Flexural strengthening of RC beams

The research on the potential use of FRP composites in structural strengthening was first started for the flexural strengthening of RC beams. Prior to this research on FRP plate bonding, a considerable amount of research had already accumulated on steel plate bonding for flexural strengthening of RC beams and much of what was learnt in this research is relevant to FRP plate bonding. 

Until very recently, the most pultruded FRP plates on the market were unidirectional (UD). However, a new generation of bi-directional (BD) pultruded FRP plates is now available which make it possible to anchor the FRP soffit plates directly onto the RC member surface by anchor bolts. A detailed summary of different anchorage schemes and experimental results are given by Hollaway and Mays [49]. 

In practical applications, mechanical end-zone anchorage of the FRP plate must be considered whenever possible. In some practical situations, end-zone anchorage in the form of FRP U strips may not be possible or effective as in the case of wide and/or shallow beams. 

The idea in this scheme is to arrest the required anchorage force in the end zone by first transferring it to the steel plate glued over the FRP and then anchoring it to concrete base by anchor bolts and as contact stresses between the plate and the concrete base. 

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Kim, Y. J., R. G. Wight and M. F. Green (2008). Flexural strengthening of RC beams with prestressed CFRP sheets Development of nonmetallic anchor systems. Journal of Composites for Construction 12(1) pp. 35-43. 

De Lorenzis, L., Micelli, F. and La Tegola, A. (2002), Passive and active near surface mounted FRP rods for flexural strengthening of RC beams . Proceedings of the International Conference on Fibre Composites in Interface - ICCI-02, 10-12 June 2002, San Francisco, CA (CD ROM). 

As a flexural member, the behaviour of one-w ay slabs is very similar to flexural behaviour of beams and, as far as the FRP reinforcement is concerned, the behaviour of two-v ay slabs can be taken as uncoupled bending in two orthogonal directions. It is probably for this reason that there is much less work reported in the literature on the flexural strengthening of RC slabs using FRP composites. 

The flexural strengthening of RC bridge beams by the technique of Near Surface Mounted (NSM)... 

Anania, L, Badala, A. and Failla, G. (2005), Increasing the flexural performance of RC beams strengthened with CFRP materials . Construction and Building Materials, Vol. 19, Issue 1, pp. 55-61. 

Badawi, M. (2007), Monotonic and fatigue flexural behaviour of RC beams strengthened with prestressed NSM CFRP rods , PhD thesis. University of Waterloo, Waterloo, Ontario, Canada. 

Kotynia, R. andKaminska, M. (2003), Ductility and failure mode of RC beams strengthened for flexure with CFRP , Report No. 13, Department of Concrete Structures, Technical University of Lodz, 2003, 51pp. 

Aram, M. R., C. Czaderski and M. MotavaUi (2008a). Debonding failure modes of flexural FRP-strengthened RC beams. Composites Part B Engineering 39(5) pp. 826-841. 

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