Externally bonded flexural reinforcement

Externally bonded flexural reinforcement (EBFR) for the strengthening of concrete members using unstressed fibre reinforced polymer (FRP) strips... 

Chaallal, O., Nollet, M. J. and Perraton, D. (1998), Strengthening of reinforced concrete beams with externally bonded fiber-reinforced-plastic plates Design guidelines for shear and flexure , Canadian Journal of Civil Engineering, Vol. 25, Issue 4, pp. 692-704. 

PeSic, N. and Pilakoutas, K. (2005), Flexural analysis and design of reinforced concrete beams with externally bonded FRP reinforcement . Materials and Structures, Vol. 38, Issue 2. pp. 183-192. 

The advantages of externally bonded reinforcement over other methods of strengthening concrete structures include the ability to strengthen part of a structure whilst it is still in use, minimum effect on headroom, low cost and ease of maintenance (see Fig. 6.8, for example). The method has been in use for over 20 years, mainly to enhance flexural capacity, and has been found to produce effective and economical solutions to particular problems. 

In 1985 cracking was noticed in the floor slabs of a multi-storey office building in Leeds. The cracks were adjacent to the external columns and the central lift well and design checks indicated a deficiency in both shear capacity and top flexural reinforcement. A combination of soffit supporting brackets and steel plates bonded to the top surface adjacent to supports was adopted to restore capacity and control cracking (Fig. 6.11). Subsequent load tests revealed that the steel plates were attracting tensile stresses up to 40 N/mm at 1.35 times design load. 

If concrete removal is not required or supplementary reinforcing bars cannot be used, external reinforcement can be applied. For instance, steel bars may be encased in a shotcrete layer or steel plates may be bonded onto the concrete surface. Recently, the use of steel plates has been substituted by fibre-reinforced plastics (F. R.P.), that are composite materials with glass, aramide or carbon fibres embedded in a polymeric matrix (usually an epoxy system). F. R.P. are available in the form of laminates or sheets that are bonded to the concrete surface using an epoxy adhesive [11]. They are typically used to improve the flexural and shear strength or to provide confinement to concrete subjected to compression. The... 

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