Research progress on the flexural behaviour of externally bonded RC beams

The flexural behaviour of strengthened reinforced concrete (RC) beams is more complicated compared to the normal beams due to the different bond conditions and properties of the externally bonded material. A significant number of research studies have been reported on the use of different types of material for flexural strengthening of RC beams using the external bonding (EB) technique. Although most research has focused on the conventional strengthening materials, namely, steel plates, FRP and ferrocement; unconventional materials, such as sprayed FRP and cement-based composites, have shown that they also have a significant effect on the behaviour of bonded beams. This paper presents a comprehensive state-of-the-art review of the different materials used for strengthening RC beams using the EB technique and their evaluation criteria. The behaviour of the strengthened beams is discussed in terms of load carrying capacity, stiffness under service loads, and ductility and failure modes. In addition, the effect of elevated temperatures on the externally bonded materials is also discussed. The critical review of the existing data can help for a better utilization and usage of the different materials for strengthening projects, which contributes significantly to the current efforts of developing optimum and feasible strengthening systems.