Shear reinforcement systems in rectangular reinforced concrete beams

Abstract

Shear failure in beams is characterised by diagonal cracks in the shear span or near support. Consequently, any form of well anchored bar placed to cross these cracks will be able to carry shear to some extent. This project report presents the results of a study in which the development and application of various types of shear reinforcement for the design of reinforced concrete beams were reviewed and discussed. The structural concept of these reinforcement and the behaviour of beams containing them were investigated and compared. The results indicate that the conventional vertical links is still the sole type of shear reinforcement preferred and applied by designers is almost all construction works. Although the bent-up bars had been used before, it has not been adopted since the last fifty years or so. This perhaps due to the unavailability of sufficient number of mid-span reinforcement to be extended and bent-up near the support. Alternative systems of shear reinforcement have also been tested namely the independent bent-up bars which configuration has later been improved and renamed the welded inclined bars, inclined links, independent horizontal bars and the swimmer bars. Of these the welded inclined bars proved to have relatively good shear resistance. Furthermore, since it is in the form of vertical longitudinal sheets tied to the top and bottom reinforcement, installation in beams is more practical.