Shear strengthening of RC deep beams using externally bonded FRP systems

According to the available methods of analysis and design for reinforced concrete deep beams, addition of web reinforcement beyond the minimum amount provides only a marginal strength gain, if it does at all. This casts serious doubts on the feasibility and extent of strengthening by placing external reinforcement in the web, whenever such a need arises. This study therefore explores the prospect of strengthening structurally deficient deep beams by using an externally bonded fibre reinforced polymer (FRP) system. Six identical beams were fabricated and tested to failure for this purpose. One of these beams was tested in its virgin condition to serve as reference, while the remaining five beams were tested after being strengthened using carbon fibre wrap, strip or grids. The results of these tests are presented and discussed in this paper. Test results have shown that the use of a bonded FRP system leads to a much slower growth of the critical diagonal cracks and enhances the load-carrying capacity of the beam to a level quite sufficient to meet most of the practical upgrading requirements.