness, are proposed.

The Influence of FRP spike and patch anchors on the bond performance of FRP-to-concrete joints

2015

It has been demonstrated that the governing failure mode of concrete structures strengthened with fiber reinforced polymer composites (FRP) is by premature debonding of the FRP material from the concrete substrate. Research has shown that one means by which the FRP-to-concrete bond performance may be improved is to provide anchorage measures that resist the interfacial shear and peeling stresses that are generated along the FRP bond line. FRP spike anchors and bidirectional fiber patch anchors are a proven means to enhance the bond performance of FRP materials when bonded to concrete. Although the above mentioned anchorage systems have shown significant promise when investigated independently, the present research aims to combine their unique properties into a hybrid anchorage system. In this study, FRP spike anchors were used to anchor bidirectional fiber patches and used to restrain FRP laminates tested in direct shear resulting in a superior anchorage strength which was demonstra...

Finite Element Assessment on Bond Behaviour of FRP-to-Concrete Joints under Cyclic Loading

World Academy of Science, Engineering and Technology, International Journal of Civil and Environmental Engineering, 2015

Over the last two decades, externally bonded fiber reinforced polymer (FRP) composites bonded to concrete substrates has become a popular method for strengthening reinforced concrete (RC) highway and railway bridges. Such structures are exposed to severe cyclic loading throughout their lifetime often resulting in fatigue damage to structural components and a reduction in the service life of the structure. Since experimental and numerical results on the fatigue performance of FRP-to-concrete joints are still limited, the current research focuses on assessing the fatigue performance of externally bonded FRP-to-concrete joints using a direct shear test. Some early results indicate that the stress ratio and the applied cyclic stress level have a direct influence on the fatigue life of the externally bonded FRP. In addition, a calibrated finite element model is developed to provide further insight into the influence of certain parameters such as: concrete strength, FRP thickness, number ...

Finite Element Assessment On Bond Behavior Of Frp-To-Concrete Joints Under Cyclic Loading

2015

A new discrete method to model unidirectional FRP-to-parent material bonded joints subjected to mechanical loads (original) (raw)

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